Green Paper Technical Paper No.1
Water Recycling Scenarios for Melbourne
September 2003
Securing Our Water Future This report has been prepared by the Department of Sustainability and Environment and the four metropolitan water businesses – Melbourne Water, City West Water, South East Water and Yarra Valley Water. Its production has been managed by a Steering Committee consisting of representatives from these businesses and the Department of Sustainability and Environment.
Department of Sustainability and Environment PO Box 500, East Melbourne Victoria 3002 © State of Victoria, Department of Sustainability and Environment 2003 ISBN 1 74106 674 3 This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. Find out more information about DSE on the internet at www.dse.vic.gov.au Green Paper Technical Paper No.1
Water Recycling Scenarios for Melbourne
September 2003 2
How to have your say
The Government is releasing Water Recycling Scenarios for Melbourne for a period of public review and comment as part of the Water Review’s Green Paper consultation process. The initial comment period, up to 31 October 2003 is to give all interested parties the chance to comment or make a submission on Water Recycling Scenarios for Melbourne. In particular, Government is interested to hear your opinion on the scenarios within the report. We need to understand issues such as:
• Do you consider the scenarios to be feasible and viable?
• Are there any other benefits and costs that need to be considered in any of the scenarios?
• Are there other scenarios that Government should be considering?
• What role do you consider that the scenarios should play in future sustainable water resources management for Melbourne?
Comments or submissions on the Technical Paper Water Recycling Scenarios for Melbourne and specific feedback on its content should be submitted to the Department of Sustainability and Environment by 31 October 2003 and should be lodged on the website or directed to:
Project Manager – Technical Paper No. 1, Water Sector Development Group Department of Sustainability and Environment PO Box 500 East Melbourne Victoria 3002 Submissions In order to ensure the integrity of the consultative process, you are asked to provide your name and address with your submission. Unfortunately we will not be able to accept submissions which do not include this information. However, all personal identifying information will be removed after it is received if that is your request. If this is the case, or there are any other parts of your submission that you wish to treat confidentially, please make this clear in your submission Water Recycling Scenarios for Melbourne 3
Contents
How to have your say 2 Foreword 5 Introduction 6 Melbourne’s water infrastructure 10 Background 10 Melbourne’s potable water supply system 12 Melbourne’s sewerage system 13 Melbourne’s stormwater system 14 Melbourne’s groundwater system 15 Integration of water systems 16 Recycled water schemes in Melbourne 18 Scenario Analysis 22 Potable Substitution Scenarios 23 Scenario 1 – Retrofit third pipe system throughout Melbourne 23 Scenario 2 – Third pipe systems in new growth areas 25 Scenario 3 – Target existing high volume water users 28 Scenario 4 – Mandated recycled water use in proximity of treatment plants 31 Scenario 5 – Placing recycled water into potable water supply system 34 Scenario 6 – Placing recycled water into potable water supply system and increase the use of bottled water for drinking 36 Scenario 7 – Sewer mining 38 Scenario 8 – Use of greywater 40 Economic Development Scenarios 42 Scenario 9 – Werribee Plains (Balliang) 42 Scenario 10 – Eastern Irrigation Scheme, Cranbourne-Koo Wee Rup Corridor 45 Environmental Scenarios 47 Scenario 11 – Thomson River Environmental Flows 48 Scenario 12 – Werribee River Environmental Flows 50 Scenario 13 – Pumping Melbourne’s recycled water north of divide - option 1 52 Scenario 14 – Pumping Melbourne’s recycled water north of divide – option 2 54 Other Potential Water Source Scenarios 56 Scenario 15 – Stormwater harvesting 58 Scenario 16 – Increased utilisation of rainwater tanks 60 Scenario 17 – Utilisation of storm water to reduce salinity in sewage flows to WTP 63 Scenario 18 – Desalination 64 Scenario 19 – Aquifer storage and recovery 65 References 67 Glossary 68 4
To deliver maximum benefits from water recycling in the long term, the Government has been exploring a range of scenarios for the Melbourne region which vary considerably in scale and scope. It is important to think broadly at this stage to make sure that we explore and obtain community feedback on a diverse range of possibilities. Water Recycling Scenarios for Melbourne 5
Minister’s Foreword
In my Ministerial Statement Valuing Victoria’s Water – Securing Victoria’s Future, I announced that a Green Paper would be prepared that would provide a framework for consultation with the community and industry so that the next round of water reform is well founded and enjoys broad support. The Green Paper Securing Our Water Future has now been released for public comment.
A key strategy in the Green Paper is to substitute This report, released in conjunction with the drinking water with alternative water resources, such Green Paper, provides the reader with a high level as recycled water from sewerage systems, rainwater understanding of Melbourne’s water systems, the collected in rainwater tanks, urban stormwater current status of water recycling, a snapshot of the runoff and greywater, for non-potable uses. Several water recycling scenarios considered, with new initiatives are proposed, and current initiatives information about economic, environmental and extended, to promote and encourage increased use social benefits and costs. of these resources. Your feedback on these scenarios will help guide the Regional Victoria recycles about one third, and Government in the future development of water Melbourne less than 5 percent (not including treatment recycling in the region. process recycling), of their respective treated sewage effluent. There is only limited recycling of rainwater, greywater and stormwater. However, the water industry, regionally and in Melbourne, is pursuing many water recycling opportunities and projects. The next 18 months will see many important milestones reached in the development of the use of recycled water and other alternative water resources and the management and utilisation of water resources in Victoria. John Thwaites MP To deliver maximum benefits from water recycling in the long term, the Government has been exploring a Minister for Water range of scenarios for the Melbourne region which vary considerably in scale and scope. It is important to think broadly at this stage to make sure that we explore and obtain community feedback on a diverse range of possibilities. Some scenarios are currently undergoing feasibility assessment, and for most, this is the first high level analysis. 6 Introduction
Introduction
Valuing Victoria's Water – Securing Victoria's Future: Minister's Statement
The State Government recognises that water recycling has a key role to play in sustainable water resource management and is promoting greater recycling in the urban environment throughout Victoria. In particular, a target of 20 percent recycling of Melbourne’s ‘waste’ water by 2010 has been established.
On 10 April 2003, the Minister for Water announced a Where we are today new agenda for sustainable water management to Regional Victoria recycles about one third of its treated support sustainable rural industries, healthy rivers and sewage and Melbourne currently recycles approximately floodplains, and growth in towns and cities. This 30,000 ML per annum (including on site process challenge is to be met by: recycling) which is about 10 percent of treated sewage. >> protecting water flows in rivers, waterways and However, this is less than 5 percent with on-site groundwater systems; process recycling not included (2001/02 figures). The >> Reducing our use of pure drinking water and greatly water industry in Melbourne is pursuing many water increasing the use of recycled and reclaimed water recycling opportunities and projects. The next eighteen for irrigation, industrial and urban use; months will see many important milestones in the development of water recycling and the management >> Investing in efficient irrigations systems to lift and utilisation of water resources in Victoria. production with less water; and >> better catchment management — recognising that The need for a strategic approach to water supply, river and farm management, sewerage, water recycling re-use of water, drainage, coastal protection and The water strategy for Melbourne titled 21st Century flood control are linked and part of one system. Melbourne: A WaterSmart City referred to in this paper The Minister also announced that a Green Paper would as the Water Resources Strategy (Water Resources be prepared which would provide a framework for Strategy Committee, 2002) identified a target of 13,000 consultation with the community and industry so that ML/year of potable water replacement within 50 years the next round of water reform is well founded and from installation of rainwater tanks and water recycling enjoys broad support. The Green Paper Securing our initiatives. The target is to assist in achieving the policy Water Future (DSE, 2003) has now been released for of no new dams for Melbourne. The need for a strategic, public comment. holistic planning approach to water recycling is required to deliver greater value for money in relation to triple A key strategy in the Green Paper is to substitute bottom line benefits if a sustainable water industry is to drinking water with alternative water resources such as develop in Melbourne in the 21st Century. recycled water from sewerage systems, rainwater collected in rainwater tanks, urban stormwater runoff About this report and greywater. Several new initiatives are proposed, This report aims to provide the reader with — and current initiatives extended, to promote and encourage increased use of these resources. >> A high level understanding of what water recycling is and how it works. Recycling of treated sewage from Melbourne’s treatment plants is limited and has great potential to >> An overview of the water, sewerage and drainage positively impact future water resource management in infrastructure systems and related water balance Melbourne including; for Melbourne. >> The current status of recycling schemes in the >> reducing the nitrogen load to Port Phillip Bay; Melbourne region. >> reducing effluent discharge to local waterways and >> A snapshot of proposed schemes being planned by Bass Strait: the water industry. >> contributing to higher amenity; and >> A snapshot of various water recycling scenarios for >> having a positive impact on the economy. future use of alternative resources. Use of other ‘non-traditional’ water resources, such as >> Information to compare these scenarios based on rainwater captured in rainwater tanks, urban triple bottom line costs and benefits. stormwater and greywater, is also limited and the >> An understanding of issues and information gaps. potential of these opportunities needs to be explored further in the Melbourne region. Nineteen scenarios were examined. The scenarios are listed and described in Table 1. This report aims to clarify the status and potential of water recycling in the Melbourne region for the reader and to put various recycling scenarios into perspective. Water Recycling Scenarios for Melbourne 7
Boundary of study Scenario estimates of cost This report focuses on water recycling within the The scenarios analysed in this document contain boundaries of the four metropolitan water businesses. estimates of cost that have been prepared as first level It recognises the growing interdependence of ‘order of magnitude’ costs. They are not supported by metropolitan Melbourne and the regional cities, towns detailed analysis however they have been prepared by and rural areas in the wider Melbourne region. Several the water industry and it is considered reasonable to of the scenarios considered involve the exporting of use them to compare scenarios. recycled water into regions outside of the boundary of the metropolitan water businesses.
