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Research Report 51 Study of Industry • Melbourne Water Corporation • Monash University • Orica Australia Pty Ltd Practices • Power and Water Corporation • Queensland Health Pathology & Scientific Services • RMIT University • South Australian Water Corporation • South East Water Ltd • Sydney Catchment Authority • Sydney Water Corporation • The University of Adelaide • The University of New South Wales The Cooperative Research Centre (CRC) for Water Quality and Treatment is Australia’s national drinking water research • The University of Queensland centre. An unincorporated joint venture between 29 different • United Water International Pty Ltd organisations from the Australian water industry, major universities, CSIRO, and local and state governments, the CRC • University of South Australia combines expertise in water quality and public health. • University of Technology, Sydney

The CRC for Water Quality and Treatment is established • Water Corporation and supported under the Federal Government’s Cooperative • Water Services Association Research Report Research Centres Program. of Australia • Yarra Valley Water Ltd 51 Literature Review on Discoloured Water Formation and Desktop Study of Industry Practices

Peter Teasdale, Kelly O’Halloran, Corinna Doolan and Lisa Hamilton

Research Report No. 51

LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

© CRC for Water Quality and Treatment 2007

DISCLAIMER The Cooperative Research Centre for Water Quality and Treatment and individual contributors are not responsible for the outcomes of any actions taken on the basis of information in this research report, nor for any errors and omissions.

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Telephone: +61 8 8259 0351 Fax: +61 8 8259 0228 E-mail: [email protected] Web site: www.waterquality.crc.org.au

Literature Review on Discoloured Water Formation and Desktop Study of Industry Practices

Research Report 51 ISBN 18766 16776

2 CRC FOR WATER QUALITY AND TREATMENTRESEARCH REPORT 51

FOREWORD

Literature Review on the Processes Involved in the Formation of Discoloured Water, Including Data on the Occurrence of Discoloured Water and Customer Complaints for Participating Water Utilities.

Program Leader: Dammika Vitanage

Project Leader: Dr. Peter Teasdale, School of Environmental & Applied Sciences, Griffith University Gold Coast.

Research Staff: Corinna Doolan (Sydney Water) Lisa Hamilton (Griffith University) Kelly O’Halloran (Griffith University)

Research Nodes: Sydney Water, Griffith University

CRC for Water Quality and Treatment Project No. 2.5.0.2 - Understanding The Generation Of Discoloured Water At The Customer's Tap And The Development Of Monitoring Methods To Assess The Potential For Discoloured Water Formation In Distribution Systems

3 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

EXECUTIVE SUMMARY

This project took a holistic approach in assessing the cause and effect relationships related to critical discoloured water formation processes from the catchment through to the customer’s tap. Its uniqueness is in the development of a Decision Support System that comprises of practical tools and techniques to guide water utilities in taking a step-by-step approach to manage discoloured water events. This literature review and industry desktop study form Stage 1 of the project. Stage 2 showcases the ‘Discoloured Water Toolbox’ which includes a web-based Discoloured Water Management Support Tool to assess the cause and effect of critical discolouration issues, quantitative particle models, characterisation procedures, customer complaint survey and measurement and monitoring techniques. The benefit of this Decision Support System is that the tools can be used in isolation or combination depending on the needs of a particular system.

The occurrence of discoloured water at customers’ taps or the discolouration of washing is a major source of customer dissatisfaction. The degree to which the different forms of discoloured water occur varies, depending on the source water, the treatment used and conditions within the distribution pipes. The aim of this report is to develop a greater understanding of the processes prior to distribution, within the distribution system and within the customers’ taps that contribute to dirty water formation. Iron and manganese are the most important and widely studied elements in relation to discoloured water, however other elements such as aluminium, silicon, calcium and copper, as well as organic matter may also become part of a discoloured water event. Treatment methods include aeration, chemical oxidation, disinfection, filtration, coagulation and pH adjustment. The identification of methods for the prediction and preventative treatment of these problems will also be reviewed to ultimately reduce the number of customer complaints due to discoloured water. Any gaps in knowledge (either observed within the literature or suggested by water corporations) will also be discussed. Post treatment chemical interactions, such as oxidation processes, lead to the formation of new material and subsequent sedimentation within the distribution system. Biofilm formation and microbial oxidation of iron and manganese also contribute to the accumulation of material. Corrosion processes can also create particles, either through the release of iron or the formation of scale. The release or resuspension of accumulated material is generally driven by physical changes in water velocity and flow regime. Cleaning procedures (flushing, swabbing and air scouring) use this process to remove sediment and scales from the pipes. Within the household, corrosion of copper pipes and fixtures, and the staining of laundry are both discoloured water related problems that can arise. The detection of discoloured water events is generally in the hands of the consumer. The lodgement of complaints can be used to trigger an assessment of the discoloured water event to determine the extent and primary cause of production of the discoloured water. Post-event assessment is beneficial in instigating remedial action, however, preventing, monitoring and predicting events is much more desirable. Participating water utilities have provided data of discoloured water and dirty washing customer complaints, including data on methods of complaint collection, categorisation and reporting; catchment characteristics; treatment processes; water quality in the distribution systems; and system performance and operations. The participating utilities have also provided their top five queries regarding discoloured water. The level to which these questions can be answered by this project and by scientific approaches within the literature is summarised.

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TABLE OF CONTENTS

Foreword ...... 3 Executive Summary ...... 4 List of Figures...... 8 List of Tables ...... 9 1 Significance of Discoloured Water Research...... 10 1.1 Introduction ...... 10 1.2 Purpose and Objectives of this Project...... 13 1.2.1 Purpose...... 13 1.2.2 Broad Objectives and Report Outline ...... 13 2 Literature Review on Discoloured Water Formation ...... 14 2.1 Pre-Distribution Processes that Influence Discoloured Water Formation ...... 14 2.1.1 Chemistry and concentration of elements in raw water ...... 14 2.1.1.1 Iron...... 15 2.1.1.2 Manganese...... 18 2.1.1.3 Aluminium...... 19 2.1.1.4 Silicon ...... 20 2.1.1.5 Calcium...... 20 2.1.1.6 Copper...... 21 2.1.1.7 Metal complexes with organic matter ...... 21 2.1.2 Effect of various treatment processes...... 23 2.1.2.1 Reservoir manipulation...... 23 2.1.2.2 Oxidation / disinfection ...... 24 2.1.2.3 Coagulation / flocculation ...... 31 2.1.2.4 Filtration...... 32 2.1.2.5 Treatment train ...... 34 2.1.2.6 Sequestering techniques...... 35 2.1.2.7 Influence of NOM in treatment process...... 36 2.2 Processes within Distribution Systems that Influence Discoloured Water Events ...... 37 2.2.1 Corrosion processes leading to discoloured water ...... 37 2.2.1.1 Water chemistry that influences corrosion ...... 37 2.2.1.2 Types of pipes ...... 40 2.2.1.3 Fe2+ release from pipe wall...... 40 2.2.1.4 Scale formation...... 40 2.2.2 Physiochemical processes leading to the formation of new particles that can cause discoloured water ...... 43 2.2.2.1 Development of chemical films...... 43 2.2.2.2 Accumulation of sediments...... 43 2.2.2.3 Composition of particles and coatings...... 45 2.2.2.4 The release of Mn or Fe from deposits ...... 46 2.2.3 Microbiological processes leading to discoloured water...... 48 2.2.3.1 Factors leading to the formation of biofilms...... 48 2.2.3.2 Biofilm content ...... 51 2.2.3.3 The contribution of microbial processes to discoloured water ...... 53 2.2.4 Operational procedures to manage discoloured water ...... 56 2.2.4.1 Cleaning...... 56

5 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

2.2.4.2 Hydraulics...... 57 2.3 Post Distribution Causes of Discoloured Water...... 58 2.3.1 Copper corrosion at customers taps ...... 58 2.3.1.1 Effect of pH and alkalinity...... 58 2.3.1.2 Corrosion types ...... 60 2.3.1.3 Microbial influenced corrosion...... 60 2.3.1.4 Treatment ...... 60 2.3.2 Dirty washing...... 61 2.4 Prediction of Dirty Water Events...... 63 2.4.1 Monitoring discoloured water ...... 63 2.4.2 Modelling research...... 63 2.4.2.1 Modelling oxidation rates...... 63 2.4.2.2 Disinfectant residual ...... 64 2.4.2.3 Biofilm and bulk water bacteria...... 66 2.4.2.4 Contaminant modelling...... 67 2.4.2.5 Simulated distribution systems...... 67 2.4.3 Predictive tests...... 68 2.5 Identification of Gaps in Knowledge ...... 69 2.5.1 Pre-Distribution processes that influence discoloured water formation...... 69 2.5.1.1 Chemistry and concentration of elements in raw water ...... 69 2.5.1.2 Effect of various treatment processes ...... 69 2.5.2 Processes within the distribution system that influence discoloured water events...... 70 2.5.2.1 Corrosion processes leading to discoloured water ...... 70 2.5.2.2 Physicochemical processes leading to discoloured water ...... 70 2.5.2.3 Microbiological processes leading to discoloured water ...... 71 2.5.2.4 Operational procedures to manage discoloured water ...... 72 2.5.3 Post-distribution causes ...... 72 2.5.3.1 Copper corrosion at customers taps ...... 72 2.5.3.2 Dirty washing ...... 72 2.5.4 Prediction of dirty water events...... 73 2.5.4.1 Monitoring discoloured water...... 73 2.5.4.2 Modelling research ...... 73 2.5.4.3 Predictive tests ...... 73 3 Assessment of industry data ...... 74 3.1 Objectives ...... 74 3.2 Background...... 74 3.2.1 Utilities...... 74 3.2.1.1 Sydney Water Corporation – New South Wales ...... 74 3.2.1.2 Hunter Water Corporation – New South Wales...... 74 3.2.1.3 Power and Water - Northern Territory ...... 74 3.2.1.4 Brisbane - Queensland...... 75 3.2.1.5 Gold Coast Water - Queensland ...... 75 3.2.1.6 Water Corporation - Western Australia ...... 75 3.2.1.7 Yarra Valley Water - Victoria ...... 75 3.2.1.8 South East Water - Victoria ...... 75 3.2.2 Practices...... 76 3.2.2.1 Customer complaint collection and categorisation...... 76 3.2.2.2 Customer complaint investigations...... 76

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3.2.2.3 Operational and maintenance ...... 77 3.2.2.4 Treatment ...... 77 3.3 Assessment ...... 78 3.3.1 Customer complaints ...... 78 3.3.1.1 South East Water ...... 79 3.3.1.2 Sydney Water Corporation ...... 79 3.3.1.3 Yarra Valley Water ...... 79 3.3.1.4 Brisbane Water...... 79 3.3.1.5 Power and Water...... 79 3.3.1.6 Gold Coast Water ...... 80 3.3.1.7 Hunter Water Corporation ...... 80 3.3.1.8 Water Corporation ...... 80 3.3.2 Industry data ...... 80 3.3.3 Comparison of water quality data with customer complaint data...... 82 3.4 Issues & Gaps in Knowledge...... 86 3.4.1 Treatment...... 86 3.4.1.1 Chemicals...... 86 3.4.1.2 pH ...... 86 3.4.2 Distribution ...... 86 3.4.2.1 Manganese...... 86 3.4.2.2 pH ...... 86 3.4.2.3 Oxidation...... 86 3.4.2.4 Detergents ...... 86 3.5 Conclusions ...... 88 3.6 Recommendations...... 89 4 Industry Partner Questions ...... 90 4.1 Questions from Participating Utilities ...... 91 4.1.1 Sydney Water...... 91 4.1.2 Hunter Water...... 92 4.1.3 Gold Coast Water...... 93 4.1.4 Water Corporation (WA)...... 94 4.1.5 Power and Water (N.T.) ...... 95 4.1.6 Brisbane Water ...... 96 4.1.7 Yarra Valley Water ...... 97 4.1.8 South East Water ...... 98 5 Summary and Conclusions ...... 99 6 Recommendations ...... 102 7 References ...... 105 8 Appendices ...... 116

7 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

LIST OF FIGURES

Figure 2.1: Forms of aluminium in natural waters. Modified from Srinivasan et al. (1999)...... 20 Figure 2.2: Comparison of the least squares mean concentration of a) iron and b) manganese in Hinze Dam between 1983 and 1988 for the whole year (before and during artificial aeration commenced in 1986) (Zaw and Chiswell 1999)...... 24 Figure 2.3: The effect of temperature on the oxidation of Fe(II)...... 26 Figure 2.4: The removal of metals vs ozone dosage (1min contact time)...... 28 2+ Figure 2.5: Bench Scale Comparison of Oxidation of Mn by KMnO4, ClO2 and O3 at three initial Mn2+concentrations (Gregory and Carlson 2003)...... 30 Figure 2.6: Post treatment concentration of manganese in the Wyong Water Supply (Khoe and Waite 1989)...... 31 Figure 2.7: The treatment train used by the Upper San Leandro treatment plant demonstrates the increasing complexity of the treatment process (Wilczak et al. 2003)...... 34 Figure 2.8: Release of iron from pipe wall including changes in DO. Initial DO = 1.0 mg/L, pH 8.9 (Beckett et al. 1998)...... 39 Figure 2.9: Iron concentration from three treatments in iron pipe loops at Lone Rock, Wis. (Cantor et al. 2003)...... 40 Figure 2.10: Schematic of a corrosion scale on a distribution system pipe (Sontheimer et al. 1981)...... 41 Figure 2.11: Changes in observed rate coefficient following spike additions of Fe(II) for different concentrations of Fe(III)...... 44 Figure 2.12: Flow rate in two dead end mains...... 47 Figure 2.13: Typical turbidity patterns created by diurnal alternations in stagnation and flow due to consumer demand over a five day period (Smith et al. 1998)...... 47 Figure 2.14: Data from water utilities in the USA, demonstrating the adverse effect of higher alkalinity on copper release, especially for waters with low pH (Edwards et al. 1996)...... 59 Figure 2.15: Differences in the effect of alkalinity on copper release for pipes of different age (Edwards et al. 2002)...... 59 Figure 2.16: a) Effect of adding phosphate (PO4) on the concentration of copper released from test system. b) Effect of adding silicate (SiO2) on the concentration of copper released from test system...... 61 Figure 2.17: Iron oxidation rates in the presence and absence of monochloramine for four different pH values...... 65 Figure 3.1: Discoloured water complaints per ‘000 properties...... 78 Figure 3.2: Comparison of average iron and manganese concentrations with average number of complaints for each utility...... 82 Figure 3.3: Comparison of average turbidity levels with average number of complaints for each utility...... 83 Figure 3.4: Comparison of average alkalinity with average number of complaints for each utility...... 83 Figure 3.5: Comparison of total organic carbon concentrations with average number of complaints for each utility...... 84 Figure 3.6: Comparison of average pH levels with average number of complaints for each utility...... 85

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LIST OF TABLES

Table 1.1: Symptoms and cause of common discoloured water events. Modified from U.S. Environmental Protection Agency (2002) ...... 10 Table 1.2: Size fractionation of substances within water. Modified from Kiely (1997)...... 11 Table 1.3: National and International Drinking Water Quality Guidelines for parameters relevant to discoloured water...... 12 Table 2.1: Comparison of the concentrations of Iron, Manganese and turbidity from selected raw water storages, treated waters and a distribution system...... 15 Table 2.2: Oxidising agents, in order of effectiveness (weakest to strongest) under standard laboratory conditions (Wallace and Campbell 1991)...... 25 Table 2.3: Types of filtration used in water treatment...... 33 Table 2.4: Iron solids that could possibly be present in corrosion scales. Modified from McNeill and Edwards (2001)...... 42 Table 2.5: Percentage of dry weight for metals and volatile solids from the literature...... 46 Table 2.6: Species of micro-organisms found in or associated with distribution system biofilms and their ability to oxidise manganese and iron ...... 52 Table 2.7: Half-lives of microbial oxidation of Mn(II) in freshwater sources. Modified from Wehrli (1995)...... 54 Table 2.8: Kinetic Expressions and Model Parameters Describing Iron Oxidation and Monochloramine Reduction (Vikesland and Valentine 2002)...... 66 Table 3.1: Utility Treatment, Disinfection and Catchment Characteristics ...... 76 Table 3.2: Mainscleaning Summary ...... 77 Table 3.3: Discoloured Water Complaint Rates Per ‘000 Properties ...... 78 Table 3.4: Range of Averages (1997 – 2001) for Water Quality in the Distribution Systems ...... 81

9 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

1 SIGNIFICANCE OF DISCOLOURED WATER RESEARCH

1.1 Introduction

The occurrence of discoloured water at customers’ taps or the discolouration of washing is a major source of customer dissatisfaction. Prevention of this occurrence is one of the highest priorities within the water industry and considerable effort is put into monitoring programs, assessing and reviewing operations, and cleaning of the distribution systems when customer complaints occur. A study by the UK Drinking Water Inspectorate (UKDWP) found discoloured water to be the largest source of customer dissatisfaction in 2001, responsible for 38% of all complaints (UK Drinking Water Inspectorate 2001). In Australia, from 1997 to 2002, discoloured water complaints ranged from 1.7 to 14.8 per 1000 properties/connections across eight water utilities/corporations (see Chapter 3 of this report for more information). There is a wide variety of contaminants or processes that cause the appearance of drinking water to be unacceptable to customers. The US Environmental Protection Agency (USEPA) considers turbidity, acid water, red iron water, yellow water, milky water and very high chloride content to be contaminants or impurities that are visually distinguishable. Table 1.1 lists the symptoms, and underlying causes of common types of discoloured water. This table is not necessarily exhaustive as many customers also experience black water, which can be due to iron or manganese precipitates. Also, some of these impurities are given different names, such as brown water for soil/clay particles. This table is a useful summary, however. Table 1.1: Symptoms and cause of common discoloured water events. Modified from U.S. Environmental Protection Agency (2002). Impurity or Symptom Cause Contaminant Turbidity Dirt, sand, clay Suspended matter in surface water Sand grit, silt or clay Well sand from new well or defective well substances screen Rust in water Acid water causing iron “pick up” Grey string-like fibre Organic matter in raw water algae, etc. Acid water Green stains on sink and silver Water which has high carbon dioxide content porcelain bathroom fixtures. (pH below 6.8) reacting with brass and copper Blue-green cast to water pipes and fittings Discoloured Brown-red stains on sinks and 1. Dissolved iron in influent (more than 0.3 water: Red “iron” other porcelain fixtures. Water ppm Fe) water appears clean when first water turns brown-red in cooking or drawn at cold water faucet. Above 0.3 ppm Fe upon heating. Clothing causes staining. becomes discoloured. 2. Precipitate iron (water will not clear when drawn) Yellow water Yellowish cast to water after Tannins (humic acids) in water from peaty soil softening and/or filtering and decaying vegetation Milky water Cloudiness of water when 1. Some precipitant sludge created during drawn heating of water 2. High degree of air in water from poorly functioning pump or mainbreaks /bursts 3. Excessive coagulant-feed being carried through filter Very high Blackening and pitting of 1. Excessive salt content chloride content stainless steel sinks and 2. High temperature drying creates chloride in water commercial dishwashers concentration accelerating corrosion

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The most common cause of water discolouration is from a sudden increase in particles or due to a gradual build-up of iron and manganese in the distribution system (Slaats 2001). The degree to which the different forms of discoloured water occur varies, depending on the source water, the treatment used and conditions within the distribution pipes. Overall, there are three sources of material that can eventually lead to discoloured water/washing. In the case of discoloured washing, a fourth source may be a particular type of washing powder used. 1. Material present within the raw water, which is not removed by treatment and therefore passes into the distribution system. Raw water is a complex mixture of natural organic matter, soluble ions, colloids and particulates comprising numerous elements, which each have components that can contribute to discoloured water events if they are not removed during treatment. Particles can directly lead to discoloured water and colloids often coagulate into particles. Soluble species, particularly high levels of organics can sometimes impart colour in water. Natural organic matter can cause heterotrophic biofilm growth within distribution systems, which often slough off creating discoloured water. Soluble inorganic ions, such as iron and manganese, can become oxidised and form particulates or abiotic films, and also interact with biofilms. 2. Material that is added to the water as part of a treatment procedure, with residual amounts passing into the distribution system. Forms of iron, aluminium, and silicon are used in various treatment procedures, which may contain these or other elements, such as manganese, as impurities. 3. Material that originates from distribution mains or household pipes. This includes corrosion products from metal pipes or solutes from cement-lined pipes. Corrosion of unlined iron pipes leads to iron particles, and household copper pipes can also corrode. Breakdown of cement- lined pipes leads to calcium carbonate particles and solutes entering the distribution system. Material from these sources may produce characteristic particles or they may combine together in some way to generate discoloured water. All solutes and particles that enter the distribution system are likely to eventually come out. Ideally this will occur as part of a cleaning operation or will occur very gradually at low levels that are not noticeable by customers. It is on occasions when particles, films or solutes are presented rapidly at customers’ taps that discoloured water events occur, leading to a possible complaint. Table 1.2: Size fractionation of substances within water. Modified from Kiely (1997). Description Size (mm) Appearance Particulate >10-1 Dust Suspended 10-3 to 10-1 Turbidity Colloidal 10-6 to 10-3 Clay Minerals Dissolved <10-6 Humic/tannic acid, colour

Table 1.2 describes the appearance of material of various sizes within drinking water. However, it is important to remember that description of particles of certain sizes can vary enormously in different fields (for instance in aquatic chemistry particles are >0.45x10-3 mm and some colloids can be <10-8 mm, see section 2.1.1). Guidelines have been established for discoloured water, highlighting acceptable levels of important measurements and element concentrations. Table 1.3 compares the drinking water guidelines established by the World Health Organisation, USEPA, UKDWI, and Australia and New Zealand (NHRMC). The guideline levels for iron, manganese and aluminium for aesthetics is lower than the concentrations at which they are considered a human health risk (National Health and Medical Research Council and Agriculture and Resource Management Council of Australia and New Zealand 1996), although this may be changing for aluminium. These guideline levels have been found to reduce incidences of discoloured water complaints to reasonable levels. However, discoloured water complaints will still arise when the guidelines are being met, as all solutes and particles entering the distribution systems will eventually come out. Clearly, the lower the concentration of these parameters in the treated water, the fewer customer complaints are likely to occur.

11 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

Table 1.3: National and International Drinking Water Quality Guidelines for parameters relevant to discoloured water (World Health Organization 1993-1998; National Health and Medical Research Council and Agriculture and Resource Management Council of Australia and New Zealand 1996; UK Drinking Water Inspectorate 2001; U. S. Environmental Protection Agency 2002). WHO US EPA UK DWI (1998 Australia NHMRC European Directive) ARMCANZ

Acceptability Secondary Indicator Parameters Aesthetic aspects Maximum Contaminant Levels Colour 15 TCU (True 15 colour units Acceptable to 15 HU (Hazen Units) Colour Units) consumer and no abnormal change Turbidity 5 NTU Acceptable to 5 NTU consumer and no abnormal change Aluminium 0.2 mg/L 0.05-0.2 mg/L 200 μg/L 0.2 mg/L (acid soluble) Iron 0.3 mg/L 0.3 mg/L 200 μg/L 0.3 mg/L

Manganese 0.1 mg/L 0.05 mg/L 50 μg/L 0.1 mg/L

PH 6.5-9.5 (<8 for 6.5-8.5 6.5-8.5 disinfection with chlorine) Total 600 mg/L 500 mg/L 500 mg/L Dissolved Solids

The conditions that lead to the production of discoloured water are difficult to quantify due to the various mechanisms and reactions involved. The mechanisms that occur depend upon the raw water quality, the treatment procedures applied, and numerous aspects relating to the distribution system and customer water consumption habits. Different water utilities have discoloured water generated through different mechanisms. Often more than one mechanism will be occurring within each utility. Therefore each system needs to be thoroughly characterised in order to understand the causes of discoloured water events occurring and to implement appropriate operational and management responses in order to limit the occurrences. Most utilities already have a good understanding of the causes of discoloured water, but there may still be some processes that are not fully understood or able to be managed satisfactorily. A number of workshops have been held by the Cooperative Research Centre (CRC) for Water Quality and Treatment over the last few years to assess such knowledge gaps. These workshops identified the following areas where increased knowledge was required. • Understanding particle generation, characterisation, transport, and impacts within the total system, which led to the development of the Particles Project (2.5.0.1). • Improved understanding of interaction between Mn, Fe and Al and biofilms on surfaces within the distribution system in relation to customer complaints (with respect to both discoloured water and discoloured washing). • Understanding the physical and chemical nature of Mn, Fe and Al precipitation within the distribution system and how it impacts on customers. The last two points were incorporated into the Discoloured Water Project (2.5.0.2) from which the following objectives were developed.

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1.2 Purpose and Objectives of this Project

1.2.1 Purpose

To develop an improved understanding of how dirty water events occur, to investigate monitoring techniques to allow prediction of when dirty water events are likely to occur, and ultimately to develop knowledge or approaches that reduce the incidences of discoloured water and thus the number of customer complaints. 1.2.2 Broad Objectives and Report Outline

1. To determine the role of iron, manganese, aluminium and other elements in processes leading to dirty water and/or dirty washing events. 2. To investigate whether variability of pH, oxidation-related processes, such as rechlorination in distribution systems, and levels of natural organic matter contribute to the formation of dirty water. 3. To evaluate the influence of different operational and maintenance processes, from treatment to customers’ taps, on the occurrence of dirty water events. 4. To develop methods that enable evaluation of the potential for dirty water formation under various conditions (e.g. washing water) that can be deployed as part of a field-monitoring network or for laboratory testing. Further workshops with representatives of participating water utilities/corporations and the CRC determined that this project should initially undertake a comprehensive literature review into the processes that influence discoloured water events, focussing particularly on processes occurring within the distribution system and identifying important gaps in knowledge. This literature review is in Chapter 2. Chapter 3 contains a review and assessment of water industry data between 1997 to 2002, for eight participating water utilities/corporations [Sydney Water Corporation, Hunter Water Corporation, Brisbane City Council, Power and Water Authority (Northern Territory), Water Corporation (Western Australia), Yarra Valley Water Ltd, South East Water Limited (Melbourne) and Gold Coast Water]. Finally, as part of the process into understanding gaps in knowledge, each utility provided five questions that they needed to answer. These questions are discussed in Chapter 4 with respect to information and knowledge gaps identified as part of Chapters 2 and 3. Chapter 5 sums up the findings and looks ahead to the other activities being undertaken as part of this project.

13 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

2 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION

The focus of this literature review is processes within the distribution system that lead to formation of discoloured water, as determined by the outcome of the CRC for Water Quality and Treatment workshops described in Chapter 1. However, in order to determine how these processes arise, it is important to consider the water quality and treatments upstream of the distribution system. These pre- distribution conditions and operations have a major influence on the water quality in the distribution system. Similarly, processes within the distribution system can influence the formation of discoloured water within household pipes or the discolouration of washing. Therefore, the review begins with three main sections. 1. Pre-distribution conditions and operations (Section 2.1). 2. Processes and operations within the distribution system (Section 2.2). 3. Post-distribution processes (Section 2.3). Within this structure there are several key topics that have been reviewed. (i) The role of Fe, Mn and other important elements on processes leading to discoloured water events, with a focus on particles that form within the distribution system. This has three main aspects:

• Corrosion of pipe material that leads to particle formation. • Physico-chemical processes and reactions that influence precipitation or dissolution of elemental forms and release of particles in the distribution systems. This topic includes oxidation and precipitation processes, influence of natural organic matter and disinfection by-products on the formation of particles, formation of abiotic films on distribution pipes and pipe corrosion processes. • Interaction of elements with microbiological processes that influence precipitation of elements and release of particles in the distribution system. This topic includes interaction with micro-organisms (biofilms or otherwise) that influence the form of elements present and which leads to adhesion or deposition onto biofilms, the elemental composition of biofilms, and processes that lead to sloughing off of biofilms. (ii) The impact of operational procedures within the distribution system on discoloured water events, including various cleaning approaches, as well as the effect of lined and unlined pipes. This review chapter then deals with two more issues. 4. Identification of methods for detecting/predicting discoloured water events, including experimental and modelling research (Section 2.4).

5. Identification of gaps in knowledge within the research literature relating to discoloured water formation, particularly within the distribution system (Section 2.5).

2.1 Pre-Distribution Processes that Influence Discoloured Water Formation

This review of pre-distribution processes and operations focuses on factors that influence the composition of water in the distribution system. The two main topics are the chemistry of important elements in raw water (section 2.1.1) and the role of various treatment operations (section 2.1.2). There has been much more research conducted in these areas, than into processes within the distribution system. Where research is of major relevance to the latter (such as rates of oxidation), it will be touched on here, but will be described in more detail as part of the synthesis on processes within the distribution system (section 2.2).

2.1.1 Chemistry and concentration of elements in raw water

The concentration of elements in freshwaters is ultimately dependent upon the geology and climate of the catchment. Dissolved minerals in source waters can, therefore, vary greatly between water bodies.

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Of most relevance to this review are iron and manganese, which are redox-active metals that play a very important role in the cycling and transport of elements in raw waters, as has been described in several reviews (Khoe and Waite 1989; Waite et al. 1989; Chiswell et al. 1992; Zaw and Chriswell 1995), and in discoloured water formation. The chemistry of other elements that are also relevant to discoloured water formation, such as aluminium, silicon, calcium and copper are described here briefly, although the raw water is often not the most important source of these elements with respect to discoloured water formation. A section is also devoted to interactions of these elements with organic matter, which is a very important process in the formation of discoloured water. Understanding the oxidation-reduction behaviour of iron and manganese in natural waters is important for several reasons of significance to discoloured water events. Firstly, the thermodynamically stable ions of iron and manganese in oxygenated waters are generally insoluble meaning that they are present as solid forms, which also have surfaces readily able to adsorb other elemental species. Particulate forms of iron and manganese are often responsible for discoloured water complaints. On the other hand, the reduced ions are soluble and, therefore, also very mobile, which means they are readily taken up with drinking water. Secondly, the effectiveness of various treatments used to remove the different elemental species determines both the concentrations and speciation of manganese, iron and other elements entering the distribution system. This aspect will be discussed further in section 2.1.2. Finally, the behaviour of metal ions within natural water systems has been widely studied and can be used to help predict behaviour within the distribution system. 2.1.1.1 Iron Concentrations of iron in fresh water lakes range from low µg L-1 to mg L-1 levels. Concentrations reported for raw water storages are listed in Table 2.1. Iron can be present in various dissolved, colloidal and particulate forms, as well as in two main oxidation states, Fe(II) and Fe(III). The Fe(III) forms are stable in oxygenated waters and are generally quite insoluble, forming colloids and particles. Conversely, Fe(II) forms are usually soluble but are thermodynamically unstable in the presence of oxygen. Some interactions with natural organic matter provide exceptions to these general observations, which will be discussed in more detail below. Table 2.1: Comparison of the concentrations of Iron, Manganese and turbidity from selected raw water storages, treated waters and a distribution system. Location Iron Manganese Turbidity Reference Raw Water Australia Sydney Nepean 0.06-3.44 0.003-2.75 System Yarra Valley <0.05-1.2 <0.01-0.08

USA New River 0.02-0.07 mg/L <0.005-0.007 1.0-2.6 ntu (Knocke et al. 1987) mg/L Chickahominy 0.3-0.6 mg/L 0.02-0.06 mg/L 3.0-17 ntu (Knocke et al. 1987) River Harwood’s Mill 0.08-0.25 mg/L 0.02-0.08 mg/L (Knocke et al. 1987) Reservoir Delaware River 0.050-0.170 mg/L 9.0-17.6 ntu (Wilczak et al. 1993)

Europe Strathclyde 0.26-0.45 mg/L 1.9-2.5 NTU (Bache and Hossain Region, Scotland 1991) Nancy, France 0.36±0.14 mg/L 0.01±0.01 13.95±9.23 NTU (Clark et al. 1994)

Treated Water Australia Hunter 0-1.59 0-0.27 Perth 0.004-1.6 0.002-0.22 Sydney Nepean 0.007-0.54 0.001-0.215 System Darwin 0.02-1.08 0-0.1

15 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

Denmark 0.04 mg/L <0.005 mg/L 0.28 FTU (Boe-Hansen et al. 2002)

Within the Distribution System Fredericton N.B. 0.02-0.28 mg/L 0.01-0.38 mg/L (Viraraghaven et al. 1987)

When discussing iron speciation (and that of any element), it is important to understand the difference between a theoretical understanding of the species present and our ability to measure these various species. Most measurement approaches used do not allow a comprehensive analysis of all of the forms of iron present. Usually convenient analytical operations are undertaken, which separate a group of forms with similar properties relating to the operation. The most common operation uses a filter membrane (often 0.45 µm pore size, chosen because it will trap micro-organisms) to collect solid phase material, which is measured and interpreted as the “particulate” fraction. The fraction that passes through a 0.45 µm membrane used to be called the soluble fraction, but it is now recognised that many colloidal solids, which are often chemically indistinguishable from the larger “particulate” solids, also pass through a 0.45 µm pore-size membrane (Stumm and Morgan 1996). Colloids have a mean diameter in the range 0.5 –0.05 µm, but can be a few nm in diameter, and therefore can remain in suspension for long periods. Colloids can be isolated and then measured for iron and other elements using ultra-filtration (Olivie-Lauquet et al. 1999; Pokrovsky and Schott 2002; Benedetti et al. 2003). This measurement is time-consuming and technically difficult, so it is not used routinely. Some measurements can also be used to selectively measure Fe(II) forms in solution (colourimetric, voltametric) but, again, these are not used commonly. There are also mineralogical methods that allow identification of specific mineral types but these measurements are very expensive and rarely undertaken (Knipe et al. 1995; Costa et al.). Particulate forms of iron include minerals washed into the raw water storage by weathering and erosion, such as hematite [Fe(III)2O3] and clays (aluminosilicates forming in sheet-like layers, with amounts of Fe2+, Fe3+, Mg2+, or K+) that have a high, unreactive iron content (Davison 1993, Krauskopf and Bird 1995). These forms settle out of the water column in lakes quite rapidly (Davison 1993) and, therefore, are usually only taken up for use in drinking water at low concentrations. The Particles Project in the CRC for Water Quality and Treatment covers the role of these particles in discoloured water events. 2+ Phosphate is known to form insoluble Fe3(PO4)2 when reacting with Fe and insoluble FePO4 when reacting with Fe3+ (Nealson and Saffarini 1994). Phosphate adsorption to iron hydroxide colloids also affects iron hydroxide colloid formation as increased P/Fe ratio leads to larger agglomerates (He et al. 1996). Iron (III) oxyhydroxides, which have low solubilities (<5 x 1010 mol l-1 for Fe(III)), form due to oxidation of Fe(II) within freshwater lakes and storages. These solids range from finely dispersed amorphous forms [Fe(III)O3.nH2O], such as ferrihydrite (n = 0.5), to more crystalline, aged forms like goethite [HFe(III)O2], lepidocrosite [Fe(III)OOH] and hematite [Fe(III)2O3] (Krauskopf and Bird 1995). While these iron oxyhydroxides often coat clay and silt particles, they also form solids ranging in size from particulate (>0.45 µm) to colloidal (<0.45 µm), with the latter remaining in suspension for long periods (Davison 1993). Because of this slow settling, amorphous iron (III) oxyhydroxides are usually the most common form of iron in freshwater lakes/raw water storages and the most likely form taken off for drinking water treatment. However, there are likely to be exceptions. A study of Esthwaite Water in Cumbria, UK, found that iron was almost exclusively present as amorphous iron oxyhydroxide colloids (<0.5 µm), containing small amounts of Ca, Si, P and S, and organic matter (Tipping et al. 1982), supporting the statement outlined above. The adsorbed organic matter provides the negative surface charge required to keep the material as colloids (Davison 1993). However, a study in Hunchun Basin, China, found that iron released from weathering products was largely present as organic complexes (Moon et al. 2001). Transformation of amorphous iron such as Fe(OH)3 and Fe3(OH)8 to more stable phases (in water) such as goethite and hematite, as well as the transformation of ferrihydrite into Fe oxides was thought to be inhibited by the acidity of the waters (Moon et al. 2001). Another study, by (Waite et al. 1989), on the Avon and Woronora raw water storages in southern Sydney found that a large fraction of iron in the water was present in particulate forms (>0.45 µm). In this study, size fractionation (using 0.45, 0.10, 0.05 and 0.01 µg membrane filters) was coupled with determination of the oxidation state of the ‘dissolved’ component, which was assumed to be whatever passed through