Table 1. Scenario analysis summary No Scenario Scenario description
1 Retrofit third pipe systems This scenario considers potable water replacement for toilet throughout Melbourne flushing and garden watering with Class A recycled water in all existing and new residential developments, (including the CBD), and in commercial and industrial premises by targeting the larger water consumers in industrial and recreational sectors. 2 Third pipe systems in This scenario considers mandating the use of third pipe systems new growth areas in all new residential developments within the urban growth boundaries specified by Melbourne 2030 (DOI, 2002). Recycled water would substitute potable water for toilet flushing, and garden and public open space watering. 3 Target existing high volume This scenario examines the feasibility of targeting existing high water users water volume users, encouraging them to use recycled water in place of their existing potable source. The 200 largest users consume around 10 percent of the total water consumption in Melbourne. 4 Mandated recycled water use This scenario explores the opportunity to mandate the use of recycled water in areas adjacent to sewage treatment plants and trunk sewer infrastructure for non-potable use, provided public health, safety and environmental risks are managed. 5 Placing recycled water into This scenario presents the option of further treating and potable water supply system pumping all the discharge from the Western Treatment Plant (WTP) into Greenvale and Winneke reservoirs, and from the Eastern Treatment Plant (ETP) into Cardinia Reservoir. The treated water would be mixed with the existing potable water and the mixture further treated to ensure potable standards are met, and supplied to much of the western and south eastern suburbs of Melbourne. 6 Placing recycled water into In this scenario all discharge from the WTP and ETP is pumped into the water supply system and reservoirs as in Scenario 5, however the discharge from both treatment increase use of bottled water plants would be treated to an enhanced standard suitable for human for drinking contact, but not to WHO drinking water standard. (i.e. same bacterial quality as drinking water but higher nutrients, TDS, colour etc). Recycled water would be mixed with fresh potable water in the reservoirs and the shandy would be used for all purposes except drinking. The public would be supplied with bottled water through supermarket retail distribution outlets for drinking and cooking purposes. 8 Introduction
Table 1. Scenario analysis summary cont. No Scenario Scenario description
7 Sewer mining This scenario considers sewer mining, which is the local treatment of raw sewage to provide recycled water for nearby beneficial uses such as open space watering, industrial uses etc. In an urban environment the expectation is that it is treated to a Class A standard (unrestricted use) 8 Use of greywater This scenario considers the use of greywater, which is defined in a residential context as treated sewage from the kitchen, laundry and bathroom but excluding toilet wastewater. Greywater use is becoming increasingly popular with the community, particularly with the current drought. 9 Vision for Werribee Plains: The area north-west of the Western Treatment Plant has the Balliang potential to use recycled water for agriculture, intensive horticulture, new urban development and to improve Werribee River flows for environmental and recreational use. This scenario considers the Balliang project which investigates the provision of recycled water to the Balliang District, which is bounded by the Brisbane Ranges, the You Yangs and the Werribee River. 10 Eastern Irrigation This scenario considers the Eastern Irrigation Scheme which is Scheme, Cranbourne – based on the provision of recycled water from the Eastern Koo Wee Rup Corridor Treatment Plant to horticultural, agricultural, manufacturing and recreational industries in the Cranbourne to Koo Wee Rup corridor. 11 Thomson River The Thomson River has been classified as an Environmental Flows environmentally stressed river downstream of the Cowwarr Weir. This scenario considers treated water from the Eastern Treatment Plant being further improved by polishing through a dual membrane treatment plant and discharged to a location just below the Thomson Dam. 12 Werribee River The Werribee River downstream of Melton Reservoir is Environmental Flows degraded requiring significant riparian works and environmental flows to improve the ecological health of the river. Farmers in the Werribee Irrigation District use around 11,000ML to 13,000ML annually from the Werribee River primarily for agriculture and horticulture. This water is sourced from the Melton Reservoir and pumped from the river. This scenario considers substituting this irrigation water with recycled water from the WTP. 13 Pumping Melbourne’s This scenario involves recycling 100 percent of the suitably recycled water north treated sewage from the ETP and WTP by pumping it across of the Divide option 1 the Bay from ETP to combine the flow with the WTP. This combined flow would then be pumped north to the Great Dividing Range and discharged into existing irrigation channels. Water Recycling Scenarios for Melbourne 9
Table 1. Scenario analysis summary cont. No Scenario Scenario description
14 Pumping Melbourne’s This scenario considers diverting sewage from the northern recycled water north of parts of Melbourne, treating the sewage to produce high quality the Divide option 2 recycled water and transferring this water into the Goulburn Valley. The recycled water would be used to supplement current irrigation schemes in the region to the north and west of the State 15 Stormwater harvesting This scenario involves increasing the use of retarding basins as a source of storage of stormwater and ‘harvesting’ the stormwater for use. Stormwater would be treated through combinations of pollution traps, settling ponds and environmental wetlands and where appropriate, more sophisticated processes would be utilised. 16 Increased utilisation Rainwater tanks are a traditional source of domestic water of rainwater tanks supply for isolated properties and small communities, but they are not commonly used in urban areas. This scenario considers increased use of rainwater tanks in the Melbourne region which have the potential to provide substitutes for potable water where water is used for garden watering and toilet flushing. 17 Utilisation of stormwater High salt levels exist in the sewage that flows into the to reduce salinity in Western Treatment Plant at Werribee. This scenario considers sewage flow to Western diluting the sewage flow with stormwater flows. Treatment Plant 18 Desalination This scenario considers the potential for desalination in Melbourne, which involves converting seawater into potable water. 19 Aquifer storage and recovery This scenario considers the use of treated recycled water for temporary storage in aquifers for later use when there is demand. Recycled water can be stored in a bubble within an aquifer with little intrusion from groundwater effectively acting as a stand-alone storage due to the different characteristics (such as salinity) of the recycled water and the groundwater. 10 Melbourne’s Water Infrastructure
Melbourne’s Water Infrastructure
Background
The water cycle is an integral element in Urbanisation interrupts the natural water cycle through supporting the health of the community the following processes — • Water collection, storage, treatment and transfer and the environment. The requirements systems. of modern cities impact on the water • Sewage collection, transfer treatment and cycle, and the management of water, discharge systems. sewerage and drainage services play a • Greater production of stormwater through the vital role in determining how great that introduction of impervious surfaces and related impact is. Melburnians enjoy one of the stormwater management systems. best environments of any major city in • Changing land use. the world. The challenge for the future is • The introduction of water recycling systems. to continue to develop sustainable water The following diagrams represent Melbourne’s water systems that permit the people of cycle (Figure 1) and Melbourne’s water balance which presents Melbourne’s average annual water and sewage Melbourne to enjoy the benefits of our flows (Figure 2). built environment, parks, gardens, waterways, bays and ocean coast into the future.