16 CRC FOR WATER QUALITY AND TREATMENTRESEARCH REPORT 51

the 0.01 µg pore-size membrane. Colloidal iron was considered to be the fraction retained on the 0.10 µg filter after passing through the 0.45 µm filter. At the Avon and Woronora Dams, total iron concentrations were 140 µg L-1 and 400 µg L-1, respectively. For Woronora water, 37-60% of iron passed through the 0.45 µg filter, while the Avon water only had 6-10% of iron passing through 0.45 µg. Only the Woronora dam had a measurable amount of ‘dissolved’ iron with 3-4% passing through the 0.01 µg filter membrane. In this fraction, the Fe(II) concentration was found to be 6-13 µg L-1 (1.2 –3.3%) and another 15 µg L-1 (3 –3.75 %) was found to be exchangeable Fe(III) (Waite et al. 1989). This soluble fraction of iron, although present in small concentrations, has a strong influence on the formation of discoloured water events, as it is difficult to remove during treatment (see sections 2.1.2 and 2.2). The presence of Fe(III)-NOM complexes is expected, as most heavy metal ions are readily complexed by natural organic matter. Some NOM complexes catalyse the oxidation of Fe(II) by dissolved oxygen. Some ligands also behave as oxidising agents and are reduced while oxidising the Fe(II) to which they are bound (Davison 1993). Interactions of inorganic species with natural organic matter are described in more detail in section 2.1.1.7. Transmission Electron Microscope (TEM) analysis of iron hydroxide colloid showed that the colloid is a highly porous sponge-like precipitate with a branched chain structure that extends in three dimensions (He et al. 1996). Fresh iron hydroxide has a great adsorptive capacity that can be attributed to both the small primary particle size (1-4 nm) and this branched chain structure (He et al. 1996). The presence of soluble Fe(II) in oxygenated waters requires the occurrence of reductive processes, of which there are several, as described in Davison (1993). The main mechanism is photochemical reduction of Fe(III), which can occur with solution or solid Fe(III) species, called respectively, homogenous and heterogenous photoreduction (Davison 1993). Photoreduction has been found to occur more rapidly with Fe(III)-NOM complexes. At neutral pH, even some humic material can cause the reduction of Fe(III) to Fe(II) (Davison 1993). Hydroxyl and carboxyl groups can form surface complexes with solids and facilitate electron transfer to produce Fe(II). Furthermore, some heterotrophic bacteria use Fe(III) as an electron acceptor which also produces Fe(II) (Arnold et al. 1986, Lovley and Phillips 1988). Reduction rates by phytoplankton assemblages in oxygenated, high pH, surface waters ranged from 0.1 to 10 nM/h (Shaked et al. 2002). Shaked et al. (2002) also found that when reduction by natural phytoplankton in lake waters is taken into account, the rate of Fe(II) oxidation is often much slower than published values based on abiotic oxidation. Therefore, calculated oxidation rates for Fe(II) in lake waters may be overestimated. These processes are discussed in more detail in the references indicated but, for our purposes, it is important to recognise that, even in oxygenated fresh waters, a small soluble iron fraction is present and some of this will include Fe(II)-NOM complexes. The main reactions (non- balanced) involving the reduction and oxidation of iron are given below (modified from Davison 1993). Fe(II) oxidation 2+ 3+ 4Fe (aq) + O2(aq) → 4Fe (aq)

Fe(II)L oxidation

4Fe(II)L + O2(aq) → 4Fe(III)L(aq)

Oxidation of Fe(II) by ligand

Fe(II)Lox(aq) → Fe(III)Lred(aq)

Homogenous photoreduction of Fe(III) 2+ 2+ Fe(III)OH (aq) + hv → Fe (aq) Heterogenous photoreduction of Fe(III) 2+ Fe(III)OOH(s) + hv → Fe (aq) Ligand-catalysed photoreduction of Fe(III) 2+ Fe(III)OOH(aq) + L → Fe(III)L + hv → Fe + L Ligand-catalysed reduction 2+ Fe(III)OOH(aq) + Lred → Fe(III)Lred → Fe(II)Lox + L → Fe + Lox Of course in raw water storages that become seasonally anoxic, the Fe(II) concentrations can increase dramatically. Fe(II) concentrations as high as 0.4 mg L-1 have been observed in surface waters of Lake Vesdre (pH 4.1 –4.5) while it was stably stratified (Davison 1993). If sulphide is also produced, up to 20% of the Fe(II) can be Fe(II)S, which is very insoluble. It is due to this increase in Fe(II) that raw water storages that are prone to turning anoxic after stratification are often treated by

17 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

mixing to produce overturn and reoxygenation of bottom waters. This will be discussed more as part of the reservoir manipulation section (2.1.2.1). 2.1.1.2 Manganese Total concentrations of manganese in freshwaters (see Table 2.1) are about 5-10 times less than those of iron (Nealson and Saffarini 1994). Like iron, the oxidation state of manganese in natural waters can vary. The oxidation of Mn(II) to Mn(III, IV) is thermodynamically favoured under oxygenated conditions and at neutral or basic pH. However, the activation energy required to oxidise Mn(II) is high and thus the reaction is slow (Gounot 1994). Therefore, the oxidation of Mn(II) to Mn(III, IV) oxides is usually much slower than the oxidation of Fe(II) to Fe(III) (Stumm and Morgan 1996). Subsequently, many dams have significantly high reduced soluble manganese concentrations that can be taken up into the treatment plant. Manganese can also be present in particulate, colloidal or dissolved forms, and there are similar limitations on measurement of these as there is for iron. However, the Mn(III, IV) oxide species are about 106 – 107 times more soluble (and thus more mobile than) the corresponding Fe(III) species (Chiswell et al. 1992). These characteristics mean that soluble concentrations of manganese are often higher than those for iron in raw water storages. Furthermore, the predominant soluble species in raw water supplies is often Mn2+, as was shown in North Pine Dam near Brisbane, Australia, using electron paramagnetic resonance spectroscopy (EPR) and selective pore size membrane techniques (Chiswell et al. 1992). Within Avon and Woronora dams, Waite (1989) found that total manganese concentrations were lower than iron, yet a greater proportion of the total was present in the reduced dissolved form (65% for Avon’s reservoir and around 15% for Woronora’s reservoir). Inputs of manganese into lakes and raw water storages can fluctuate through a variety of mechanisms (Salomons and Forstner 1984). Two main inputs are the erosion of weathered particles and the influx of soluble Mn(II) from oxygen-deficient soils (Davison 1993). Rainfall events can cause increased run off that may shift the dominant species within the water. The proportion of manganese in particulate form can vary between 0 and 100% (Laxen et al. 1984). Examination of the flux of manganese within a mountain stream environment found that manganese concentrations can vary considerably over a 24 hour period (Scott et al. 2002). Mn(II) is present in many rock-forming minerals where it can replace Fe(II) in the crystal lattice. These minerals settle very quickly and are therefore only a minor contribution to the water manganese. The dominant form of oxidised manganese is authigenic MnO2 (birnesite or vernidite), which is the thermodynamically stable form that is produced in oxygenated waters. However, due to the kinetic limitations, many metastable oxidised forms occur in natural waters (e.g. Mn(III)OOH and Mn(III)2Mn(II)O4) (Davison 1993). MnOOH (manganite) is unstable undergoing disproportionation (i.e. 2+ self-reaction) to produce Mn and MnO2(s) (Davison 1993). Mn3O4 (hausmanite) is the only stable form of Mn(III) but the Mn(II) is prone to substitution by other divalent ions (Hastings and Emerson 1986). MnO2 can form an amorphous colloidal phase (Gounot 1994; Moon et al. 2001), as well as particulates and coatings on organic material or even organisms (Davison 1993). Vernidite has a high Ca content as well as some Mg, Si, P, S, Cl, K, Ba and Fe. Low levels of humic matter are incorporated, but planktonic cells can contribute 20-30% of the mass. (De Vitre and Davison 1993) have provided a thorough account of manganese particles in freshwater. Particulate MnO2 and MnOOH also settle quickly in lakes, but the manganese can be recycled rapidly from the sediment (see below). The speciation and oxidation state of manganese in water can be misinterpreted, as Mn(II) can bind to particulate matter including manganese oxides (Gounot 1994). This binding will also affect the oxidative behaviour of Mn(II) and catalyse the rate of oxidation. Oxidation and precipitation of Mn(II) to MnO2 in natural waters, by exposure to air, occurs within a time scale of days, which is much more rapid than was observed in synthetic waters at the same pH (6-8) (Tipping et al. 1984). Filtration slows the reaction, indicating that a particulate catalyst is involved. Also, the oxidation state for oxides in natural waters was in the range of 3.1-3.9, which is greater than that of manganese oxides in synthetic waters (Tipping et al. 1984). There is now overwhelming evidence for bacterial catalysis in the oxidation of Mn(II) (Tipping 1984). Leptothrix discophora excrete proteins that catalyse Mn(II) oxidation (Adams and Ghiorse 1987), and Pseudomonas sp. may also (Kepkay and Nealson 1987). Nealson et al. (1988) have thoroughly reviewed the role of bacteria in the oxidation of manganese. The main factor causing manganese reduction is a decrease in the oxidation-reduction potential, usually as a result of bacterial metabolism consuming the dissolved oxygen (producing anoxic conditions). When manganese oxyhydroxides enter anoxic waters, the manganese is chemically reduced by reaction with inorganic or organic reductants present or reduced directly by micro-

18 CRC FOR WATER QUALITY AND TREATMENTRESEARCH REPORT 51

organisms (Davison 1993). Common reducing agents are Fe2+ and sulphide. Manganese actually serves as an electron carrier between dissolved oxygen in surface waters and sulphide in bottom waters or sediment. Organic compounds containing alcoholic carbonyl, carboxyl and phenolic functional groups are able to reduce manganese oxides (Stone and Morgan 1986). This includes the commonly present, humic and fulvic acids (Davison 1993). Reduction of manganese can also be mediated by nitrate (Gounot 1994). Photochemical processes can cause the reduction of manganese oxides on rock surfaces (Scott et al. 2002). The reduction of manganese oxides by humic and fulvic acids is also enhanced by light (Davison 1993). The rate of oxidation of Mn(II) increases during the day due to photosynthetically elevated dissolved oxygen levels. This oxidation dominates any effect due to photoreduction (Scott et al. 2002). Due to the same reason, Mn(II) concentrations tend to be lower in summer than in winter (Davison 1993). Not only do seasons affect the presence of soluble-reduced manganese, they will also affect the structure of oxidised manganese, as Mn-oxide particles have been found to have a different morphology between summer and winter, suggesting a different process of formation (Tipping et al. 1984). Thermal stratification leading to anoxic bottom waters is a major contributor to increasing the reduced soluble manganese concentration within lakes. Bacterial action on carbohydrates in the sediment produces acid, which then reduces the manganese oxides in the sediment and mobilises them as Mn2+ ions into the water (Chiswell et al. 1992). Other reduction processes can also occur and some bacteria are capable of both oxidising and reducing manganese depending on the oxygen conditions (Chiswell et al. 1992). Concentrations of soluble Mn as high as 50 mgL-1 have been found in sediment pore water taken from a North Pine Dam near Brisbane (Chiswell et al. 1992). The released soluble Mn passes into the hypolimnion and, under certain wind conditions, may proceed to the epilimnion where it may be discovered at treatment plants as large "spikes" from a background level of 10 to 20 µg L-1 up to several 100 µg L-1 (Chiswell et al. 1992) or even 600 µg L-1 (Waite 1991). Fractions of manganese show considerable variability with depth, especially when thermal stratification occurs. Large, sudden shifts in speciation and concentration were linked to rainfall events that increased riverine input and, hence, also increased the overall concentration for a short period after the event. 2.1.1.3 Aluminium Aluminium chemistry is governed by changes in pH rather than oxidation-reduction potential. In raw water, aluminium is relatively insoluble under neutral conditions (pH 6 to 9) unless organically complexed (Molot and Dillon 2003, Baird 1995). The dissolved forms of Al can be either inorganic (e.g. Al3+, Al(OH)2+, AlF2+) or complexed with dissolved organic carbon, the latter often being the dominant form (Schintu et al. 2000). In Italy, the raw water concentrations averaged 960 µg/L with only 3-17% being in dissolved form (Schintu et al. 2000). In Canadian lakes, aluminium levels have also been found to be highest in waters with increased DOC levels (Molot and Dillon 2003). Aluminium increases in solubility at extreme acid and alkaline conditions (Srinivasan et al. 1999). In exceptionally acidic waters (i.e. below pH 4.5), Al3+ can become the principal cation, even exceeding Ca2+ and Mg2+(Baird 1995). The block diagram taken from (Srinivasan et al. 1999), below, shows the different forms of aluminium in natural waters. Apart from waters with extreme pH values that produce very high Al concentrations, the raw water is not the main source of significance to discoloured water events. Aluminium is, therefore, discussed in more detail in the section on coagulation (2.1.2.3).

19 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

Al3+

Figure 2.1: Forms of aluminium in natural waters. Modified from Srinivasan et al. (1999)

2.1.1.4 Silicon Compounds of silicon occur in all natural waters as either suspended solids or in solution (Hofmann et al. 2002). In the natural pH and temperature range, (i.e. pH 6-9 temp 0-30 degrees), all dissolved silicon occurs as silicic acid (SiOH4) (Mizertzky 2004). Silicon is an important component of the ubiquitous silicate minerals such as quartz (SiO2), feldspars and clays and, therefore, is present in many particulate forms. Silicon can also exist as amorphous hydrated silica oxide, in particulate form (Hofmann et al. 2002). Even though silicon is a major component of rocks, the seasonal cycle of dissolved silicon is caused by biological activity and not dissolution from lake surroundings (Mizertzky 2004). Dissolved silicon concentrations can change considerably after uptake by diatoms and sedimentation or adsorption onto particles. The silicon contained in diatoms (also called biogenic silica) is known to dissolve up to five orders of magnitude faster than mineral silicates, even though little work has been done on silica dissolution in lake water (Hofmann et al. 2002). Mineral silicon dissolves slowly enough not to be considered a source of available silica (Hofmann et al. 2002). Biogenic silica dissolution depends on a number of factors including pH, temperature, total dissolved solids, the species of diatom involved and bacterial activity (Mizertzky 2004). While some factors e.g. pH directly affect the reaction, the presence of iron and aluminium oxides and hydroxides indirectly decreases solubility by providing a buffering effect (Gehlen et al. 2002; Mizertzky 2004). Raw water silicon may not be an important source to discoloured water events compared to treatment procedures e.g. sand filtration. 2.1.1.5 Calcium The calcium concentration of natural waters varies greatly depending on whether the underlying soil is calcareous (Baird 1995). Ground waters generally have a much higher calcium ion content than surface waters. Calcium is a major ion responsible for the ‘hardness’ of water, but other cations such as magnesium, strontium, iron, manganese and barium can also contribute (National Health and Medical Research Council and Agriculture and Resource Management Council of Australia and New Zealand 1996). Hardness is the sum of these ions expressed as calcium carbonate equivalent. The degree of hardness according to the Australian Drinking water guidelines is:

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<60 mg/L CaCO3 soft but possibly corrosive

60- 200 mg/L CaCO3 good quality

200-500 mg/L CaCO3 increasing scaling problems

>500 mg/L CaCO3 hard with severe scaling

The calcium content of soft water lakes remains well below saturation levels and seasonal changes are small, while lakes with hard water can undergo distinct changes in calcium concentration seasonally with depth (Wetzel 1983). During the summer months dissolved Ca concentration decreases due to precipitation of CaCO3(s). Decreases can also be attributed to photosynthetic activity. Levels of calcium in the raw water can be adjusted easily by treatment procedures, but dissolution of cement pipe lining can reintroduce calcium into water in the distribution system (see section 2.2.1). 2.1.1.6 Copper Copper is a trace metal, usually only present at levels above the aesthetic drinking water guideline (1mg/L) in badly contaminated waters. Copper is known to bind strongly to natural organic matter, both dissolved and particulate. The main source of copper with respect to discoloured water is within copper pipes in households (see section 2.3.1). 2.1.1.7 Metal complexes with organic matter The influence of natural organic matter on the formation of discoloured water is thought to be important. Natural organic matter (NOM) can both complex with dissolved metals and adsorb to particulate forms. As such, the effects on metal behaviour and transportation are highly variable. NOM can be present in dissolved (DOM) or particulate (POM) forms (Wetzel 1983). The measurement of the dissolved fraction is usually practically defined as matter that is smaller than 0.45 m, so may include small colloidal particles as well as the truly dissolved fraction (Wetzel 1983). Concentrations of NOM reaching the treatment plant are dependent on catchment vegetation, soils and climate. Organic matter in lakes can originate from a number of sources, including biological and chemical degradation of animal, plant and microbial products. These can be divided into humic substances and non-humic substances, with the former generally being the dominant type of organic matter in natural waters. Non-humic substances include carbohydrates, proteins, amino acids, fats and other low-molecular-weight organic substances, and tend to be readily assimilated by micro- organisms (Wetzel 1983). Humic substances are more slowly biologically degraded and consist of acidic compounds (e.g. humic and fulvic acids) of high molecular mass (Wetzel 1983). A variety of techniques have been used to investigate interactions between NOM and metals. In Britain, it was found that upland water sources from peaty moorland areas are rich in humic substances, resulting in moderate organic matter concentrations, whereas ground waters and most surface waters will have low levels (Gray 1994). Lowland surface waters contain high levels of dissolved NOM that will be significantly reduced in the mains (Gray 1994). An important factor in dissolved organic carbon (DOC) concentrations in natural water is the ability of the soil in the catchment area to retain the DOC. Comparisons between two streams in the Mt Lofty Ranges in South Australia found that the higher the clay content of the soil, the greater the retention of DOC (Nelson et al. 1990) leading to lower DOC in the water body. Tadanier (1999) investigated the distribution and recovery of DOM, Al, Fe, Mn from water when separated using a method called the Dissolved Material Matrix (DMM) Fractional Protocol. The DMM Fractional Protocol uses sequential hydrophobic and ion exchange resins to separate and concentrate DOM into the following forms: hydrophobic acid (HPO-A), base (HPO-B), and neutral (HPO-N); and hydrophilic acid (HPI-A), base (HPI-B), and neutral (HPI-N). Results showed that the HPO-A fraction was the largest portion of DOC (72% for a sample taken from a lake and 66% for a sample taken from a river), with the HPI-N fraction being 11% and 14%, respectively. The remaining DMM fractions contributed less than 10% each. Ninety-six percent of the aluminium recovered in the raw water samples was found collectively in the HPO-A, HPO-B, and HPI-B fractions. Recovered iron was also found in the HPO-A fraction accounting for 88% (lake) and 81% (river), with HPO-B the only other fraction with a significant iron content (>5%). The manganese fractionation was notably different, with a significant portion (37%) in the Lake Drummond untreated water being found in the HPI-N fraction. The basic fractions collectively

21 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

accounted for 45% and 60% of the manganese recovered. The authors suggest that results of studies using fractionated DOM should be critically evaluated concerning the potential loss or redistribution of metals by this method (Tadanier et al. 1999).

For manganese and iron, the distribution coefficient, Kd, between particulate phase and the filterable phase, in the relatively organic-rich Vienne River (France) were significantly higher during summer than in winter, meaning that, during summer more of the metals were found in the solid phase (Garnier et al. 1997). Removal of Fe and Mn from solution appeared to be controlled by binding to particulate organic matter or biogenic material (Garnier et al. 1997). Lofts and Tipping (1998) used a model named SCAMP (Surface Chemistry Assemblage Model for Particles) to describe the equilibrium adsorption of metals and protons by natural particulate matter. For a riverine sample, organic matter was the major determinant of surface (proton) charge (Lofts and Tipping 1998).

2.1.1.7.1 Non-humic substances The majority of non-humic substances in natural waters (especially carbohydrates and their derivatives) are able to form complexes with metal ions (Nagy and Szorcsik 2002). Fe(III)-carbohydrate complexes precipitated from alkaline solutions are brown amorphous solids (Nagy and Szorcsik 2002). Interaction of Fe(III) with the O atom of carbohydrates may be either pH-dependent or pH-independent (Nagy and Szorcsik 2002). pH dependent processes include the deprotonation of the -COO- groups of sugar acids or sometimes the alcoholic -OH groups of polyalcohols or sugars that occur when conditions are slightly acidic (Nagy and Szorcsik 2002). Alternatively, Fe (III) can also be co-ordinated by the –OH or aldehyde groups of ligands in a pH-independent step (Nagy and Szorcsik 2002). While attempting to simulate the metal interaction with non-humic substances in natural waters, (Nagy and Szorcsik 2002) prepared several brown-coloured solids made of manganese–carbohydrate complexes in different oxidation states. Fourier Transform Infra-Red (FTIR) analysis of these complexes shows that ligands were co-ordinated to the central metal ion through N and O (Nagy and Szorcsik 2002).

2.1.1.7.2 Humic substances There are a number of interactions with humic substances that may influence the transport and/or treatment of metals. Soluble iron and manganese can form complexes with humic substances, and particulate oxides can provide a surface on which NOM can adsorb. The presence of humic substances may also influence the photo-oxidation of manganese. Knocke et al. (1985) found that a significant portion of iron in raw waters was complexed with large molecular organics (>10000 molecular weight range) i.e. humics. Conversely, manganese was more greatly associated with the 5000-500 molecular weight range indicating that it was more likely to be complexed with fulvic acids than humics (Knocke et al. 1985). Complexation studies indicate that Fe(II) is efficiently complexed by humic acid at pH conditions above 5 – 5.5, and treatment oxidants (e.g. KMnO4 and ClO2) could not easily oxidise the complexed form (Knocke et al. 1991). Dissolved Mn(II) is less readily complexed by both humic and fulvic acids than Fe(II), and the rate of oxidation by treatment chemicals is not significantly slowed by the presence of these organic substances (Knocke et al. 1991). Humic and fulvic acids have been shown to adsorb to iron oxide surfaces (Gu et al. 1994). When pH is acidic or slightly acidic, the dominant interaction in this process is the ligand exchange between carboxyl/hydroxyl functional groups (Gu et al. 1994). Under certain conditions desorption of NOM from iron oxide can be very difficult (Gu et al. 1994). Adsorption of humic acid onto an iron oxide surface is high when pH is low and ionic strength is high (Kim and Walker 2001). This adsorption will decrease as pH increases (Kim and Walker 2001).

Adsorption of silica onto preformed Fe(OH)3 was found to interfere with adsorption of fulvic acid (Davis et al. 2001). Increasing both pH and initial silica concentration reduces the adsorption of organics as measured by TOC and UV254 absorbance (Davis et al. 2001). Both pH and silica concentration also affected the proportion of Fe(OH)3 that became soluble or occurred in very small colloidal form (Davis et al. 2001). The concentration of mobilised Fe was only above 0.2 mg/L when the zeta potential was ≤ -15 mV (Davis et al. 2001).

Interactions between humic substances and hydrous iron oxides (α-FeOOH, α-Fe2O3 and amorphous Fe(OH)1-4 gel) will differ based on the nature of the water chemistry (Tipping 1981). In a solution with + - - Na -Cl , -HCO3 at an ionic strength of 0.002 M, adsorption of humics decreases with increasing pH 2+ 2+ 2- (Tipping 1981). In a second medium that contained Mg , Ca and SO4 at concentrations

22 CRC FOR WATER QUALITY AND TREATMENTRESEARCH REPORT 51

comparable to natural Esthwaite Water (where the humic substances were taken from), also with an ionic strength of 0.002 M, the adsorption of humics onto goethite is twice as great as the previous solution at pH 7 (Tipping 1981). Some types of NOM can influence the dissolution of the solid MnOOH to Mn(III) by stabilising the Mn(II) ion. Formation of aqueous Mn(III) and Mn(II), through reactions between MnOOH and ligands, was studied by Klewicki and Morgan (1999). In this study, citrate created a 50-times faster rate of dissolution than natural decomposition. It is possible that in natural waters a variety of ligands may kinetically stabilise aqueous Mn(III) (Klewicki and Morgan 1999). Organic reductants, such as organic acids, phenolic compounds and quinones will reduce both Mn and Fe oxides. Conversely, when in the presence of humic substances, abiotic photo-oxidation of Mn(II) can produce significant concentrations of MnOx (Nico et al. 2002). Nico et al. (2002), suggest that humic-produced reactive - oxygen species are responsible for the oxidation reaction, primarily O2 . Aluminium oxides and the edge sites of aluminosilicates can also form complexes with weak acidic functional groups of NOM (Davis 1982). At pH greater than 6.5 the adsorption of organic matter led to small amounts of alumina dissolution through the formation of soluble Al(III)-organic complexes (Davis 1982). The enthalpy of the interaction between humic substances and Al3+ was measured in aqueous solutions of various ionic strengths by Bryan et al. (1998). Reactions were found to be predominantly endothermic which was not expected as many simple functional groups within humic substances are known to complex with metal ions in an exothermic reaction (Bryan et al. 1998). Ion binding by humics is considered to be driven predominantly by the entropy associated with the discharge of the double layer of humic molecules (Bryan et al. 1998). 2.1.2 Effect of various treatment processes

The results from studies into water treatment procedures also provide useful information on likely processes occurring within distribution systems. Most of the literature on drinking water quality and processes is strongly focussed on the effects of treatment and optimising treatment to minimise undesirable water qualities. As raw water quality and composition can differ greatly, optimum treatment conditions can also vary greatly. The most common treatment goal for discoloured water minimisation is to reduce the total concentration of iron and manganese entering the distribution system. Treatment processes of reservoir manipulation, oxidation, coagulation and filtration can all be optimised for the removal of iron and manganese in drinking water. However, some of the chemicals used in these processes may actually increase the residual concentration or soluble fraction of iron, manganese and aluminium. Waters with high organic content can produce large amounts of disinfection by-products. Optimising treatment for the minimisation of disinfection by-products can potentially reduce the removal efficiency of iron and manganese. The removal of NOM is also important for discoloured water minimisation due to its role in microbial growth and biofilm formation within the distribution system. This section looks at the role of different treatment methods in reducing discoloured water formation, primarily through the effect on residual iron and manganese. The most common chemicals and processes used will be discussed in regard to their effectiveness and limitations. 2.1.2.1 Reservoir manipulation As discussed in section 2.1.1, thermal stratification of productive water storages can lead to increased dissolved concentrations of a number of metals, including manganese and iron. This is due to the heterotrophic consumption of dissolved oxygen in bottom waters and the onset of reducing conditions. Mn2+ and Fe2+ diffuse from the sediment into the bottom anoxic water and can build up to high concentrations. In the past, multi-level inlet towers in dams helped to target the oxygenated layers (with inherently lower dissolved Mn and Fe concentrations). As there are problems with this approach (Khoe and Waite 1989), methods of artificially preventing the stratification or anoxification of reservoirs have been widely used to reduce the concentration of these metals entering the treatment plant or distribution system (Waite et al. 1993). Since the introduction of this technique into Australia in the 1960s, a number of utilities have employed aeration/destratification with varying degrees of success (Waite et al. 1991). Increasing the dissolved oxygen concentration in the water accelerates the oxidation of many metals to form insoluble metal oxides, as the equations below indicate (Wallace and Campbell 1991).

4Fe(HCO3)2 + O2 + 2 H2O Æ 4Fe(OH)3 +8CO2

3Mn(HCO3)2 + 2O2 Æ 3MnO2 + H2O + 2 CO2

23 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

Methods of reservoir manipulation aim to destratify the water body either by mixing the bottom and surface layers or through direct aeration of the lower anoxic waters. Although destratification and aeration are often used interchangeably, it is possible to do one without the other and, as such, they should be considered different processes (Kirke and El Gezway 1997). Most aeration systems used in Australian reservoirs work by introducing compressed air into the hypolimnion via a perforated pipe without disrupting the thermal stratification (Waite et al. 1991). More recent developments of mechanical mixing have a lower power usage than traditional compressed air systems. The ‘top down circulation’ system uses about 10% less energy and works by skimming water off the surface and discharging it at the bottom of the reservoir (Elliot and Morgan 2002). The benefit of this system is that it also reduces algae by moving the algae-containing aerobic surface waters to the bottom where algae are unable to photosynthesise, leading to a reduced occurrence of algal blooms (Elliot and Morgan 2002). For low productivity waters, aeration can be achieved by moving anoxic bottom waters to the surface to be naturally oxygenated, thus creating a maximum diffusion of atmospheric oxygen by exposing waters with the lowest DO levels (Kirke and El Gezway 1997). While aeration can effectively remove iron, it is generally not as effective for the removal of manganese at natural pH levels (Casale and LeChavellier 2002). While iron can undergo complete oxidation in under 15 minutes at a pH of 7.5 unless it has been complexed with organic compounds, manganese oxidation rates are very slow below pH 9 (Odell et al. 1998). A study by Zaw and Chiswell (1999) of a Gold Coast raw water source showed a significant reduction in the concentration of soluble iron at two sampling points of greater depth (i.e. 15 m and 0.5-2 m above the bottom) after artificial aeration was introduced. Aeration did not have as great an effect on manganese concentrations in the water column (Figure 2.2), most probably due to the near-neutral pH levels of the water (Zaw and Chiswell 1999) and the slower oxidation rates.

a)

b)

Figure 2.2: Comparison of the least squares mean concentration of a) iron and b) manganese in Hinze Dam between 1983 and 1988 for the whole year (before and during artificial aeration commenced in 1986) (Zaw and Chiswell 1999).

2.1.2.2 Oxidation / disinfection Oxidation and disinfection are two different components of drinking water treatment. The role of a disinfectant is to kill or render harmless pathogenic micro-organisms, while the role of an oxidant is to oxidise and precipitate soluble metals including iron and manganese (Kiely 1997). Although the roles

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of an oxidant and disinfectant are different, some of the most commonly utilised disinfectants are also strong oxidants. The most widely used oxidant is chlorine, which has been utilised in water treatment since the 19th century as a disinfectant (Kiely 1997). Similarly, other oxidants, such as chloramine and ozone, are primarily employed for the purpose of disinfection, thus providing a dual purpose. At the treatment stage, it is the oxidation of iron and manganese that is important for the mitigation of discoloured water. The addition of a strong oxidising agent, when employed prior to coagulation, can increase the amount of iron and, especially, manganese that is removed by changing the reduced soluble forms into a more readily precipitated form. The occurrence of disinfection at the treatment stage is for the removal of pathogens and is not restricted to manganese and iron removal. It is at the distribution stage that disinfectants become more relevant to discoloured water as a suppressor of biofilm growth. This section will primarily focus on the oxidation capacity of chemicals that are utilised as both oxidants and disinfectants and also discuss other oxidants that have no disinfection ability. As the role of a disinfectant, in affecting discoloured water, occurs within the distribution system, this will be discussed further in the section 2.2.

2.1.2.2.1 Oxidation The simplest method of applying an oxidant is through aeration and the increase of oxygen in the water, though there are limitations with the level of oxidation that can be achieved through aeration. Aeration, coupled with increasing the pH, is one of the techniques used to decrease Mn solubility before filtration. While, Rahman et al. (2000) found that 100% Mn removal could be achieved by raising the pH to 9.7 before filtration, the efficiency of this method decreased to only 60% if aeration was also conducted prior to filtration. This was attributed to the dissolution of CO2 in the water during aeration, forming carbonic acid and effectively lowering the pH (Rahman et al. 2000). As Table 2.2 below indicates, most of the commercially applied oxidising agents have a greater oxidising potential than oxygen so are theoretically better than aeration at controlling manganese and iron removal. The most commonly used oxidants are chlorine, chloramine, ozone, potassium permanganate and chlorine dioxide, which are described in more detail below. Table 2.2: Oxidising agents, in order of effectiveness (weakest to strongest) under standard laboratory conditions (Wallace and Campbell 1991).

Oxidising Agent Oxidation potential at 25°C, Relative oxidation power+ V* Hypochlorite ion 0.81 0.60 Oxygen (air) 1.23 0.90 Chlorine dioxide 1.28 0.94 Chlorine 1.36 1.00 Hypochlorus acid 1.49 1.10 Permanganate ion 1.49 1.10 Hydrogen peroxide 1.77 1.30 Ozone 2.07 1.52 Hydroxyl free radical 2.80 2.05 *relative to the hydrogen electrode +based on chlorine as a reference (=1.00)

The oxidation potential is temperature dependent, with lower temperatures retarding the rate of oxidation. Figure 2.3 demonstrates the effect of temperature on the oxidation rate of iron under fixed conditions. Other variables that are important for the oxidation rate are pH and organic concentration and ionic composition (Knocke et al. 1985). Similarly, temperature and pH affect the oxidation rate of manganese. The oxidation of Mn(II) by strong oxidising agents KMnO4 and ClO2 can proceed through three different mechanisms: solution- phase oxidation, adsorption onto MnO2(s), and surface oxidation (Van Benschoten et al. 1992). Under conditions representative of natural waters (pH 5.5-8.0, temperature 2-25oC and initial Mn(II) -1 concentrations of 0.4-1.25 mgL ), adsorption of Mn(II) to the MnO2(s) surface is the rate-limiting step for oxidation of Mn(II). The rate of reaction was found to be pH-dependent as, when the pH is above 7,

25 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

the solution phase oxidation reaction predominates. Temperature also affects the rate of reaction. Under conditions of low temperature, low pH and low initial Mn(II) concentration, the solution-phase oxidation is reduced enough to make surface oxidation significant (Van Benschoten et al. 1992). Manganese oxidation most commonly produces the product MnOx which is used to describe the insoluble oxides and oxyhydroxides formed (Nealson et al. 1988). The oxidation of soluble Mn(II) generally follows the stoichiometry of the three reactions below (Nealson et al. 1988): 2+ + Mn + ½ O2 + H2O ↔ MnO2 + 2 H 2+ + Mn + ¼ O2 + 1½ H2O ↔ MnOOH + 2 H 2+ + 3 Mn + ½ O2 + 3 H2O ↔ Mn3O4 + 6 H

Figure 2.3: The effect of temperature on the oxidation of Fe(II). Experiments were conducted under the conditions of 0.11 M ionic strength adjusted with NaClO4; alkalinity = 9 mM as NaHCO3; PO2 = 0.2 atm; pH~6.82; [Fe(II)]0 = 34.7 μM. (Sung and Morgan 1980).

Amorphous iron (III) oxyhydroxides are usually the most common form of iron in freshwater lakes/raw water storages and the most likely form taken off for drinking water treatment (Davison 1993). Perhaps fortunately, the true soluble/very small colloidal fraction is often the smallest fraction of iron present in freshwaters. This fraction is the most difficult to remove during treatment and makes its way into the distribution system most readily. Soluble iron is difficult to study directly but it seems as if it is largely Fe(III) and/or Fe(II) complexed to natural organic matter (Stumm and Morgan 1996). It is well known that Fe(II) complexed to NOM is much more slowly oxidised to Fe(III). This soluble fraction is well known to be very resistant to oxidation (for Fe(II)-NOM) and coagulation/flocculation (for Fe(III)- NOM) treatments to remove them (Knocke et al. 1985); (Knocke et al. 1990); (Ma et al. 1997). Fe(II) complexes of chloride and sulphate have also been shown to retard oxidation (Millero 1985). Therefore, the soluble fraction is likely to mostly pass into the distribution system. As manganese has a greater reduced soluble fraction than iron, it is often of more significance to the water treatment process as it is not readily removed and requires a more sophisticated treatment procedure to remove. Soluble manganese is more likely to pass through the treatment plant and into the distribution system where it can then be oxidised within the distribution system through microbial

26 CRC FOR WATER QUALITY AND TREATMENTRESEARCH REPORT 51

and chemical reactions. This is why oxidation is often employed prior to coagulation, as the oxidised solids are more readily removed through coagulation.

2.1.2.2.2 Chlorine Chlorination is the most commonly used disinfectant and oxidant. In general, chlorine oxidises iron very rapidly over a wide pH range, while the reaction rate with manganese is much slower (Odell et al. 1998). The reactions (below) generally proceed more quickly as pH increases. However, the change in rate is not linear with increasing pH (Odell et al. 1998).