Figure 1. The urban water cycle (Source: MWC)
retail water businesses Water Recycling Scenarios for Melbourne 11
Figure 2. Melbourne’s water balance – average annual flows (Source: South East Water)
Toorourong Reservoir 17 GL
Western Water Yan Yean 13 GLReservoir Maroondah 3 GL Greenvale Reservoir Reservoir Sugarloaf 40 GL O'Shannassy Reservoir 31 GL Reservoir 75 GL Upper Yarra 32 GL Coranderrk 90 GL 35 GL Reservoir 125 GL 10 GL Regional STP's 265 GL City West 8.8 GL Yarra Tribs 0.2 GL 30 GL Thomson Water Reservoir Yarra Valley Silvan Altona STP Water 253 GL Reservoir 5.7 GL 189 GL 113 GL Cardinia 17.2 GL Reservoir Western STP (MW) Tarago 136.5 GL 113 GL Reservoir 183.4 GL 11 GL South East Water Eastern STP (MW) Cranbourne STP Port Phillip Pakenham STP Bay 1.4 GL Longwarry STP N Blind Bight STP 1.7 GL Koo-wee-rup STP Mornington STP 0.6 GL Lang Lang STP Retail water businesses STPs 4.6 GL MWC STPs 0.7 GL South-eastern outfall sewer Hastings STP Regional recycling 1.4 GL Water inflows Rosebud STP Western Port Treated outflows Boags Rocks 2.9 GL Sewage outflows 145 GL Storage transfers 12 Melbourne’s Water Infrastructure
Melbourne’s potable water supply system
Melbourne's drinking water is Melbourne's storage reservoirs ensure water is available in dry periods and provide carry-over storage for recognised as some of the best in the drought years. The storage reservoirs supply water via world. The main reason for this is that large transfer mains to service reservoirs that are our catchments are largely protected located throughout the metropolitan area to meet daily and hourly consumption needs. The water is then from human interference and provide transferred to the retail water companies that provide for uncontaminated rainfall collection reticulated water to domestic, commercial and into a network of major storages. industrial customers in the greater Melbourne area. Melbourne's water harvesting and distribution system Melbourne's drinking water comes from streams and consists of uninhabited catchments, 13 large storage rivers running naturally through these uninhabited dams, 57 service reservoirs and 1,280 kilometres of catchment areas that have been closed to the public for up water mains, reticulation pipelines, aqueducts and to 100 years. The water is collected from more than siphons, and 5 filtration and 65 water treatment plants. 140,000 hectares of natural forest in the Yarra Ranges. It Melbourne's water harvesting and trunk water transfer is then stored for up to five years to help purify it through system, managed by Melbourne Water (MWC) is shown a natural settling process. The result is water so pure that in Figure 3. To provide clarity in the diagram the it requires only minimal treatment. Approximately 20 branch and reticulation network comprising 20,000 percent of catchments are not closed and water from kilometres of water mains, managed by the retail water these regions receives additional treatment. businesses, has not been shown.
Figure 3. Melbourne’s major potable water supply system (Source: MWC)
Toorourong Reservoir Running Creek Reservoir Yan Yean Reservoir Yarra Valley Water Maroondah Greenvale Sugarloaf Reservoir O'Shannassy Reservoir Reservoir Yarra Glen Reservoir Plenty Upper Yarra Broadmeadows Yering Gorge Reservoir Pumping Station Preston Lilydale St Albans Olinda Thomson City West Reservoir Water Silvan Melbourne Reservoir Cowies Hill Mt View Monbulk Cardinia Reservoir Dandenong Tarago Hallam Nth Reservoir
Pakenham Garfield Port Phillip Cranbourne Bay Frankston Reservoir South East Water N Mornington
Tyabb Water supply catchment Water storage reservoir French Devilbend/Bittern Island Water service reservoir Dromana Reservoir (Decommissioned) Water pumping station Water treatment plant Western Port Water pipelines/aqueducts Phillip Retail water Island business boundaries Water Recycling Scenarios for Melbourne 13
Melbourne’s sewerage system
Melbourne’s stormwater and sewerage The sewerage system carries approximately 90 percent of Melbourne’s sewage for treatment at MWC’s Western systems, as in most Australian cities, are Treatment Plant (WTP) in Werribee (approximately 500 separate systems designed to operate ML/day) and the Eastern Treatment Plant (ETP) in independently. Much of the planning for Bangholme (approximately 400 ML/day). The remaining sewage flow (approximately 90 ML/day) is treated at Melbourne’s robust sewerage system can regional treatment plants, managed by the retail water be traced to planning that occurred in companies, in the outer areas of Melbourne. The WTP uses an activated sludge/aerated lagoon system, while the 1890s to avoid the public health, the ETP uses an activated sludge process. environmental and odour problems Melbourne’s sewerage system collects, transfers and associated with discharge of waste treats about 330 GL/year. It comprises an extensive directly to gutters and streams that system of sewerage mains, pumping stations and treatment plants. Figure 4 shows the major transfer occurred prior to this period. system, managed by MWC. For simplicity, the branch and reticulation network comprising over 20,000 kilometres of sewers managed by the retail water businesses, is not shown. The sewage consists of a mixture of domestic sewage, inflow and infiltration from rainfall and from groundwater, and trade waste.
Figure 4. Melbourne’s major sewer transfer system (Source: MWC)
Yarra Valley Water
City West Water Werribee River Brooklyn Kew
Little River Hoppers Western Crossing North Rd Treatment Plant Mordialloc No.1&2 Thames Promenade Eastern Bondi Rd Treatment Plant South East Water Port Phillip Bay N
Sewage treatment plants Extent of drainage French rating boundary Island Sewerage pipeline Sewerage pumping station Major waterways Boags Western Port Rocks Phillip Retail water Island business boundaries 14 Melbourne’s Water Infrastructure
Melbourne’s stormwater system
Water that runs off properties, roads and and on beaches. Many of these pollutants are toxic to fish, plants and animals that live in our waterways. The other impervious surfaces when it rains is main pollutants of concern found in our waterways are stormwater. This stormwater is gathered pathogens, nutrients, toxicants, litter and suspended by a network of pipes and drainage solids. channels and is transported, mostly Local government is responsible for the management of local drainage. This includes street and property untreated, to our waterways or bays. The drainage and the 25,000 kilometres of local drains stormwater network is totally separate which feed into regional drains and waterways. MWC is responsible for regional drainage, flood protection and from the sewerage system. waterway management involving the protection and improvement of the water quality of most of the Port When it rains, pollutants such as engine oil, plastic Phillip and Western Port catchments. The land bags and other litter, and bacteria from animal waste management responsibilities relating to stormwater lie are washed from our roads, nature strips and gutters with the Port Phillip and Western Port Catchment into stormwater drains. There are more than 100,000 Management Authority. The MWC drainage system points around Melbourne where litter can enter the consists of 4,391 kilometres of waterways, 1,780 drainage system. It is then carried in our creeks, rivers kilometres of drainage channels, 140 retarding basins and drainage channels before ending up in the bays and 25 wetlands. The system is shown in Figure 5.
Figure 5. Melbourne’s waterways and regional drainage system (Source: MWC)
Wallan
King Lake
Sunbury Hurstbridge Yarra Healesville Glen Melton Warburton Seville
Melbourne Werribee Emerald
Port Phillip Pakenham Bunyip Bay Cranburn Frankston Drouin Geelong 01020 Cardinia Channel drain Kilometres Koo Wee Rup Warneet Underground drain Mornington Melbourne water drainage metropolis boundary Dromana Extent of drainage rating boundary Hastings Waterways French Island Drainage pumping station Crib Point Retarding basin Shoreham Western Port Phillip Island Water Recycling Scenarios for Melbourne 15
Melbourne’s groundwater system
Figure 6 indicates the interpreted depth Moving away from plains adjacent to the coast, watertable levels and salinity are less influenced by to watertable across the Port Phillip and tidal movement and depth to watertable increases. On Western Port catchments. Adjacent to the basalt and alluvial plains, watertable depth and the east and north-east perimeter of Port salinity is generally influenced by subtle variation in the landscape. On the basalt plains, incised streams are Phillip Bay, and the northern perimeter prone to receiving brackish to saline groundwater of Western Port watertables are shallow inflow. This is partly a natural condition, but is significantly exacerbated by land management change. across coastal swamps, and alluvial and Depressions in the landscape are also at risk where high basalt plains. watertables are found within capillary reach of the surface. In the sand belt country to the south-east of These watertables are strongly controlled by sea level Melbourne, salinity will generally be contained due to conditions. A delicate interaction exists between land better system permeability. In the uplands north of management and the coastal hydrogeological Melbourne, the Mornington Peninsula and the islands of environment. In general, the groundwater system has Western Port there are significant though localised areas watertables within five metres of the surface. These of high watertable and salinity associated with fractured watertables are strongly influenced by surface water rock aquifer systems. Salinity characteristically develops management including drainage and irrigation at the break-of-slope and groundwater depth is strongly management. Seawater intrusion impacts have been controlled by topography. recognised in some areas where groundwater is The Gippsland and Southern Rural Water Authority is pumped or drained. responsible for groundwater management in the region.
Figure 6. Melbourne’s groundwater system (Source: DSE)
CMA boundaries Lilydale LGA boundaries Prime development zones Roads Melbourne Rivers Salinity discharge WPDZ 1 Depth to Watertable 1998 < 2m (source SKM) 2 – 5m 6 – 10m > 10 Anakie No data WPDZ 2 WPDZ 3 Dandenong
Lara
EPDZ 1 Geelong EPDZ 2
Dromana Tankerton EPDZ 3
Cowes Highfield 16 Melbourne’s Water Infrastructure
Integration of water systems
Melbourne’s water systems are large-scale engineering schemes designed to protect public health and the environment. They include systems which: • reticulate potable water; • collect and treat sewage; and • manage stormwater runoff. They are not systems that are necessarily empathetic to the objectives of modern water resource management which is focused on: • resource conservation; • valuing treated sewage, stormwater, rainwater and greywater as valuable resources and not ‘waste’ products; and • integrated water planning providing for substitution of sources and ‘fit for purpose’ supplies. Water is a resource — we take it from the environment, use it, pollute it, treat it and return it to the environment. Modern water resource management will ensure that water recycling initiatives reclaim the water we have polluted and recycle it as much as possible before returning it in a less polluted state to the environment. Water Recycling Scenarios for Melbourne 17 18 Recycled Water Schemes in Melbourne
Recycled Water Schemes in Melbourne
This section presents a high level summary of the current status of water recycling from Melbourne’s sewerage systems and treatment plants and includes a plan showing existing and proposed schemes. A stocktake of existing and proposed recycled water schemes was undertaken by the four metropolitan water businesses and the result of this is presented in Appendix 1. In summary, there are currently 16 recycled water schemes operating in Melbourne and 20 proposed schemes. A summary of these schemes is presented in the following table.