2Fe(HCO3)2 + Cl2 + Ca(HCO3)2 Æ 2Fe(OH)3 + CaCl2 + 6CO2

Mn(HCO3)2 + Cl2 + Ca(HCO3)2 Æ 2MnO2 + CaCl2 + 4CO2 + 3H2O Stoichiometrically, 1mg/L of chlorine will oxidise 1.61mg/L of iron or 1.28mg/L of manganese. However, interactions with other constituents (e.g. organics, sulphides, ammonia) mean much larger doses are usually required (Knocke et al. 1990; Odell et al. 1998; Casale and LeChavellier 2002). Knocke et al. (1990) found that addition of free chlorine even at four times the stoichiometric concentration, over a three-hour period, only resulted in a reduction of Mn from 1.0mg/L to 0.7mg/L. In these experiments, increasing the solution pH greatly increased the rate of reaction for both manganese and iron, as did increasing the temperature (Knocke et al. 1990). Interestingly, when Fe(II) was complexed with fulvic and humic acids, addition of chlorine at very high concentrations did not produce any oxidation (Knocke et al. 1990). The addition of large quantities of chlorine is not appropriate in water treatment due to its strong odour and the potential for the production of trihalomethanes (THMs) and other potentially toxic by-products upon reaction with NOM. While this potential is decreased with the use of chloramines in disinfection processes, chloramines are ineffective as an oxidant for Mn (Wallace and Campbell 1991). Water that has a high organics content is, therefore, best treated by other oxidants that do not form THMs (e.g. ozone).

2.1.2.2.3 Monochloramine/chloramines Chloramines, in particular monochloramine are more commonly used as secondary disinfectants and are generally not employed as oxidants. Chloramines are a product of chlorine and ammonia (NH3) and monochloramine has the same oxidising capacity as chlorine but is a weaker disinfectant (Vikesland and Valentine 2000). Although it has the same oxidising capacity of chlorine, the contact time required by chloramines for disinfection is 100 times longer than that of chlorine (Gray 1994). This can be inhibitory during the treatment process, as manganese may not be fully oxidised before coagulation begins, which is why monochloramine is more commonly used as a secondary disinfectant. The other disadvantages of chloramines are a weaker disinfection ability than chlorine, a detrimental effect on taste and colour and an efficiency that is strongly dependent on pH (Kiely 1997). The formation of chloramines occurs via the following reactions: + NH4 + HOCl Æ NH2Cl + H2O + H Monochloramine

NH2Cl + HOCl Æ NHCl2 + H2O Dichloramine

NH2Cl + HOCl Æ NCl3 + H2O Trichloramine At pH greater than 7.5 the predominant reaction is the formation of monochloramine. When the pH is between 4.5 and 5.0 the formation of dichloramine also occurs and predominates at the lower end of the pH range. Trichloramine will only form at low pH (below 5) (White 1999). Monochloramine is the preferred chloramine as dichloramine is more odourous. Higher levels of dichloramine can be found in the extremities of the distribution system when free chlorine is available to react with monochloramine (Gray 1994). Conversely, the dissociation of monochloramine into free chlorine and ammonia can also be detrimental as the ammonia will support ammonia-oxidising bacteria that cause nitrification of the water (Wilczak et al. 1996). The advantages of chloramines are that they are more persistent than chlorine, have an algicidal effect and do not react with organic materials and phenols (Kiely 1997). Most importantly, in the distribution system chloramine has a lower reactivity with corrosion products than free chlorine (LeChavellier et al. 1993) and the chloramine demand of amino acids and carbohydrates is lower than that of chlorine

27 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

(Koudjonou et al. 1998). Under conditions of a corrosion rate of 3-5 mpy and an initial average biofilm bacteria count of 2.5 x 106 cfu/cm2 on black iron, when a chloramine residual of 4.0 mg/L (initial dose 5.1 mg/L) was applied, a 100-fold decrease in biofilm viable counts was measured, while a chlorine residual of 3.6 mg/L (initial dose 4.5 mg/L) produced no significant reduction over the two-week test period (LeChavellier et al. 1993). Under conditions of lower corrosion rates (0.2 and 1.2 mpy), the introduction of chlorine (4.8 mg/L dose, 3.8 mg/L residual) was also able to reduce biofilm viable counts by 100-fold (LeChavellier et al. 1993). This shows that, although chlorine is a better disinfectant, its higher reactivity means it will also more readily oxidise iron and manganese post-treatment. The stronger reactivity of chlorine means it can react with organic material reducing its persistence. Koudjonou (1998) suggests that polysaccharides and proteins within the exopolymer component of the biofilm, may act as a passive barrier to chlorine diffusion. The lower reactivity of monochloramine allows it to penetrate further into the biofilm (Koudjonou et al. 1998).

2.1.2.2.4 Ozone Ozone is a strong oxidant (approximately 50% stronger than chlorine) that reacts rapidly with both Fe and Mn. The oxidation of iron and manganese by ozone is shown in equations below (Knocke 1990).

2Fe(HCO3)2 + O3 + 2H2O Æ 2Fe(OH)3 + O2 + 4CO2 + H2O

Mn(HCO3)2 + O3 + 2H2O Æ 2MnO2 + O2 + 2CO2 + 3H2O It has been used in water treatment for over a century, but the application has been limited as it is expensive to set up compared to other available methods (Casale and LeChavellier 2002). Ozonation is often used for difficult-to-treat, organically bound iron and manganese, as it does not form undesirable by-products like the THMs produced by chlorination. However, most oxidation by-products of ozonation are biodegradable, which causes an increase in biodegradable organic material leading to biological growth in the treatment facilities and in the distribution system (Singer 1994). Nieminski (1995) studied the viability of introducing ozonation to control Mn and Fe at a small water treatment plant in Utah, USA. Analysis of the pilot ozone plant revealed lower metal concentrations, lower turbidity and, more importantly, THM formation compared to the full-scale plant that used chlorine as the chemical oxidant.

Variation in metal concentration with increasing ozone dosage

350 35 Iron

300 Manganese 30

250 25 g/L) g/L) μ μ 200 20

150 15

100 10 Fe concentration ( Mn concentration (

50 5

0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Ozone Dose (mg/L)

Figure 2.4: The removal of metals vs ozone dosage (1min contact time). Reproduced from Nieminski and Evans (1995).

28 CRC FOR WATER QUALITY AND TREATMENTRESEARCH REPORT 51

Figure 2.4 (above) clearly shows the reduction in iron concentration after oxidation with a range of ozone doses. Manganese concentration was also dependent on ozone concentrations. However, increasing doses above 1.5 mg/L caused an increase in manganese. At doses greater than 4mg/L, permanganate was formed instead of manganese dioxide, and a visibly pink filtrate resulted (Nieminski and Evans 1995).

2.1.2.2.5 Potassium permanganate Potassium permanganate is a stronger oxidant than chlorine, but it is also a strong oxidant of organic matter, so levels of potassium permanganate above the stoichiometric requirements are often necessary. However, the pink colour indicative of manganese dioxide formation can also be a problem if excessive amounts of potassium permanganate are used in treatment procedures. The required dosage becomes even more difficult to predict as freshly formed oxyhydroxide catalyses further oxidation, reducing the required amount (Waite et al. 1991). Potassium permanganate has been demonstrated to oxidise a variety of substances under acid, neutral or alkaline conditions (Casale and LeChavellier 2002) including iron and manganese:

3Fe(HCO3)2 + KMnO4 + 7H2O Æ 3Fe(OH)3 + MnO2 + KHCO3 + 5H2CO3

Mn(HCO3)2 + 2KMnO4 + 2H2O Æ 5MnO2 + 2KHCO3 + 2CO2 + 2H2CO3

Experiments conducted by Knocke et al. (1990) on the rate of oxidation of iron by KMnO4 indicated that the reaction was effectively instantaneous in the absence of dissolved organic carbon. The addition of organic carbon (in the form of humic acids) significantly worsened the capacity of KMnO4 to oxidise iron. Gregory and Carlson (2003) found that potassium permanganate requires considerably longer reaction times than ozone and chlorine dioxide to achieve acceptable manganese II oxidation (see Figure 2.5 below). At higher starting concentrations for manganese, (i.e.1000ug/L) the differences in reaction rates are not as pronounced as for lower concentrations, e.g 60 µg/L and 200 µg/L (Gregory and Carlson 2003) at their optimum doses under controlled pH, temperature and organic matter conditions.

2.1.2.2.6 Chlorine dioxide Chlorine dioxide has been used as both an oxidant and a disinfectant and is often used as a replacement for chlorine as it does not form THMs as readily. However, as with all disinfectants, it does produce its own disinfection by-products. Chlorine dioxide is also more effective than permanganate in reducing the formation of THMs (Wallace and Campbell 1991). As shown below (Figure 2.5), the preferred oxidant for the conditions used by Gregory and Carlson (2003) (temp: 9 degrees, pH: 7 and TOC: 3.4 mg/L) was chlorine dioxide, due both to its faster reaction time (especially for the lower initial concentrations of Mn) and the absence of MnO4 as a by-product of the reaction (Gregory and Carlson 2003). Like permanganate, the reaction of chlorine dioxide and uncomplexed iron is almost instantaneous, with most of the oxidation occurring within 2-3 seconds even at low temperatures. Oxidation of iron, however, is greatly inhibited when the iron has been complexed with organic matter. The equations below describe the reaction between chlorine dioxide and iron and manganese (Knocke et al. 1990). 2+ - + Fe + ClO2 + 3H2O Æ Fe(OH)3 (s) + ClO2 + 3H 2+ - + Mn + 2ClO2 + 2H2O Æ MnO2 (s) + 2ClO2 + 4H

29 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

2+ Figure 2.5: Bench Scale Comparison of Oxidation of Mn by KMnO4, ClO2 and O3 at three initial Mn2+concentrations (Gregory and Carlson 2003).

Oxidation can be an important step in reducing discoloured water formation when the major source of manganese and/or iron in the distribution system is from the raw water supply. The oxidation of high levels of reduced soluble manganese is of particular importance, as this fraction is often the largest entering the distribution system after treatment. Figure 2.6 shows the high concentrations of filterable manganese in the Wyong water supply after treatment. The ability of the oxidant employed to oxidise manganese to a form more readily coagulated can play a significant role in reducing discoloured water formation potential.

30 CRC FOR WATER QUALITY AND TREATMENTRESEARCH REPORT 51

Figure 2.6: Post treatment concentration of manganese in the Wyong Water Supply (Khoe and Waite 1989).

2.1.2.3 Coagulation / flocculation Generally coagulation follows oxidation. The role of a coagulant in the treatment process is to destabilise colloids, thus promoting an agglomeration of particles, causing them to increase in size and settle out (Wallace and Campbell 1991). As most suspended particles are of a negative electrostatic charge, addition of a chemical that can change this charge causes them to attract instead of repulse, group together and fall out (Kiely 1997). A pH of around 7 will cause the surface of iron precipitates to have a net neutral charge called the zero point of charge (ZPC) (Wallace and Campbell 1991). The ZPC of precipitates of Mn occurs at a more acidic pH (between 2.8 and 4.8) (Wallace and Campbell 1991). For both iron and manganese, the further the pH is below the ZPC, the higher the positive charge on the particle and, conversely, as pH rises above the ZPC, the electrostatic charge becomes more negative (Wallace and Campbell 1991). The three most common coagulants are aluminium sulphate, ferric sulphate and ferric chloride as they have high positive charge density that can destabilise the negatively charged particles in the water. The major inhibitor to the coagulation process is the presence of high concentrations of silica in the raw water. Davis (2001) found that the adsorption of silica onto preformed Fe(OH)3 colloids could prevent flocculation. Concentrations between 50 and 75 mg/L as SiO2 at a pH of 7.25 when mixed with Fe(OH)3 for 50 hours resulted in 35% of the total iron (10 mg/L) being present in a form which was small enough to pass through 0.45 μm pore size filter. Conversely, the stabilising ability of silica on iron can be utilised to sequester iron that is released in the distribution system. High silica content in bulk water can also translate into high silica content in particles (Sly et al. 1989), corrosion scales (Sarin et al. 2001) and even stains (Waite et al. 1989).

2.1.2.3.1 Aluminium sulphate (Alum) Aluminium based coagulants have been used for the treatment of discolouration in surface water for over one hundred years (Srinivasan et al. 1999), but have come under scrutiny in recent years due to concerns about metal residuals in the water supply due to possible health effects (Kvech and Edwards 2002). Failure to dose at an optimum concentration or pH may lead to aluminium concentrations in the treated water that are higher than the raw water concentrations (Srinivasan et al. 1999). Bache et al. (1991) conducted a series of ‘jar’ tests to identify the optimum alum dose and pH. Their research found that the maximum mass of floc solids was found at a pH of 4.75, irrespective of coagulant dose (Bache and Hossain 1991). Increasing the dose of alum increased the dry mass of the floc as expected, but the optimum dose was found to be 5 mg/L, as that produced the most dense flocs (Bache and Hossain 1991). Different results were found by Waite et al. (1991), as the optimal dose

31 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

was found to be 6 mg/L at an optimal pH of 6.3. Failure to dose at the optimal pH and dosage level for the particular water type can lead to increase dissolved Al in the treated water. Although present in raw water, the primary source of aluminium in drinking water is associated with the addition of aluminium sulphate or poly aluminium chloride as part of the treatment process. Therefore precipitation of aluminium in the distribution system is usually associated with water that has been treated using an aluminium-based coagulant (Costello 1984). Residual aluminium after treatment will consist of higher fractions of soluble cationic inorganic form. Schintu (2000) found that the dissolved fraction in the raw water consisted primarily of soluble organic complexes, whereas treated water had 40-62% as the inorganic and monomeric form. At pH 6-7, the principal cationic species in both raw water + and water treated with alum from Mornington Peninsula was Al(OH)2 (McCormick et al. 1993).

2.1.2.3.2 Ferric salts In general, ferric salts are effective over a broader range of pH, than aluminium based coagulants, and form larger amounts of sludge (Wallace and Campbell 1991). However work by Van Leeuwen (1995) comparing the effect of a range of coagulants on water colour, did not find ferric sulphate effective in reducing the colour of the water (van Leeuwen and Traksel 1995). Bench tests conducted by Waite et al. (1991) found that ferric chloride could effectively reduce turbidity, colour and iron concentrations with an optimum dose of 8 mg/L and an optimum pH around 6 (Waite et al. 1991).

Non-retention of Fe(III)Cl3 or ferric sulphate that is used as a flocculant will also contribute to the Fe load entering the distribution system. Contribution of iron from coagulant residual is usually only a problem if filtration is inadequate and filter break through occurs. However, it appears that added Fe(III) settles out more readily than Fe(II), which oxidises during the treatment process (Henderson et al. 2001). Fe(II)SO4 is also used as a coagulant, which could contribute Fe(II) in various forms to the treated water. Oxidation of Fe(II) within water produces particles that have a significantly reduced ability to settle out of solution than Fe(III) solids that are formed by ferric chloride addition, with a turbidity of 7.4 NTU and 4 NTU respectively in jar tests (Henderson et al. 2001). Contamination of ferric salts by manganese has also been recognised as a problem, as high doses of the coagulant may significantly increase dissolved manganese concentrations (Casale and LeChavellier 2002). Contact filtration (i.e. dosing the coagulant directly onto the filters), can lead to a reduction in turbidity (and pathogens), but can increase the dissolved salt concentration (Parker 2004).

2.1.2.3.3 Coagulant aids Coagulant aids can be effective in improving manganese oxide removal. At pH 5-11, the net surface charge on manganese oxidises is negative. The addition of cationic coagulant aids can potentially reduce surface charge and improve destabilisation, whereas anionic coagulant aids can be used to prevent restabilisation at pH levels below the isoelectric point. Thus, coagulant aids can be employed to increase the pH range at which the primary coagulant is effective (Posselt et al. 1968; Waite et al. 1991). Coagulation is an important process for removing suspended colloidal and particulate matter from drinking water. The removal of solids can decrease iron and manganese and also organic matter that can contribute to biofilm growth. However, addition of coagulants can also increase the potential of discoloured water when overdosing leads to high residuals of aluminium or iron within the finished water. 2.1.2.4 Filtration Filtration is an approach that is used either as an alternative to coagulation or as a following step after coagulation. There are three filtration techniques that can be used in water treatment including: • granular filtration, • membrane filtration and • biologically activated filtration.

Historically, granular filters (e.g. sand or anthracite filters) have been more widely used, but advancing membrane and biologically activated technologies have recently become a viable option for treatment plants. Fabric filters such as Kalsep, have also been used in the UK (Parker 2004), but publications about this in relation to discoloured water are scarce.

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2.1.2.4.1 Granular filtration There is a range of filter media that are commonly employed in granular water filtration units, including sand, anthracite coal, greensand, pyrolysite and granular-activated carbon. Sand and anthracite coal filters (and mixtures of these components) can remove manganese and iron from solution (in addition to trapping particulate forms of these metals) (Knocke et al. 1990; Odell et al. 1998). The mechanisms that influence this soluble metal removal are similar to those that produce the adsorptive properties of the purpose-made ‘greensand’ (see next section). Over time, in sand and anthracite filters, manganese oxides coat the granular particles, turning them black in colour. This naturally occurring ‘greensand effect’ coined by Knocke et al. (1987), has been found to be a useful, viable mechanism in the removal of dissolved metals. Detailed studies of this phenomenon by Knock et al. (1988, 1990), showed the efficiency of removal for manganese depended on the oxide concentration, its oxidation state and the water pH. Above a pH of 6.1, the addition of chlorine just before the filter aided the Mn2+ adsorption, while stronger oxidants produced higher levels of colloidal manganese increasing the possibility of colloidal Mn breakthrough (Knocke et al. 1988). A more recent study by Hargette et al. (2001) demonstrated that manganese oxide coatings could continue to remove soluble manganese and remains on filter media over extended periods of time (Hargette and Knocke 2001). Iron oxides can also aid in the removal of soluble manganese (Dewhirst et al. 1995). Greensand is zeolite or glauconite sand that has been coated with manganese dioxide by the addition of manganous sulphate and potassium permanganate (Knocke et al. 1990; Odell et al. 1998; Casale and LeChavellier 2002). Greensand requires periodic or continuous conditioning with a strong oxidising solution (typically potassium permanganate). Once conditioned, greensand can remove iron and manganese by filtration and adsorption (Casale and LeChavellier 2002). Removal rates of this material are 0.01 lb (4.5g) of manganese and 0.13 lb (59g) of iron per cubic foot (0.028m3) (Casale and LeChavellier 2002). Pyrolysite is the mineral form of manganese, and is generally crushed into specific sizes and mixed with sand for use as a filter media (Casale and LeChavellier 2002). This media is highly porous, providing an extensive surface area and, hence, a faster flow capacity (Odell et al. 1998). A study of different granular filter media by Odell et al. (1998), found pyrolysite could remove between 80 and 95% of iron and over 90% of manganese, and could cost between 50 and 75% less than other systems.

2.1.2.4.2 Membrane filtration Membrane filtration technology uses a fibrous sheet instead of granular media to separate particles from water. There are a number of categories of membranes with differing sizes shown in Table 2.3 below:

Table 2.3: Types of filtration used in water treatment. Membrane Filtration Particle size removal range (microns) Microfiltration 0.06-14

Ultrafiltration 0.001-0.1

Nanofiltration 0.0005-0.008

Reverse Osmosis 0.0001-0.005

Iron and manganese oxides (in their solid forms) can be removed from drinking water using microfiltration (Ellis et al. 2000). There are problems, however, with the use of nanofiltration and reverse osmosis, as iron and manganese oxides can clog the membranes. If the metals are maintained in a reduced state, they do not cause a problem and the nanofiltration membrane will remove the iron or manganese (Casale and LeChavellier 2002). To avoid metal oxide clogging of the membrane, iron and manganese can either be removed by pre-treatment or stabilised in their reduced forms, by the lowering of pH or minimising oxidant contact (Wallace and Campbell 1991). Wallace and Campbell (1991) suggest that reverse osmosis is not a valid treatment for iron and manganese removal unless this filtration system is required to treat other problems. In contrast, Ellis (2000) found that microfiltration can very efficiently remove iron and manganese, even at high metal concentrations.

33 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

2.1.2.4.3 Biological filtration The same processes that cause biofilms in distribution systems to trap iron and manganese can be used in the treatment process to remove these metals from solution (Sly et al. 1993) Natural colonisation of filters by biofilms capable of oxidising iron and manganese, increases the removal efficiency of the filtration process, but this colonisation can take up to 2 months to establish (Sly et al. 1997). Immobilisation of bacteria onto filter media is advantageous as it can overcome the delays and uncertainties of natural colonisation (Sly et al. 1997) Sly (1993) found promising manganese removal efficiencies by immobilising the manganese-oxidising bacterium Pedomicrobium manganicum onto magnetite particles smaller than 300 m in diameter, in a continuous recycle fluidised-bed bioreactor. The use of filtration to reduce the concentration of iron and manganese entering the distribution system can be very beneficial as it is able to remove both dissolved and colloidal forms. Different depths of filter may be required, as specific conditions are often needed for the growth of iron and manganese bacteria. The limitations of filtration in reducing discoloured water is the potential for filter breakthrough to allow spikes of manganese and/or iron to pass into the distribution system. This can also be the case in granular filtration, especially when returning the filters to service after washing. 2.1.2.5 Treatment train There are many considerations for the order and timing of different treatment processes to maximise the removal of iron and manganese. Adequate time is needed between the oxidation and coagulation step to ensure that the maximum oxidation of manganese has occurred, while the time between coagulation and filtration needs to be optimised for settling to improve filtration efficiency and to minimise filter breakthrough. Most of the information above on treatment methods has been determined through optimisation experiments used to determine the best dose and application time for the combination of treatments and the water chemistry of the source water utilised.

Figure 2.7: The treatment train used by the Upper San Leandro treatment plant demonstrates the increasing complexity of the treatment process (Wilczak et al. 2003).

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Figure 2.7 (above) is an example of the increasing complexity of the treatment process. The use of multiple oxidants at different stages of treatment has been employed to satisfy the need to remove metals and organics while reducing the formation of disinfection by-products and still producing a disinfectant residual adequate to minimise biofilm formation within the distribution system. Increasing concern over the formation of disinfection by-products has caused changes in the treatment train to minimise their formation. However this can potentially have a negative impact on the removal of iron and manganese. For example when chlorination is moved from being the first step in the treatment to just prior to filtration (to minimise the reaction time available for DBPs to form) it also reduces the time for manganese oxidation to occur (Knocke et al. 1987). 2.1.2.6 Sequestering techniques Sequestration is the formation of a colourless, water-soluble compound that prevents the formation of objectionable colour, without actually removing the iron and manganese (Pacholec and Wiedemann 1995). In this process, the hardness ion is chelated (tightly held) and not able to precipitate to form scale in pipes and equipment (Pacholec and Wiedemann 1995). As mentioned in the Coagulation/Flocculation section, elements such as silica have an ability to stabilise colloids and prevent flocculation and, subsequently, prevent the removal of colloids from the water. Although this is a problem during treatment processes that are aimed at removing iron and manganese though settling out flocculated particles, it can be advantageous in preventing particle formation within the distribution system. Sequestering is generally not used as a replacement for iron and manganese removal techniques. Sequestering agents such as sodium silicate and sodium chloride have been tested for their ability to sequester manganese. However, the effectiveness is a lot lower than for iron (Robinson and Ronk 1987). Robinson and Ronk (1987) suggest that this is due to the slower oxidation rate of manganese by oxygen alone that limits the usefulness of adding sequestering agents. More commonly, sequestering agents are used to sequester iron that has been released within the distribution system through corrosion. Inorganic phosphates and sodium silicate are the most commonly discussed sequestering agents. Except for orthophosphate, all condensed phosphates (or polyphosphates) have similar sequestering abilities (Pacholec and Wiedemann 1995). This is important, as polyphosphates undergo hydrolysis or reversion (Pacholec and Wiedemann 1995). The use of polyphosphates has been found to reduce apparent colour and turbidity of iron suspensions, especially for Fe concentrations below 1 mg/L where suspensions have been rendered colourless (Lytle and Snoeyink 2002). Sodium silicate and inorganic phosphates may also inhibit corrosion. However, research by Boase (1987) found that although corrosion reduction can occur in new or relatively uncorroded pipes, the main action of sodium silicate and inorganic phosphates is an ability to sequester iron and minimise visibly discoloured water. Variable results have also been reported by McNeill (2000) who found no simple relationship between iron release through corrosion and water quality parameters such as pH, alkalinity, buffer intensity, stagnation and phosphorus residual. Negative effects of scale build-up and increased iron release were noted for some waters when polyphosphate and orthophosphate were used (McNeill and Edwards 2000). This highlights the limitations of phosphates and silicates as corrosion inhibitors. There are some concerns that the addition of phosphates will increase bacteria growth within the distribution system. However, the effect of polyphosphate addition appears to vary, depending on the raw water quality, with some research indicating a reduction in bacteria and biofilm with the addition of phosphates. Appenzeller (2001) found a reduction in both corrosion rate and bacterial growth for highly corroded cast iron. Butterfield (2002) found weak evidence that phosphate addition improved the effectiveness of chlorine at minimising biofilm formation. Batte (2003) found that the use of phosphates did not affect bacterial densities in biofilms, even though there was an increase in the phosphate accumulation within the biofilm. Although evidence suggests that sodium silicate and polyphosphate have limited success as corrosion inhibitors, they are more successful as sequestering agents and, thus, should minimise discoloured water formation in many systems. The following section on Processes within the Distribution System (2.2) further discusses the processes and changes that occur within the distribution system and how they relate to discoloured water.

35 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

2.1.2.7 Influence of NOM in treatment process Even with effective treatment dissolved organic material will only be slightly reduced (20-25%). The enhancement and optimisation of the coagulation process to aid the removal of dissolved organic material as well as particulate matter, improved the removal of dissolved organic carbon (DOC) from an average of 29% removal to an average of 43% at 10 sites in the US (Volk et al. 2000). However, the results of the study found that assimilable organic carbon (AOC) was not easily removed through coagulation and was mostly unaffected by the optimisation process. It was concluded that the differences in coagulation are because the BDOC fraction probably consists of humic substances, large molecules and substances bound to humic material whereas the AOC fraction consisted of small, non-humic molecules (Volk et al. 2000). Research by (Kinniburgh et al. 1999), involves evaluating a particular model called the NICCA-Donnan model, which is a recent advancement over previous models. This model accounts for the extreme binding heterogeneity of natural humics, the variable stoichiometry of binding (monedentate, bidentate etc), competition between specifically bound ions (especially protons and metal ions), and electrostatic effects which give rise to ionic strength effects, and the non-specific binding of counterions. When compared with data of H+, Ca2+, Cd2+, Pb2+, and Al3+ binding to a purified peat humic acid the model captured the non-linearity of the observed isotherms, even at very low free metal ion concentrations. The model was able to be calibrated on single ion systems but was able to predict sorption behaviour in mixed metal ion systems reasonably well (Kinniburgh et al. 1999).

Oxidation of Fe(II) during treatment with oxidants KMnO4, ClO2, O3 will be almost instantaneous, however the presence of humic material will greatly reduce the oxidation rate (Van Benschoten et al. 1989). Complexes of Fe(II) with higher molecular weight compounds are particularly resistant to oxidation and will effect the removal of iron from raw water during treatment (Knocke et al. 1990). Stronger complexation of Fe(II) with organic material inhibits the oxidation of Fe(II) during treatment to a much greater extent than Mn(II). Knocke (1991) found that although the oxidation ability of Mn(II) by KMnO4 and ClO2 was reduced in the presence of DOC it was still effective, however Fe(II) oxidation is inhibited through the presence of DOC due to the stronger complexing. The actual type of dissolved organic carbon that is present will have an impact on the way it interacts with reduced iron. Results of another treatment study by Knocke (1994) found that the presence of DOC inhibited the formation of particulate iron. When no DOC was present, essentially all Fe(II) is converted to particulate solids upon oxidation whereas the presence of DOC would stabilise colloidal iron and inhibit coagulation. This result was not replicated when the source of DOC was changed. Instead tests with a different source of organic matter found significant particulate iron forming after oxidant addition and no DOC removal even when practically all Fe(II) had been oxidised, highlighting the importance of the nature of DOC present (Knocke et al. 1994). Interaction between organic matter and iron salts was investigated through the use of salicylic acid. Removal of salicylic acid and hence formation complexation with iron was optimal at pH 5.5 (Rahni and Legube 1996). However, only partial precipitation occurred and it is thought that initial interactions between iron and salicylic acid results in the formation of a soluble complex that is then hydrolysed. At pH 8.5 the complexation was weak as precipitation of iron is the predominant reaction. Aluminium forms strong complexes with NOM, though at the lower end of its solubility (pH 6.5-7.0) it exists in predominantly inorganic forms (Srinivasan et al. 1999). Complexation and speciation of aluminium in treated waters differs to that of raw waters due to treatment processes that remove particulate matter from the water. Hence the aluminium that passes into the distribution system has a higher proportion of mononuclear species (Srinivasan et al. 1999). Although residual aluminium is both dissolved and particulate, the particulate aluminium can be removed though filtration after coagulation. Dissolved aluminium can be found complexed with natural organic matter, fluoride, phosphate, sulphate, and hydroxyl ion (Srinivasan et al. 1999).

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2.2 Processes within Distribution Systems that Influence Discoloured Water Events

There are a number of processes that can lead to the formation of dirty water within distribution systems. Particles can only reach customers’ taps by either being introduced into the distribution system or by forming during delivery. There are only two ways particles are introduced into distribution systems; either directly from the treatment plant or source water or by inadequate installation and maintenance. The treatment methods that can be used to reduce both dissolved and particulate forms of metals entering the mains have been discussed previously. Maintenance and cleaning will be discussed in more detail within this section, along with the formation of new particles within the distribution system. Accumulation of particles within the distribution system occurs through physical, chemical and biological processes. The term postprecipitation is commonly used to describe the accumulation of matter within the distribution system and encompasses corrosion-tubercules, deposition, encrustations, growth, scale, scum, sediment and slime (Costello 1984). Postprecipitation includes deposition of calcium carbonate, precipitation of soluble iron as iron oxides, precipitation of aluminium hydroxide from residual aluminium sulphate, flocculation of particles present because of filter breakthrough and precipitation of Zn, Pb, Mg and Mn (Voyles). This chemical oxidation and precipitation increases the significance of the physical process of settling of particles. Changes in hydraulic conditions can then lead to the resuspension of these particles and notably discoloured water may result. Iron and manganese can also accumulate in both inorganic and organic deposits on the surface of the pipe wall. The former is often, but not always, associated with corrosion whereas the latter is through microbial growth as biofilms which will be discussed later in the section on microbial processes in the formation of discoloured water (section 2.2.3). The location of deposits that have accumulated within the distribution system is related to the mechanism of accumulation. Chemical deposits of manganese will occur throughout the distribution system when residual chlorine oxidises manganese that has not been removed by treatment. Deposition usually occurs close to the treatment plant when manganese in the treated water remains >0.02 mg/L for a number of days (Khoe and Waite 1989). Microbial deposition occurs in areas where chlorine residual is inadequate (Sly et al. 1989). Sloughing of biofilm can increase sediment accumulation in peripheral parts of the system, and accumulated sediments will provide a substrate for further microbial growth (Slaats 2001). Different mechanisms of deposition can be occurring in the one distribution system. Gauthier (1996) found that, despite the samples being taken from reservoirs and pipes fed from the same water distribution system, there was great variation in the composition of deposits which may indicate that there is more than one mechanism for loose deposit formation. Dirty water incidents can be distinguished as either chemical or microbiological by the presence or absence/low numbers of budding hypha bacteria (Sly et al. 1990). Physiochemical deposition of coatings in the distribution system usually contains high concentrations of Mn, Fe, Al, Ca, Si and organic matter (Khoe and Waite 1989). Sly (1990) recommends that treated water manganese should be reduced to 0.01 mg/L to ensure that there is minimal deposition within the distribution system. For iron, the lessening of deposition is more complicated due to the contribution of corrosion processes. 2.2.1 Corrosion processes leading to discoloured water

Studies into corrosion constitute a large component of research on processes within distribution systems. Corrosion processes contribute to discoloured water through two mechanisms, the first being the dislodgement of encrusted material on the pipe surface and the second being continuous release of iron through dissolution followed by oxidation (Slaats 2001). The significance of the latter form of corrosion to discoloured water is the release of Fe2+ ions into the water column. These can then undergo chemical or microbial oxidation forming particles, inorganic coatings and be incorporated into biofilms. On the other hand, corrosion encrustations on pipe walls will continually have small particles flaking or breaking off (Gray 1994). 2.2.1.1 Water chemistry that influences corrosion Corrosion is a complicated process with many variables affecting the ability of water to react with pipe material. For corrosion to occur, the water must be aggressive and the piping material susceptible to corrosion (Voyles). Dissolved oxygen, chlorides, sulphates, calcium, alkalinity, buffer capacity and

37 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

immersion time have all been found to influence corrosion. The Langlier Saturation Index (SI) is used to assess the potential of calcium carbonate deposition or dissolution (deposition can help reduce corrosion rate). However, this index has not always been found to be reliable. Use of the Langelier index is not recommended by the American Water Works Association due to contradictions in empirical evidence on which it is based (McNeill and Edwards 2001). Many researchers have tried to quantify the conditions that cause waters to be corrosive. Studies generally focus on one of three aspects: pipe degradation, scale formation or by-product release. Five types of water have been identified by (Gray 1994), which can increase corrosion rates: 1) soft waters with a low alkalinity 2) waters rich in chloride and sulphate 3) the deposition of sediment and growth of organisms that leads to local oxygen depletion 4) bacterial action (e.g. sulphate-reducing bacteria) 5) water with low dissolved oxygen concentrations (< 4 mg/L). Increasing the alkalinity of water within the system has been shown to reduce pipe weight loss, corrosion rate and discoloured water complaints (references within (McNeill and Edwards 2001). (Gray 1994) suggests soft waters with an alkalinity less than 50 mg CaCO3/L are more likely to influence corrosion. A study by (Naylor et al. 1993) used a galvanic cell corrosion test to investigate the effects of alkalinity and pH on the corrosivity of water. The results demonstrated that corrosion was markedly reduced within the pH range 7.5 –8 when alkalinity was higher than 50mg CaCO3/L. From this research, the Hunter Water Corporation set their pH target at 7.8, and 50-60 mg CaCO3 /L was considered optimal for alkalinity (Naylor et al. 1993). Changes in pH have different effects on three aspects of corrosion. Increasing the pH has a detrimental effect on the rate of corrosion and scale build-up, but will be beneficial in reducing the corrosion by-product release (McNeill and Edwards 2001). + - Higher concentrations of Ca and HCO3 within water may reduce corrosion rate and lead to the development of protective corrosion coatings. El Din (1986) found that in jar tests using water that has pH of 8.9-9.2, the corrosivity of the water produced an orange-red ferric oxide in much greater quantity 2+ - (by visual inspection), than the same water when 100 mg/L Ca and 122 mg/L HCO3 was added (El Din 1986). - Increases in sulphate and chloride will increase the corrosion rate. However, if HCO3 is present, the 2- - corrosivity of the chloride is reduced (Gray 1994). Both SO4 and Cl are able to form ion pairs with Fe(II) that are not easily oxidised (Millero 1985). The presence of sediments in a distribution system, and the associated micro-organisms, causes localised oxygen depletion, leading to increased corrosion (Lee et al. 1980; Gray 1994). However, Sontheimer (1981) reported that higher concentrations of humics reduce the corrosion rate in both galvanised steel and cast iron. Certain micro-organisms, such as sulphate-reducing bacteria, will directly cause corrosion, (Lee et al. 1980) especially pitting (Rao et al. 2000). Oxygen concentration can have varying effects on the corrosion of iron, as it can act as an electron acceptor (see equation below) or, as previously discussed, can oxidise ferrous iron (McNeill and Edwards 2001). 2+ - Fe(metal) + ½O2 + H2O ↔ Fe + 2OH Gray (1994) suggests dissolved oxygen concentrations less than 4 mg/L can enhance corrosion, while Sontheimer et al. (1981) noted that increased oxygen caused higher iron concentrations within the bulk water. High DO can also be involved in waters that have low corrosivity due to its possible association with low turbidity and high buffering capacity (McNeill and Edwards 2001). Beckett et al. (1998) found that, during pipe loop experiments, iron released from the pipe was low when the water was kept circulating even at low DO concentrations (<0.5 mg/L). However, stagnation leads to an increase in iron release. Figure 2.8 shows the concentration of total iron and ferrous iron released from a pipe section after periods of stagnation. Each point represents a separate experiment after 3, 6, 12, 18, 24, 48 and 120 hours stagnation, while dissolved oxygen levels remained between 0.3 and 1.14 mg/L. While most of the iron measured was in ferric form, Beckett et al. (1998) thought it was initially released in ferrous form and then oxidised by chlorine or oxygen.