Table 2. Summary of Melbourne’s recycled water schemes
Melbourne Water City West Yarra Valley South East Melbourne Corporation Water Water Water Total Number of existing schemes * 6 0 3 8 16 Total existing on site recycled 11,000 0 40 750 11,790 water scheme (ML/year) Total existing off site recycled 18,700 0 100 1,320 20,120 water scheme (ML/year) Existing schemes (class of water) B&C NA B C B & C Number of proposed schemes 5 4 8 3 20 Total proposed on site recycled 12,000 0 300 170 12,470 water scheme (ML/year) Total proposed off site recycled 86,000 1,900 4,100 780 92,780 water scheme (ML/year) Proposed schemes (class of water) A & B A A & B A & C A, B & C
* Many schemes identified have multiple customers, each of which could be defined as a separate scheme. Eg. The South East Water Hastings outfall pipeline has 11 users and the MWC scheme that involves recycling water from the ETP outfall has 35 customers.
Figures 7 and 8 provide maps of existing and potential recycling sites around Melbourne respectively. Only schemes that are currently managed by the four Melbourne water businesses have been considered. Water Recycling Scenarios for Melbourne 19
Technical issues
There are a number of technical issues that will have to 5. Salinity: Treated sewage is typically high in salinity be addressed if water recycling is to fulfil its potential with discharges from WTP in excess of 1000 mg/L. within a future, sustainable water industry in If there is to be widespread use of recycled water in Melbourne. Many of the issues were identified in agriculture, a solution is required to reduce this Victoria’s Water Recycling Action Plan (NRE, 2002) and concentration and to develop a method for irrigating strategies for managing these issues are underway. in an environmentally sustainable manner. Others have arisen within the development of projects 6. Quality: Confusion exists as to the required quality including the preparation of this report. These issues of recycled water. Should EPA licence requirements or are described as follows. recycled water requirements drive treated sewage 1. Beneficial discharge of recycled water to surface quality? Should recycled water be fit for purpose waters: The recently gazetted Variation to State and/or Class A, B or C? environment protection policy (Waters of Victoria) (State Following public consultation on the Green Paper and Government of Victoria, 2003) allows for the potential this report, issues 1, 2 and 4 will either be addressed or for recycled water discharge to surface waters for the have a plan developed. This will be achieved as part of environment or other uses (eg diversions for high value the White Paper, the second phase of the Government’s uses downstream of the discharge point) to be an Water Review process. acceptable form of reuse, provided beneficial uses are protected. There is a need for the Government to Issues 3, 5 and 6 will be addressed by the relevant develop clear criteria to be met to enable proponents to water businesses, and where appropriate, in develop cases for approval of such reuse. consultation with EPA Victoria. 2. Consistent approach to Triple Bottom Line (TBL) assessment: Many water recycling schemes rely on TBL assessed environmental and social benefits to justify the gap between water recycling cost, and the revenue from users. The need to develop a practical method to undertake a TBL assessment of water recycling programs was recognised in Victoria's Water Recycling Action Plan (NRE, 2002). To respond to this need the Government is developing guidelines for water recycling planning and reporting which will guide water authorities and businesses in carrying out TBL assessment and determining a TBL justifiable recycled water program in a consistent manner. The guidelines are targeted towards recycling from existing treatment plants. Feedback will be sought on draft guidelines in 2003. 3. Quantification of actual environmental benefits: Quantification of actual environmental benefits that result from reduced river, ocean and bay discharges is required. 4. 20 percent recycling target: Clarification is required of how and to whom the 20 percent water recycling target applies. A definition of how the target will be calculated is also required. 20 Recycled Water Schemes in Melbourne
Figure 7. Map of existing recycling sites in the Melbourne region (Source: South East Water)
Toorourong Reservoir Whittlesea Cades Rd STP Western Water Yan Yean 100 Reservoir Maroondah Greenvale Craigieburn STP Reservoir Reservoir Sugarloaf O'Shannassy Reservoir Reservoir Upper Yarra Yarra Valley Healesville STP Reservoir Water Lilydale STP Brushy Yarra Tribs City West Creek STP Upper Yarra Thomson Water 50 Dalry Road STP Reservoir Silvan Reservoir Altona STP Monbulk Baynes Park STP Symons Rd Emerald STP 160 Cardinia Ferres Rd Emerald STP Reservoir Western STP (MW) Tarago 11,000 South East Water Reservoir 17,000 On Site On Site Eastern STP (MW) 1,060 Cranbourne STP Port Phillip Pakenham STP Bay 100 80 Longwarry STP Blind Bight STP 120 75 Koo-wee-rup STP Lang Lang STP Mornington STP 1,700 N 50 500 95 Retail water businesses STPs Hastings STP MWC STPs South-eastern outfall sewer Rosebud STP Western Port Boags Rocks Water recycling (in ML) ML Water Recycling Scenarios for Melbourne 21
Figure 8. Map of potential recycling schemes around Melbourne (Potential schemes from local treatment plants not shown) (Source: MWC)
Werribee / Laverton / Altona Residential and Industrial Areas ? GL Sewer Mining Opportunities Dandenong / Officer / Pakenham Balliang Scheme Dandenong / Officer / Pakenham Industrial & Residential Recycling Scheme 35 GL by 2010 Industrial & Residential Recycling Scheme ? GL
Eastern Irrigation Werribee Scheme – Stage 2 Irrigation 5 GL District Eastern Irrigation Scheme – Stage 3 15 GL Sandbelt Recycling 5 GL Western Scheme 2+ GL Including Treatment Golf Courses Plant 30 GL by Eastern Treatment Plant 2006
Port Phillip Bay
Eastern Irrigation Future Scheme – Stage 1 Boneo 5 GL Scheme 4+ GL Peninsula Scheme ? GL 22 Scenario Analysis
Scenario Analysis
A diverse range of water recycling scenarios is presented in this section. The scenarios have been considered within the context of promoting sustainable development and under the objectives of: 1. potable substitution; 2. economic development (eg. development of agriculture and horticulture businesses); and 3. environmental improvements (eg. increasing environmental flows). In addition, water sources other than recycled water derived from sewage have been analysed.
The scenarios selected have arisen from the various water recycling schemes proposed within and outside the water industry. They attempt to cover the broad range of development scenarios for water recycling schemes into the future. Other scenarios are possible. The details contained within this report have been assembled from the collective knowledge of the water businesses at this time based upon work previously completed and the intellectual property existing within the businesses. It should be noted that the costing information used for this report is based only on the capital and operating costs for the scenarios. No attempt has been made to estimate revenue which will be dependent on price and customer acceptance. Each scenario is presented with a scenario description and a preliminary TBL analysis.
The scenarios, by major objective, include: Environmental Projects
Potable Substitution 11 Thomson River environmental flows 1 Retrofit third pipe systems throughout 12 Werribee River environmental flows Melbourne 13 Pumping Melbourne’s recycled water north of 2 Third pipe systems in new growth areas the Divide option 1 3 Target existing high volume water users 14 Pumping Melbourne’s recycled water north of the Divide option 2 4 Mandated recycled water use in proximity of treatment plants Other Water Sources 5 Placing recycled water into the potable water 15 Stormwater harvesting supply system 16 Increased utilisation of rainwater tanks 6 Placing recycled water into the water supply 17 Utilisation of stormwater to reduce salinity in system and increase use of bottled water for sewage flows to WTP drinking 18 Desalination 7 Sewer mining 19 Aquifer storage and recovery 8 Use of greywater
Economic Development 9 Vision for Werribee Plains (Balliang) 10 Eastern Irrigation, Cranbourne-Koo Wee Rup Corridor Water Recycling Scenarios for Melbourne 23
Potable Substitution Scenarios
Scenario 1 – Retrofit third pipe system throughout Melbourne
Scenario description This scenario focuses on potable water replacement for toilet flushing and garden watering with Class A recycled water for all existing and new residential development including the CBD. It includes an estimate for substitution in commercial and industrial premises, and targets the larger water consumers in industrial and recreational sectors. Third pipe systems have been introduced in several greenfield developments across Australia, however their widespread introduction within an existing urban environment has not been attempted anywhere in the world. It involves placing pipelines along all Melbourne streets that would duplicate the existing water supply system in scope and complexity. The following schematic details the features of this scenario.