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In the same pipe loop system, also at pH 8.9, water with an initial DO concentration 17.5 mg/L stimulated half the amount of iron release as water with a DO of 6.2 mg/L (Beckett et al. 1998). There was little difference between initial DO concentrations of 1 and 6.2 mg/L (Beckett et al. 1998). Dissolved oxygen appears to be the most important parameter for controlling corrosion, but the influence of micro-organisms promoting localised corrosion through tubercule formation becomes more important as exposure time progresses (Lee et al. 1980).

Figure 2.8: Release of iron from pipe wall including changes in DO. Initial DO = 1.0 mg/L, pH 8.9 (Beckett et al. 1998).

Disinfection residuals are thought to increase the corrosion rate, unless the corrosion is microbially mediated (McNeill and Edwards 2001). Polyphosphate corrosion inhibitors and pH adjustment have been shown to prevent and control corrosion-induced discoloured water (McNeill and Edwards 2001). Figure 2.9 shows the effect of chlorine and pH adjustment on the corrosivity of the water (measured by iron concentration in the water) (Cantor et al. 2003). The chlorinated water was much more corrosive, however, elevating the pH from around 7.7 to 8.2, brought the corrosivity back to that of the untreated water. A similar trend was seen after the addition of orthophosphate (Cantor et al. 2003).

39 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

Figure 2.9: Iron concentration from three treatments in iron pipe loops at Lone Rock, Wis. (Cantor et al. 2003).

2.2.1.2 Types of pipes Replacement or relining of corroded pipes is a costly and difficult exercise. However, the cost of relining cast-iron pipe with cement is approximately one third to one quarter of the cost of replacing the pipe (Burstall 1997). Even lined pipes are vulnerable to corrosion. Holes in plastic linings or cracks in inner skins of metallic protective barriers lining the pipe, will allow corrosion to occur (Gray 1994). Galvanic corrosion has been seen to occur where ferrous and cuprous materials are joined together without use of insulation materials (Voyles). The stability of the corrosion scale product, Cu2O, formed on copper plumbing is dependent on the pH, ratio of dissolved inorganic carbon and chloride of the water (Palit and Pehkonen 2000). The increase in dissolved iron from steel and PVC pipes was assessed by Lee et al. (1980). A decrease in the initial DO and an increase in the dissolved iron concentration indicated the iron was being oxidised from the steel pipe (Lee et al. 1980). The steel pipe had 86% of DO depleted within 2 days compared to a 20% decrease in PVC pipe loop. Alkalinity and hardness showed an initial reduction in both systems, however, both parameters then stabilised within the PVC system. A continued decrease over time in the steel pipe loop indicated that ferrous carbonate and calcium carbonate may be precipitating at the pipe surface (Lee et al. 1980). 2.2.1.3 Fe2+ release from pipe wall During pipe loop experiments, Clark (1994) found that the iron concentration increased as the treated water moved though the pipe loops, indicating that corrosion was occurring. This was subsequently followed by a drop in iron concentration, indicating that deposition of particles was occurring. Laboratory based experiments on corrosion by McNeill (2000) found no simple relationship between pH, buffer capacity, alkalinity and phosphorus residual with the total iron released from the pipe wall. The iron released from the pipes during stagnation was highly variable. Soluble iron accounted for 0- 25% of the total iron released into the water, with a general trend of increasing proportion of soluble iron with decreased pH or raised alkalinity (McNeill and Edwards 2000). Within 4 hours of the water sample being removed from the pipe all soluble iron was oxidised and an orange or dark brown precipitate had formed. Oxidation of Fe2+ released from corrosion will most likely not precipitate until it reaches the consumers water storage tank or until the water runs out of the tap. 2.2.1.4 Scale formation Corrosion scales can contribute to iron in the water through dissolution of soluble species or detachment of scale particles (Waite et al. 1989; McNeill and Edwards 2001). Solubility of corrosion scale is difficult to predict due to the poorly crystallised and heterogeneous structure (McNeill and

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Edwards 2001). Changes in the hydraulic regime such as diurnal changes in water usage can easily destabilise corrosion deposits (Smith et al. 1998). Scales can also be problematic by reducing the internal diameter of pipes and making them more susceptible to main breaks. While the structure of scales is diverse and largely dependent on the type of corrosion, (Sontheimer et al. 1981) published a schematic (Figure 2.10) showing the typical layers found in corrosion scales. Table 2.4 also shows the variety of iron compounds that can be present in corrosion scales, many of which can form a protective coating on the pipe wall slowing further corrosion. The formation of corrosion-resistant scales is demonstrated through a reduction in red water production as some pipes age (Smith et al. 1998). A simplified model has been developed to determine if corrosion resistant scales will form based on the formation of siderite, which is considered to be associated with protective scales. The most important aspect of the model is the competition 2+ between the formation of siderite (FeCO3(s)) and direct oxidation of Fe (Sontheimer et al. 1981). Siderite forms when dissolved inorganic carbon is greater than 50 mg C/L and pH and Eh are low (Clement et al. 1998). Calcium carbonate and ‘green rust’ have also been proposed as protective scales (McNeill and Edwards 2001). A highly corroded 40-50 year old 1.5 m section of steel/iron pipe was taken from a Melbourne property and the corrosion layer was analysed. Samples taken from the surface and close to the original side of the pipe had similar percentages of iron oxide, indicating that the material accumulated in the pipe was derived predominantly from the corrosion process and not from accumulation of particles from the water within the distribution system (Lin et al. 2001). Fe(III) accounted for more than 90% of the total iron content (Lin et al. 2001).

Figure 2.10: Schematic of a corrosion scale on a distribution system pipe (Sontheimer et al. 1981).

41 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

Pipe wall scale was analysed on lead, cast iron and galvanised steel pipes by (Clement et al. 1998). Iron pipes were coated with goethite (α-FeOOH) and magnetite (Fe3O4). Siderite (FeCO3) was not found, which was expected based on water chemistry. Magnetite was found in higher proportions than other scale materials. Lead pipes had mainly hydrocerrusite (Pb3(CO3)2OH) though one tubercule contained iron as well. Silica was found in all scales formed on the cast iron pipes, with chlorine and sulphur also being commonly present elements. Aluminium was commonly found in scales formed on pipes in two systems where the water is treated with alum coagulant. Sulphate reducing bacteria were found in many pipes (nearly all of the iron pipes). Cement-lined pipe examined had a reduction of pipe wall material and deposits contained oxidised iron, giving a rust-like appearance to the lining (even though there was no exposed ductile iron) (Clement et al. 1998). Furthermore, calcium carbonates can precipitate with pH changes. The deposition of calcium carbonate can greatly reduce the carrying capacity of the pipe. Seasonal occurrence of high iron and manganese can cause the formation of coloured layers in calcium carbonate deposits, giving an appearance similar to growth rings in trees (Costello 1984). Gauthier (1996) found that even only slight pH increases (0.1-0.3 pH units) can be associated with increased calcium deposition in the French distribution system studied.

Table 2.4: Iron solids that could possibly be present in corrosion scales. Modified from McNeill and Edwards (2001). Name Chemical Formula Iron Oxidation State

Ferrous hydroxide Fe(OH)2 II Ferric hydroxide Fe(OH)3 III Wustitie FeO II Goethite α-FeOOH III Akaganeite β-FeOOH III Lepidocrosite γ-FeOOH III Hematite α-Fe2O3 III Maghemite γ- Fe2O3 III Magnetite Fe3O4 (FeO·Fe2O3) II and III Ferric oxyhydroxide FeOx(OH)3-2x III Sidrite FeCO3 II Iron hydroxycarbonate Fex(OH)y(CO3)z III “Green rust Fe(III)x1Fe(II)x2(OH)y(CO3,SO4)z II and III Vivanite Fe3(PO4)2·8H2O II Strengite FePO4 III Schrebersite Fe4P Not known

In the Thames Water distribution system in England, five different types of corrosion deposits were found on pipe walls, with the predominant compounds in the deposits being siderite, magnetite, lepidocrocite, goethite, calcite and quartz (Smith et al. 1997). A weak association was found between calcium and iron that indicated that calcium may influence tuberculation. The most common two of the five types of pipe wall deposits were solid encrustations with an outer layer of magnetite with goethite underneath. Some deposits were considered "passive", whereas others are "problematic" in relation to the formation of discoloured water. Flushed hydrants that did not have discoloured water all had pipes with deposits that are rich in magnetite. Hydrants with red water during flushing may have had compounds that were identified as being from corrosion deposits such as lepidocrocite, whereas other hydrants had red water without corrosion products in the netted deposits indicating that the source of the discolouration may not be local. It was observed that joints promoted the accumulation of deposits (Smith et al. 1997). Tubercules from pipes in the Columbus, Ohio distribution system in America consisted largely of iron oxides with other minor trace elements and an array of microbial organisms including sulphate reducers, nitrate reducers, nitrite oxidisers, ammonia oxidisers and sulphur oxidisers (Tuovinen et al. 1980). The abundance of other elements followed the order Ca>Mg>Al>Mn (Tuovinen et al. 1980). Tuovinen (1980) found that iron was not the only element at elevated concentrations in red water when compared to clear water in the distribution system. The elements Mn, Pb and Cu also were at

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increased concentrations in red water. There may be an association between other layers of tubercules and red water as the outer layers also had increased Cu and Mn (as well as Ba, Cr and As) when compared to inner layers (Tuovinen et al. 1980). 2.2.2 Physiochemical processes leading to the formation of new particles that can cause discoloured water

Reactions that cause the oxidation and precipitation are advantageous when they occur prior to settlement and filtration processes. However, when they occur during distribution they can potentially contribute to the formation of discoloured water. The major differences between oxidation processes in the natural environment (as discussed previously) and those within the distribution system are: • a lack of sunlight (necessary for growth of primary producers); • the presence of treatment residuals (e.g. disinfectants); and • the presence of a pipe wall surface. Particles in the distribution system are either found adhered to the pipe wall, in sediment deposits, or entrained in the water column. Discoloured water events occur when pipe wall films shear off or sediment deposits become mobile, and the particulate matter is carried through to customers’ taps. 2.2.2.1 Development of chemical films Pipe walls often provide a surface on which biofilms can grow, however, when disinfectant residuals are high, a chemical film may develop (Sly et al. 1990). The chemical film is most likely to be manganese oxide, with aluminium, silica, calcium, iron and copper co-deposited (Sly et al. 1990). The deposition of manganese oxide decreases with distance from the treatment plant due to the concentration of manganese and the capacity of the pipe surface to adsorb manganese oxide (Sly et al. 1990). The average water velocity and the width of the boundary layer controls the equilibrium between deposition and detachment of accumulated manganese oxide (Sly et al. 1990). The oxidation reaction required in the formation of a manganese oxide film may be triggered by the presence of disinfectant residuals or surface interactions. Sly et al. (1990) showed that chemical deposition of manganese oxide increases markedly when chlorine levels are increased. Adequate disinfection residuals are, however, necessary to hinder the development of bacterial films that can also cause dirty water (see section 2.2.3). The importance of surface interactions between the pipe walls and the oxidation of dissolved manganese and other metals such as iron and aluminium was demonstrated by a manipulative experiment by Scott et al. (2002). Batch experiments, in dark conditions, confirmed the process of surface-catalysed oxidation on rocks (Scott et al. 2002). Prior to the addition of rocks, the concentration of manganese was stable in the water for 60 minutes. After rocks were added, there was a decline in the filterable manganese concentration. This decline was attributed to oxidation processes (Scott et al. 2002). The mere presence of iron and manganese oxides has been shown to accelerate the overall oxidation rate through the formation of surface complexes (Vikesland and Valentine 2000; Scott et al. 2002). 2.2.2.2 Accumulation of sediments Due to their large surface area, particles within the water will scavenge metal ions from solution and are hence important for the transportation of metal ions within the system (Stumm and Morgan 1996). The mechanism of metal incorporation in particles can follow two different processes. The first is through colloidal intermediates and the second is through direct incorporation into particles. In estuarine water, Wen (1997) used radiotracers to assess the transferral of trace metals from solution to particle phase. In relation to iron and manganese, iron appeared to follow the first mechanism, with the particulate fraction increasing as the colloidal fraction decreased. Manganese increased in the particulate phase while the low molecular weight fraction (≤1 kDa) decreased, indicating a greater portion of the manganese being adsorbed directly from soluble form into particulate phase. This mechanism is in agreement with studies that have found that manganese oxidation includes surface- catalysed oxidation (e.g. Scott et al. as previously mentioned). Vikesland and Valentine (2000) conducted an experiment to determine if ferric oxide precipitate accelerated oxidation reactions between iron and monochloramine. When Fe(II) was sequentially spiked into a concentrated monochloramine solution, the rate of reaction increased linearly as shown in Figure 2.11.

43 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

Vikesland (2000) found that the oxidation of Fe(II) by monochloramine is rate limited by the aqueous phase of the reaction where the reaction between monochloramine and Fe(II) produced Fe(III) • precipitate and an NH2 radical.

Figure 2.11: Changes in observed rate coefficient following spike additions of Fe(II) for different concentrations of Fe(III). Conditions of experiment were [NH2Cl]0 = 0.980 mM, [Fe(II)0 = 0.0895 mM with each spike. PH0 = 7.354, CT,CO3 = 0.006 M, DO <1.0 mg/L. Average Fe(III) concentration for each spike = the amount of Fe(III) present when the sample was spiked plus half the Fe(II) added with each spike. (Vikesland and Valentine 2002).

Changes in pH and dissolved oxygen levels can influence the formation of particles (Gray 1994). Dissolution of oxygen in water produces hydroxide ions under neutral conditions. When Ca+ and - 2+ HCO3 is at low concentrations, the hydroxide is free to react with Fe ions, forming precipitates of Fe(OH)2 which will further react with oxygen to produce solid ferric hydroxide, Fe(OH)3 (El Din 1986). Precipitation can also occur when the water chemistry is altered because two water sources are mixed (i.e. ground and surface water) (Gray 1994). As the particles move throughout the distribution system, they can increase in size as Clark et al. (1994) demonstrated in pipe loop experiments. The size of particles increases as the water moves through the loops, with particles greater than 10 µm increasing from about 0.5% to 4% of total particles, regardless of treatment method used (Clark et al. 1994). Once in the distribution system, organics are fairly rapidly reduced due to the following interactions: co- precipitation with iron, manganese or aluminium; utilisation by micro-organisms; or adsorbing onto corrosion products. Once removed from solution, the organic matter will exist in loose deposits that can be a food source for microbial growth and can be resuspended during periods of high flow (Gray 1994). Accumulation of sediments often occurs at the end of the distribution system and in dead ends (Gray 1994). Once sediment has settled in the distribution system, deposits will form into islands that have the least resistance to the flow of water (Slaats 2001). The loose particles that are too heavy to remain in suspension during normal flow can become resuspended during periods of increased flow. One way of addressing this issue is to keep the flow velocity at a high enough level to inhibit deposition of particles. At a velocity of 0.35 m/s, all types of sediments will move along the bottom of the pipe.

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However, reducing fittings and tap in points will impede sediment movement (Slaats 2001). Davies (1987) has used turbulence theory to create a theoretical equation to fit empirical data for the flow velocity required to keep a solid particle in suspension in a horizontal pipe. 2.2.2.3 Composition of particles and coatings Sediments that cause discolouration through turbidity are usually organic matter (including micro- organisms) or insoluble material (iron and manganese). The actual constituents of distribution system particulates have been studied intensively in some French, Australian, Finnish and Canadian systems. The results of these investigations are discussed in this section. Gauthier et al. (1999) has contributed a large proportion of the information in the literature on the constituents of particles and coatings within a distribution system in France. Hydrant flushing of water mains produced sediments with high iron content, even though half the samples were taken from PVC mains (Gauthier et al. 1996). The main elements within deposits were volatile solids, insolubles, iron, calcium, aluminium and manganese. The iron content of sediments was higher in the pipes than the reservoir, with iron oxides (when assumed to be in the form of FeOOH) accounting for up to 76% of total mass in pipe deposits (Gauthier et al. 1996). Aluminium and manganese contents were generally lower in pipe deposits. However, this may be an artefact of the use of a 100 µm mesh sieve which excludes very small particles from the analysis. Calcium carbonates will precipitate with pH changes, as can be seen by an increase in calcium content of deposits further along the system (range of 0 to approx. 10-12%) (Gauthier et al. 1996). In a study of organic matter in the same distribution system, it was found organic carbon content of the loose deposits ranged from 2.0% to 11% and nitrogen from 0.17% to 1.1% (Gauthier et al. 1999). The C/N ratio was relatively constant throughout the system (within the range 5.5-8.5). Volatile solid measurements in reservoir sediments and pipe deposits varied between 5.9 - 28% and 11-20% respectively (Gauthier et al. 1999). This could be compared to the work of Sly et al. (1990) who found volatile solids measurements of 23% and 21-32% in deposits and suspended particles in an Australian system. Soft deposits analysed from 16 distribution systems in Finland found that the deposits are generally brown or black in colour, with the major inorganic constituents being iron (18%), manganese (3.7%), aluminium (4.5%) and calcium (3.0%) (Zacheus et al. 2001). After one year, the flushing process was repeated to determine changes in the composition of deposits after the initial swabbing. The results found that the major constituents were similar, though there were some changes in the relative percentage composition, with iron being 31%, manganese 0.58%, aluminium 1.0% and calcium 5.4% (Zacheus et al. 2001). The carbon/nitrogen ratio was similar between the two sampling times with 16.3 and 17.7 respectively which was considered to be quite low. Elemental analysis of particulate matter in the distribution systems of the Avon Dam using PIXE showed that the highest concentration elements were iron (155.4 μg retained on a 0.2 μm membrane filter from 10 mL of water), silica (49.9 μg/filter) and manganese (36.9 μg/filter) (Waite et al. 1989). Sediments from the distribution system fed from the Woronora Dam had lower concentrations of iron (72.8 μg/filter), silica (30.4 μg/filter) and manganese (24.9 μg/filter), though these elements were still an order of magnitude higher than other elements measured (Waite et al. 1989). Analysis of particles using transmission electron analysis, with elemental analysis by X-ray emission (TEM/EDX), found that the majority of particles from the Woronora system contain Fe, Al, and Si, with very few particles containing large quantities of Mn despite high Mn concentrations measured when using PIXE (Waite et al. 1989). Particles from the Avon system were characterised as having large quantities of hydrous iron oxide, with manganese oxides found in association with the larger quantities of iron oxide (Waite et al. 1989). Table 2.5 is a comparison of common parameters measured by authors studying various locations, with the results shown as percentages of the dry particulate matter. In Gauthier’s (1996) analysis, results are also shown as percentages when the mineral form of the element (e.g. FeOOH for iron and MnO2 for manganese) is used in the calculation. While this might give a better indication of the extent of the respective compounds in the particulate matter, it makes it difficult to compare to other authors’ work, so the elemental percentage has been shown here as opposed to the mineral percentage. The analysis of the Gold Coast distribution system categorised the deposits by colour and form before metal concentrations were determined (Hamilton). Type A deposits were hard nodules with brown and black coloured bands that had red dust when ashed. Type B were soft black/grey deposits and type C were soft and red/brown in colour. As discussed earlier, the work of Zacheus et al (2001) involved sampling sediments from a Finnish distribution system (old results) and then sampling again one year later (new results).

45 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

Table 2.5: Percentage of dry weight for metals and volatile solids from the literature. Distribution Volatile System Type Fe Ca Al Mn solids Insolubles Reference Nancy, France Pipe Deposits 38.8 3.6 2.1 0.4 19 18 (Gauthier et al. Reservoirs 12.7 4.4 5.3 2 12.9 3 1996)

Finland Old 18 3 4.5 3.7 (Zacheus et al. New 31 5.4 1 0.58 2001)

(Smith et al. UK Thames 25.4 0.860.29 0.16 1997)

(Gauthier et al. Canada Montreal 43-65 2001)

Australia Sydney Avon 36.7 (Waite 1990) Woronora 29.8

Gold Coast Type A (n=7) 40 <1 14 Type B(n=19) 13.2 13.9 24 Type C(n=21) 23.9 3.44 29.1 (Hamilton)

2.2.2.4 The release of Mn or Fe from deposits Although the accumulation of manganese and iron within the distribution system is predominantly a chemical process through the oxidation of elements and interactions with other substances within the bulk water, mechanisms of release that cause discoloured water are physical processes that relate to the hydraulics of the system. Two common mechanisms for red water are the physical entrainment of loose deposits caused by changes in flow dynamics and the occurrence of particles that remain suspended in the bulk water. Detachment of deposits following increased water velocity can lead to further detachment through abrasive shearing (Waite et al. 1989). Discoloured water problems are especially prevalent in dead- ends where absence of flow leads to settling of material that can then be resuspended (Slaats 2001). Small and lightweight material is more likely to cause discolouration (Slaats 2001). Hydraulic processes are usually the cause of consumer complaints. Sudden changes in flow velocity or direction can lead to the resuspension of sediments. Diurnal water demand creates alternating stagnation and high flow conditions that lead to the resuspension of particles and the scouring of inorganic coatings on the pipe wall. Increased flow from overnight to daytime velocities can be sufficient to cause scouring (Sly et al. 1989). Figure 2.12 shows a typical diurnal flow in two mains attached to end hydrants.

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Figure 2.12: Flow rate in two dead end mains. Peaks coincide with morning and evening high demand (Smith et al. 1999).

Experiments by Smith (1998), at a pilot scale distribution system in south-west London, found that conditions most likely to produce red water are when there are alternating periods of stagnation, anaerobic conditions and elevated temperatures (>20ºC). Red water events were worst during periods of stagnation. Iron uptake from pipes was the greatest contributing mechanism. Figure 2.13 shows the changes in flow, and associated changes in turbidity, that may be created by a diurnal flow pattern with stagnant periods in between.

Figure 2.13: Typical turbidity patterns created by diurnal alternations in stagnation and flow due to consumer demand over a five day period (Smith et al. 1998).

Interestingly, in this study, an opalescent discolouration that is caused by the presence of sub-micron ferric hydroxide particles was discovered. Through further oxidation and aggregation, the white particles will convert to a red precipitate. This finding could indicate possible misdiagnosis of complaints, as iron has not previously been considered to be a potential cause of milky-coloured water (Smith et al. 1998).

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2.2.3 Microbiological processes leading to discoloured water

Microbes utilise many components of the water distribution environment. They can be found in the bulk water phase, living on settled particles and as biofilm on the pipe wall. Microbial contribution to discoloured water is two-fold. Some species within the distribution system are able to oxidise iron or manganese and will increase the deposition of manganese and iron within the distribution system. Micro-organisms also contribute to discoloured water as a physical component of matter that, when eluted, appears discoloured. Bacteria can produce a range of water quality degradation problems. Investigation of an initial odour complaint in Connecticut, America, found that bacteria counts were above the Maximum Contaminant Level (MCL) (Jodiatis et al. 1979). During a 20-day period in which the contamination incident was assessed and treated, around 50 complaints were made regarding dirty water, chlorine odour, and requests for bacteriological samples. The formation of biofilms has been the key focus of the literature on the microbial contribution to discoloured water. This may be, in part, because biofilms create a range of problems for deteriorating water quality as they are physically attached to the pipewall and can potentially accumulate to greater masses than bulk water micro-organisms. The term biofilm is used to describe the stable ecosystem that comprises a mixture of microbial cells that are embedded in a matrix of excreted extracellular polymers (Block et al. 1993; Donlan et al. 1994). Although some information will be included about the conditions that lead to biofilm growth, this information is already covered in the Biofilm project (Project # 4.2.3). The main focus of this section will be on species that are particularly relevant to discoloured water and the microbially mediated accumulation and release of iron and manganese within the distribution system. Species that oxidise iron or manganese are present within distribution systems. Iron oxidising species can be of particular significance in distribution systems with cast iron or steel pipes as they can contribute to the corrosion process. Manganese oxidising species are common within distribution systems and have been more widely studied in relation to discoloured water. Biofilms have a capacity to biomagnify metals within the water. Biofilms grown in a polluted river in Germany were found to have a biomagnification factor of 1.5 x 104 in summer and 5.8 x 104 in winter for manganese and 9.6 x 103 in summer and 3.2 x 104 in winter for iron (Friese et al. 1997). Species that form biofilms can become dislodged during changes in hydraulic state and enter the bulk water phase causing discoloured water. A major objective when improving drinking water quality is the control of biofilm growth in distribution systems (Block et al. 1993). The growth of biofilms on pipe walls constitutes the main portion of the biomass within the system. The ability of biofilms to either bioaccumulate or oxidise metal ions (e.g. iron and manganese) from the bulk water leads to a direct influence on dirty water formation. Bacterial regrowth can also degrade water quality by promoting the occurrence of pathogenic bacteria (LeChavellier 1990) and favouring growth of superior organisms (Niquette et al. 2001). This section discusses the factors leading to biofilm formation, methods of research and how biofilms relate to the formation of discoloured water. 2.2.3.1 Factors leading to the formation of biofilms A number of physical and chemical processes have been studied as to how they contribute to the growth of biofilms. These factors include environmental conditions, nutrient availability, disinfection techniques, system hydraulics and composition of the pipe material. Conflicting results are often found between studies, as some find no relationships between these factors and biofilm regrowth. An example of this is a sampling program set up within the Sydney Water Board (Australia) drinking water distribution system. General data analysis indicated that system parameters had little or no influence on bacterial numbers. Correlations were apparent, however, between certain parameters, such as turbidity and distance from the initial treatment point, and bacterial numbers (Power and Nagy 1999).

2.2.3.1.1 Environmental factors Temperature of water may be the most important factor influencing microbial growth rates of bacteria within distribution systems (LeChavellier 1990). Temperature can also influence treatment plant efficiency, disinfection efficiency, corrosion rates and flow (through seasonal customer demand). All of these factors may affect biofilm growth (LeChavellier 1990). Most investigators observed significant microbial activity in water above 15ºC (Niquette et al. 2001). Other seasonal effects, e.g. rainfall, may impact source water by stirring of nutrients, thus increasing bacterial growth rates (LeChavellier 1990). A study by Niquette, (2001) showed the quality and origin of the water in the distribution system had a

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great impact on bacterial dynamics. Ground water was found to be less prone to bacterial growth than surface water. This may be due to the lower organic content of ground waters.

2.2.3.1.2 Nutrient availability In general, bacteria need bioavailable forms of the nutrients phosphorus, nitrogen and carbon to remain viable in distribution systems. Trace nutrients are also required but these have not been investigated in drinking water systems (LeChavellier 1990). Excessive organics can support biofilms that may cause taste, odour and discolouration problems. Micro-organism counts greater than 103 /mL are likely to cause discolouration problems. Counts this high are more likely to occur in lowland surface water supplies (Gray 1994). A number of methods for measuring the bioavailable fraction of total organic carbon (TOC) have been developed, as simply dissolved organic carbon (DOC) measurements have been seen to be insufficient. Camper et al. (1998) suggested it could be this lack of consistency between measurements that causes the unpredictability in statistical relationships between organic matter measurements and biofilm growth (Camper et al. 1998). Used frequently in the literature are the terms: • assimilable organic carbon (AOC) • biodegradable dissolved organic carbon (BDOC) • biodegradable organic matter (BOM) Assimilable organic carbon (AOC) often comprises only a small portion of the DOC in a water sample (LeChavellier 1990). In their 1995 study of biofilm growth, van der Kooij et al. found that the formation of biofilms is strongly enhanced by the presence of easily available substrates. Bacterial growth will not occur at AOC levels of less than 10 ug ac-C eq/L, while bacterial growth was always observed in waters containing AOC levels above 50 ug ac-C eq/L (van der Kooij et al. 1995). These levels are difficult to compare to the BDOC concentration found to promote regrowth of fixed bacteria in a distribution system fed with surface water, of > 0.25mg C/L (Niquette et al. 2001). It is evident that monitoring a suite of organic constituents in water would provide a better insight into regrowth within distribution systems. The BOM in the water can be made up of a number of substrates e.g. carbohydrates and carboxylic, amino and humic acids. Carboxylic acids were found to be the biggest component of the BOM in a study of three Canadian treatment plants. However, amino acids were more highly preferred by biofilms in a laboratory study by the same researcher (Camper et al. 1998). In this study, biological treatment was found to be as effective as chlorination in reducing the number of biofilm organisms (Camper et al. 1998). A reduction in carbon may have a two-fold benefit as Butterfield et al. (2002) suggests bacteria may use carbon to protect the biofilm from the effects of free chlorine (Butterfield et al. 2002). Biodegradable organic matter (BOM) is a substrate for coliform growth in distribution systems. Volk (2000) found a weak yet significant correlation between biodegradable dissolved organic carbon (BDOC) and assimilable organic carbon (AOC) in samples taken from 31 treatment plants in the United States and Canada. The likelihood of coliforms growing in distribution systems can be assessed based on three suggested threshold parameters; (i) temperatures at or above 15°C, (ii) disinfectant residuals at dead-ends being at or below 0.5 mg/L chlorine or 1 mg/L chloramine, and (iii) AOC concentrations greater than 100 μg/L leaving the treatment plant (Volk and LeChavellier 2000). It was found that the probability of coliform growth within a distribution system increased from 1.9% to 16% when the three threshold parameters were exceeded (Volk and LeChavellier 2000). Adsorption of humic substances onto iron oxide may enhance biofilm growth through the provision of a higher nutrient environment (Butterfield et al. 2002). In the absence of free chlorine, the presence of humic substances with corrosion products led to an increase in biofilm production. The presence of humic substances in the water will therefore have increased importance in dead ends where the chlorine levels are often diminished or absent (Butterfield et al. 2002). Chandy and Angles (2001), considered it crucial to understand the contribution of both organic and inorganic nutrients to biofilm development. This study of a system in Sydney (Australia) found the addition of an easily bioavailable substrate (acetate) increased biomass in chloraminated water, suggesting growth was carbon-limited, even though very low levels of phosphorus (typically less than 2ug/L) suggested phosphorus may have been the limiting nutrient (Chandy and Angles 2001). The variation of AOC is dependent on the consumption by bacterial activity as well as oxidation by chlorine or chloramines, meaning operational conditions may greatly affect biofilm formation (Liu et al. 2002).

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The addition of phosphate-based corrosion inhibitors is another operational condition that can influence biofilm growth. There are suggestions in the literature (LeChavellier et al. 1996) that corrosion control contributes to improving microbial water quality, although increased phosphorus concentrations in phosphorus-deficient waters may increase growth rates (Batte et al. 2003). Biofilm regrowth is thought to be more efficient at phosphate concentrations >5 ug/L, and typical additions for corrosion control are generally up to 1000 times this (1-5mg/L) (Batte et al. 2003). The most recent study in this field by Batte (2003) showed no increase in biofilm density with the addition of corrosion control products to a controlled lab-based system.

2.2.3.1.3 Disinfection techniques The most commonly used technique in attempts to disinfect distribution systems is the maintenance of a chlorine or chloramine residual throughout the system. These two chemicals behave differently in their effectiveness and persistence. A lot of work has been carried out on this topic, with a variety of conclusions. In general, chloramine is believed to be a less effective biocide for free cells, but more stable over long residence times than free chlorine. Their effect on attached cells in biofilms, however, is more difficult to measure (Zhang and DiGiano 2002). Manganese depositing biofilms were found to rapidly develop in the distribution system on the Gold Coast in areas where there were insufficient chlorine levels (Dixon et al. 1989). The maintenance of residual chlorine at 0.2 mg/L was considered to be adequate to control biofilm formation. As biofilm growth can be strongly influenced by disinfectant residual, the persistence of chlorine within the distribution system can be indicative of potential high growth areas. Beatty (1995) developed a model using new transformation functions and curve-fitting algorithms created by Montgomery Watson (1994) to produce an equation that was able to accurately predict changes in the rate of decay for Sydney water using water quality factors (eg pH, turbidity) and decay environment factors (initial chlorine dose, pipe diameter).

2.2.3.1.4 In situ measurements Although thought to be an indication of biofilm growth, measurements of free cells (e.g. by way of heterotrophic plate counts) are not always a good guide to attached biomass. Still, this measurement is used in a number of studies, as access to the internal surface of pipes is usually very difficult. Zhang et al. (2002) used this technique in an attempt to examine the effect of the two disinfection methods on regrowth in the system. While their study concluded there was difficulty in capturing important interactions among chemical, physical and operational parameters because sampling was only monthly at 10 stations throughout the large distribution systems, correlation analysis indicated that disinfectant residual is the most important factor determining heterotrophic plate count (HPC) level. In comparison, a French study by Delahaye, (2003) found no correlation between HPC and residual chlorine concentration and suggested this may be due to the low density of culturable bacteria.

2.2.3.1.5 Laboratory based measurements A comprehensive study of the effect of chlorine and chloramine on drinking water biofilms was carried out by Koudjonou et al. (1998), under laboratory conditions. A steady state biomass was grown on glass beads, in stainless-steel reactors before different concentrations of chlorine and chloramine were added (Koudjonou et al. 1998). Results showed that chlorination led to an equilibrium of active biomass (smaller that the control) while a constant decrease was observed in the chloraminated reactor, as it better penetrated the biofilm (Koudjonou et al. 1998). Butterfield et al. (2002) also found a reduction in the biofilm biomass with the addition of free chlorine to his polycarbonate annular reactors, but did not include chloramination in his study (Butterfield et al. 2002).

Concentrations of free residual chlorine less than 0.07 mgCl2/L are considered low enough to promote regrowth of fixed bacteria in systems fed with surface water (Niquette et al. 2001). However, high residuals alone cannot be relied upon to prevent bacterial occurrences (LeChavellier 1990). The efficiency of the disinfectant seems to also be dependent on the type of pipes throughout the system. In a study by LeChavellier (1990), low levels of free chlorine or monochloramine (1mg/L) reduced viable cell counts by 100-fold for biofilms grown on galvanised, copper or PVC pipes. However, free chlorine residuals at relatively high concentrations (3 and 4 mg/L) could not control biofilm growth on iron pipes. Where higher chlorine residuals failed, monochloramine residuals above 2 mg/L were successful in reducing viable biofilm numbers on iron pipes, most probably because it is less reactive and, therefore, less likely to be consumed before it penetrates the biofilm (LeChavellier 1990).

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In an attempt to fit a computer model to the shedding of biofilm in a medium density polyethylene pipe rig, Maier et al. (2000) found that when monochloramine was present in the water, the net biofilm shear-off was reduced. Other observations were that, in an unchlorinated system pipe wall, biofilm shear-off was highest at the start of the system and for a chlorinated system the shear-off was highly non-uniform, as measured by a particle counter (Maier et al. 2000). See Section 2.2.4.2 for further information on modelling disinfection residuals.

2.2.3.1.6 System Hydraulics Biofilm formation and detachment may be influenced by flow dynamics either through affecting transfer of disinfectants and nutrients to the biofilm surface or the direct action of shear forces on cell adhesion (Donlan et al. 1994). Turbulent flow, causing higher radial diffusion rates, can have a beneficial or deleterious effect on biofilm growth rates, depending on the concentrations of both the nutrients and disinfectants in the system (Lu et al. 1995). While there is generally a negative relationship between flow velocity and attached biomass (Donlan and Pipes 1986), biofilms formed under higher flow regimes are often thinner but firmer (Becker 1998). Water velocity will have an effect on the dominant species of micro-organisms present within biofilms on the pipe wall surface. Sly (1988) found that water velocity significantly influenced the nature of the biofilm especially at the early stage of micro-organism development. Biofilm found at a water velocity of 0.01 ms-1 did not deposit manganese and deposited lower amounts of iron than biofilms found when the water velocity was 0.5 ms-1. At the higher velocity budding hyphal bacteria were the dominant species and included the manganese oxidising and depositing species. Biofilms formed at higher velocities are more likely to accumulate Fe and Mn (Sly et al. 1988), leading to a higher likelihood of dirty water events.