Figure 9. Diagram of third pipe household reticulation system
Recycled water outlet different from normal design. Top of box level with ground
Standard approved pipe material Hose tap Tap with removable Backflow prevention service top & left hand thread Pipe to supply WC cistern Standard water meter Distance apart 350mm below ground Meter control ball valve estic Dom 150mm above ground Top of hose Meter tap box coloured Ball valve Meter control ball valve Recycled water pipelilac marked 'Recycled Water'. Outlet within box Ball valve
Property service Main tap Property boundary Main tap Property service Ball valve Ball valve Recycled water
Potable watermain 24 Scenario Analysis
TBL Assessment
Costs Comments Economic cost • Cost to retrofit Melbourne is approximately $15 billion. • Treatment costs $32 million per year. • Recycling system operational costs $40 million per year. • A workforce of 20,000 could take 10 to 15 years to complete. • Income from potable water sales will fall. Environmental • Salinity of discharge to sewer likely to increase as recycling causes concentration of salt. cost This has potential environmental impacts that can be offset by additional treatment costs. • Widespread use of recycled water has associated risk of salination of soils and nutrient runoff to waterways. • Increased energy consumption from pumping and treatment and so increases to greenhouse gas emissions. Social cost • Potential to be unpopular with large portion of the community, especially if water use is compulsory. • Installation of system would cause significant disruption to streets, front and back yards and houses in established urban areas. • Lack of preparedness to pay at current potable water prices.
Benefits Comments Economic • Could replace up to 120,000 ML of potable water per year in residential, industrial, benefits parks and recreational sectors. • Would create thousands of short term jobs. • Demand for recycled water could be promoted to gain maximum benefit from the system with resulting increased revenue from sales. • Reduces the need for augmenting upstream water supply and downstream sewerage infrastructure and treatment plants. Environmental • Discharge of treated sewage to rivers, ocean and bays would be reduced by benefits 120,000 ML per year (actual environmental value of benefit to be determined). • Reduced demand on water supply catchments would make additional river flows available for environmental purposes. Social benefits • Water restrictions for gardens and open space watering would be greatly reduced. • Gardening activities could be promoted through the use of recycled water to benefit the environment.
Discussion Currently, the retrofit of a third pipe system throughout Melbourne is not practical due to the magnitude of the work, expenditure required (estimated at $15 billion) and the potential inconvenience to the public from the need to retrofit extensive infrastructure into existing urban developments, resulting in disruption to streets and private properties. However, third pipe systems are considered viable within areas where new residential developments are proposed and close to existing or future treatment plants. Water Recycling Scenarios for Melbourne 25
Scenario 2 – Third pipe systems in new growth areas Scenario description This scenario considers government mandating the use of third pipe systems in all new residential developments within the urban growth boundaries specified by Melbourne 2030 (DOI, 2002). This scenario focuses on potable water replacement for toilet flushing, garden watering and public open space uses. A third pipe system is the provision of recycled water (Class A as per the Guidelines for Environmental Management: Use of Reclaimed Water, EPA Victoria, 2003) via a reticulated pipe network for non-potable uses. An opportunity also exists for new major developments to treat the sewage generated at a local treatment plant and supply recycled water to customers via a third pipe, rather than it being transferred and treated at a centralised treatment plant. The provision of a third pipe system may be more attractive for developments that are in close proximity to existing sewage treatment plants, and the South Eastern Outfall which is a potential recycled water supply source for neighbouring urban areas. Desirably, such systems should be ‘closed’ whereby the water cycle of the system does not require discharges of any water to the external environment (other than that which would occur naturally from undeveloped land). An ‘open’ system is one that requires or allows external discharge of excess flow from its system boundary. There are two existing third pipe schemes in Australia that provide potable substitution for toilet flushing and garden. They are Rouse Hill in New South Wales and Mawson Lakes in South Australia. Third pipe systems are proposed for establishment of the Sandhurst Club development at Skye in Melbourne’s south-east and VicUrban’s Aurora development in Epping North. Aurora will ultimately service 8,500 properties over 15 years. Potential Melbourne 2030 (DOI, 2002) has identified 620,000 new households that will be developed between 2001-30 within metropolitan Melbourne. The strategy has a balance of new fringe housing developments and intensive redevelopment within metropolitan Melbourne. The distribution of development has been summarised into three categories — 1. Greenfield development — 193,800 or 31 percent of new households will be developed within greenfield fringe development. 2. Activity centres or other strategic redevelopment sites — 254,760 or 41 percent of new households will be developed within major activity centres or other strategic redevelopment sites close to major public transport. 3. Dispersed residential development — 171,440 or 28 percent of new households will be developed that are not well located to major public transport. For the purpose of assessing this scenario, the 193,800 properties that have been identified for fringe greenfield development have been considered. There is an opportunity to also consider installation of third pipe systems at other major redevelopment sites identified in Melbourne 2030 (DOI, 2002). However, at this time, these have not been considered as part of this scenario. Water recycling potential should be considered in the planning stage of these developments. 26 Scenario Analysis
Figure 10. Melbourne 2030 Urban Growth (Source: Department of Infrastructure, 2001)
Hume Plenty Valley Epping North
Caroline Melton Springs
Werribee
Pakenham Port Phillip Bay
Cranbourne
Western Port
Growth area Urban growth boundary Existing urban area Possible future development front Water Recycling Scenarios for Melbourne 27
TBL Assessment
Costs Comments Economic cost • Additional infrastructure costs between $3,400 - $5,500 per lot or approximately $660 million to $1.1 billion for the 193,800 new households identified in Melbourne 2030. • Increased marginal treatment costs between $190 /ML to $500 /ML depending on the treatment process required to meet Class A. This equates to $4.6 to $12 million per annum for the 193,800 new households identified in Melbourne 2030. • Income from potable water sales will fall. Environmental • Increased energy consumption from smaller local sewage treatment plants resulting cost in greater greenhouse gases. • Potential land and waterway contamination (nutrients and salinity). Social cost • Community education to ensure appropriate use of recycled water. • Potential to be unpopular with a portion of the community, especially if scheme is compulsory.
Benefits Comments Economic • Could replace up to 24,000 ML of potable water per year in residential developments. benefit • Reduces the need for augmenting upstream water supply and downstream sewerage infrastructure and treatment plants. Environmental • Discharge of treated sewage to receiving water body (river, ocean and bay) would be benefit reduced by up to 24 GL per year. • Reduces demand on existing catchments. Social benefit • Greener public open spaces. • Greater opportunities for recreational uses. • No disruption to the community as infrastructure is installed during the construction phase and building the dwelling. • Eliminates requirement for water restrictions.
Comparison to Water Resources Strategy The Water Resources Strategy (Water Resources Strategy Committee, 2002) identified annual water savings of 9,000 ML/year by 2050 in new development from rainwater tanks or recycling. To achieve this figure completely through potable substitution via a third pipe network, it is estimated that 72,000 properties would need to use recycled water for toilet flushing and garden watering. The additional infrastructure cost is estimated to be in the range $250 - $400 million and marginal treatment costs of approximately $1.7 million per year.
Discussion A third pipe system is currently under construction at the Sandhurst Club at Skye, supplied from the initial leg of the first stage of the proposed Eastern Irrigation Scheme. This is the first third pipe system in Melbourne and will be operational by late 2003 using Class A water. A third pipe system is proposed for the new VicUrban Aurora development at Epping North. This development is expected to commence in 2004 with the third pipe system becoming operational by 2007. These schemes will provide test cases for the Victorian water industry to assess economic, social and environmental viability and the community’s willingness to use recycled water. Melbourne 2030 (DOI, 2002) identified 620,000 new households that will be developed between 2001 and 2030. To achieve the target of 9,000 ML/year recycling identified in the Water Resources Strategy (Water Resources Strategy Committee, 2002), the option of a third pipe system at all fringe growth regions and major redevelopment sites should be assessed. 28 Scenario Analysis
Scenario 3 – Target existing high volume water users Scenario description The Water Resources Strategy (Water Resources Committee, 2002) recommends that the retail water businesses complete water management plans for the top 200 industrial users across Melbourne over three years. This scenario examines the feasibility of targeting existing high water volume users to use recycled water, transported from sewage treatment plants in third pipe systems, to substitute existing potable supplies. The consumption profile of the top 200 large users in Melbourne is shown in Figure 11. The 200 largest users consume around 10 percent of the total water consumption in Melbourne and they represent only 0.2 percent of the total customer numbers within the Non Residential sector. They therefore make an attractive ‘target group’ for future recycled water projects aimed at achieving potable water substitution. The 200 largest customers are spread across Melbourne however there are two distinct clusters as shown in Figure 12 that have been used as the basis of this scenario. The two distinct geographic clusters total 91 customers and a volume of 23,000 ML/year. Users that are remote or widely dispersed have not been included. At this stage an assessment of the final use of water by the user groups has not been made. This is essential to assess the potential for likely customer acceptance. In respect to golf courses, public open space, race courses and playing fields it is expected that these are not viable unless they again can be conveniently clustered or situated near an existing treatment plant. This is the case with the Sandbelt golf course project that is currently under investigation by MWC and South East Water (SEW) in the south east of Melbourne.