2.2.3.1.7 Composition of the substratum The composition of the substratum (pipe surface) is thought to influence biofilm growth in a number of ways. The strength of the attachment of the biofilm could be affected by the surface tension of the pipe material, or the pipe material may indirectly affect the biofilm growth by consuming disinfectants (Lu et al. 1995), or providing sites for colonisation. In 1998, Becker et al. found that, after short exposure times, there were some differences between the ability of biofilms to bond to test plates with different surface tensions. As this difference seemed to disappear after eight days’ exposure time, it was concluded organisms were able to adapt to the substrate rapidly and, therefore, this was not likely to be a useful long-term approach to minimise biofilm growth (Becker 1998). There is conflicting information on the best type of pipe material to use to minimise biofilm growth. A study by Zacheus et al. (2001) found no correlation between the number of bacteria in pipe deposits and pipe material. This may be because years of biofilm accumulation diminish the influence of the base stratum (Zacheus et al. 2001). In comparison, another study found that the replacement of cement and cast iron pipes by PVC would also help to reduce bacterial levels (Niquette et al. 2001). Previously Niquette (2000) had found that the density of fixed bacterial biomass on coupons of different pipe material in Intercommunale Bruxelloise de Distribution d’Eau in France differed greatly. Grey iron had densities that were 10 to 45 times higher than those on polyethylene and PVC pipes, while cement lined pipes had intermediate densities The variability in results on the impact of pipe material on biofilm growth may relate back to the interactions of the pipe wall with compounds and ions present in the water. As mentioned in section 2.2.1, pipe wall interactions may consume disinfectant residual, which can lead to increased biofilm growth. It is, therefore, likely that the impact of pipe material is not simply related to surface tension and direct interactions between micro-organisms and the pipe wall. 2.2.3.2 Biofilm content

2.2.3.2.1 Bacterial content of biofilms Distribution system biofilms contain a variety of microbial organisms including diatoms, algae and filamentous and rod-shaped bacteria (LeChavellier et al. 1987). Culture examinations of biofilms from pipe walls in distribution systems found a large number of heterotrophic bacteria including species belonging to the genus Pseudomonas, Flavobactium, Alcaligenes, Acinetobacter, Moraxella, Agrobacterium, Arthrobacter, Corynebacterium, Bacillus and Achromobacter (LeChavellier et al.

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1987). While species of coliform bacteria in biofilms have been widely studied for health reasons, they are generally not related to dirty water complaints and will not be included in this review. Distribution biofilms contain a variety of microbial organisms, including a number of species belonging to the genus Pseudomonas, which can be found in water, floc, flushed sediment, iron tubercule and pipe surface samples (LeChavellier et al. 1987). Arthrobacter spp.were the predominant species found in sediments and tubercules (LeChavellier et al. 1987). Both of these genera have been linked to discoloured water events. LeChavellier (1987) developed a model that could account for 63% of the variation of HPC bacteria levels using chlorine, pH and temperature. Many bacteria, including members of the genus Pseudomonas, can use ferric ions as terminal electron acceptors for anaerobic respiration (LeChavellier et al. 1993) or have the ability to oxidise manganese (Murdoch and Smith 1999). Table 2.6 shows the genera of micro-organisms found in distribution system biofilms and their ability to oxidise manganese and iron. The budding hyphal bacterium, Hyphomicrobium and Pedomicrobium, have been associated with manganese-oxide biofilms on pipe surfaces in Australia, England, New Zealand and Norway (Sly et al. 1988). The optimum temperature for the oxidation of Mn(II) by Pedomicrobium sp is between 20 and 30 degrees (Larsen et al. 1999). Table 2.6: Species of micro-organisms found in or associated with distribution system biofilms and their ability to oxidise manganese and iron Genera Manganese Iron Achromobaterb Acinetobactera Agrobacteriuma Alcaligenesa Arthrobactera Yes* Bacillusa Yes Corynebacteriuma Enterobactera Yes Flavobactiuma Yes Yes Hyphomicrobium Yes* Yes* Metallogeniumb Yes Micrococcusa Yes Moraxellaa Pedomicrobiumb Yes Yes Pseudomonasa Yes Yes a (LeChavellier et al. 1987) b (Sly et al. 1988) * ability to oxidise Mn or Fe is dependent on species or strain

In a study of a chlorinated distribution system biofilm, van der Wende (1989) found that 75-90% of bacteria belonged to one species of Pseudomonas genus. This lack of species diversity was not observed in the chlorine free treatment (van der Wende et al. 1989). Table 2.6 (above) describes the species of bacteria that have been found associated with biofilms in distribution systems and their ability to oxidise either manganese or iron. The budding hyphal bacterium, Hyphomicrobium and Pedomicrobium, have previously been associated with manganese deposits on pipe surfaces. These bacteria have been associated with manganese oxidation when they were attached to a surface rather than in the bulk water solution. Manganese-oxidising micro-organisms have a superior ability to attach to pipe surfaces where they develop under turbulent conditions. Sly et al. (1988) established characteristics for the identification of manganese-oxidising bacteria, Pedomicrobium manganicum, not to be confused with Hyphomicrobia to allow early detection of manganese oxide colonies. Manganese-oxidising strains of Pedomicrobium are easily detected on manganese containing media because of black manganese oxide accumulated around the cells (Sly and Arunpairojana 1987). Budding hyphal bacteria (Pedomicrobium manganicum and Metallogenium) were the dominant micro- organisms oxidising manganese. Although morphologically similar, Hyphomicrobium sp. was also present but incapable of oxidising manganese. It is possible that any organism with a budding hyphal

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morphology could grow under these conditions. This is supported by the presence of Metallogenium in the biofilms. The dominant micro-organism in dirty water samples and biofilm in the Gold Coast distribution system was the budding hyphal bacterium Pedomicrobium manganicum (Dixon et al. 1989). Monitoring of biofilms in the Wyong distribution system confirmed high levels of deposition towards the end of the reticulation system. Pedomicrobium manganicum was cultured from biofilm samples and also observed in Wyong dirty water samples.

2.2.3.2.2 Metal content of biofilms Biofilms are known to be able to concentrate and bind ions from passing water (Friese et al. 1997). This bioconcentration of metals can occur by one of two mechanisms. A number of bacteria actively catalyse the oxidation (and therefore accumulation) of metals in the water phase, either by changing the local pH and redox conditions or by metabolic processes (Lo et al. 1996). Under oxic and suboxic conditions, Mn oxides can be deposited by biological processes (e.g. metabolism) (Lo et al. 1996). Alternatively, Fe oxides can be deposited by both active and passive processes depending on the redox environment of cell surfaces and biofilm coatings (Lo et al. 1996). Bacteria in the biofilm may directly influence metal concentration by using inorganic electron acceptors (e.g. iron) in their oxidation of organic matter (Brown et al. 1998) or by changing the local pH or redox conditions. Just the presence of bacteria can remove metal ions from solution by adsorption onto their membrane surfaces (Brown et al. 1998). While a number of metals have been associated with biofilms in natural environments (Friese et al. 1997), the oxidation by bacteria of just two metals (iron and manganese) remains the biggest factor in the formation of dirty water. A number of bacteria have been identified as being able to deposit iron and manganese from the surrounding water (Ghiorse 1984). The ability of biofilms to bioconcentrate a number of metals from river water was studied by Friese et al.(1997). The enrichment factor (i.e the ratio of metal concentration in the biofilm compared to the water) was found to be largest for manganese, even though iron concentrations were higher, in both the biofilm and passing water phase (Friese et al. 1997). It has been suggested that the reason why the composition of manganese deposits from pipelines in various parts of the world are remarkably similar is due to the ability of manganese oxides to scavenge divalent metal ions and not due to the type of organism that is depositing the manganese oxide (Sly et al. 1988). Murdoch (1999) discovered that Pseudomonas spp bacterium growing in a biofilm on the surface of pipe materials will form micro-nodules. The micro-nodules formed within two weeks and were 10 μm in diameter with a 2 μm diameter hole in the centre. Energy dispersive X-ray spectroscopy (EDS) analysis of the micro-nodules showed high manganese and oxygen levels. The micro-nodule formation was dependent on the presence of manganese-oxidising bacteria. However, the mechanism of formation is unclear. Manganese-depositing species Pedomicrobium manganicum and a Metallogenium sp. were identified along with other micro-organisms in the Gold Coast distribution system (Sly et al. 1990). 2.2.3.3 The contribution of microbial processes to discoloured water

2.2.3.3.1 Microbial oxidation interactions Oxidation of iron by molecular oxygen is rapid and, hence, out-competes oxidation by micro- organisms, whereas Mn(II) is stable under neutral conditions and requires organisms to oxidise the manganese (Nealson and Saffarini 1994). Removal of Mn(II) from solution probably involves the process of bacterial catalysis. Using 54Mn(II) as a radiotracer, Emerson (1982) found that the residence time of dissolved Mn(II) in natural water samples was between 2 and 5 days, with recognisable bacterial structures showing up in electron microscope scans of the particles formed through binding and oxidation. The ability of freshwater micro-organisms to oxidise manganese is not limited to a small group of genera. A large number of aquatic heterotrophs are capable of changing the oxidation state of manganese (Gregory and Staley 1988). Strains of manganese oxidising species isolated from Lake Washington by Gregory (1988) were all found to be chemoheterotrophs without an obligate requirement for manganese oxidation. Deposition of manganese through biological deposition is much slower than that of chemical deposition on the pipe wall surface. Sly (1990) found that even when unchlorinated water was used, the biological manganese deposition from waters with 0.05 mg/L Mn(II) was only 20% of the chemical

53 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

deposition rate for water dosed with 0.5 mg/L chlorine. Table 2.7 shows the half life of Mn(II) in freshwater sources when converted by microbial oxidation. Table 2.7: Half-lives of microbial oxidation of Mn(II) in freshwater sources. Modified from Wehrli (1995).

t1/2 (days) Temperature (° C) Location 3.6 20 Lac de Bret 3.5 Unknown Lake Greifen 2.5 Unknown Oneida Lake 1.1 10 Lake Zurich 0.94 7.5 Rhode River 1.4 5 Lake Sempach

A variety of organisms are capable of oxidising Mn, including fungi and bacteria. The spontaneous loss of the ability to oxidise manganese in bacteria may be attributed to the presence of a plasmid with either direct (by providing gene products) or indirect (by altering the environment) involvement (Gregory and Staley 1988).

Below pH 8 and above Eh 200 mV, Mn(II) oxidation can only be achieved by micro-organisms (Larsen et al. 1999). Optimal Mn(II)-oxidising activity occurs at pH 7 and 25ºC in Pedomicrobium sp. Mn(II) oxidation in Pedomicrobium sp. appears to be catalysed by a Cu-dependent enzyme as treatment of cells with a copper chelator diethyldithiocarbamate inhibited Mn(II) oxidation. Enzyme activity was restored by the addition of Cu(II) ions, but not by identical concentrations of Co(II) or Zn(II) (Larsen et al. 1999).The enzyme appears to membrane bound as spent medium has no Mn(II)-oxidising activity (Larsen et al. 1999). Micro-organisms can oxidise Mn(II) directly through enzymatic catalysation or indirectly through production of oxidising substances (Gounot 1994). Precipitates collected from aerated natural water samples had one sample that demonstrated no manganese oxides. However, Mn was found concentrated in bacteria indicating that this may be an intermediate stage in the oxidation process (Tipping et al. 1984). Conversely the reduction of manganese to Mn(II) by micro-organisms can also be through direct and indirect means and some bacteria are capable of both oxidising and reducing manganese (Gounot 1994). Similarly, iron reduction and oxidation by micro-organisms is not solely through metabolic processes. Reduction by phytoplankton such as Peridinium gatunense is through a by-product of cellular processes as iron is not a micronutrient for this species (Shaked et al. 2002). The oxidation of Mn(II) by micro-organisms to Mn oxides that are deposited on the surface of the bacteria may be a mechanism for utilising larger NOM particles such as humic and fulvic acids. The oxidation of these organics by the manganese oxides, produces low molecular weight (LMW) organics that can be utilised by the bacteria as a substrate for growth (Sunda and Kieber 1994). Natural biofilms are able to remove iron from solution. After four days of biofilm growth in jar tests, soluble Fe(II) and Fe(III) was unable to be detected as all iron appeared to have been converted to solid forms despite the oxidation state (Brown et al. 1999). Although the purpose of this study was to investigate the ability of biofilms to convert iron to new minerals within deposits, the nature of the conversion is that it occurs in an aqueous solution and the formation of coloured precipitates by biofilms demonstrates the potential of biofilms’ contribution to discoloured water. Micro-organisms can also cause the reduction of iron and manganese. Micro-organisms within a biofilm or the bulk water can include species that both oxidise and reduce iron and manganese and can, therefore, contribute to oxidative and reductive processes simultaneously (Brown et al. 1998). Brown (1999) examined the ability of microbes that are found in a natural biofilm to precipitate chelated iron at pH 8.5 due to the reduced solubility of iron at this pH. It was found that iron was rapidly precipitated primarily into Fe(III) colloids by the microbial consortium. However, the presence of iron-reducing bacteria could cause up to 40% of the precipitated iron to be reduced to Fe(II). Reductive biological processes can form minerals from hydrous ferric oxide. The rate of reduction by iron-reducing bacteria, Shewanella putrefaciens, is strongly influenced by the nature of the aqueous media. In a HCO3-buffered medium with anthraquinone-2,6-disulfonate (AQDS), the predominant

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product is siderite (ferrous carbonate), and when phosphate is also present, vivianite (ferrous phosphate) is formed (Fredrickson et al. 1998). Fine-grained magnetite also formed regardless of the presence or absence of phosphorus (Fredrickson et al. 1998). Highly crystalline magnetite was produced when the solution was buffered with 1,4-piperazinediethanesulfonic acid (PIPES) and AQDS was present (Fredrickson et al. 1998). For this medium, when phosphorus was also present, the predominant species formed was green rust (Fredrickson et al. 1998).

2.2.3.3.2 Sloughing of biofilms and the physical contribution of biofilms to discoloured water Biofilm shedding within the distribution system can contribute to discoloured water events. Strains of bacteria that have been identified in dirty water samples have been matched to strains that are found growing in biofilms within the distribution system (Sly et al. 1988). This is a strong indication that the sloughing of biofilm can contribute to, or possibly be the cause of, some discoloured water events. Detachment of biofilms can potentially occur through three different mechanisms. It is possible for biofilms to slough under increased flow conditions, penetration of disinfectant to areas that have had very low or zero chlorine residual or through chemotaxis. Manganese-depositing biofilms that develop during zero chlorine conditions will be removed from the surface once chlorine is again present in the water (Sly et al. 1990). The presence of manganese- depositing micro-organisms in the Gold Coast distribution system was only seen in the section of the distribution system that often had periods of zero chlorine residual and during the periods of no chlorine (Sly et al. 1990). Biofilm shedding in a 1.3 km pipe rig, with MDPE pipe with 1-2% of the surface being exposed or coated iron pipe, was found to be highly non-uniform in the chlorinated system (Maier et al. 2000). In an unchlorinated system, the biofilm shear-off was highest at the start of the system and the use of monochloramine reduced the net biofilm shear-off (Maier et al. 2000). Biofilm growth in a disinfected system is unlikely to occur near the treatment plant due to the higher disinfectant residual. Dixon (1989) found that, in the distribution system on the Gold Coast, detachment of deposits could occur through two different mechanisms. Increased flow rates at close proximity to the treatment plant will cause scouring of inorganic manganese coatings (Dixon et al. 1989). This phenomenon was associated with changes in water demand from low overnight to high daytime usage. Detachment of manganese-depositing biofilm would occur when increased residual chlorine reached an area of the distribution system that previously lacked sufficient chlorine to control biofilm formation (Dixon et al. 1989). The presence or absence of large numbers of budding hyphal bacteria in discoloured water samples will indicate whether the source of discoloured water is through scouring of deposits (low or absent) or through sloughing of biofilm (high) (Dixon et al. 1989). Sly (1988) identified the same strains of bacteria in dirty water samples as those that were found growing in biofilms within the distribution system, indicating that the sloughing of biofilm off the pipe wall may have been the cause of discoloured water events for this system. Correct identification of the manganese-oxidising bacteria, Pedomicrobium manganicum, is important in assessing the potential of biofilms to cause discoloured water, as Hyphomicrobia bacteria are morphologically similar. Lu (1995) has developed a two-dimensional transport model accounting for simultaneous transport of substrates, disinfectants and micro-organisms in both the bulk liquid phase and within the biofilm. Results showed that the larger the fluid shear when under turbulent flow conditions, the higher the bulk biomass concentration. Pipe material will also impact the water quality based on increases in disinfectant consumption by the pipe wall. In a turbulent flow, a higher radial diffusion rate can have a beneficial or deleterious effect depending on the relative magnitude of both the nutrient and disinfectants (Lu et al. 1995) In a bioreactor, the oxidation of Fe2+ by Thiobacillus ferrooxidans was found to be limited by the presence of dissolved oxygen (Mazuelos et al. 2000). It was also suggested that in regions of low iron concentrations within the reactor, part of the biofilm formed would detach through the process of chemotaxis (the movement of an organism along a chemical gradient) (Mazuelos et al. 2000).

2.2.3.3.3 Microbially mediated corrosion The presence of micro-organisms on the pipe surface can cause corrosion to occur. Lee (1980) found that, although the main factor controlling corrosion in a pipe loop experiment was DO, micro- organisms were responsible for localised tubercule formation. However, the contribution of micro- organisms to the corrosion process increased with exposure time, and the impact was thought to

55 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

relate to the consortium of microbes present. The presence of isolated individual species did not produce corrosion rates that were different from those in sterile water controls. Corrosion can occur through microbially-mediated processes. In a cooling system where the water was treated with both chorine (free chlorine residual 0.4-0.8 ppm) and orthophosphate, the presence of both iron bacteria (Leptothrix sp.) and sulphate reducing bacteria (Desulfovibrio sp.) was thought to be responsible for the corrosion within the system (Rao et al. 2000). Corrosion rates ranged from 3 to 13.5 mpy for coupons exposed to water with bacteria as compared to 1.75 ± 0.62 mpy under sterile conditions (Rao et al. 2000). Extensive tuberculation of carbon steel coupons was noted and SEM pictures showed the presence of ensheathed filamentous iron bacteria that were encrusted with iron, mainly in the form of iron oxides and hydroxides. Sulphate reducing bacteria were found to cause pitting in concentric ring formations. Sediments within the system consisted of 40% w/w iron with silica (24%), organic content (16%), phosphate (10%), calcium (9.4%) being the other major constituents (Rao et al. 2000). Phase analysis of the corrosion products found that γ-Fe2O3, Fe2PO5, FePS3, Fe(PO3)3 and BaFeO3 – x were the compounds present on the pipe wall (Rao et al. 2000). 2.2.4 Operational procedures to manage discoloured water

After treatment, the mitigation measures for the development of dirty water events are focussed on the design and maintenance of the distribution system. The design of the distribution system plays a major role in the transport of particles that cause discoloured water. The particles that reach customers’ taps can be reduced by careful maintenance of pipes and advanced cleaning procedures. Part one of this section (2.2.4.1) summarises the cleaning methods that can be used in the removal of particles and material adhered to the pipe walls, while part two (2.2.4.2) focuses on the design technologies that can be employed to create favourable hydraulics. 2.2.4.1 Cleaning Water utilities use various cleaning methods for removing particles that accumulate within the distribution system. These techniques are capable (to different extents) of removing biological and chemical films, sediments and corrosion scales, and include: • flushing • air scouring and • swabbing (or pigging). This section discusses these three cleaning procedures and precautions that need to be taken whilst employing these methods.

2.2.4.1.1 Flushing Flushing involves increasing the water flow velocity to above the threshold level required to resuspend and carry sediment along the pipe. Flushing also has the added advantage of removing stagnant water and restoring disinfectant residuals (Kirmeyer et al.). There are three flushing techniques available, namely: • Conventional flushing • Unidirectional flushing and • Continuous blow off. Conventional flushing involves opening hydrants in a selected area until water quality criteria are met (Kirmeyer et al.). While this method is simpler and less planning is necessary, compared with unidirectional flushing, it can often cause water quality problems rather than solving them. Valve (and therefore main) isolation is not practised, meaning lower flushing velocities may occur. Velocities slower than the required threshold tend to loosen attached particles rather than remove them and may lead to increased customer complaints during and after flushing (Friedman et al. 2002). Unidirectional flushing (UDF) is a refinement of conventional flushing that uses controlled manipulation of hydrants and valves to systematically flush areas of the distribution system. It requires more preparation and aims to maximise the flow velocity by isolating mains being flushed. These flow velocities are usually kept between 1.5 and 2.1 m/s (Antoun et al. 1999; Smith 2001; Friedman et al. 2002) to ensure movement of the particles. An advantage of this method over conventional flushing is that an estimated 40% less water is used (Friedman et al. 2002). Continuous blow off refers to the bleeding of water from oversized water mains or dead ends in order to help restore disinfectant residuals and reduce water age (Antoun et al. 1999). Typical velocities are

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less than 0.3m/s which is not capable of removing sediments (Antoun et al. 1999). This practice has the disadvantage of using large quantities of water without solving the cause of the water quality problem (Friedman et al. 2002). The few limitations of flushing listed below are generally outweighed by the many water quality improvements experienced if a good flushing plan is implemented. Limitations of flushing include: • pipes made of cast iron are difficult or impossible to scour • the pipe’s water-carrying capacity • wastage and discharge of flushing water (Slaats 2001) Barbeau et al. (1999) found an average decrease in long term turbidity and iron concentrations before and after flushing of a dead end site in a Canadian distribution system. Unfortunately, the same trend was not seen for the other site sampled or bacterial counts at the sites. This led the authors to suggest that flushing frequencies are site-specific, depending on the water quality problem (Barbeau et al. 1999).

2.2.4.1.2 Air scouring Air scouring involves the introduction of compressed air into the pipe at the same time as flushing is being carried out, increasing the cleaning effect (Slaats 2001). Studies on air scouring have found a number of disadvantages that may not be compensated by the enhanced cleaning (Slaats 2001): • with the introduction of air comes an increased risk of contamination, and extensive filtration is needed • the cleaning effect is limited to pipe diameters smaller than 250mm • there is a risk of accelerating corrosion • air has to be removed from the pipe usually requiring subsequent flushing • the cleaning effect on long pipes is reduced due to air and water separation (Slaats 2001). Industry experience indicates that air scouring uses approximately 40% less water than flushing (Kitney et al. 2001).

2.2.4.1.3 Pigging Pigging (or swabbing) is the physical removal of particles by the introduction of a pig around the same diameter as the pipe. This technique is also more effective than flushing at removing chemical and biological films and scales, but has a number of disadvantages: • it introduces a risk of contamination (pigs wear out etc) • it can not be used in some sections of corroded cast iron • the length to be swabbed may be limited by butterfly valves • it is relatively expensive • subsequent flushing still necessary (Slaats 2001). 2.2.4.2 Hydraulics Flow patterns within the distribution system can also influence the accumulation and release of discoloured water particles (Smith et al. 1997). Areas of high flow can abrade mains and mobilise deposits, while low or no flow areas act as sinks where deposits build up (Smith et al. 1997). A field survey by Smith et al. (1997) of the degree of corrosion in mains and dead ends found that hydraulic regime played more of a role in the formation of tubercules (deposits formed by corrosion) than the source water quality. Complementing this was a laboratory study using a pipe rig that showed an increase in dirty water events after periods of stagnation (Smith et al. 1998). The design of water mains is, therefore, important for the prevention of dirty water. Dead ends should be avoided and mains should not be too large so that water age is minimised. The dirty water team at Brisbane Water found that customers living in cul-de-sacs were twice as likely to make a dirty water complaint as other residents (Devlin 2003). Similar trends have been noted in other water utilities. For example, Sydney Water found that lower areas tend to accumulate more particulate matter and, therefore, dirty water complaints (Sydney Water Representatives 2003).

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2.3 Post Distribution Causes of Discoloured Water

Although the formation of the most common types of discoloured water occur within the distribution system and are then released at the customer’s tap, there are a few processes that occur post- distribution. The first is the corrosion of copper pipes and fixtures within the house, while the second is the staining of laundry. 2.3.1 Copper corrosion at customers taps

Copper pipes are used for both cold and warm water plumbing in domestic houses. The presence of copper in the water results in blue staining of porcelain fixtures. Green/blue stains can appear on household fittings from water with low copper concentrations (1mg/L) (Twort et al. 2000). The three sources of copper in consumers’ water are natural trace dissolved copper, copper dissolved from corrosion of copper piping and addition of copper salts in reservoirs for algal control (Cruse 1971). The concentration of copper in raw waters and the removal of copper in raw water is not a problem that is discussed in the literature; rather it is the corrosion of copper plumbing at the consumers’ house that has been associated with discoloured water events. 2.3.1.1 Effect of pH and alkalinity The main equilibria relevant to copper corrosion and corrosion by-product deposition are described by Pehkonen (2002): + 2+ - HOCl + H + Cu(s) ↔ Cu + Cl + H2O - + 2+ - OCl + 2H + Cu(s) ↔ Cu Cl H2O 2+ Cu + ½O2 ↔ CuO(s) Propagation of blue water is not a common problem. However, at high pH, copper corrosion causes the formation of particulate copper that is visible as a blue discolouration (Edwards et al. 2000). Soluble copper can also cause blue staining of porcelain fixtures. Copper is more soluble when the pH is below 7, and elevation of pH to around 7.2 by addition of lime has been found to reduce customer complaints of blue staining due to decreased solubility (Shull 1980). As the presence of copper in water is associated with dissolution from pipes, it is the corrosivity of the water that governs the potential of copper to cause discolouration. The more acidic the water, the greater the potential for copper corrosion. However, a confounding factor in reducing the corrosivity of water towards copper is that conditions of high pH and low alkalinity, that will reduce copper corrosion, can increase iron corrosion (Broo et al. 1997). Generally, increased alkalinity will result in an increase of copper released from pipes. Addition of sodium bicarbonate (up to 80 mg/L) caused more pronounced staining on porcelain dishes (Shull 1980). Edwards (1996) found that in a test system with synthetic water, that was adjusted with CO2 and NaHCO3 for pH and alkalinity and an inert electrolyte (NaClO4) for ionic strength, copper corrosion by-product release was a positive linear function of alkalinity at both pH 7 and pH 8. It was also suggested that 95% of the copper released was soluble, as it passed through a 0.2 µm pore sized filter membrane (Edwards et al. 1996), although it is possible colloidal particles could pass through this size. Figure 2.14 shows that Edwards’ (1996) analysis of data from operating water utilities also demonstrated an increase in copper release with increased alkalinity.

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Figure 2.14: Data from water utilities in the USA, demonstrating the adverse effect of higher alkalinity on copper release, especially for waters with low pH (Edwards et al. 1996).

Although alkalinity can have a strongly adverse effect on copper release, the effect appears to not be as strong for older pipes (Figure 2.15). This is probably due to the formation of an insoluble malachite scale (Cu2CO3(OH)2), which occurs during exposure to high alkalinity waters (Edwards et al. 2002).

Figure 2.15: Differences in the effect of alkalinity on copper release for pipes of different age (Edwards et al. 2002).

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2.3.1.2 Corrosion types There are three recognised types of abiotic pitting corrosion that occurs in copper pipes, which are briefly described by Korshin (1996) as follows: • Type 1 is pitting that occurs at neutral pH in waters that are cold and have a high mineral content; • Type 2 occurs in neutral and slightly acidic waters when the water is hot and has a low mineral content. • Type 3 occurs in water that is slightly alkaline and has low inorganic salt concentrations. Although the type of pitting is generally associated with the water quality, there have been incidences of both type 1 and type 2 pitting occurring within the one system and this has been termed type 1½ pitting (Bremer et al. 2001). 2.3.1.3 Microbial influenced corrosion Despite copper being toxic to many organisms, there are some micro-organisms that are tolerant to copper and that can be found in copper pipes (Wagner and Chamberlain 1997). The contribution of these micro-organisms to the corrosion process is termed microbially influenced corrosion (MIC) and generally causes pitting of the metal surface. MIC has a greater effect in large-scale copper plumbing (e.g. hospitals) than it does in domestic plumbing (Wagner and Chamberlain 1997). Heterogeneous biofilms are most likely to cause MIC as bulk water micro-organisms are unlikely to create a strong enough localised change in water chemistry. Dense biofilms can lead to corrosion inhibition under aerobic conditions through competition for oxygen (Wagner and Chamberlain 1997). Bremer (2001) suggests three possible mechanism by which biofilms increase copper release: (i) the production of acidic metabolites by the bacteria directly on the surface of the copper; (ii) an ability of extracellular polymeric substances (EPS) produced by the bacteria to bind copper; and (iii) an alteration of the porosity and nature of the surface oxide film through the incorporation of bacterial cells and excreted polymers. 2.3.1.4 Treatment The addition of phosphates and silicates as sequestering agents and corrosion inhibitors has already been discussed in section 2.1.2.6 in relation to iron pipes and the formation of red water. Similarly, phosphates and silicates have also been used to reduce copper corrosion. Becker (2002) found that the effectiveness of phosphate was greater than that of silicate (SiO2) in reducing the concentration of copper released from pipes in a test rig (Figure 2.16). In these experiments the phosphate was a mixture comprising of 70% orthophosphate and 30% polyphosphate. Addition of bimetallic phosphate (phosphates incorporating two types of metals in the structure) at pH 7.3 results in a decrease in the extent of staining (more so than the effect of increasing pH) (Shull 1980). Although the addition of phosphates will reduce the release of copper in the short term due to the formation of cupric phosphate scale, there is evidence that in the long term the formation of cupric phosphate scale will inhibit the formation of the even less soluble malachite, which naturally forms in the absence of phosphates (Edwards et al. 2002).

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a)

b)

Figure 2.16: a) Effect of adding phosphate (PO4) on the concentration of copper released from test system. b) Effect of adding silicate (SiO2) on the concentration of copper released from test system. Exposure time on the x-axis represents the stagnation time. Tests were run over 200 days and the reference data is for no silicate or phosphate addition (Becker 2002).

2.3.2 Dirty washing

There has been little research published on the processes that cause the formation of discoloured washing. It is commonly known that iron at levels above 0.3 mg/L stains laundry and plumbing fixtures (World Health Organization 1993-1998). Similarly, other metals such as manganese and copper have a role in staining and discolouration. Many water utilities provide a service of cleaning stained garments. However, the mechanism of stain formation is not reported in the published literature. Waite et al. (1989) examined stains on garments using two techniques. Using proton-induced x-ray emission spectrometry (PIXE), a stained shirt washed with water from Avon Dam was found to have 4- 5 times higher iron and manganese content within the stain than on other areas of the shirt (as well as sulphur, chloride, copper and zinc) (Waite et al. 1989). A stained singlet, that had been washed with water from Woronora Dam, had manganese concentrations 16 times higher and 10 times higher iron

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concentrations on the stained area than on the unstained area, with other elements showing no significant difference in concentration (Waite et al. 1989). Use of scanning electron microscopy with elemental analysis by X-ray emission (SEM/EDX) to visually analyse particles on clothing indicated that the stained garment from the Avon system had particles rich in silicon and aluminium with limited amounts of iron and manganese (Waite et al. 1989). Similarly, the garment from Woronora also had particles with high aluminium and silicon, however, they were also rich in iron and manganese. The authors suggest that the particles may therefore be aluminosilicate clays coated with iron and manganese oxyhydroxides (Waite et al. 1989). The impact of washing machine type on dirty washing formation has also been studied (Goh and Judd 1995). Top-loading machines were five times more likely to produce dirty washing than front-loading machines. The trial was based on a test group of 40 families. Half used top-loaders while the other half used front-loaders (phase I), and then half way through the trial the families swapped over to using the other type of machine (phase II). Four different, unidentified types of material were used for the study. Front-loading machines experienced dirty washing 1.4-7.4% of the time, depending on the material and phase, while top-loading machines produced dirty washing problems in 11.0-36.2% of washes. There was a notable reduction in dirty washing complaints between the two phases (i.e. when half way through the trial the participants switched machines), which was suggested to be due to an improvement in water quality. However, water quality was not actually analysed during the study, so this is speculative. The mechanism of dirty washing or a definition of dirty washing was also beyond the scope of the report (Goh and Judd 1995).

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2.4 Prediction of Dirty Water Events

The difficulty of directly measuring water quality within distribution systems also makes it difficult to predict when discoloured water events are likely to occur. Discoloured water events have been shown to involve resuspension of particulate matter, the scouring of inorganic deposits and/or the sloughing of biofilm from pipe walls. It is likely that these events will occur during periods of peak demand and high flow, but they will also depend on properties of the deposits and biofilms that are not predictable. The build up of such deposits and biofilms, within the distribution system, can occur gradually over time until a critical threshold is reached that makes the material susceptible to release during the next high flow event. A decrease in the iron and manganese levels that enters the distribution system will simply prolong the time between such discoloured water events. To be able to predict discoloured water events it is necessary to understand how material is being accumulated within the system, and at what point does this accumulation become great enough that changes in system hydraulics will result in the release of material that causes discoloured water at customers’ taps. Discoloured water events cannot be detected at the treatment plant unless they involve particles entering the system due to filter break-through. The detection of discoloured water events is therefore in the hands of the consumer. The lodgement of complaints can be used to trigger an assessment of the discoloured water event to determine the extent and primary cause of production of the discoloured water. Post-event assessment is beneficial in instigating remedial action, however preventative methods are much more desirable and the knowledge on monitoring for potential events and predicting discoloured water will be discussed below. 2.4.1 Monitoring discoloured water

Analysis of complaints should start with a look at the location of the complaints to combine with the information of origin of water, flow direction and pipe material to select sampling points. KIWA in the Netherlands uses a continuous flow device to measure oxygen, temperature, turbidity, pH, redox potential, conductivity and pressure. Additional samples are taken by hand or automatic water sampler for analysis of iron, manganese, bacteria etc. (Hulsmann et al. 1986). The period of continuous monitoring needed to make an assessment of water quality is deemed to be two weeks as it is thought that monitoring for longer than this amount of time will generally not provide any significant extra information (Hulsmann et al. 1986). All investigations start with monitoring at the point where the water leaves the pumping station. Selection of other sampling sites is based on frequency of complaints, accessibility and flow direction. 2.4.2 Modelling research

There is no universal model that takes into account particles that enter the distribution system, oxidation and corrosion processes that occur within the distribution system and biofilm development to describe discoloured water propagation. There has been some model development for specific processes that occur within the distribution system that are relevant to the production of discoloured water. Modelling of general oxidation processes has not been attempted for distribution systems. However, equations to describe both the oxidation of iron and manganese have developed both in the context of oxidation by oxygen and by oxidants used in treatment processes, as discussed below. Oxidation models generally ignore the effects of the presence of organic matter which may be important for processes in distribution systems, especially for iron as the dissolved fraction may be largely associated with organic matter. 2.4.2.1 Modelling oxidation rates The role of chemical oxidation of reduced forms of manganese and iron may be significant for distribution systems that are not greatly affected by biofilms and corrosion processes, which have a greater impact on water quality deterioration. The rate of oxidation for manganese and iron under natural environment conditions is known to differ due to the more stable nature of reduced forms of manganese, and the importance of manganese oxidation is of particular interest during water treatment. Models of manganese oxidation have been developed that include the oxidant concentration, whereas iron oxidation models are of a more general nature. Caution is required when applying rates of reaction based on synthetic water, as the composition of the water, including NOM, will influence the rate of oxidation.

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2.4.2.1.1 Iron oxidation The oxidation rate of iron is pH dependent. In the pH range of 6-8 the rate equation determined by Millero (1985) abides by the following relationship: + + 2 –d ln [Fe(II)]/dt = k1β1αFe/[H ] + k2β2αFe/[H ] where k1 and k2 are the pseudo first order rate constants, β1 and β2 are the hydrolysis constants for + 0 2+ Fe(OH) and Fe(OH) . The value of αFe is the fraction of free Fe . -1 5 -1 In natural water k1 is 1.7 min and k2 is 4.3 x 10 min . At pH greater than 7, the products of the oxidation reaction appear to catalyse aqueous Fe(II) disappearance (Sung and Morgan 1980), increasing the rate of oxidation. When using a previously derived rate law: - 2 -d[Fe(II)]/dt=k[OH ] PO2[Fe(II)] where k is the rate constant (units: M-2 atm-1 min-1), [OH-] is the concentration of hydroxyl ions, and [Fe(II)] is the concentration of total ferrous iron. Sung (1980) found that iron oxidation followed this relationship when the pH was below 7. However, autocatalysis was noted at pH higher than 7, thus changing the relationship.

2.4.2.1.2 Manganese oxidation Manganese also demonstrates autocatalytic behaviour. Modelling indicates that Mn(II) is removed through oxidation and adsorption onto MnOx(s) and is, therefore, partially a function of MnOx concentration as well as pH, oxidant type and dose (Knocke et al. 1991). Oxidation experiments by Van Benschoten (1989) also demonstrated the autocatalytic nature of Mn(II) oxidation. Higher initial Mn(II) concentrations produced faster reaction rates, indicating that oxidation is not the sole mechanism for Mn(II) removal, with Mn being removed by both oxidation and adsorption. This autocatalytic mechanism becomes more important when both pH and temperature are low (Van Benschoten et al. 1989). Mn(II) oxidation was found to be a first order reaction with respect to both Mn(II) and oxidant concentration (Knocke et al. 1991). Modelling of Mn(II) oxidation has, therefore, been developed to account for the two different removal processes of adsorption and oxidation. Manganese oxidation models have also been created to assess the removal of soluble manganese from solution during the oxidation stage of treatment (Van Benschoten et al. 1989). Van Benschoten (1989), developed a model that assumes that adsorption is always rate limiting, though this may not be true. However an alternate model that allowed either adsorption or oxidant concentration to be rate limiting produced comparable results with the original model. With no significant improvement from the second more complicated model, the first model was preferred (Van Benschoten et al. 1989). The general equation of the model is: 2+ 2+ a b - c 2+ 2+ -d[Mn ]/ dt = k1[Mn ] [OX] [OH ] + k2[Mn – Mn o][MnOx] 2+ where OX = oxidant concentration and Mn o is included to reduce the rate of adsorption to 0 when 2+ 2+ Mn o = Mn . Oxidation model developed by Knocke (1991) also accounts for the processes of direct oxidation and the autocatalytic process from Mn(II) adsorption onto MnOx by having two rate constants. The general equation developed was: a b c -d[Mn(II)]/ dt = k1[Mn(II)] [OX] [OH-] + k2[Mn(II) - Mne(II)][MnOx] where OX is the oxidant concentration (either KMnO4 or ClO2). Mne(II) is included to reduce the rate of adsorption to zero when Mn(II) = Mne(II). The term Mne(II) reflects that as oxidant is exhausted, adsorbed Mn can no longer be oxidised on the surface. The model, as written, does not account for organic matter in water, which is likely to affect the rate of oxidation due to complexation interactions with manganese and, more commonly, iron.

2.4.2.2 Disinfectant residual One aspect of the oxidation of iron within the distribution system, which has been investigated, is the interaction with disinfectants. Reactions occur between reduced iron and disinfectants that, once in the distribution system, are problematic as the end result is a loss of disinfectant residual and the oxidation of reduced soluble iron contributing to the formation of particles and coatings.

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The influence that the pipe wall has on chlorine decay rate will differ depending on the type of pipe material present. Unlined iron pipes are reactive and the limiting factor for chlorine decay by the pipe is the transfer of chlorine to the pipe wall as opposed to the actual reactivity of the pipe as seen in PVC, MDPE and cement-lined pipes (Hallam et al. 2002). The higher wall decay for cast iron pipes is probably due to the oxidation of pipe wall iron by the chlorine. Reactions between monochloramine and Fe(II) have been studied by Vikesland (2000). The residence time of treated water is considered to be long enough to make reactions between the two constituents, significant for both the loss of disinfectant residual and the propagation of discoloured water. Some of the trends found, included that at increasing pH the removal of Fe(II) from solution occurred more rapidly when monochloramine was present, though negligible Fe(II) removal occurred when monochloramine was absent in deionised water, as Figure 2.17 below shows. The formation of ferric oxide precipitates were also able to catalyse the oxidation of Fe(II) by monochloramine similarly to oxygen.

Figure 2.17: Iron oxidation rates in the presence and absence of monochloramine for four different pH values. [NH2Cl]0 = 0.704 mM [Fe(II)]0 = 0.179 mM, μ = 0.1 M, CT,CO3 = 0.006 M, DO < 1 mg/L, 25 °C (Vikesland et al. 2001).

Vikesland and Valentine (2002), have created a model that accounts for both aqueous phase reactions and surface-catalysed reactions to describe the oxidation of Fe(II) by monochloramine:

d[Fe(II)tot ] − −1 − − = Θ(k NH Clsoln [OH ] + k NH Cl,surf1K sorb1K w [> FeOH][OH ] + dt 2 2 k K K −1[> FeOH][OH− ]2 )[Fe(II) ][NH Cl] NH2Cl,surf2 sorb1 w soln 2

14.00 where Kw is the hydrolysis equation constant for water (=10 ) and [>FeOH] = α[Fe(III)]. α is a proportionality constant that correlates the number of surface sites to the total amount of Fe(III). Table 2.8 (below) shows the kinetic expressions for iron and monochloromine.

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Table 2.8: Kinetic Expressions and Model Parameters Describing Iron Oxidation and Monochloramine Reduction (Vikesland and Valentine 2002).

Chlorine decay models have been developed to try and determine the persistence of residual chlorine in the distribution system. Some researchers have developed models that are general models, while others have developed models for specific interactions with pipe wall. Beatty et al. (1995) have utilised transformation function and curve fitting algorithms to model chlorine decay that also accounts for diurnal changes in chlorine decay constant by utilising an average k factor. The authors report that it can accurately predict changes in rate of chlorine decay utilising water chemistry factors and distribution environment factors. However they also stipulate that algorithms should be developed on a site-by-site basis until there is enough data to generate a global algorithm. The decay of disinfectant materials in the distribution system can lead to the formation of biofilms which (as described in Section 2.2.3) can also lead to discoloured water formation. 2.4.2.3 Biofilm and bulk water bacteria There are a number of models developed to describe different aspects of biofilm growth and bulk water bacteria dynamics. Dukan et al. (1996) has developed a dynamic model that, coupled with Piccolo hydraulic modelling software, can be used for predictive mapping of sections of a distribution system. The model has a high degree of complexity and takes into account various major parameters such as biological dissolved organic carbon (BDOC), residual chlorine, pH, temperature and hydraulic conditions. Equations have been developed to describe aspects such as free bacteria concentration, active free bacteria concentration, mass balance in chlorinated or non-chlorinated biofilm, fixed bacteria balance equation, chlorine disappearance kinetics and mortality of free or fixed bacteria (Maier 2000; Lu et al. 1995). Maier (2000) has developed a parametric model of transient particle counts after a step increase in flow. The model is related to biofilm shedding rather than to oxidation or corrosion processes. The limitations of the model are the requirement for a step increase of flow rather than a steady increase. Lu et al. (1995) have described the simultaneous transport of substrates, disinfectants and micro- organisms as a mathematical model that utilises mass balance equations for organic substrates, ammonium, nitrogen, oxidised nitrogen, dissolved oxygen, alkalinity, biomass and disinfectants. The two-dimensional transport model is used to describe inputs that affect biofilm formation and thickness and the outputs that cause a release in biofilm thickness. The model is tested for both laminar and turbulent flow conditions and demonstrates the importance of fluid shear, pipe material and radial diffusion rate on the biofilm growth and release of biofilm.

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2.4.2.4 Contaminant modelling An algorithm to predict contaminant concentrations within the distribution system, as a dynamic model, has been developed by Boulos (1994). The model is supposed to be less sensitive, than previous models, to the structure of the network and to the length of the simulation and is a computer-orientated methodology. The output of the model is based on predicting contaminant concentrations at different ‘nodes’ in the distribution system (Boulos et al. 1994). 2.4.2.5 Simulated distribution systems Simulated distribution systems have been used to help increase the understanding of changes in water quality throughout the distribution system. These systems allow for controlled manipulations of water flow, pipe material and treatment processes to simulate different conditions. This allows for direct comparisons of different treatment methodologies as the system can be kept the same for different treatment programs without the concern of delivering water of undesirable quality to the consumer. Clark (1994) used a pipe loop rig to monitor the differences in pre- and post-treatment water quality, after different treatments, as well as changes in water quality as the water passed through the system. The simulated distribution network consisted of three pipe loops that were 10 cm in diameter and 31 metres in length each of cement lined cast iron pipe. Twenty-one sampling devices were used to monitor water quality changes and biofilm growth throughout the system. Notable results of the experiment included an increase in iron concentrations in the first two loops that indicated the occurrence of corrosion followed by a decrease by pipe loop three indicating depositional processes were occurring. The size of particles also increased in the pipe loops, with 0.5% of total particles initially being >10 µm increasing to 4% by the third pipe loop. Biofilm growth increased progressively through the loops, with a great increase after disinfectant residual fell to zero. DOC was also seen to decrease, indicating utilisation for heterotrophic microbial growth. These results indicate how much information about behaviour within the distribution system can be gained from utilising pipe loop systems. Experimental set ups allow for easier monitoring and thus allow for more time to be spent on analysing a greater range of parameters within set conditions. It also enables manipulations of hydraulic changes such as flow rate and residence time that can be difficult to measure and quantify in real distribution systems. Pipe loop systems are particularly useful for investigating corrosion processes as coupons can be placed within the pipes that are easily removed for analysis as opposed to removing sections of pipe. Lee (1980) used a simulated distribution system to investigate the contribution of microbial processes on corrosion. A decrease in DO and an increase in dissolved iron indicated corrosion processes. The DO consumption after 2 days in the cast iron pipes was 86% and was 20% in the PVC pipe. Coupons were used to compare tuberculation between sterilised and unsterilised water, the results of which demonstrated the contribution of microbes on localised tubercule formation and therefore corrosion enhancement. Beckett (1998) expanded on this concept by developing a pipe loop layout that incorporates pipes taken from real distribution systems to analyse the progression of corrosion processes that occur in existing, aged pipes. Some research points to the potential of different corrosion products to protect against corrosion due to their lower reactivity and solubility. Siderite (FeCO3) production is thought to be a compound involved in protective scales and, as such, conditions that enhance siderite formation may be beneficial in reducing corrosion. The conditions that promote siderite formation have been investigated by Sontheimer (1981) and a model of water conditions that produce corrosion resistant scales. Sander (1996) proposed a surface complex model to describe iron corrosion within drinking water distribution systems. The corrosion rate was found to decrease linearly with the logarithm of free carbon dioxide and when total carbonate is low, calcium forms part of the surface complex interactions. A protective scale is, therefore, formed to reduce iron corrosion.

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2.4.3 Predictive tests

There are only a few methods that have been developed for predicting discoloured water events, which are based on relating consumer complaints data to problem areas (Slaats 2001). Simple methods of predicting discoloured water events include: measuring soluble manganese entering the distribution system; and predicting changes in consumer demand that will provide the necessary change in hydraulic conditions to resuspend particulate matter that has accumulated within the pipes. Sly et al. (1989) found that consumer complaints occurred when levels of manganese over 0.05 mg/L were present. These were not eliminated until levels were continuously below 0.02 mg/L for 2-3 days. By monitoring the system, they were able to determine the threshold concentrations that assisted in the prediction of discoloured water events. There are a number of methods for monitoring discoloured water that utilise the measurement of turbidity, following a created disturbance, to simulate high water flow events. Measuring turbidity at different intervals along a pipe during normal flow can indicate if sediment settling is occurring or if resuspension is occurring (Slaats 2001). Measuring in different areas can indicate the relative fouling within the distribution system and can be used in conjunction with customer complaints to determine priority areas to clean. Repeating measurements in the same location can indicate the rate of fouling of the distribution area. Slaats (2001) has also established an index to allow measurements of turbidity using different turbidity meters that are used in the Netherlands to be directly compared. Dutch water companies use the Resuspension Potential Method (RPM) to measure the capability of the sediment in a network to resuspend and create visually noticeable turbidity levels (Vreeburg et al. 2004). The pipe, for which the discolouration risk is assessed, needs to be isolated by closing the valves that connect other feeding pipes (Vreeburg et al. 2004). The length of isolated pipe should be at least 315 meters (0.35 m/s for 15 minutes), to allow only water to be drawn from the monitored pipe. By opening a fire hydrant, the velocity in the pipe is increased to 0.35 m/s above of the base flow velocity (Vreeburg et al. 2004). The higher velocity is maintained for fifteen minutes, and turbidity is measured during this time. After fifteen minutes, the hydrant is closed to allow normal flow and the turbidity is monitored until it drops to the initial level, or for 1 hour (Vreeburg et al. 2004). The RPM was developed for smaller water mains ranging from 80 to 200 mm internal diameter (Vreeburg et al. 2004). The internal diameter determines the flow needed to gain the required velocity of .35m/s. The flow ranges from 1.76 L/s (6.3 m3/h) for an 80 mm pipe to 11.0 L/s (40 m3/h) for a 200 mm pipe. These velocities are much lower than those generally used in cleaning mains where the flushing velocity can be as high as 25 L/s (pers. comm. Aust. water utilities).

The advantages of using turbidity as an aid for predicting discoloured water is that it is a single type of measurement that is taken after simulation of the conditions that lead to the elution of material from within the pipe. The disadvantages are that it is a disruptive method that requires tap-in points and operation of fire hydrants to assess individual sections of pipe. It also provides little information about the mechanism of accumulation and can only be used for short-term assessment of the risk of discoloured water. Any changes in treatment process or source water quality that will impact on distribution system chemistry and biological growth will change the rate of accumulation which means reassessment is required.

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2.5 Identification of Gaps in Knowledge

2.5.1 Pre-Distribution processes that influence discoloured water formation

• There is a lot more information on pre-distribution processes that affect discoloured water formation than that available for processes that occur within the distribution system and at the customer’s tap. Obviously the information on elements in raw water is not always related to discoloured water, nevertheless fundamental studies can provide useful information relating to reactions in water storages. The treatment processes that can be used to mitigate discoloured water-causing conditions have long been studied and are constantly being developed, leading to the vast amount of information existing, on the topic. 2.5.1.1 Chemistry and concentration of elements in raw water • The chemistry and concentration of elements in raw water sources, although not always in the context of discoloured water, has been studied extensively. • The reactions that govern the solubility and concentration of iron and manganese and other elements implicated in the formation of particles in the distribution system, are part of this literature review. • A number of studies characterise the metals in the water into either their dissolved, colloidal or particulate forms. This is sometimes also used to predict the oxidation state based on the assumption that the reduced forms are generally soluble while oxidised forms will be colloidal or particulate. One important exception to this is Fe3+ complexed to organic matter, which is soluble. • Factors that have been investigated include the influence of ionic strength and pH, humic acids vs fulvic acid interactions, complexes that reduce removal efficiency (e.g. complexes with organics, especially humic material reduce removal efficiency by keeping Fe3+ in solution), reactions that consume disinfectant and the sorption of dissolved substances onto particulate substances. • There have been many laboratory-based experiments using natural water that may or may not be relevant to conditions and substances found within the distribution system. These studies generally manipulate particular components of the water composition. Knowledge of whether any substance outside the scope of natural organic substances and disinfectants has a significant role in the formation of discoloured water needs to be assessed before the results of these experiments can be utilised. • An extension on the direct interactions that has been investigated is the adsorption of iron and manganese to particulate organic matter as well as the adsorption of dissolved organics onto iron oxides (on pipe walls). 2.5.1.2 Effect of various treatment processes • There are studies on changes of metals that relate to discoloured water, but to trace discoloured water events from the source is difficult. Studies have investigated changing the point of uptake within the source water to minimise the dissolved metal concentrations that can be altered due to processes such as stratification, aeration and microbial action. • There is a wide body of research on how to limit the introduction of reduced forms of manganese and iron into the distribution system, using specific treatment measures. • Mixing of source waters has briefly been studied in relation to biofilms and particle formation due to the destabilisation of the water chemistry that leads to deterioration in the water quality. More information on this area is needed. • The use of different disinfection procedures and their efficiency and therefore their ability to reduce discoloured water events due to biofilm sloughing, has been the topic of investigation by a number of authors. Due to increased concern of disinfection by-products, alteration of the disinfectant used needs to be evaluated for the possible effect on discoloured water. A few authors have investigated this issue, though more research is needed. • Oxidants and coagulants are commonly used to aid removal of reduced metals, colloidal and particulate matter. This area is well researched. Some researchers have found that oxidants such as hydrogen peroxide and chlorine dioxide are relatively or even completely ineffective in oxidising manganese. Potassium permanganate has been demonstrated to be an effective oxidant however

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care must be taken to optimise the dose, as over dosing of permanganate causes residual manganese to enter the distribution system. Similarly coagulants such as alum and ferric oxide have been demonstrated to be effective in aiding flocculation of particles however the removal of particles must be optimised to minimise residual concentrations of iron and aluminium. • Corrosion control procedures have also been included in this area as they may reduce corrosion but fuel biofilm growth (e.g. addition of phosphates to phosphate limited water). • Different filters and filtration procedures are common in the literature and the most important aspect is the minimisation of filter breakthrough events, which can lead to a slug of increased particulates in the distribution system. Some filters have been found to function more efficiently for the removal of manganese when a biofilm or oxide coating develops on the filter media that is capable of removing manganese from the water column and therefore some filters require a ripening period before working at their optimum. • Sequestering agents have been applied with varying success. The gap in knowledge in this area is the impact of phosphates on biofilm growth. 2.5.2 Processes within the distribution system that influence discoloured water events

2.5.2.1 Corrosion processes leading to discoloured water • There is a lot of work on the types of conditions in distribution systems that lead to internal corrosion of pipes. Some of these are conflicting, for example, the Langlier Saturation Index is not recommended by the American Water Works association for determination of the deposition of protective scales. • There is a lot of research for the development of corrosion resistant scales to minimise iron dissolution into the water, which can contribute to discoloured water events. • There are some studies on the differences in pipe material. Some focus on the ability of biofilms to cling to pipes (e.g. differences in surface tension). Others study the effect of corrosion on discoloured water. Corrosion products have been linked to discoloured water through analysis of particles within the distribution system • Iron is released into the body of water through corrosion processes. Research already conducted in this area has had a strong focus on minimising the corrosivity of water and the development of corrosive resistant scales. 2.5.2.2 Physicochemical processes leading to discoloured water

2.5.2.2.1 Development of chemical films and accumulation of sediments

• Changes in the oxidation state of iron and manganese are generally not specifically studied within the distribution system. However, the literature acknowledges that the changes in oxidation state that contribute to discoloured water usually involve the introduction of reduced forms of metals that can then oxidise and precipitate within the distribution system. Those studies that do assess changes in oxidation state within the distribution system, use pipe loop experiments, which appears to be an expensive method but allows for controlled conditions and many sampling points to track changes in oxidation state.

• Generally, changes in oxidation state that occur within the distribution system are not measured in studies about water quality. However, the oxidation state and relative proportion of iron and manganese, but also other metals, have been measured in flushed sediments, corrosion tubercules and even in biofilms.

• There is a strong background of research on the oxidation state of metals entering the distribution system and the composition of sediments that accumulate in the distribution system. However, changes in oxidation state of metals within distribution networks and the processes that lead to the formation of particles are not well studied as there are many variables such as initial raw water chemistry, changes caused by treatment processes, continuing interactions with disinfectants and

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other added chemicals, changes in dissolved oxygen, interaction with microbes that may facilitate the oxidation of metals within the distribution system.

• There is also a supportive background of general chemistry and raw water chemistry on the changes of oxidation state and speciation of iron and manganese. However more research is needed to understand the processes in the context of the conditions within the distribution system.

2.5.2.2.2 Composition of particles and coatings • Although there are studies on the composition of particles and coatings within the distribution system, comparing between studies is often difficult due to different methods of collection and reporting of results. Mineral analysis of deposits seems to be minimal. • It is fairly common for the major components of sediments to be organic material and iron, with manganese, calcium, silica and aluminium being other major constituents. A few studies have also attempted to determine if iron accumulated in particles is caused by source water input or as a by- product of pipe wall corrosion. This is done by comparing the composition of accumulated sediments to the composition of the water and corrosion tubercules and the presence and absence of budding hypha that is associated with biofilms. There is also research on the flow dynamics of sediment accumulation and biofilm growth.

2.5.2.2.3 The release of Mn or Fe from deposits • Although there are many mechanisms involved in the accumulation of manganese and iron in inorganic deposits, the release mechanisms appear to be either more limited or not as well researched. Resuspension of accumulated particles and the scouring of deposits are primarily controlled by physical processes. The body of research points to changes in flow direction and water velocity as the primary cause for the elution of particles and biofilm from the consumers tap. • There appears to be a gap in the literature on the accumulation and release of manganese and iron that deposits as coatings on pipe walls that are not exposed cast iron. Some studies have compared the concentrations of iron in coatings on steel or cast iron with those of cement lined or PVC. The results indicate that accumulation and release of iron and manganese from coatings on pipes that are not cast iron or steel may still be a process that could contribute to accumulation and remobilisation of iron and manganese in the distribution system. 2.5.2.3 Microbiological processes leading to discoloured water

2.5.2.3.1 Factors leading to the formation of biofilms • There is a wealth of literature on the water quality conditions that lead to the formation of biofilms. The specific biofilms that utilise iron and manganese and contribute to discoloured water, are also well researched.

2.5.2.3.2 Biofilm content • Sly et al. has identified the bacterial species in biofilms (in local systems). Comparisons of different bacterial types internationally have also been studied especially in response to harmful bacteria in distribution systems. • There are a number of studies on the utilisation of metal species by biofilms both in distribution systems and other environments (e.g. cycling in reservoirs or rivers), but it appears to be only a small part of the research in this area. The majority of information on Mn reducing species has been the work of Sly et al. Microscopic techniques have been applied to determine binding sites of iron on bacterial cells. The metal content of precipitate build up with biofilms has also been researched. • The accumulation of iron and manganese by biofilms is only a small component of the larger area of research. Research has been done that identifies manganese and iron oxidising species that are present in distribution systems and some studies look at how iron and manganese is actually accumulated by species that utilise iron and manganese.

2.5.2.3.3 The contribution of microbial processes to discoloured water • Microbial processes in the formation of discoloured water include the deposition of manganese and iron by microbes, the physical presence of biofilm that can be released into the water during

71 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

high flow events, the contribution to bulk water oxidation processes and microbially mediated corrosion processes. • The presence of micro-organisms that utilise manganese and iron has been well documented in distribution systems. The relative contribution of micro-organisms to each of the above-mentioned processes has been covered to different degrees. The contribution of microbial oxidation appears to be more important for manganese than iron due to the more stable nature of reduced manganese and hence is more widely studied. Microbial mediated corrosion processes have more of an impact on the addition of extra iron into the distribution system and hence research on corrosion processes will sometimes cover the contribution of micro-organisms. • Generally there appears to be a lack of synthesis in the different roles micro-organisms can play in the formation of discoloured water and which processes are the most common or significant. • The majority of biofilm research has been conducted into the factors affecting biofilm attachment. Research was conducted either in distribution systems using varying sampling techniques and statistical comparisons or controlled (lab-like) conditions. Statistical comparisons generally have weak conclusions due to the number of confounding factors in this area. Biofilm research in controlled reactors is more expensive but seems to give better correlations between factors. A number of conclusions from these researchers are conflicting and may just be indicative of major differences between local distribution system conditions. 2.5.2.4 Operational procedures to manage discoloured water • While research on cleaning procedures is mainly found in utilities reports and conference proceedings (rather than scientific journals), there is some literature in this area. Generally the results in the literature suggest that cleaning procedures will not supply long-term solutions as build up will reoccur and therefore cost analysis is an important consideration that needs to be investigated for cleaning as a method of pipe remediation. • Consideration of the hydraulics of the system in relation to water quality has only recently been studied. There are some articles on dead ends mains compared to flow through mains and the design of continuous flow mains is advised.

2.5.3 Post-distribution causes

2.5.3.1 Copper corrosion at customers taps • There is some information on the corrosion of copper pipes and the formation of blue coloured water and stains. The effect of alkalinity and pH on the severity of corrosion has been discussed in this review. Corrosion types have also been reviewed. • While the influence of micro-organisms on corrosion of copper pipes has been studied, it is mainly with regard to large scale plumbing systems (e.g. hospitals) rather than individual residences. • There are a number of studies on possible preventative treatment measures (e.g. corrosion inhibitors). 2.5.3.2 Dirty washing • There is very little research in the area of discoloured washing. Only a few articles mention discoloured washing and a couple actually have attempted to study some aspect of the role of water quality on staining of clothing. Discoloured washing is an area of research that represents a large gap in the knowledge.

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2.5.4 Prediction of dirty water events

2.5.4.1 Monitoring discoloured water • Due to the difficulties associated with monitoring discolouration of water online or over time, this area is not large. There is research that use online particle counters etc in an attempt to predict discoloured water events. 2.5.4.2 Modelling research • Mathematical and theoretical models have been developed to help predict oxidation rates, corrosion processes and chlorine decay etc in distribution systems. There is no comprehensive model, however, that combines all aspects of dirty water formation. 2.5.4.3 Predictive tests • The Kiwa report gives three resuspension potential methods involving turbidity measurements and these were deployed in distribution systems in the Netherlands. • The simple ‘rule of thumb’ used by Sly et al is that if manganese levels rise above 0.05 mg/L customer complaints increase.

73 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

3 ASSESSMENT OF INDUSTRY DATA

The Australian water industry data assessment covered a 5-year period from 1997/98 to 2001/02 for eight participating Utilities. There was variation in the level of information provided; therefore analysis was based only on the data made available as well as discussions with the partners. This data included: complaint analysis that focussed on discoloured water and dirty washing as well as the methods of collection, categorisation and reporting; catchment characteristics; treatment processes and disinfection methods; water quality in the distribution systems; and system performance and operations. The Utilities vary greatly in population size, number of connections, kilometres of water mains and source water types. There are both filtered and unfiltered systems, protected and partially protected catchments, chlorinated and chloraminated supplies and different treatment processes. 3.1 Objectives

The objectives of the industry analysis were: • To assess and compare the nature of discoloured water events that customers of various Utilities experience and to compare and evaluate the Utilities’ responses to these events • To determine if there were any similarities or relationships that could be identified within and between the Utilities in terms of water quality versus discoloured water complaints • To establish what gaps exist in knowledge and issues, as well as identify best practices that exist between the Utilities in relation to discoloured water 3.2 Background

3.2.1 Utilities

The eight water utility partners in this project were Sydney Water Corporation (SWC), Hunter Water Corporation (HWC), Power and Water (P&W), Brisbane Water (BW), Water Corporation (WCWA), Yarra Valley Water (YVW), South East Water (SEW) and Gold Coast Water (GCW) (the latter two being part of the review committee). 3.2.1.1 Sydney Water Corporation – New South Wales Sydney Water provides water and wastewater services to approximately 4 million people in the Sydney, Illawarra and Blue Mountains regions with 1.7 million connections. It utilises 20,587 kilometres of water mains, 14 delivery systems, 259 service reservoirs, 146 water-pumping stations and 10 water-filtration plants to provide the services. Sydney Water manages the Cascade, Greaves Creek, Nepean, North Richmond, Orchard Hills and Warragamba water filtration plants. In the larger water supply systems at Woronora, Illawarra, Prospect and Macarthur, Sydney Water commissioned private companies to build, own and operate plants for 25 years. Sydney Water buys water for treatment from the Sydney Catchment Authority, which manages catchments and dams in the in the Sydney, Illawarra, Blue Mountains and Southern Highlands areas. 3.2.1.2 Hunter Water Corporation – New South Wales Hunter Water Corporation provides water and wastewater services in the Lower Hunter region of NSW for Newcastle, Lake Macquarie, Maitland, Cessnock and Port Stephens to a population of 495,000 with around 197,000 connections. There are 5 water-treatment plants, 4,270 kilometres of water mains, 77 service reservoirs and 74 water-pumping stations. Hunter Water draws its water supplies from three major sources (Chichester Dam, Grahamstown Dam and Tomago Sandbeds) and a minor source at Anna Bay Sandbeds. 3.2.1.3 Power and Water - Northern Territory Power and Water is the smallest of the eight Utilities in this project. Darwin River dam was built in 1972 and provides 90% of Darwin’s water supply, whilst McMinns borefield is groundwater that supplements the supply from the dam. A population of 110,000 people with approximately 26,000 connections is serviced. It covers both major and minor centres, as well as remote communities. There are 11 water-pumping stations and 2 storage reservoirs. There are 870 kilometres of reticulation water mains and 280 kilometres of trunk mains.

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3.2.1.4 Brisbane - Queensland Brisbane has 3 water sources which are: Wivenhoe Dam, Somerset Dam and North Pine Dam. There are 3 treatment plants: North Pine, Mt Crosby Eastbank and Mt Crosby Westbank. There are 24 reservoirs, 376,000 properties and 6200 kilometres of water mains. A population of 850,000 is serviced directly and this increases to more than 1.2 million when the customer councils of Redlands, Logan, Gold Coast, Pine Shire, Redcliffe and Ipswich are included. 3.2.1.5 Gold Coast Water - Queensland Gold Coast Water has two catchment areas for raw water, the Hinze Dam and Little Nerang Dam. Treated water also comes from Logan. There are two water purification plants in operation – Mudgeeraba and Molendinar. There are 2,756 kilometres of water mains, 76 reservoirs and 60 water- pumping stations. Gold Coast Water has 197,952 connections, and services a population of 454,084 permanent residents and up to 900,000 temporary residents (vacation) at one time. 3.2.1.6 Water Corporation - Western Australia Water Corporation serves more than 701,000 residential customers and 51,000 business customers in 255 cities, towns and rural areas spread across 2.5 million km2. It operates and maintains 6 water treatment plants, 108 dams and reservoirs and 707 bores in 105 borefields through 29,733 kilometres of water mains. The Perth metropolitan area and Mandurah share a supply system that draws on both surface water (from 9 dams) and groundwater sources. Country areas are largely supplied from rivers, dams or groundwater schemes although, in Denham and Ravensthorpe, water is supplied from small desalination plants. There are two major regional supply networks: the Great Southern Towns Water Supply Scheme and the Goldfields and Agricultural Water Supply Scheme. 3.2.1.7 Yarra Valley Water - Victoria Yarra Valley Water is the largest of Melbourne’s three retail water companies. Established in 1995, its wholesaler is Melbourne Water Corporation. Yarra Valley Water’s Operating Licence covers approximately 4,034 square kilometres across Melbourne’s northern and eastern suburbs and provides water and wastewater services to more than 1.5 million people, with around 593,000 connections. Water supplies are mainly harvested from the catchments of the Upper Yarra and Thomson Reservoirs, with a smaller amount taken from the Maroondah, Yan Yean and Sugarloaf Reservoirs. The water supply system consists of 8,572 kilometres of mains, 36 water reservoirs, 11 elevated water supply tanks and 62 water-pumping stations. 3.2.1.8 South East Water - Victoria With a customer base of more than 1.3 million people in Melbourne’s southeast, this area covers residences and businesses from Port Melbourne to Portsea, and from Port Phillip Bay to Bunyip and Longwarry. The supply and distribution system comprises 7,880 kilometres of water mains, 81 water- pumping stations, 71 water-storage facilities, and 7 disinfection plants. Approximately 541,000 properties are supplied through this system. The water is harvested, stored and treated by the wholesaler – Melbourne Water Corporation. The majority of water is delivered to the service region via two storage reservoirs at Silvan and Cardinia. Sugarloaf reservoir supplies a small proportion of water that is treated at Winneke Treatment Plant. The table below (3.1) summarises the Utilities’ disinfection regimes and catchment characteristics as well as highlighting the filtered and unfiltered systems. Most Utilities favour chlorination as their primary means of disinfection and a majority of systems are filtered. Most catchments are fully protected.

75 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

Table 3.1: Utility Treatment, Disinfection and Catchment Characteristics FILTERED UNFILTERED Chlorinated Chloraminated Chlorinated Chloraminated Sydney Water Corp. Sydney Water Corp.Power & Water South East Water · 8 systems · 6 systems · Silvan Hunter Water Corp.Brisbane Water Hunter Water Corp. Yarra Valley Water · Dungog · Anna Bay · Silvan · Grahamstown · Glovers Hill · Lemon Tree Passage South East Water South East Water · Winneke · Cardinia Yarra Valley Water Yarra Valley Water · Winneke · Cardinia · Yarra Glen · Healesville · Yan Yean Water Corp. Water Corp. · Northern area · Southern Gold Coast

CATCHMENT TYPES FULLY PROTECTED PARTIALLY PROTECTED Brisbane Sydney Water South East Water Hunter Water Yarra Valley Water Gold Coast Power and Water Yarra Valley (minor) Water Corporation

3.2.2 Practices

3.2.2.1 Customer complaint collection and categorisation In all cases, complaints are received by either a call centre or a 24-hour operations centre, where they are logged into a database and a work order is generated where necessary. Each Utility uses a different database. These include OASIS, AOMS, WAMS, Grange, Waterlog, FIS and AIMS. Discoloured water complaints are the predominant complaint type for all the Utilities, usually 80 – 90% of the total. For discoloured water complaints, the initial response by all Utilities is to reactively flush. If the problem is not eliminated, then further investigations are carried out, either at the customer’s end or within the system to determine the cause of the problem. The different categories for water quality customer complaints vary widely, from an extensive list of 23 in YVW, followed by HWC with 14 categories. WCWA has 9, with SEW, P&W and BW all having 8. SWC has only 4 categories and finally GCW has 3. In terms of discoloured water some of the sub- categories include brown, black, yellow, blue/green, white, orange and stained washing. For most Utilities, stained washing makes up less than 5% of the total discoloured water complaints. (For the details of the categories refer to Appendix 1). 3.2.2.2 Customer complaint investigations Initiation of the investigations varies between the Utilities because of the different drivers, resources, commitment to customers and number of complaints. Some Utilities investigate every discoloured water complaint, whilst others will respond at the customer’s request, if they are a high profile

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business or critical customer (such as schools, hospitals) or if they have trigger levels before further work is instigated. For example, as part of GCW HACCP system, investigations are not carried out unless there are more than 6 discoloured complaints in one day in a particular area. Sydney Water provides a rebate to all customers who complain about discoloured water and investigations are carried out on either the customer’s request or if the water quality team determines it to be necessary. If the same customer complains more than 3 times in 3 months, investigations are undertaken to try and determine the cause of the problem and if any further compensation can be justified. At SEW, if there are more than 3 customer calls for the same complaint type in a 2km radius within a 24-hour period, then investigations are carried out. At Water Corporation, because most discoloured complaints are caused by flow disturbances and do not persist beyond a day, the ability to investigate is, therefore, severely constrained. Investigative activity is reserved primarily for other water quality events such as the health issues of microbial activity, taste and odour. 3.2.2.3 Operational and maintenance Discoloured water complaints can be caused by sudden changes in the direction or velocity of water, allowing accumulated particles to resuspend. These changes can be due to operational or maintenance activities such as operating valves, bringing mains back into service after repair, mainbreak, rezoning, capital works or shifts in demand causing flow changes. Water Corporation has a significant number of flow reversals due to changes in demand and blending of ground, surface and sub-artesian waters in spring and winter, leading to the highest discoloured complaint rates in Australia. Power & Water experiences low velocities in the wet season (November to March) resulting in sediment build up, which then predictably cause discoloured water when the population increases in the dry season and, thus, demand increases. The hydraulic processes which result in, or contribute to, discoloured water cannot always be eliminated but can be minimised through better management practices, optimisation of the system and maintaining a high level of skills, knowledge and training of the field crews. All Utilities have reactive flushing programmes in response to discoloured water customer complaints. Prior to the drought and subsequent water restrictions, the planned mains cleaning programmes varied greatly in both the amount of the system cleaned as well as the methods of cleaning. There are no planned mains cleaning programmes in place at present due to the ongoing drought across Australia. Table 3.2 reflects the percentage of the system typically cleaned on a yearly basis, as part of the planned programme, for each of the Utilities. Table 3.2: Mains cleaning Summary Utility Flushing Air Scouring Swabbing Sydney Water 24% 0% 1% Yarra Valley Water 15% 1% <0.5% South East Water 9% 5% <0.5% Power and Water 12% 0% 0% Hunter Water <1% 0% <0.5% Gold Coast Water Ceased 5 years ago Brisbane Water 2 years ago cleaned the entire system except the trunk/feeder mains Water Corporation No program for ~20 years

3.2.2.4 Treatment The treatment processes are many and varied between the Utilities. Of those that use filtration, the methods include direct filtration, conventional filtration, rapid sand filtration and microfiltration. Most Utilities use aluminium sulphate as the main coagulant whilst Sydney Water uses ferric chloride. Other treatment chemicals that are added include fluoride, chlorine, ammonia, lime, potassium permanganate, caustic soda, carbon dioxide, sodium chloride, hydrochloric acid, sulfuric acid and calgon as well as various polymers. (The treatment processes are summarised in Appendix 2).