Figure 11. Distribution of water use – top 200 users in Melbourne (Source: South East Water)
3000
2500
2000
1500
Annual water use (ML) 1000
500
0 1 20 40 60 80 100 120 140 160 180 200
Ranking Water Recycling Scenarios for Melbourne 29
Figure 12. Large water user market (clusters) (Source: South East Water)
Toorourong Reservoir Whittlesea Cades Rd STP Western Water Yan Yean Reservoir Maroondah Greenvale Craigieburn STP Reservoir Reservoir Sugarloaf O'Shannassy Reservoir Reservoir Upper Yarra Yarra Valley Healesville STP Reservoir City West Water Lilydale STP Brushy Yarra Tribs Water Creek STP Upper Yarra Thomson Dalry Road STP Reservoir 21.5 GL Silvan Reservoir Altona STP Monbulk Baynes Park STP Symons Rd Emerald STP Sandbelt Golf Course 0.6 GL Cardinia Ferres Rd Emerald STP Project (In Progress) Reservoir Tarago Western STP (MW) 1.5 GL South East Water Reservoir
Eastern STP (MW) Cranbourne STP Port Phillip Pakenham STP Bay Longwarry STP Blind Bight STP Koo-wee-rup STP N Mornington STP Lang Lang STP
Retail water businesses STPs Hastings STP MWC STPs South-eastern outfall sewer Rosebud STP Western Port Boags Rocks Large water user market 30 Scenario Analysis
TBL Assessment
Costs Comments Economic cost • Capital cost of the system is in the order of $110 million. • Many users would require treatment to a higher standard than current treatment standard and some may need greater than potable water quality with additional cost to be paid for by the customer. (Note that this already occurs with some industries treating the present potable supply to their needs). • Operation and maintenance costs around $3 million/year. Environmental • Increased concentration of sewage discharged to the system resulting in unknown issues cost including potential treatment issues. For example if onsite recycling occurs to a large extent, the resultant sewage must contain greater concentration of contaminants. Also, if recycled water is imported from external sources the resultant sewage must contain greater concentration of contaminants including salts. • Increased energy consumption from pumping and treatment and so increases to greenhouse gas emissions. Social cost • Large scale disruption within the affected clusters and also onsite with retrofitting large industrial sites. • Customer acceptance is unknown at this stage.
Benefits Comments Economic benefit • The project is able to be staged hence less capital required to be outlaid up front and therefore a lower risk. • Provide a commercial advantage to industry if the price of recycled water is lower than the potable supply. Environmental • Demand on catchments reduced by around 5,000 ML/year. benefit • More water available for other urban uses and/or environmental flows.
Social benefit • Use of recycled water by industry and on parks and playing fields is likely to be supported by the public. • Greener public open space. • Increased reliability in times of drought.
Discussion Preliminary evaluation shows this scenario to be expensive because of the cost of retrofitting industrial and commercial properties, and mains and reticulation systems in established urban areas. It would also be very disruptive for the community. The economics for this scenario could be improved by gaining a better understanding of the market for recycled water within this user segment, since the demand volume is critical for determining the economics. The scenario warrants further consideration of opportunities for ‘cherry picking’ individual clusters that are geographically attractive and likely to be delivered at a fraction of the cost estimated in this report. For example, initial scoping reveals that recycled water could be delivered to areas in Altona and Laverton for approximately $600/ML. This scenario should be considered within the context of developing water management plans for the 200 biggest industrial users in Melbourne as recommended in the Water Resources Strategy (Water Resources Strategy Committee, 2002). Water Recycling Scenarios for Melbourne 31
Scenario 4 – Mandated recycled water use in proximity of treatment plants
Scenario description This scenario explores the opportunity to mandate the use of recycled water in areas surrounding recycled water sources, including treatment plants and trunk infrastructure works for non-potable use, provided public health, safety and environmental risks are managed. Significant capital investments would be required to retrofit compatible customers to receive recycled water within the mandated boundary.
The City of San Diego experience The City of San Diego adopted a Mandatory Reuse Ordinance in 1989 to accelerate the productive use of recycled water for residential, industrial and agricultural uses where appropriate. Through this ordinance, the City Manager was authorised to make determinations as to which existing potable water customers were to convert to recycled water use. The City Manager was also directed to place conditions on all future development works within existing or proposed recycled water service areas to mandate use of recycled water for non-potable use. The Federal US EPA, which paid for sewage treatment plant upgrades under its grants agreement, required the City of San Diego to achieve recycled water use targets within a specific period. For example, the US EPA required the City to recycle 50 percent of its treated sewage from the North City Water Reclamation Plant by 2010. Operating to achieve this regulatory requirement, the City initially paid the full cost of infrastructure works required to retrofit customers who could use recycled water with minimum risk. The City spent around $36 million over three years retrofitting approximately 200 customers, replacing their potable water use with recycled water. The City has prepared a Recycled Water Master Plan to achieve recycled water targets imposed by US EPA. The master plan included proposed expansions to the trunk recycled water distribution system. The City has priced recycled water to be around 55 percent of the price of potable water to attract new customers. Although the Mandatory Reuse Ordinance was adopted in 1989, the City has struggled to enforce the ordinance in full. The City is in the process of developing a public consultation program to establish criteria for enacting the Mandatory Reuse Ordinance in full. Based on the San Diego experience, it is feasible to mandate the use of recycled water around the Western and Eastern Treatment Plants, the twenty local treatment plants around Melbourne and along the outfall sewer from the ETP to the Boags Rocks outlet to Bass Strait (Figure 13). With the completion of the proposed improvement works at the WTP and ETP, high quality treated sewage will be available for value added use from the two treatment plants. However, a number of complex issues require further investigation. In particular — 1. Incentives to reduce costs of providing mandatory third pipe connections to new homes. 2. Pricing of recycled water to attract increased use. 3. Developing criteria including funding arrangements to compel current high use consumers who do not require potable supply to connect to recycled water. 4. Implications of prohibiting potable water use for non-potable purposes within the mandated area. For example, land developers will not be permitted to use potable water for maintaining water features within mandated areas. 32 Scenario Analysis
Figure 13. Possible application of mandated recycled water to Melbourne (Source: MWC)
Yarra Valley Water
City West Water Werribee River Brooklyn Kew
Little River Hoppers Western Crossing North Rd Treatment Plant Mordialloc No.1&2 Thames Promenade Eastern Bondi Rd Treatment Plant South East Water Mandatory use of Port Phillip N recycled water Bay Sewage treatment plants Extent of drainage rating boundary Sewerage pipeline French Island Sewerage pumping station Major waterways Retail water business boundaries Madatory use of recycled water Boags Rocks Phillip Island Water Recycling Scenarios for Melbourne 33
TBL Assessment
Costs Comments Economic cost • There may be a requirement for government to cover the cost of retrofitting potential users and fund the building of a trunk sewer to service potential customers. New customers within the mandated area will require dual systems with third pipes for non- potable use. This may result in increased costs to developers and ultimately new home buyers in the designated areas. Environmental • Widespread use of recycled water has associated risk of salination of soils and nutrient cost runoff to waterways. Social cost • Disruption to the built environment. • Industry will have to be educated of the value of replacing valuable potable water with recycled water. • Communities may view they are disadvantaged or negatively targeted. • Potential to increase costs of dwellings in the targeted areas (eg Werribee Corridor) making it less attractive to new home buyers. • General aversion to mandatory requirements.
Benefits Comments Economic benefit • Conservation of potable water contributing to increased security of water supply for Melburnians. • Reduction in the need for augmenting upstream water supply and downstream sewerage infrastructure and treatment plants. Environmental • Reduction in discharges to the bay and ocean, with level of environmental benefit benefit to be determined. • Deferral of the need for Melbourne's water supply augmentation. Social benefit • Likelihood of needing water restrictions reduced.
Discussion There are opportunities to mandate the use of recycled water around local, WTP and ETP and outfall sewers, provided adequate subsidies are provided to make compulsory connections economically feasible. This scenario warrants further study. 34 Scenario Analysis
Scenario 5 – Placing recycled water into potable water supply system
Scenario description This scenario presents the option of pumping all discharge from the Western Treatment Plant into Greenvale and Sugarloaf reservoirs and pumping all discharge from the Eastern Treatment Plant into Cardinia Reservoir (Figure 14). The water would be mixed with the existing potable water and the mix of recycled water and fresh water, with additional further treatment as required, would form the potable supply to much of the western and south-eastern suburbs of Melbourne. Discharge from both treatment plants would be treated to WHO drinking water standard, including salt reduction to current drinking water level of 50 TDS. Due to the mixing of recycled water it is assumed that the water leaving the reservoir would lose the protected catchment status that allows the water to presently not be filtered and it would require additional treatment.