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3.3 Assessment

3.3.1 Customer complaints

For the purpose of this study, only discoloured water (brown, black, red, yellow, orange) and dirty washing complaints, were reviewed. The customer complaint rates for the 5 year period were calculated on a per thousand property basis. Five of the Utilities (SWC, SEW, HWC, WCWA, P&W) calculated these rates based on their most current connection figures, whilst the other three (YVW, GCW and BW) calculated the rates based on the total connections for each of the respective years. The former method is less accurate; hence the calculated complaint rates for these Utilities are slightly lower than the true figure, as connections tend to increase over time. Table 3.3 summarises the complaint rates for each of the Utilities over the 5-year period. The data is also represented graphically in Figure 3.1. Details of those areas with the highest and lowest rates within each of the Utilities are provided in Appendix 3. Table 3.3: Discoloured Water Complaint Rates Per ‘000 Properties 97/98 98/99 99/00 00/01 01/02 Sydney Water 3.0 5.0 3.9 2.3 1.7* Yarra Valley Water 3.6 3.4 2.8 3.9 4.4 Hunter Water 6.5 11.1** 5.6 6.1 6.8 South East Water 2.4* 2.3* 2.1* 2.1* 1.9 Power & Water (NT) 12.3** 5.7 4.8 4.5 1.8 Brisbane Water Not available 3.8 5.0 3.6 2.7 Gold Coast Water Not available Not available 9.3 2.7 6.5 Water Corporation (WA) Not available Not available 12.4** 14.8** 11.9** * Lowest complaint rate ** Highest complaint rate

DISCOLOURED WATER COMPLAINTS WITHIN THE VARIOUS WATER UTILITIES ACROSS AUSTRALIA

16.0

12.0

8.0

connections 4.0 Complaints per '000

0.0 97/98 98/99 99/00 00/01 01/02 Year Sydney Water Yarra Valley Water Hunter Water South East Water Power & Water NT Brisbane Water Gold Coast Water Water Corporation WA

Figure 3.1: Discoloured water complaints per ‘000 properties

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3.3.1.1 South East Water South East Water had consistently the lowest complaint trend and lowest total average for the five years, with a majority of the systems being unfiltered. The highest complaint rates were consistently in Lang Lang (4 years) due to a bore water supply that has now been decommissioned. Numerous water quality zones had no discoloured water customer complaints. The secure natural catchments provide protection for the water supply, safeguarding water stocks from contamination and pollution. The uppermost catchments flow into Upper Yarra and Thomson reservoirs, where water is stored for up to several years before being used. Holding the water for long periods of time helps natural sediments to settle, purifying the water naturally. 3.3.1.2 Sydney Water Corporation Sydney Water had the 2nd lowest total average over the period for discoloured water customer complaints and currently the lowest rate for an individual year (01/02). In 98/99 there was an increase in complaint numbers. This was probably a result of greater customer sensitivity to water quality following Sydney’s Cryptosporidium and Giardia incident. During that year, the Nepean system had the highest rate due to Water Filtration Plant failures under dam flooding conditions. Due to a high portion of unlined mains/fittings (~ 70% in the small Greaves Creek system), there was a repeated high rate of complaints for three of the years. In 99/00 the Warragamba system had the highest rate due to a dirty water incident. The lowest complaint rates were consistently in Prospect East (4 yrs) & Ryde, due to minimal detention times and no storage reservoirs, as well as being at the head of the network in close proximity to the WFP. There was an improvement in the trend over the last three years that can be attributed to a combination of the planned mains cleaning programmes, reservoir cleaning and improvements, process improvements at the WFPs, and, possibly, the impact of the drought. 3.3.1.3 Yarra Valley Water Yarra Valley Water had a fairly consistent discoloured water complaint trend with the 3rd lowest total average over the five years. The highest complaint rates were in the water quality zones of: Emerald (unfiltered) in 97/98 due to system operations; Yarra Glen (microfiltration) and Upper Yarra (unfiltered) in the following years due to the small number of connections rather than an excessive number of complaints. Ridge/Monbulk (01/02), which is an unfiltered system, was a reflection of a taste and odour incident. The lowest rates were in Keon (97/98), a partially filtered zone, which has not been fully cleaned. Eltham, which is fully filtered, consistently performed the best for 3 years, despite not being cleaned for 7 years. Wantirna, which also had a low rate (01/02) is a very small shared zone; 10% is part of YVW and 90% is part of SEW. 3.3.1.4 Brisbane Water Brisbane Water had a variable trend with the 4th lowest total average. The highest complaint rates are in North Pine, due to characteristics of source water having naturally higher levels of dissolved metals. The reasons as to why the two zones of Bracken Ridge and Eildon Hill have the highest individual rates as opposed to others zones within the North Pine system are unknown. The lowest complaint rates are in the Mt Crosby system, in particular Moreton and Mt. Coot-tha zones, which are very small, with only 277 and 16 connections, respectively. 3.3.1.5 Power and Water Power and Water had the 4th highest total average complaint rate for the 5 years. An increase in complaints within a year occurs during changeover between the wet and dry seasons. P&W had the most significant improvement in trend over the 5 years due to a number of factors. These included: the introduction of major flushing programmes (typically 12% of the system) at the end of the Wet Season to remove sediment which had built up over this time under low velocities; pro-active advertising in the media informing the public of the activities being done within the Utility; improvements to hydraulic arrangements such as the elimination of dead ends within the system as well as a better design of new subdivisions and use of PVC pipes. Numerous suburbs had no complaints due to minimal number of connections. This can also work in reverse in that it only takes a few complaints to make the rate high.

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3.3.1.6 Gold Coast Water Gold Coast Water had a variable trend with the 3rd highest total average. The data for the Beenleigh, Ormeau and Gaven areas are not comparable over the years because the source water is from both Brisbane Water and Gold Coast Water during this period. It is currently on Brisbane Water and will remain so indefinitely. In 2001/02 the change in operation of a booster pump caused elevated complaints in the entire southern region (ie. Coolangatta, Currumbin, Elanora, Reedy Creek, Simpsons Rd), whilst later that year the Mudgeeraba plant lost control of the manganese reduction process, a fact which generated complaints in the same areas again. Routine mains cleaning ceased in 1995/96 as there were no sustainable improvements. 3.3.1.7 Hunter Water Corporation Hunter Water had a variable trend and the 2nd highest total average over 5 years for discoloured water customer complaints. It is suspected that the highest complaint rates (in the Anna Bay area) were possibly due to corrosion of unlined bore fittings. The lowest complaint rates were in Nelson Bay, possibly due to stainless steel bore fittings. 3.3.1.8 Water Corporation WAWC has the highest per thousand properties complaint rate for the three individual years and the total average. It blends ground surface and sub artesian waters and has been in drought for the last 20 years so there has been no programmed mainscleaning in this time. Discoloured water complaints are usually triggered by maintenance and operational activities or reversal of flows due to increasing spring demands. More than 99% of discoloured water issues do not persist for more than a day and disappear by the settlement of mains clearing, through normal consumption patterns. Despite having the highest complaint rates of all the Utilities, there are numerous zones that also have no complaints. 3.3.2 Industry data

The industry partners shared information and experiences at various workshops and meetings on the issues and gaps in knowledge in relation to discoloured water. Data was also provided on the water quality and operational information for their respective distribution systems. The comprehensiveness of this data varied because the monitoring programmes were different, with different sampling frequencies as well as different parameters being measured. Because the eight Utilities have different system characteristics, source waters, treatment processes and complaint rates, it was difficult to categorise the water quality data. So, for the purpose of representing the water quality data in a simplistic manner, the two categories of filtered and unfiltered water were used to show the range of averages for various parameters in Table 3.4. (For detailed data on each Utility refer to Appendix 4).

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Table 3.4: Range of Averages (1997 – 2001) for Water Quality in the Distribution Systems

PARAMETER UNFILTERED* FILTERED** ‘96 NHMRC GUIDELINES

Aluminium mg/L 0.02 - 0.09 0.013 - 0.10 0.2 Calcium mg/L 1 - 16 1.1 - 53 Colour (True) 0.8 - <2 15 Colour (Apparent) Hazen units 1 - 12 1 - 5 Copper mg/L 0.004 - 0.469 <0.001 - 0.210 1 Iron mg/L 0.04 - 0.11 0.001 - 0.18 0.3 Manganese mg/L 0.003 - 0.01 0 - <0.02 0.1 pH units 5.7 - 8.2 6.8 - 8.1 6.5 - 8.5 Silica as SIO2 mg/L 2.5 - 89 0.001 - 19.4 Total Alkalinity as CaCO3 mg/L 3 - 39 8 - 121 Total Dissolved Solids 40 - 165 <1 - 260 500 Total Hardness mg/L 15 - 89 7 - 167 Total Organic Carbon mg/L 1.1 - 3.7 1.7 - 4.3 Turbidity NTU 0.1 - 2.1 0.1 - 0.8 5 Zinc mg/L 0.002 - 0.02 <0.001 - 0.051 3 * Unfiltered systems were found in Hunter Water Corporation, Yarra Valley Water, South East Water, Power and Water, Water Corporation ** Filtered systems were Sydney Water, Hunter Water Corporation, Yarra Valley Water, South East Water, Brisbane Water, Gold Coast Water, Water Corporation.

A summary of the data findings were as follows: • Aluminium levels were low, with most results <0.04mg/L, well below the Australian Drinking Water Guidelines • Calcium levels were consistent in both water types • True colour is monitored only by Brisbane Water and Sydney Water and was low in both Utilities • Apparent colour measured in the remaining Utilities was higher in the unfiltered systems • Copper levels were low, with most Utilities having averages <0.02mg/L. There was an exception with one unfiltered system in Yarra Valley Water (0.469mg/L) and one filtered system in Water Corporation (0.210mg/L). Both were still well below the Guidelines • Iron levels were low in both filtered and unfiltered systems, though the former tended to have slightly higher averages • Manganese levels were low compared to the Guidelines. However, from the literature and communications with the partners, levels >0.020mg/L can be an issue • pH was variable, particularly in Water Corporation, and most Utilities had exceptions within their systems, some as high as 10.1 and as low as 5.7 • Silica levels were high in unfiltered waters (up to 89mg/L) • Total hardness and alkalinities levels were higher in filtered systems due to treatment processes • Total dissolved solids were consistent in both water types and below the Guidelines • Total organic carbon levels can be considered to be elevated in both water types • Turbidity levels were generally low, with most systems having <0.3NTU. However the levels were slightly higher in the unfiltered systems • Zinc levels were low, mostly <0.005mg/L, and well below the Guidelines. However, one filtered system had an average exception of 0.051mg/L and Water Corporation had a couple of systems both filtered and unfiltered with averages around 0.02mg/L. All these levels, however, are well below the Guidelines.

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3.3.3 Comparison of water quality data with customer complaint data

The water quality data that has been provided does not appear to reflect the number of discoloured customer complaints that some of the Utilities are experiencing. There are several reasons for this, which include the fact that the monitoring programmes, whether routine or random, may not be in the same immediate location as the discoloured complaints, or even at the same time. Complaints are often isolated incidents, or exist for a brief period of time and are very difficult to capture. Solely from this data, no direct relationships can be identified between the various parameters and the discoloured water complaints. Some Utilities have a ‘rule of thumb’ that assists in interpreting discoloured water events, such as Hunter Water’s: 1. Fe/Mn ratios of <10 are suggestive of bryozoan, iron bacteria sources, ie. biolfilm 2. Fe/Mn ratios of > 20 are suggestive of rust/corrosion 3. Fe/Mn ratios of 10 to 20 are of uncertain interpretations. However, the literature on the use of this method has not been documented. A graphical comparison of the average water quality and average customer complaint number over the five-year period did not indicate any convincing relationships. The figures 3.2, 3.3 and 3.4, below, show the weak trends (indicated by the very low R2 values), between the selected water quality parameters, (iron, manganese, turbidity and alkalinity) and the average customer complaint number per 1000 connections for each utility. The trends in these three figures were not found to be significant according to a Pearson Correlation. Each point represents a separate utility, and as some utilities do not measure all parameters they may have been excluded from the analysis.

Iron and Manganese concentrations vs complaint numbers Iron Manganese 0.08 0.012 0.07 R2 = 0.2455 0.010 0.06 0.008 0.05 0.04 0.006 0.03 2 Iron (mg/L) R = 0.1822 0.004 0.02 0.002 Manganese (mg/L) 0.01 0.00 0.000 0 2 4 6 8 10 12 14 Average Complaint numbers

Figure 3.2: Comparison of average iron and manganese concentrations with average number of complaints for each utility. Low R2 for the lines of best fit indicate there is no relationship between the variables. Neither line is significant (Fe p= 0.401; Mn p=0.351).

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Turbidity vs complaint numbers

1.2

1.0

0.8

0.6 R2 = 0.0296 0.4 Turbidity (NTU) 0.2

0.0 02468101214 Average Complaint numbers

Figure 3.3: Comparison of average turbidity levels with average number of complaints for each utility. Low R2 for the line of best fit indicates there is no significant relationship between the variables (p= 0.712).

This method of averaging the water quality data (both between zones and over time) and the customer complaint data (over time) makes it more difficult to recognise a relationship between the variables if one is present. Clement et al. (2002) found a strong relationship between red water customer complaints and alkalinity, as complaint numbers were substantially reduced if alkalinity was kept above 60 mg/L. As Figure 3.4 shows, no strong relationship is evident in the data collected, however only one utility averaged over this 60mg/L alkalinity trigger value in this study.

Total Alkalinity vs complaint numbers

90 80 70 60 50 40 30 R2 = 0.0079 20 10

Total alkalinity as CaCO3 (mg/L) as CaCO3 alkalinity Total 0 02468101214 Average Complaint numbers

Figure 3.4: Comparison of average alkalinity with average number of complaints for each utility. Low R2 for line of best fit indicates there is no relationship between the variables (p= .834).

Interestingly, for the utilities that provided data, total organic carbon (TOC) and pH may show a linear trend. Again, these graphs may not show genuine correlations, as the comparison of the means of so many variables can lead to erroneous results. The TOC relationship, for instance, has only three points due to lack of information from the participating utilities. Therefore, not too much bearing should be placed on the perfect R2 obtained for the line of best fit in this graph (Figure 3.5), even though the result is significant to the α 0.01 level (p= 0.001). While increased concentrations of TOC seem to promote an increased complaint level, more data is needed to assess this relationship.

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Total organic carbon vs complaint numbers

6.0 R2 = 1 5.0

4.0

3.0

TOC (mg/L) 2.0

1.0

0.0 02468101214 Average Complaint numbers

Figure 3.5: Comparison of total organic carbon concentrations with average number of complaints for each utility. R2 for line of best fit indicates there is a significant positive correlation between the variables (p=0.001).

As organic matter is generally only a small component of deposits in drinking water systems (e.g. <11% as organic carbon in Gauthier et al. 1999), increased TOC concentrations are likely to indirectly affect discolored water formation. There is conflict in the literature on the relationship between organic matter and biofilm regrowth, possibly due to an inadequate number and type of organic matter measurements, and significant interaction of other factors (Camper et al. 1998). In general, increased available organic carbon would provide a food source for biofilms that could later slough off to form discoloured drinking water, however other studies have not found a correlation between distribution system biodegradable dissolved organic carbon, suspended bacteria and fixed biomass (Kernis et al. 1994). Organic matter may also indirectly affect discoloured water formation by forming complexes with iron and manganese reducing removal efficiencies during treatment. Figure 3.6, below, shows the graphical relationship between pH and customer complaints. It appears that as pH decreases, the average number of complaints significantly increases (p=0.048). As pH determines the solubility of the main elemental species contributing to discoloured water, this may be a valid trend. There were no relationships found, however, between pH and those elemental species, iron and manganese (data not shown). Again, more data is needed to validate this relationship. Vikesland and Valentine (2002) suggest that increasing pH helps to stabilise monochloramine, and this could be beneficial in reducing discoloured water events by controlling biofilm regrowth. Beckett et al. (1998) found that a reduction in pH led to an increase in iron release (in unlined pipes) also supporting the relationship below.

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pH vs complaint numbers

8.0

7.8

7.6

7.4

pH units 7.2 R2 = 0.5059 7.0

6.8 02468101214 Average Complaint numbers

Figure 3.6: Comparison of average pH levels with average number of complaints for each utility. R2 for line of best fit indicates there is a significant negative correlation between the variables (p=0.048).

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3.4 Issues & Gaps in Knowledge

3.4.1 Treatment

3.4.1.1 Chemicals Different chemicals are added at the various treatment plants. Examples include ferric chloride, aluminium sulfate, potassium permanganate and lime. The impact of these chemicals as well as their impurities, individually or in combination on the downstream customers, is unknown in terms of discoloured complaints. The different treatment processes that exist between the Utilities, impact on the distribution system. Exactly how and whether they are beneficial or detrimental in terms of discoloured water formation, is a gap in knowledge that needs to be explored. 3.4.1.2 pH The level of pH in the treatment process is critical to the stability of the water and removal of specific metals. Whilst at higher pHs manganese can be removed by using chemicals such as potassium permanganate (as practised by Sydney Water), at lower pHs, aluminium and iron can be removed. This raises the issue of what the optimisation priority for each of the Utilities is. Is it manganese, iron, pH, aluminium, turbidity or some other parameter? 3.4.2 Distribution

3.4.2.1 Manganese Research carried out by Gold Coast Water indicates that when water treatment plants fail to keep soluble manganese levels below about 0.02mg/L in the treated water, there is an increase in discoloured water complaints within days. Sydney Water optimised manganese removal in the Woronora system from 0.020mg/L down to <0.005mg/L resulting in a considerable reduction in customer complaints. However, the same degree of benefit was not seen in the Prospect system. These examples demonstrate the uniqueness of every system and indicate that a targeted lower level of manganese would vary between the systems. The average manganese concentrations collected from the participating utilities did not seem to impact the customer complaint levels, but an in depth look at each utility may provide more understanding into the trigger values for manganese in relation to complaints. The gap in knowledge is not only what these lower levels are for each system to minimise these customer complaints, but also what the impact is of organics and the interactions with manganese. 3.4.2.2 pH The pH of water entering the distribution system can influence the solubility of elements within the system. The impact of pH on the formation of discoloured water, while thought to be minor compared to other water quality aspects, should be analysed more closely in light of the weak negative trend found in this analysis of industry data. 3.4.2.3 Oxidation Most of the systems in this project are chlorinated, with the exception of Brisbane Water, 6 of Sydney Water’s 14 Delivery Systems, and two systems supplying Yarra Valley Water that are chloraminated. (Refer to Appendix 1 for details). The gap in knowledge exists here as to what the different oxidation levels of dissolved materials (such as iron and manganese) are, depending on the disinfection regime as well as the rechlorination processes in the distribution system. Is there a difference in reactions with the types of dosing (liquid or tablet form) or the strength of the disinfectant used? What are the impacts of impurities from dosing? There will always be some iron and manganese present in treated water. How, when and exactly where these are then brought out of solution by the various oxidation processes (including the washing process which involves oxidising agents), and their potential to cause customer complaints, are unknown. 3.4.2.4 Detergents The interactions of detergents with dissolved materials is another gap in knowledge for water utilities, however an amount of research has been done into this issue by detergent manufacturers. It appears from the literature review, that the research that has been conducted on this issue, has not been published. This data source needs to be made available to the water industry, if possible. What levels

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cause staining? What detergents have a greater impact? What conditions or combinations will cause staining? Why do some customers always experience dirty washing whilst their neighbours do not? These are all gaps in knowledge for the Utilities.

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3.5 Conclusions

The conclusions have been drawn from the data provided by the Utilities on water quality, customer complaints and system characteristics as well as anecdotal evidence from various workshops and meetings. Most Utilities can account for 80 - 90% of their discoloured water complaints, which are usually a result of operational activities, source water or system characteristics of the utilities, themselves, or are due to the customers’ internal plumbing. There are also a small number of customers who complain as a matter of course. The cause of the remaining complaints is often unknown. Many Utilities have improvement strategies in place to optimise their systems and minimise the impact of the operational activities in order to try to minimise the potential for discoloured water and subsequent complaints. Also, some Utilities have a better appreciation of what is happening in their system than others. Some Utilities have Customer Contracts in place that outline the commitment and responsibilities these Utilities have to their customers in terms of the service and quality that they provide. It also details the customers’ rights and responsibilities in relation to not only water quality, but also any other services that are available. The customer complaint assessment identified South East Water as being the most consistent performer in achieving the lowest complaint trend over the 5-year period, followed then by Sydney Water, Yarra Valley Water, Brisbane Water, Gold Coast Water, Power and Water, Hunter Water and, well below the others, Water Corporation. Power and Water had the most significant improvement in the number of complaints due to various improvement strategies and better management practices being implemented. The major peaks in the performance trends were usually a result of operational changes in the distribution system or treatment plant failures. The Utilities have the same initial response to discoloured complaints of reactively flushing. However, the recording systems and management of these complaints vary. Stained or dirty washing complaints, which usually make up less than 5% of the discoloured water complaints, are not thoroughly investigated and therefore gaps in knowledge still exist in understanding the relationships between the occurrence of discoloured water, use of detergents and resulting stained washing. Based on the information provided, there appears to be no pattern amongst the Utilities between the number of complaints and whether a system is unfiltered or filtered. For the purpose of this study, the best performing systems were in both filtered and unfiltered systems, as were the poorer performers. In general terms, it can be said that those Utilities who have regular mains cleaning programmes seem to have generally lower discoloured water complaint levels. The data provided also did not show any relationship between iron and manganese concentrations, alkalinity, turbidity and the average customer complaint rate. Total organic carbon and pH, however, may be related to customer complaint numbers according to the data obtained from the utilities. Further research needs to be done on these factors. Based on discussions with, and experiences of, the partners rather than just the analysis of the data provided, there are numerous issues and gaps in knowledge that still exist in the industry at the treatment and distribution level in relation to discoloured water. These gaps are consistent with those gaps identified in the literature review. These include the impact of the different treatment chemicals, optimisation priorities, target levels for manganese (as well as the interactions with organics), the impact of pH, oxidation processes and their impact on the distribution system and the interactions of detergents with dissolved materials. The theory behind any ‘rules of thumb’ within the industry also needs to be understood and maybe shared with other utilities with similar systems.

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3.6 Recommendations

• The best practices and experiences from each of the Utilities can be shared and developed into a generic format which can give commonality to the Australian water industry in terms of customer complaint collection, categorisation, investigations, management and reporting. • The database that is used for the recording of complaints needs to be robust, user-friendly, flexible and reliable. The categorisation of complaints needs to be comprehensive yet simplistic. If the data is not recorded or categorised properly, then it makes analysis and interpretation of the complaints very difficult. The following are suggested categories for discoloured water: 1. Discoloured water: water that has a distinct colour from the customers’ perspective. 2. Particles/sediment: water that has particles or sediment (and may or may not also be coloured) 3. Stained washing: washing that has become stained as a result of tap water. 4. Stained fittings: fittings (e.g. sinks/bathtubs) that have become stained as a result of tap water. Under each of these categories, a class that would best describe the colour being experienced should be noted. These colour classes can be important in determining the type of discoloured water, however, as the range of colours experienced can be similar (e.g. brown could look like red or orange to some people), the list of classes below may be condensed. • Brown • Red/rusty • Black • Yellow/orange • White/cloudy • Blue/green • Other • The area of dirty washing needs to be more thoroughly understood. Detergent manufacturers may be able to provide more information on the impact of washing powders/liquids on iron and manganese oxidation within the washing machine. • Further study is needed into impact of total organic carbon and pH on the formation of discoloured water. • The water industry needs to share information, for example rules-of-thumb (such as iron to manganese ratios), to help with interpretation of discoloured water and to make this area of water quality consistent.

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4 INDUSTRY PARTNER QUESTIONS

Participating water utilities/corporations have provided the questions they consider most important in understanding the processes that lead to discoloured water. The participating corporations have submitted five questions each, which range from broad questions about the general processes, to specific questions about discoloured water propagation and minimisation under specified conditions. The most commonly asked questions are:

• What causes discoloured water?

• What are the most effective ways to manage dirty water?

• Does the disinfectant process at the WFT and/or rechlorination within the distribution systems create oxidation and precipitation? Where does it happen, how does it happen, and what interactions take place?

• What is the composition of particles/stains in dirty water?

• Can the location and extent of the discoloured water be identified?

The specific questions are listed below with an evaluation of whether currently available literature is able to provide answers to these questions. Some questions posed are outside of the scope of this review and as such, the potential for current research to address these questions may be greater than what is specified.

The questions give a range of what information is needed by water utilities to understand the discoloured water process. Therefore the answers to these questions are a response to whether the knowledge required for the corporations can be found in the literature or whether further research is needed. Many questions have been partially addressed by the literature and in these cases the degree to which the literature can answer the question has been included.

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4.1 Questions from Participating Utilities

4.1.1 Sydney Water

Q: Why are we getting customer complaints when testing shows our system does not have high turbidity/metals or sedimentation problems?

A: This question is partially answered but as all systems are different the answer will not be clear-cut. However, the current research points to the role of biofilms, which are influenced by capacities and hydrodynamics more than metal and particle concentrations. Logically, though, distribution systems that have lower concentrations of metals/particles are likely to have fewer dirty water events.

Q: What happens between the treatment, reservoirs and distribution in relation to water chemical and physical characteristics?

A: There are studies that investigate changes in metal speciation and changes in other chemical parameters such as pH, residual chlorine, alkalinity etc. more so for reservoirs upstream of treatment. Even in the same geographical area different trends can be found in ratios of constituents.

Q: Why do some customers get dirty washing whilst others in same street do not?

A: There is very little in the research literature that aids in answering this question. Utility publications seem to suggest it may have to do with particular makes of washing machines and interaction with particular washing detergents. THIS IS A CLEAR GAP. Sometimes a local depression in the pipe combined with a 'twisted' tapping in the pipe can explain why some customers are affected and neighbours are not (Vreeburg 2004).

Q: Is there a biological process where biofilms generated discoloured water? How can this process be monitored and controlled?

A: There are many ways that biofilms contribute to discoloured water. There are a number of methods for monitoring biofilm growth in the literature, including the identification of manganese and iron utilising species. Removing organic matter (i.e. food) in the treatment is the best way to slow biofilm growth. Although there is a lot of information on this topic it still represents a knowledge GAP.

Q: Does the disinfectant process at the WFT and/or rechlorination within the distribution systems create oxidation and precipitation? Where does it happen, how does it happen, and what interactions take place?

A: There is some research that may provide answers to this question though it is usually studied in the context of how do metals in the distribution system contribute to the removal of residual chlorine, rather than focusing on the changes that occur with the metal speciation. THIS IS A CLEAR GAP.

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4.1.2 Hunter Water

Q: What level of manganese will cause a problem in terms of increased dirty water problems?

A: There are conflicting opinions in the literature as to what level of manganese will cause a problem. There is some evidence to suggest that this is because the level of reduced soluble manganese is more important that the total concentration. Also, due to the influence of biofilms, even low levels of Mn can eventually lead to discoloured water events. Utilities need to decide whether increased expenditure on treatment/cleaning leading to reduced incidence of customer complaints is worthwhile.

Q: What is best practice for resolving recurrent dirty water complaints?

A: There are a number of proposed methods (cleaning etc.), though to date there is no resolved best practice. This is a management issue that is not an objective of this project, although outcomes of this project may lead to development of a best practise management protocol.

Q: How effective are flushing, air cleaning and slug cleaning?

A: The general effectiveness of cleaning methods have been evaluated in the literature. Air cleaning is more powerful but can increase corrosion. Cleaning processes only provide short-term remediation (though possibly years). Lehtola (2004), found an improvement in water quality immediately following cleaning (i.e. within one week) but improvements after 3 months were minor.

Q: Are automatic flushing devices worthwhile?

A: No literature found answering this question. A possible GAP in knowledge.

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4.1.3 Gold Coast Water

Q: Confirmation that discoloured water is cause of customer complaints.

A: GCW have a good understanding of the mechanisms that produce discoloured water (an abiotic cause near the treatment plants and biofilms after the disinfectant declines). This question may be addressed by the customer survey.

Q: What is the material causing discolouration?

A: Particle project answers this question as well as a number of overseas studies. The collection of material as part of the customer survey will enable this to be done on a site-specific basis. This is also what is being addressed by the collection of samples in stage 2 of this project.

Q: Problem sources of material

A: Raw water, treatment and corrosion studies answer this question. The relative proportion of each source is dependent on source water quality, treatment efficiency and presence of unlined mains.

Q: What are the knowledge gaps and how do you fill them

A: See responses provided in this chapter and in summary chapter.

Q: What management approach is available to deal with them?

A: This is not an objective of the project and outside our expertise. We have not covered this topic in the literature review.

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4.1.4 Water Corporation (WA)

Q: What causes discoloured water?

A: Reviewed literature indicates several different potential causes of discoloured water.

Q: Can location and extent of the discoloured water be identified?

A: Sampling programs such as those developed by KIWA (using turbidity measurements) help answer this question but there is no simple method and it is quite expensive. The alternative approach is modelling such as done in the particles project.

Q: Can the cause of dirty water be eliminated?

A: Research indicates methods to reduce rather than eliminate causes due to the myriad of contributing factors. The main problem seems to be that treatments cannot be optimised for different parameters at the same time, e.g. metal ions and organics (thus treatment is always a compromise).

Q: What is the best way to manage discoloured water and is there some form of trigger point to the need for implementation remedial action?

A: Trigger levels have been set based on measured parameters but they are based on specific water quality of the catchment and are not infallible. Some trigger levels are based on customer complaint levels but these are reactive. This represents a GAP in capability rather than knowledge.

Q: Is the cost of eliminating /managing the discoloured water justified in terms of reducing customer complaints?

A: Some cost benefit analysis has been done. Generally though this is outside the scope of the project.

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4.1.5 Power and Water (N.T.)

Q: What parameters (physical/chemical/biological) are best monitored in the source water to indicate potential formation of dirty water and the need to instigate operational process to reduce impacts?

A: Organic matter, manganese and iron, though there are different ways to quantify these parameters (for example organic matter as NOM, TOC, AOC, DOC). Turbidity has also been used (see KIWA report). There are studies that compare how well the different surrogates for organic matter correlate with microbial growth and AOC appears to be the best general predictor. Reduced manganese has also been shown to predict post-treatment high manganese concentrations. The applicability of these measurements to different systems is dependent on the interaction of controlling factors for discoloured water propagation.

Q: Does our current chlorination system contribute greatly to the formation of dirty water formation (i.e. chlorination at supply and re-chlorination at distribution reservoir)? Could our chlorination processes or type of chlorination be changed to reduce the formation of dirty water in mains/customer taps without compromising disinfection?

A: Research indicates that chlorination routine can affect discoloured water and there are methods for optimising the disinfection procedure. Otherwise response is site-specific. An understanding of the major cause of discoloured water is needed to assess the role chlorine will play. Chlorine can increase discoloured water through oxidation of iron (important for unlined pipes) or reduce discoloured water by reducing biofilm growth.

Q: Does our practice of blending ground water with surface water contribute to the formation of dirty water in the distribution system?

A: Mixing of source waters has been shown in the literature to contribute to water quality deterioration including increasing biofilm growth. Changes in water chemistry will occur when ground and surface waters are mixed e.g. reduced forms of metals found in groundwaters will oxidise when coming in contact with surface waters.

Q: What are the best ways of operating reservoirs to increase the precipitation of heavy metals (common inlet/outlet, top filling)? Should we be trying to increase oxidation to encourage heavy metals to settle out in the reservoir?

A: There is some research about the changes in water quality before, during and after it enters a reservoir. Oxidation and increased settling can be beneficial though reduced soluble manganese is quite stable (has slow oxidation kinetics) in the presence of O2 and requires stronger chemical - oxidants (ie MnO4 ).

Q: What are the most effective ways to manage dirty water (i.e. velocities/volumes/type of main)?

A: Critical velocities have been studied in regards to scouring and sloughing. Type of pipe surface discussed also. Turbulence theory has been utilised to determine the necessary flow to keep sediments in suspension.

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4.1.6 Brisbane Water

Q: What are the circumstances or mechanisms triggering dirty water events in the distribution system?

A: Previous research has investigated many different triggers of the causes of discoloured water. Brisbane is likely to have one or two main mechanisms. Current data suggest abiotic mechanisms related to the flow hydrodynamics and subsequent oxygen solubility.

Q: What features can we design into new distribution systems to minimise these events?

A: The main options are well understood already (i.e. better treatment, disinfection, cleaning etc.). No new options have been identified by the literature review relating particularly to the distribution system.

Q: What forms do Fe and Mn (and Al) take in forming dirty water?

A: There are many studies that have investigated changes in metal speciation especially for iron and corrosion products. Manganese oxides are generally just referred to as MnOx, whereas iron precipitates in many forms (e.g. iron oxides and hydroxides such as goethite) though the dominant form is determined by the local water chemistry, as other elements will complex with iron species.

Q: What is the relative importance of microbially mediated processes in the formation of dirty water?

A: Plenty of research indicates that biofilm processes are a very important factor leading to discoloured water events. Most systems will have biofilms present. Biofilms seem to become the main contributor when metal levels are generally low.

Q: What is the difference in dirty water formation, if any, between chlorinated and chloraminated systems?

A: Mechanisms for disinfection for chlorinated and chloraminated systems have been analysed. These mechanisms indirectly affect dirty water formation based on oxidative power and persistence within the distribution system.

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4.1.7 Yarra Valley Water

Q: What causes dirty water?

Reviewed literature indicates several different potential causes of discoloured water.

Q: How can we predict locations of potential dirty water considering only up to 15% of customers complain?

This is not dealt with by the literature review, although methods for measuring drinking water turbidity etc could be used to make predictions. Modelling projects attempt to answer this question. Also the customer survey could be used further study these locations.

Q: What is the composition of particles/stains in dirty water?

There is a lot of research on the composition of particles but very little on the composition of stains (perhaps because of the obvious colouration, suggesting iron). Particles are commonly composed of iron, organic material, manganese, aluminium and calcium. The speciation is dependent on the mechanism of formation i.e. direct oxidation or corrosion or microbial oxidation.

Q: How can we predict potential incidents?

Very little research in this area. Extensive use of on-site turbidity sensors. Also the modelling project attempts to answer this question.

Q: Impact of seasonal variations?

Temperature affects growth of biofilms and rates of reactions. Also raw water quality changes seasonally due to stratification and increased anaerobic activity over summer.

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4.1.8 South East Water

Q: Where does the material that generates dirty water customer complaints originate?

Raw water, treatment processes and further processes within the distribution system. Quite a lot of information is available.

Q: Where does this material accumulate within the distribution system?

Research indicate storages, dead-ends and joints that restrict flow are areas of accumulation. Models have also been employed to predict particle movements.

Q: What conditions are required to cause a discoloured water customer complaint?

Little information currently. May be elucidated by customer survey.

Q: What is the most cost-effective method for removing discoloured water from a pipe (flushing, air scouring, and swabbing)?

Some cost benefit analysis has been done. Not actually part of the literature review.

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5 SUMMARY AND CONCLUSIONS

The conditions that cause discoloured water events are highly variable due to the different mechanisms of discoloured water formation. Chemical oxidation, biologically mediated processes and corrosion are all mechanisms of particle accumulation within the distribution system, that can ultimately result in discoloured water being released at the consumers tap after increases in water velocity and flow. Therefore, understanding the processes involved in the formation of discoloured water requires a holistic look at pre-distribution processes (e.g. source water and treatment), distribution processes (including chemical, biological and physical) and post distribution processes occurring at the customers tap. At the water source level, it is well known that the concentrations of naturally occurring iron and manganese can differ greatly between water bodies depending on the geography of the region. However, aside from changing water sources, the natural conditions that govern the inputs of manganese, iron, organic material and other potentially important substances are generally beyond the control of the water utility. What can be manipulated, to an extent, is the dissolution and oxidation of manganese and iron within lakes and dams through artificial aeration and destratification. The point of uptake within the source water can also be changed to minimise the dissolved metal concentrations. The chemistry and concentration of elements in raw water sources, although not always in the context of discoloured water, has been studied extensively. The use and quality of available surface water or ground water, and mixing of these waters can cause problems with the formation of particles further down the delivery system. Many alternative methods can be used to treat source water prior to distribution with the aim of reducing the introduction of potential colour-causing metals, organic matter and particulates. The treatment procedures that can be used to reduce discoloured water formation include oxidation, disinfection, coagulation, flocculation, filtration and sequestering. The order of application of these methods, as well as the initial content of the water, determines the efficacy of the treatment process. There is a large body of research on the use of a variety of disinfection procedures and their efficiency and therefore their ability to reduce discoloured water events due to biofilm sloughing. More research is needed, however, into the effect of alternative disinfection techniques and residuals on the chemical processes that contribute to dirty water. Oxidants and coagulants that are commonly used to aid removal of reduced metals, colloidal and particulate matter are well researched. Some researchers have found that oxidants such as hydrogen peroxide and chlorine dioxide are relatively or even completely ineffective in oxidising manganese. Potassium permanganate has been demonstrated to be an effective oxidant, however, care must be taken to optimise the dose, as over-dosing of permanganate causes residual manganese to enter the distribution system. Similarly coagulants such as alum and ferric oxide have been demonstrated to be effective in aiding flocculation of particles however the removal of particles must be optimised to minimise residual concentrations of iron and aluminium. Different filters and filtration procedures are common in the literature and the most important aspect is the minimisation of filter breakthrough events, which can lead to a slug of increased particulates in the distribution system. Some filters have been found to function more efficiently for the removal of manganese when a biofilm or oxide coating develops on the filter media that is capable of removing manganese from the water column and therefore some filters require a ripening period before working at their optimum. Sequestering can be used to reduce discoloration caused by iron and manganese by forming a colourless compound, rather than removing the metals. Sequestering is generally not used as a replacement for iron and manganese removal techniques. More commonly, sequestering agents are used to sequester iron that has been released within the distribution system through corrosion. Inorganic phosphates and sodium silicate are the most commonly discussed sequestering agents. The impact of phosphates on biofilm growth is not well understood and needs further study. Within the distribution system, there are a number of chemical, biological and physical processes that can lead to the formation of discoloured water. Chemical changes in the oxidation state of metals within distribution networks and the processes that lead to the formation of particles are not well studied as there are many variables within the system that may facilitate the oxidation of metals within the delivery system. Changes to water chemistry caused by treatment processes, continuing interactions with disinfectants and other added chemicals as well as changes in dissolved oxygen, pH and temperature can all influence chemical oxidation within the pipes. Those studies that do assess

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changes in oxidation state within the distribution system, use a pipe loop apparatus, or similar, to control the water conditions. There is also a supportive background of general chemistry and raw water chemistry on the changes of oxidation state and speciation of iron and manganese. However more research is needed to understand the processes in the context of the conditions within the distribution system. The internal corrosion of pipes is one of the chemical processes that is well researched. Research already conducted in this area has had a strong focus on minimising the corrosivity of water and the development of corrosive resistant scales. It is fairly common for the major components of sediments to be organic material and iron, with manganese, calcium, silica and aluminium being other major constituents. Comparisons between studies that have determined particle constituents are often difficult due to different methods of collection and reporting of results, indicating more research is needed in this area. Information on mineral analysis of deposits is also minimal. A few studies have attempted to determine if iron accumulated in particles is caused by source water input or as a by-product of pipe wall corrosion. This is done by comparing the composition of accumulated sediments to the composition of the water and corrosion tubercules and the presence and absence of budding hypha that is associated with biofilms.

While the formation, growth and content of biofilms is a biological process that affects water quality, the sloughing off of these films that leads to discolouration at the tap is often due to physical processes (increased flows etc). The mechanism that leads to bulk biofilm-sloughing needs to be more thoroughly researched as flow changes and increases in disinfectant cannot always explain the phenomenon. The mechanisms involved in the release of manganese and iron in inorganic deposits, also appears more limited or not as well researched. Resuspension of accumulated particles and the scouring of deposits are also primarily controlled by physical processes, including changes in flow direction and water velocity. Microbial processes, in the formation of discoloured water, include the deposition of manganese and iron by microbes, the physical presence of biofilm that can be released into the water during high flow events, the contribution to bulk water oxidation processes and microbially mediated corrosion processes. There are a number of studies on the utilisation of metal species by biofilms both in distribution systems and other environments (e.g. cycling in reservoirs or rivers). The metal content within biofilms has been studied and microscopic techniques have been applied to determine binding sites of iron on bacterial cells. Generally, there appears to be a lack of synthesis in the different roles micro-organisms can play in the formation of discoloured water and which processes are the most common or significant. The contribution of microbial oxidation appears to be more important for manganese than iron, due to the more stable nature of reduced manganese and hence is more widely studied. Microbially mediated corrosion processes have more of an impact on the addition of extra iron into the distribution system and hence research on corrosion processes will sometimes cover the contribution of micro-organisms. Once particles have entered or formed in the distribution system, they come out either through the customer’s tap or during cleaning procedures. Cleaning measures that can be used include flushing, air scouring and swabbing (or pigging). Generally the results in the literature suggest that cleaning procedures will not supply long-term solutions as build up will reoccur and therefore cost analysis is an important consideration that needs to be investigated for cleaning, as a method of pipe remediation. Consideration of the hydraulics of the system in relation to water quality has only recently been studied. There are some articles on dead ends mains; compared to flow through mains, and the design of continuous flow mains is advised. Consequently, the uni-directional flushing method as opposed to unplanned flushing is known as the best practice technique. Post distribution processes that cause customer complaints generally either involve dirty washing or blue water. Blue coloured water and stains are the result of the corrosion of copper pipes, within the household. There are a number of studies on possible preventative treatment measures (e.g. corrosion inhibitors). There is very little research in the area of discoloured washing. Only a few articles mention discoloured washing and a couple actually have attempted to study some aspect of the role of water quality on staining of clothing. Discoloured washing is an area of research that represents a large gap in the knowledge. Due to the complexity of discoloured water formation, the prediction of discoloured water events is demanding. Due to the difficulties associated with monitoring discolouration of water online or over time, the body of research in this area is not large. Mathematical and theoretical models have been developed to help predict oxidation rates, corrosion processes and chlorine decay etc in distribution

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systems. There is no comprehensive model, however, that combines all aspects of dirty water formation. The KIWA report gives three resuspension potential methods involving turbidity method and these were deployed in distribution systems in the Netherlands. Other simpler ‘rule of thumb’ type methods (e.g. if manganese levels rise above 0.05 mg/L customer complaints also rise) may also be helpful in this area if identified. The conclusions from the industry data assessment have already been discussed in section 3.5 of this report so they will only be reviewed briefly here. In short, the study found no link between discoloured water complaints and whether the water was filtered or unfiltered. Of course, due to the general nature of this study, this is not a convincing incentive to change current filtering practices. A possible relationship was noted between customer complaint numbers and pH and total organic carbon, so these areas need to be more thoroughly researched. There were vast differences in how the participating utilities collected and collated the customer complaints, but the initial response (to reactively flush) was the same. There were generally lower complaint numbers from those utilities with a regular mains cleaning program, for example South East Water, who consistently had the smallest number of complaints. The gaps in knowledge identified, were similar to those found from the literature review, namely; the impact of different treatment chemicals, target levels for manganese, the impact of pH and interactions with laundry detergents and organic materials. The questions provided by the utilities relating to discoloured water, had a number of themes including the best way to manage discoloured water, the prediction of possible dirty water events, the role of the disinfectant process on oxidation and precipitation of discoloured water and the composition of particles and stains.

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6 RECOMMENDATIONS

The concluding observations highlight a number of key gaps in knowledge that form the basis for the recommendations for future study. Of primary importance to this project are the chemical changes that occur within the distribution system. Biological changes that can occur are being studied in a complementary project (biofilms project). The two gaps in knowledge found relating to this area (i.e. the impact of phosphates on biofilm growth and the lack of understanding of which biological processes are the most significant) will be studied by the biofilms project. Research on the chemical changes in the oxidation state of metals within the distribution system, which leads to the formation of particulates, was found to be lacking. Changes to water chemistry caused by treatment processes, continuing interactions with disinfectants and other added chemicals as well as changes in dissolved oxygen, pH and temperature can all influence chemical oxidation within the pipes. It was also found that more research is needed into the effect of alternative disinfection techniques and residuals on the chemical processes that contribute to dirty water. The questions provided by the industry partners also highlighted this as an area requiring more information on its impact on dirty water formation. Recommendation 1a: is to study the extent to which the water chemistry changes affect the oxidation state of metals in the distribution system. Initially, for this study, the particulate material needs to be characterised, as well as concentrations of the soluble metal fraction. These results can then be compared to water chemistry parameters e.g. disinfectant residual, temperature, total organic carbon and pH etc to gauge the effect of other parameters on the metal oxidation state. The above method would also go a long way towards fulfilling the gap in knowledge in the area of mineral analysis and the lack of comparative information between utilities on the constituents of particulate matter. The composition of the particles was also a question raised by the industry partners. The possible links between pH and TOC and customer complaint numbers may also be verified by such a study. Due to the complexity of discoloured water formation, the prediction of discoloured water events is demanding. The resuspension potential methods (RPM), discussed in the KIWA report, help determine the relative degree of particulate material within a pipe. Further research into the usefulness of this method (and other predictive tools or rules-of-thumb) is necessary. Collaboration through the Global Water Research Coalition has lead to similar RPMs being conducted in Australia. Recommendation 1b: is to extend this research on the RPM method in Australian distribution systems. A dearth of research in the area of discoloured washing was noted. Industry partners also asked the question why some customers complained of dirty washing but their neighbours didn’t. Recommendation 2: is to carry out a survey of customers who have complained to determine their washing procedures, water use and any other information on discoloured water occurrences e.g. timing of events. Recommendation 3: is to develop a conceptual model to provide a tool for utilities to access information about discoloured water and interactively represent their treatment and distribution systems in relation to discoloured water formation. In order to do this, a thorough investigation into the individual utilities’ experiences with dirty water needs to be conducted. A series of workshops with water operations personnel from the participating utilities should help to gather the information necessary to develop the conceptual model. In summary, the recommendations that came from this report are: 1a) Characterise the particles that form discoloured water, and how this is related to water chemistry 1b) Extend the research on the RPM method in Australian distribution systems 2 Survey customers that have encountered discoloured water to assess personal experiences 3) Develop a conceptual model as a tool for the management of discoloured water

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Outcomes

Stage 2 of the CRC project ‘Understanding the generation of discoloured water at customers taps’ has addressed most of these recommendations. A significant outcome from this work has been the development of a web-based Discoloured Water Management Support Tool to assess the cause and effect of critical discolouration issues. This tool is a comprehensive knowledge-capture process and facilitates a risk assessment approach to enable water utilities to take a step-by-step approach to resolving discoloured water issues. (www.discolouredwater.com)

Discoloured Water User Guidelines have also been developed using a broad toolbox approach of practical solutions to improve the management of discoloured water in drinking water systems. The tools that have been developed include quantitative models of particles within distribution systems, discoloured water characterisation procedures, customer complaint surveys and several field-based monitoring techniques.

For further information on these tools, please contact the Project Leader, Dr Peter Teasdale at Griffith University [email protected] or Industry Co-ordinator Corinna Doolan [email protected] at Sydney Water.

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7 ACKNOWLEDGMENTS The authors acknowledge the funding given by the CRC for Water Quality and Treatment as well as the in-kind contributions from Sydney Water, Brisbane Water, Hunter Water, Power and Water Corporation, Griffith University Gold Coast, Water Corporation of Western Australia, Yarra Valley Water, South East Water and Gold Coast Water. Thankyou to the industry partners for finding time to attend and present at early meetings to direct this project, specifically David Waite, Damian Devlin and Kerry Rock who shared their research on the topic at the Sydney meeting in January 2003, and Asoka Jayaratne, Prem Mathes and Wei Ju for presenting results from their particles project in Melbourne in July 2003. Attendees of these meetings, although not listed personally, were instrumental in providing the large body of knowledge and variety of information on which this report is built. The data for the desktop review was sourced by a number of people including Ted Evans and Ines Zic (Water Corporation WA), Jennifer Sage (Power and Water NT), Greg Ryan (South East Water, Vic), Damian Devlin and Paul Neuendorf (Brisbane City Council, Qld), Geoff Hamilton and David Smith (Gold Coast Water, Qld), Pam O’Donoghue (Hunter Water, NSW), Asoka Jayaratne (Yarra Valley Water) and Corinna Doolan (Sydney Water, NSW), who also analysed and reported on the data. More recently, comments received from Greg Ryan (South East Water) and George Ruta (City West Water), were much appreciated and helped shape chapter three of this document. Appreciation is also extended to the external reviewers: Jo Parker (Veolia Water UK), Jan Vreeburg (KIWA, The Netherlands) and Fiona Welby - Manager Communications - CRC WQ & T, in anticipation. Also significant to the completion of this review is the Distribution Programme Leader: Dammika Vitanage. The authors thank you for your direction, leadership and patience throughout the composition of this document.

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7 REFERENCES

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8 APPENDICES

Appendix 1

WATER QUALITY CUSTOMER COMPLAINT CATEGORIES IN VARIOUS WATER UTILITIES ACROSS AUSTRALIA

Yarra Valley Water Water Corporation Brisbane Water WA 1 Dirty water blue/green 1 Cloudy water 2 Dirty water black 1 Alleged Illness 2 Dirty water 3 Dirty Water brown 2 Copper Blue stains 3 Washing stained 4 Dirty water orange 3 Chlorine 5 Dirty water white 4 Dirty Water 6 Dirty water yellow 5 Foreign bodies in Odour/Taste 7 Fluoride water 8 Suspected illness 6 Miscellaneous 4 Chlorine taste 9 Skin irritations 7 Stained Laundry 5 Smelly water 10 Odour, chlorinous 8 Taste & Odour 6 Fish tank water 11 Odour, chemical 9 White Water 7 Fluoride 12 Odour, musty/earthy 8 Hard water 13 Stained fittings, blue/green

14 Stained fittings brown 15 Stained washing 16 Taste, bitter SE Water 17 Taste, Odour Sydney Water chemical Taste, Dirty Water Corporation Odour chlorine Taste chemical 1 Brown 1 Discoloured water 18 Taste metallic 2 Black 2 Bad Taste 19 Taste musty/earthy 3 Yellow 3 Bad Smell 20 Taste & Odour other 4 Washing 4 Sickness 21 Other 5 Other

Taste Odour 6 General Gold Coast Water Hunter Water 7 Chlorine Corporation 8 Other 1 Dirty water/ illness 2 Dirty water/ colour 1 Dirty Water 3 Dirty water/ odour & 2 Stain taste 3 Brown 4 Air 5 Chlorine Power and Water NT 6 Taste 7 Odour 1 Dirty water 8 Green 2 Bad taste 9 Black 3 Sand/Grit 10 Sand 4 Chlorine taste 11 Worms 5 Cloudiness 12 Blue 6 Turbidity 13 Health 7 Poor quality 14 Other 8 Odour

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Appendix 2

WATER TREATMENT PROCEDURES IN PARTICIPATING UTILITIES ACROSS AUSTRALIA BY ZONE/CATCHMENT

Sydney Water Reservoir Treatment Processes 1. Greaves Ck Ferric dosing & polyelectrolyte - coagulation/flocculation, rapid sand filtration, buffering with lime & CO2, fluoridation & chlorination 2. Nth Richmond Ferric dosing & polyelectrolyte - coagulation/flocculation, DAF, rapid sand filtration & GAC, pH correction using caustic soda, fluoridation & chlorination 3. Orchard Hills Ferric dosing & polyelectrolyte - coagulation/flocculation, rapid sand filtration, pH correction using caustic soda at start & end of plant, fluoridation & chlorination 4. Prospect Sth Coagulation/filtration/chlorination - chemicals are lime, potassium permanganate, sulfuric acid, ferric coagulant, cationic and nonionic polymers, chlorine, fluoride 5. Prospect Nth Coagulation/filtration/chlorination - chemicals are lime, potassium permanganate, sulfuric acid, ferric coagulant, cationic and nonionic polymers, chlorine, fluoride, ammonia 6. Prospect East Coagulation/filtration/chlorination - chemicals are lime, potassium permanganate, sulfuric acid, ferric coagulant, cationic and nonionic polymers, chlorine, fluoride, ammonia 7. Ryde Coagulation/filtration/chlorination - chemicals are lime, potassium permangate, sulfuric acid, ferric coagulant, cationic and nonionic polymers, chlorine, fluoride, ammonia 8. Potts Hill Coagulation/filtration/chlorination - chemicals are lime, potassium permanganate, sulfuric acid, ferric coagulant, cationic and nonionic polymers, chlorine, fluoride, ammonia 9. Warragamba Ferric dosing & polyelectrolyte - coagulation/flocculation, rapid sand filtration, pH correction using caustic soda at end of plant, fluoridation & chlorination 10.Nepean Ferric dosing & polyelectrolyte - coagulation/flocculation, buffering with lime & CO2 at head of plant, pre-oxidation with KMnO4, rapid sand filtration, roughing filters, fluoridation & chlorination 11.Macarthur Ferric dosing & polyelectrolyte - coagulation/flocculation, rapid sand filtration, pH correction with lime, fluoridation & chloramination 12.Illawarra Direct filtration with conventional dual media filters high pH coagulation with Ferric Chloride. Co-polymers to assist coagultion. Lime CO2 buffering with lime clarifier 13.Woronora Coagulation/sand filtration/chloramination. Potassium permanganate, lime, fluoridation, ammonia, ferric chloride, pH corrected, CO2, chlorine, polymers 14.Cascade Ferric dosing & polyelectrolyte - coagulation/flocculation, rapid sand filtration, pH correction with lime, fluoridation & chlorination Hunter Water Dungog Alum + poly coagulation, contact filtration, lime / CO2 alkalinity, chlorine fluoride Grahamstown Alum + poly coagulation (Pre-lime for Tomago Source) Sedimentation Filtration Lime Chlorine Fluoride Lemon Tree Passage Aeration Polymer coagulation 2 Stage Filtration Lime Chlorine and Fluoride Anna Bay Aeration, lime, chlorine and fluoride

117 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

Glovers Hill Aeration, caustic soda, pH correction, chlorine and fluoride Brisbane Eastbankk WTP Chemical coagulant addition and mixing, flocculation, horizontal flow sedimentation, filtration and disinfection by chloramination Westbank Chemical coagulant addition and mixing, flocculation, horizontal flow sedimentation, filtration and disinfection by chloramination, dissolved air flotation Northpine Chemical coagulant addition and mixing, flocculation, horizontal flow sedimentation, filtration and disinfection by chloramination Enoggera Chemical coagulant addition and mixing, flocculation, horizontal flow sedimentation, slow sand filtration and disinfection by chloramination SE Water Silvan Chlorination fluoridation2, chloramination 1 Cardinia Chlorination, fluoridation Winneke Conventional filtration, alum, chlorination, fluoridation, polyelectrolyte Power and Water Darwin River Dam No filtration Water Corporation Wanneroo Filtered - anthracite/sand deep bed filters. Groundwater Lexia Filtered - anthracite/sand deep bed filters. Groundwater Mirrabooka Filtered - anthracite/sand deep bed filters. Groundwater Neerabup Filtered - anthracite/sand deep bed filters. Groundwater Gwelup Filtered - anthracite/sand deep bed filters. Groundwater Jandakot Filtered - anthracite/sand deep bed filters. Groundwater South Dandalup North Dandalup Victoria Churchmans Conjurunup Wungong Canning Mundaring Stirling Serpentine Pipehead Gold Coast Molendinar WTP Filtered, chlorinated Mudgeeraba Filtered, chlorinated Yarra Valley Silvan Chlorination, fluoridation2, chloramination 1 Winneke Conventional filtration, alum, chlorination, fluoridation, polyelectrolyte Greenvale Chlorination Yarra Glen Micro filtration, alum, chlorination Healesville Micro filtration, alum, chlorination Cardinia Chlorination, fluoridation Yan Yean Direct filtration, alum, chlorination fluoridation

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Appendix 3

CUSTOMER COMPLAINT RATES PER ‘000 PROPERTIES FROM 1997 TO 2001 IN PARTICIPATING UTILITIES ACROSS AUSTRALIA

UTILITY 97/98 98/99 99/00 00/01 01/02 /1000 connections /1000 connections /1000 connections /1000 connections /1000 connections Sydney Water (14 Delivery Systems comprising of 206 water quality zones) 1,697,763 1,697,763 1,697,763 1,697,763 1,697,763 Maximum 19.2 Greaves Creek 59.8 Nepean 56.2 Warragamba 13.4 Greaves Creek 25.5 Greaves Creek Minimum 0.9 Prospect East 1.2 Prospect East 0.6 Prospect East 1.0 Ryde 0.8 Prospect East Total 3.0 5.0 3.9 2.3 1.7 Yarra Valley Water (34 water quality zones) 554,358 565,857 584,189 592,627 604,469 Maximum 34.6 Emerald 13.4 Yarra Glen 7.4 Upper Yarra 12.9 Upper Yarra 12.1 Ridge/Monbulk Minimum 0.9 Keon Park 1.5 Eltham 0.4 Eltham 0.6 Eltham 1.3 Wantirna Total 3.6 3.4 2.8 3.9 4.4 Hunter Water (5 WTP's) 196,681 196,681 196,681 196,681 196,681 Maximum 11.8 Anna Bay 31.9 Anna Bay 11.9 Anna Bay 10.6 Anna Bay 10.4 Anna Bay Minimum 2.8 Lemon Tree Passage 4.3 Nelson Bay 4.1 Nelson Bay 2.2 Lemon Tree Passage 1.1 Lemon Tree Passage Total 6.5 11.1 5.6 6.1 6.8 South East Water (29 water quality zones) 470,400 470,400 470,400 470,400 511,167 Maximum 66.7 Lang Lang 23.3 Lang Lang 40 Lang Lang 6.7 Lang Lang 4 Malvern 0 Bunyip, Tynong, Koo 0 Bunyip, Tynong, Koo Wee 0 Bunyip,Tynong, Koo Wee Rup, Minimum 0 Tynong & Koo Wee Rup Wee Rup Rup, Flinders 0 Bunyip, Tynong, Flinders Balnarring, Lang Lang Total 2.4 2.3 2.1 2.1 .9

119 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

Power & Water (52 suburbs) 25,851 25,851 25,851 25,851 25,851 Maximum 41.7 Mararra 13.3 Milner 23.8 Mararra 19.4 The Gardens 16.9 Woolner 0 Howard Springs, Hudson Ck, Humpty Doo, Knucky 0 Hudson Ck, Humpty Doo, 0 Hudson Ck, Knucky Lagoon, 0 Hudson Ck, Knucky Lagoon, Lagoon, Livingstone, Ludmilla, 0 Hudson Ck, Humpty Doo, Knucky Lagoon, Livingstone, Larrakeyah, Livingstone, Marlow Livingstone, Ludmilla, Marlow Marlow Lagoon, Moil, Knucky Lagoon, Livingstone, Noonamah, Palmerston, Lagoon, Noonamah, Palmerston, Lagoon, Moil, Noonamah, Noonamah, Parap, The Noonamah, The Narrows & Parap, Tiwi, Roseberry, The Parap, Roseberry, The Gardens, Palmerston, Roseberry, Virginia Gardens, The Narrows, Virginia Minimum Woolner Narrows, Virginia & Woolner The Narrows, Virginia & Woolner & Wagaman & Wagaman Total 12.3 5.7 4.8 4.5 1.8 UTILITY 97/98 8/99 99/00 00/01 01/02 /1000 connections 1000 connections /1000 connections /1000 connections /1000 connections Brisbane Water 361,000 369,000 376,000 383,000 (27 water quality zones) Maximum Not available 7.9 North Pine 23.8 Bracken Ridge 11.3 Bracken Ridge 4.8 Eildon Minimum Not available 3.1 Mt.Crosby 0 Moreton, Mt Coot-tha 0 Moreton, Mt Coot-tha 0 Moreton, Mt Coot-tha Total 3.8 5 3.6 2.7 Gold Coast Water (14 Distribution systems) 170,000 180,000 190,000 Maximum Not available Not available * 257 Molendinar 4, 5 & 6 * 105 Molendinar 4,5 & 6 * 298 Reedy Creek Minimum Not available Not available * 6 Coolangatta * 6 Coolangatta * 27 Coolangatta Total 9.3 2.7 6.5 Water Corporation (23 water supply zones) 661,395 661,395 661,395 Maximum Not available Not available 18.4 Eliza 28.3 Wanneroo 30.3 Whitfords Minimum Not available Not available 0.6 Yanchep 1.7 Two Rocks 0 Yanchep Total 12.4 14.8 11.9 * GCW maximum and minimum figures are actual complaint numbers because the number of properties per system was not available and therefore the per '000 complaint rate could not be calculated. However, the total per ‘000 rate could be calculated as the total number of connections each year was available.

120 CRC FOR WATER QUALITY AND TREATMENTRESEARCH REPORT 51

Appendix 4

AVERAGE WATER QUALITY OF TREATED WATER FOR PARTICIPATING UTILITIES ACROSS AUSTRALIA

FILTERED BRISBANE WATER SYDNEY WATER CORPORATION

Brisbane Brisbane Greaves Nth Orchard Prospect Prospect Prospect Potts Warra Mac Parameter NHMRC* Mt Crosby Nth Pine Ck Richmond Hills Sth Nth East Ryde Hill gamba Nepean arthur Illawarra Woronora Cascade

MEANS

Aluminium mg/L 0.2 0.074 0.052 0.06 0.02 0.025 0.013 0.013 0.012 0.016 0.016 0.013 0.038 0.048 0.025 0.031 0.033 Calcium mg/L 22 16 Colour (True) Hazen 15 1.2 0.8 units <2 <2 <2 <2 <2 <2 <2 <2 <2 <2 <2 <2 <2 <2 Colour (Apparent) Hazen units Copper mg/L 1 <0.001 <0.001 0.013 0.012 0.025 0.02 0.019 0.013 0.012 0.02 0.018 0.01 0.02 0.011 0.007 0.018 Iron mg/L 0.3 <0.01 <0.01 0.076 0.024 0.022 0.023 0.021 0.019 0.022 0.032 0.024 0.026 0.031 0.029 0.043 Manganese mg/L 0.1 0.008 0.013 0.009 0.002 0.002 0.002 0.002 0.002 0.002 0.003 0.005 0.007 0.005 0.005 0.005 0.007 pH units 6.5-8.5 7.9 7.7 8.1 8 7.7 7.7 7.9 7.9 7.8 7.8 7.8 7.7 8 7.9 8 7.8 Silica as SIO2 mg/L 4.0 1.3 0.004 0.001 0.005 0.003 0.003 0.003 0.003 0.003 0.004 0.002 0.002 0.001 0.002 0.004 Total Alkalinity (CaCO3 90 72 mg/L) 20 29 40 37 37 37 37 37 38 38 38 30 40 31 Total Dissolved Solids 500 260 181 100 167 126 117 117 117 117 117 116 98 102 71 104 110 Total Hardness mg/L 106 73 49 36 60 57 57 57 57 57 50 54 50 Total Organic Carbon mg/L Turbidity NTU 5 Raw <0.1 Raw 0.125 0.5 0.2 0.3 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.3 <0.00 Zinc mg/L 3 <0.001 0.001 <0.006 <0.005 <0.005 <0.005 <0.005 <0.005 5 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005

121 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

FILTERED GOLD HUNTER WATER COAST YARRA VALLEY WATER SEW WATER CORPORATION RANGE Lemon Tree Molen Yarra Heales Wann Mirra Neera Janda FILTERED Parameter NHMRC* Dungog Tomago Passage dinar Yan Yean Glen Winneke ville Winneke eroo Lexia booka bup Gwelup kot MEANS Yan Yean Yarra Winneke - Outlet Main Glen Preston Creswell MEANS at Mernda Reservoir Main @ Reservoir - Pumphouse - Outlet Research Outlet Aluminium mg/L 0.2 0.07 0.09 0.05 <0.2 0.04 0.10 0.01 0.04 0.014 0.01 - 0.10 Calcium mg/L 20 20 14 4.7 1.3 6 1.1 5.9 26.4 52.7 35.3 42.1 49.8 44.0 1.1 - 53 Colour (True) Hazen 15 units 0.8 - <2 Colour (Apparent) Hazen units <5 5 <5 <5 2 3 2 5 2 1 2 3 1 1 4 1 - 5 Copper mg/L 1 0.015 0.003 0.014 0.01 0.009 0.012 0.057 0.022 0.210 <0.001 - 0.210 Iron mg/L 0.3 0.02 0.04 0.05 0.06 0.18 0.006 0.001 0.01 0.02 0.01 0.02 0.01 0.02 0.01 0.001 - 0.18 Manganese mg/L 0.1 0.005 0.01 0.009 <0.02 0.005 0.002 0.003 0.00 0.004 0.020 0.008 0.002 0.004 0.002 0.020 0 - <0.02 pH units 6.5-8.5 7.5 7.3 7.4 7.2 7.4 7.4 7.2 7.3 6.9-7.8 6.9 7.2 6.8 7.7 7.1 6.9 6.8 - 8.1 Silica as SIO2 mg/L 13 4 7 4.3 6.9 5 8.2 5.0 14.4 12.6 13.7 19.4 16.5 14.1 0.001 - 19.4 Total Alkalinity as 59 55 54 121 94 88

CaCO3 mg/L 51 33 34 35 13 8 14 11 13 8 - 121 Total Dissolved Solids 500 114 194 124 <1 57 42 77 43 72 <1 - 260 Total Hardness mg/L 59 74 40 20 7 25 8 23 100 148 134 156 167 170 7 - 167 Total Organic Carbon mg/L 2.7 4.3 3.9 <2.5 2.5 1.8 1.8 3.7 1.7 1.7 - 4.3 Turbidity NTU 5 0.4 0.3 0.3 <0.2 0.6 0.8 0.2 0.1 0.1 - 0.6 0.6 0.3 0.2 0.4 0.2 0.2 0.1 - 0.8 Zinc mg/L 3 0.051 0.005 0.006 0.004 0.003 0.005 0.004 <0.001 0.02 <0.001 - 0.051

122 CRC FOR WATER QUALITY AND TREATMENTRESEARCH REPORT 51

UNFILTERED HUNTER WATER SOUTH EAST WATER YARRA VALLEY WATER POWER & WATER Glovers Parameter NHMRC* Anna Bay Hill Silvan Cardinia Cardinia Greenvale Silvan

Cardinia - Greenvale Silvan - N/Hill Outlet Silvan - Silvan - Waverley MEANS Main @ Main at Olinda Preston Main at Hallam Kenny Main at Main at Mt Mt Nth_ Prs Street Mt Evelyn Evelyn Evelyn Aluminium mg/L 0.2 0.09 0.03 0.04 0.03 0.03 0.02 0.03 0.04 Calcium mg/L 16 1 3.3 3.7 3.7 3.6 3.2 5 Colour (True) Hazen units 15 Colour (Apparent) Hazen units <5 <5 12 4 4 4 12 6 8 Copper mg/L 1 0.004 0.004 0.052 0.017 0.067 0.083 0.469 Iron mg/L 0.3 0.1 0.06 0.11 0.05 0.04 0.04 0.11 0.08 0.08 Manganese mg/L 0.1 0.007 0.003 0.011 0.005 0.005 0.002 0.01 0.004 0.007 pH units 6.5-8.5 7.4 7.2 7.1-7.7 7-7.8 7.6 7.3 7.3 7.4 7.4 7 Silica as SIO2 mg/L 9 9 7.7 6.2 6.2 6.2 7.7 89 TotLal Alkalinity as CaCO3 mg/L 39 14 13 15 16 15 14 3 Total Dissolved Solids 500 165 122 40 90 103 47 39 Total Hardness mg/L 55 15 14 16 17 16 15 Total Organic Carbon mg/L 1.8 1.1 2 3.1 3.7 3.4 2 Turbidity NTU 5 0.8 0.2 1.2 0.9 0.9 0.9 1.4 1.1 1.3 0.1 Zinc mg/L 3 0.009 0.007 <0.01 <0.01 0.002 0.002 0.002

123 LITERATURE REVIEW ON DISCOLOURED WATER FORMATION AND DESKTOP STUDY OF INDUSTRY PRACTICES

COMPARISON

1996 Parameter UNFILTERED FILTERED NHMRC Aluminium mg/L 0.02 - 0.09 0.01 - 0.10 0.2 Calcium mg/L 1-16 1.1 - 53 Colour (True) 0.8 - <2 15 Colour (Apparent) Hazen units 1-12 1 - 5 Copper mg/L 0.004 - 0.469 <0.001 - 0.210 1 Iron mg/L 0.04 - 0.11 0.001 - 0.18 0.3 Manganese mg/L 0.003 - 0.01 0 - <0.02 0.1 pH units 5.7 - 8.2 6.8 - 8.1 6.5-8.5 Silica as SIO2 mg/L 2.5 - 89 0.001 - 19.4 Total Alkalinity as CaCO3 mg/L 3 - 39 8 - 121 Total Dissolved Solids 40 - 165 <1 - 260 500 Total Hardness mg/L 15 - 89 7 - 167 Total Organic Carbon mg/L 1.1 - 3.7 1.7 - 4.3 Turbidity NTU 0.1 - 2.1 0.1 - 0.8 5 Zinc mg/L 0.002 - 0.02 <0.001 - 0.051 3

HWC SWC YVW HUNTER SEW YVW POWER & WATER SEW WCWA BRISBANE GOLD COAST WCWA

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• ACTEW Corporation • Australian Water Quality Centre Water Quality • Australian Water Services Pty Ltd • Brisbane City Council and Health Risks CRC for Water Quality and • Centre for Appropriate Treatment Technology Inc Private Mail Bag 3 • City West Water Limited from Urban Salisbury SOUTH AUSTRALIA 5108 • CSIRO Tel: (08) 8259 0351 • Curtin University of Technology Fax: (08) 8259 0228 Rainwater Tanks • Department of Human Services E-mail: [email protected] Victoria Web: www.waterquality.crc.org.au • Griffith University Research Report 42 • Melbourne Water Corporation • Monash University • Orica Australia Pty Ltd • Power and Water Corporation • Queensland Health Pathology & Scientific Services • RMIT University • South Australian Water Corporation • South East Water Ltd • Sydney Catchment Authority • Sydney Water Corporation • The University of Adelaide • The University of New South Wales The Cooperative Research Centre (CRC) for Water Quality and Treatment is Australia’s national drinking water research • The University of Queensland centre. An unincorporated joint venture between 29 different • United Water International Pty Ltd organisations from the Australian water industry, major universities, CSIRO, and local and state governments, the CRC • University of South Australia combines expertise in water quality and public health. • University of Technology, Sydney

The CRC for Water Quality and Treatment is established • Water Corporation and supported under the Federal Government’s Cooperative • Water Services Association Research Report Research Centres Program. of Australia • Yarra Valley Water Ltd 42