Figure 14. Schematic showing recycled water for potable water system (Source: MWC)
Greenvale Reservoir Sugarloaf Reservoir
City West Water Werribee River Brooklyn Kew Yarra Valley Water
ittle River Hoppers Crossing Cardinia Western North Rd Reservoir Treatment Plant Mordialloc No.1&2 Thames Promenade Eastern Bondi Rd Treatment Plant South East Water Port Phillip Bay N
Sewage treatment plants Extent of drainage French rating boundary Island Sewerage pipeline Sewerage pumping station Major waterways Retail water business boundaries Boags Rocks Phillip Island Water Recycling Scenarios for Melbourne 35
TBL Assessment
Costs Comments Economic cost • Capital cost of treatment plants and transfer system is in the order of $2.5 billion based on additional treated sewage cost and treatment of water supply prior to consumption. • Treatment and pumping costs would be in the order of $120 million/year. • Melbourne loses protected catchment status of its water supply causing all water to be treated. Environmental • Could be perceived to contaminate the present ‘pristine’ potable water supply. system cost • 100 percent of recycled water required to be treated to drinking quality standard, but only a portion of it used for drinking, personal bathing, etc. • Increased energy consumption from treatment and pumping resulting in greater greenhouse gas emissions. • Potential for increased flooding downstream of existing storages. Social cost • Unlikely to be acceptable to the community. • Perceived risk to public health. • Use of alternative sources for drinking likely to be increased, eg, rainwater tanks. • Melbourne loses protected catchment status of its water supply. • Potential inequity of quality of supply between various customers, (eg some will have ‘clean water’ and others ‘recycled water’).
Benefits Comments Economic benefit • If the decision was made today, avoidance of the need for the ETP outfall extension, a saving of $60 million capital cost. • Boost to water supply could allow for increased economic development from reallocating excess supply to water intensive industries and/or use for irrigation and environmental flows. Environmental • 320 GL of water recycled annually. benefit • Elimination of discharges to the bay and ocean. • Reduced demand on catchment yields so more water available for downstream uses and environmental flows. Social benefit • Likelihood of needing water restrictions reduced. • Additional water available for parks and gardens.
Discussion This scenario involves direct potable reuse whereby the recycled water is placed directly into the water supply reservoir and occurs in only a small number of countries in the world (eg Namibia in Africa). Indirect potable reuse whereby recycled water is discharged into a waterway and the water is subsequently harvested has been contemplated nationally, and is practiced throughout the world, including Europe and America. At this stage it is considered socially unacceptable for Melbourne because of public perception regarding health risk. The Water Resources Strategy (Water Resources Strategy Committee, 2002) concluded that this is unlikely to be necessary for the next 50 years. Technical developments and experience with implementation elsewhere should continue to be monitored. 36 Scenario Analysis
Scenario 6 – Placing recycled water into potable water supply system and increase the use of bottled water for drinking
Scenario description This scenario is similar to Scenario 5 and includes pumping all the discharge from the Western Treatment Plant into Greenvale and Sugarloaf reservoirs, and all the discharge from the Eastern Treatment Plant into Cardinia Reservoir. In this scenario, the discharge from both treatment plants would be treated to an enhanced standard suitable for human contact, but not to WHO drinking water standard. (i.e. same bacterial quality as drinking water but higher nutrients, TDS, colour, etc). Recycled water would be mixed with fresh potable water in the reservoirs and the mixed water would be used for all purposes except drinking. The public would be supplied with bottled water through supermarket retail distribution outlets for drinking and cooking purposes. Water Recycling Scenarios for Melbourne 37
TBL Assessment
Costs Comments Economic cost • Capital cost of treatment plants and transfer system is in the order of $2.3 billion. • Treatment and pumping costs would be in the order of $120 million per year. • Cost of supplying 4,000 ML of bottled water to a population of 3.6 million people is $2 billion per year. Environmental • Would create a significant waste control issue with an estimated 400 million water bottles cost in circulation each year. • Additional consumption of resources, energy and greenhouse emissions from manufacturing water bottles. • Increased energy consumption from pumping and treatment and so increases greenhouse gas emissions. • Quality issues could be created with water stored in the reservoirs arising from salt, nutrients and other contaminants in recycled water differing from the fresh water. Social cost • Imposition on the community to have to purchase and transport water in bottles. • Unlikely to be acceptable to the community at large. • Increased risk to public health with associated costs. • Use of alternative sources for drinking likely to be increased, (eg, rainwater tanks). • Use of less desirable potable substitutes such as soft drinks and carbonated products would increase, with associated health issues. • Recycled water could be seen to contaminate the present ‘pristine’ potable water system.
Benefits Comments Economic • If a decision was made today, it avoids the need for the ETP outfall extension, saving benefit of $60 million capital cost. • Increased business for water companies with profits from a margin on the retailing of bottled water. • Business opportunities in the bottled water industry and the water bottle recycling industry. • Boost to water supply could allow for increased economic development. Environmental • Would eliminate discharges to the bay and ocean and allow recovery from existing benefit environmental impacts. • Reduced demand on catchment yields so more water would be available for downstream uses and environmental flows. Social benefit • Likelihood of needing water restrictions reduced. • Ample water available for parks and gardens.
Discussion Refer to Scenario 5 38 Scenario Analysis
Scenario 7 – Sewer mining Background Sewer mining is the local treatment of raw sewage to provide recycled water, fit for purpose, for nearby beneficial uses such as open space watering, industrial uses etc. In an urban environment the expectation is that it is treated to a Class A standard (unrestricted use) as per the Guidelines for Environmental Management: Use of Reclaimed Water Guidelines (EPA Victoria, 2003). It is characterised by a modular sewage treatment plant that is compressed within an urban setting. By-products from the process are returned to the sewer. The process is only generally considered viable for sewers greater than 450 mm diameter, as continuous and minimal volume flows are required. For Melbourne the total length of sewers equal to or greater than 450mm diameter is around 5 percent, so application will only make a small contribution to recycling. The concept is shown diagrammatically in Figure 15.
Figure 15. Typical arrangement for a sewer mining operation (Source: South East Water)
Treat sewage Recycled water Extract sewage (typically Class A)
Sludge
Sewer Water Recycling Scenarios for Melbourne 39
TBL Assessment
Costs Comments Economic cost • A plant producing Class A recycled water for an open space application will cost in the order of $1,800/ML to $2,000/ML. The optimum application applies where there is a continuous demand (eg. an industrial area). Environmental cost • Higher energy consumption than centralised treatment, therefore has an adverse greenhouse impact. • Potential soil salinity problems. Social cost • Plants can generate noise and odour problems. • Community concerns may be reflected in permit difficulties. • Community education required to ensure understanding that Class A recycled water is not drinking water quality.
Benefits Comments Economic benefit • Small increases in employment through the need to operate and maintain these facilities. • For commercial and industrial applications it provides businesses a secure source of water (long term). • Reduction in the need for augmenting upstream water supply and downstream sewerage infrastructure and treatment plants. Environmental • Enhance environmental flows. benefit • By 2030 there could be six sites in Melbourne most likely in the industrial west with a demand of 5 ML/day representing 11,000ML/year. Social benefit • In open space applications (e.g. Albert Park) maintenance of aesthetic value to the community in times of water shortage. • Recycling is visible to the community and thereby raises water conservation awareness.
Trends Sewer mining to date has only been applicable in situations where there is a severe shortage of water. A project supported by the Government’s Smart Water Fund is about to trial a non-biological process with the potential to break through the current unit price by around 30 percent. Recent demonstrations of sewer mining have been conducted at the Domain and Albert Park. Evidence from these and other trials are that the cost is very dependent on whether the scheme is for summer-only use, or continuous, and is also very sensitive to volume requirements. For example, very small schemes (0.5 ML/day) operating only in summer may cost as much as $3,300/ML and larger schemes (2.5 ML/day) operating continuously may cost less than $1,000/ML.
Discussion The water industry is investigating sewer mining opportunities to irrigate golf courses, sporting fields and industry in Kooyong and Yarra Bend and are pursuing many favourable opportunities such as the scheme at Albert Park. Within 12 months through the completion of existing proposed schemes, the water industry will be in a position to more accurately determine the costs and benefits of sewer mining opportunities. 40 Scenario Analysis
Scenario 8 – Use of greywater Background Greywater is defined in a residential context as treated sewage from the kitchen, laundry and bathroom but excluding toilet wastewater. Greywater diversion for garden watering is becoming increasingly popular with the community, particularly with the current drought. The use of untreated greywater presents a potential health risk which is reduced if managed appropriately (EPA, 2001). Treatment is preferred from a public health viewpoint, however, treatment systems are expensive and require ongoing maintenance for the owner. A schematic layout is shown in Figure 16. Greywater systems can be divided into: • onsite temporary systems; • onsite permanent systems; and • communal systems (onsite or offsite).
Figure 16. Layout of the Inkerman Oasis project (example of a communal system) (Source: South East Water)
to sewer if failure filter/balance Stormwater tank
Supplementary Aeration supply Shower and basin plant Toilet wastewater flushing Disinfection Wetland
Storage
Irrigation Water Recycling Scenarios for Melbourne 41
TBL Assessment
Costs Comments Economic cost Temporary systems • In times of water scarcity simple diversion systems (untreated) are not costly. Permanent systems • A typical residential permanent system costs in the order of $6,000 excluding any storage provision, with operating costs of $350/year and represents a cost in the order of $19,000/ML (toilet flushing) or $9,200/ML (toilet flushing and garden watering). • To oversee the management of these systems if widely adopted will require additional resources for local government. Communal systems • Based on the budget at Inkerman Oasis where a permanent system is being constructed for 236 units, the estimated cost is around $450,000 with an operating cost of $20,000 representing a cost of $5,500/ML. Environmental cost • Potential for soil, waterway and groundwater contamination through nutrients, salinity, etc. • Adverse impact on greenhouse gases from energy consumed in pumping and treatment. Social cost • Greywater systems have the potential to cause a public nuisance if they are not managed well (such as runoff, odours, noise, etc). • Requires an investment in time to manage permanent household systems.
Benefits Comments Economic • If undertaken on a wide scale will create business opportunities and employment for new benefit systems and maintaining existing systems. • Reduces the need for augmenting downstream sewerage infrastructure and treatment plants. Environmental • Savings up to 40 percent of potable water per household providing there is a suitable benefit storage provision for peak flows. For Melbourne, if adopted in greenfield sites only, the annual water saving could be up to 19,000 ML by 2030. Social benefit • Meeting a community need since there is a high level of community interest, particularly with temporary systems.
Discussion At the start of 2003, the Government commenced an incentive program for permanent greywater systems offering a $150 rebate. These schemes are very expensive per megalitre, impose ongoing management responsibilities on the home owner or system operator and local government, and could pose potential environmental problems if introduced on a wider scale. At this stage, it is unlikely that these systems will make a significant contribution to potable substitution in Melbourne. The preferred approach from a financial and public health viewpoint are communal systems where the management responsibility could reside with qualified managers such as water businesses rather than individual householders or bodies corporate. 42 Scenario Analysis
Economic Development Scenarios
Group scenario description These scenarios consider schemes that are based on future uses of recycled water primarily for productive purposes (eg agriculture). The use of recycled water has the potential to provide a net benefit to the State. These scenarios will require detailed business case preparation and approval prior to implementation. They will be assessed against rigorous triple bottom line criteria to demonstrate value for money. Opportunity exists to consider economic development schemes at the Western Treatment Plant, Eastern Treatment Plant and the twenty local treatment plants in the Melbourne region. Currently MWC are investigating two projects, the Balliang scheme and the Eastern Irrigation Scheme which at full development have the potential to add $200 million to Victoria's economy. In addition Yarra Valley Water are currently investigating opportunities from local treatment plants in the Yarra Valley, and at Whittlesea and Craigieburn. Scenario 9 – Werribee Plains (Balliang) The Balliang District north-west of the Western Treatment Plant, generally bounded by the Brisbane Ranges, the You Yangs and the Werribee River (Figure 17), has the potential to use recycled water for agriculture and horticulture. The study area covering around 70,000 hectares would require a trunk pipeline around 45 kilometres in length. Broader options in relation to provision of third pipes in new residential developments for non-potable use and replacing river water with recycled water in the Werribee Irrigation District are also being considered. These uses, respectively, would substitute Melbourne’s precious drinking water supplies and free-up flows in the Werribee River catchment for environmental and/or other uses. Western Waters’ Sunbury-Melton Recycled Water Project in the Werribee Plains region is an existing scheme which has successfully secured mainly agricultural and horticultural markets for recycled water. At full development the project could initially use up to 35,000 ML/year with potential to use 70,000 ML/year, irrigating approximately 10,000 hectares eventually. The development of agriculture has the potential to stimulate economic activities in the region creating employment opportunities in a number of sectors including agriculture, food processing and tourism. Water Recycling Scenarios for Melbourne 43
Figure 17 Werribee Plains (Balliang) (Source: MWC)
Lerderderg Pykes Creek Gorge Djerriwarrh Reservoir State Park Reservoir Merrimu Reservoir
Bacchus Marsh Melton
Melton Reservoir
Brisbane Ranges Ballan Road Balliang District WerribeeWyndham River Balliang Urban
Targeted Little RiverOpportunities
Marsh Road Werribee Werribee South Werribee You South Yangs Little Market River Western Gardens Geelong – Bacchus Treatment Plant
Princes Freeway Lara Port Phillip Moorabool Bay
Geelong
Corio Bay 44 Scenario Analysis
TBL Assessment
Costs Comments Economic cost • The capital cost of the project is estimated to be around $130 million with operating costs around $4.6 million/year. The scheme is planned to use Class A recycled water. Environmental cost • Salinity levels from WTP are high (>1,000 mg/L) and would require active management. • Increased aggregate demand for water. Social cost • Price of water may be prohibitive. • Acceptance of produce grown using recycled water in local and overseas markets is unknown.
Benefits Comments Economic • The annual agricultural production value has been estimated to be around $120 million. benefit • Creation of approximately 2,000 jobs.
• The area would benefit through the application of recycled water high in nutrients. The benefits are costed at $100/ML of recycled water applied when you take into account delivery and spreading costs of nitrogen.
Environmental • Discharge of treated sewage to the bay would be reduced by 35,000 ML/year at full benefits development. Actual environmental value of benefit to be determined. • Reduction in nitrogen load to the Bay through offsite use of recycled water. • Potential to free river water for environmental flows and urban supply. Social benefit • Increased economic activity will create around 2,000 jobs. • The provision of recycled water has the potential to positively change the image of the Werribee Plains into a ‘green’ region.
Discussion The Government has initiated a full business case study to explore all water recycling options for the extended Balliang region as part of the Vision for the Werribee Plains. This study is to be completed by December 2003. Water Recycling Scenarios for Melbourne 45
Scenario 10 – Eastern Irrigation Scheme, Cranbourne – Koo Wee Rup Corridor The Eastern Irrigation Scheme (EIS) concept is based on further treatment and transport of recycled water from MWC's Eastern Treatment Plant to the Cranbourne – Koo Wee Rup corridor (Figure 18). The main markets for recycled water from the EIS are the horticultural, agricultural, manufacturing and recreational industries in the corridor.
Figure 18. Eastern Irrigation Scheme (Source: MWC)
Stage Two
Sandhurst
Stage Two
Stage One
Stage Three 46 Scenario Analysis
TBL Assessment
Costs Comments Economic cost • The cost of the project is estimated by MWC to be around $24 million. The scheme would provide Class A recycled water. Environmental cost • Generally the soils south east of the treatment plant are of suitable quality except for a strip of land between the Cranbourne and Koo Wee Rup areas that contain heavier clay soils. Users would have to be aware of the impact of increased irrigation in the area, particularly with respect to long term sustainability of irrigation on the particular soil types, the drainage of increased water supplied and the impact on the ground water level. Although salinity levels would increase over time, the 480 mg/L for recycled water is considered acceptable to growers. • Increased aggregate demand for water. • Requirement to manage potential increased run-off. Social cost • Acceptance of produce grown using recycled water in local and overseas markets is unknown, though it should be noted that vegetables grown on recycled water are being successfully exported from Virginia in South Australia.
Benefits Comments Economic benefit • The net present value of economic benefits resulting from the transport of recycled water to the demand nodes over the initial 20-year project period is estimated by MWC at approximately $85 million. Environmental • Discharge of treated sewage to the ocean would be reduced by 5,000 ML/year benefit for Stage 1. Stages 2 and 3 would provide additional reduction of 10,000 ML/year. Actual environmental value of benefit to be determined. Social benefit • Increased economic activity by the eighth year of operation estimated by MWC to create around 135 jobs.
Discussion Negotiations between MWC and a private sector operator Earth Tech to develop the commercial structure and terms for Stage 1 of the project have been continuing. A detailed business case for Stage 1 will be completed shortly and MWC Board and Government approval will then be sought. Water Recycling Scenarios for Melbourne 47
Environmental Scenarios
Group scenario description Scenarios 11 and 12 utilise suitably treated recycled water for environmental purposes such as restoring environmental flows within degraded rivers and creeks. The strategy has the potential to contribute significantly to the Victorian River Health Strategy (NRE, 2002b). The major issue with these projects is the very low level of nutrient levels specified in the State environment protection policy (Waters of Victoria) (SEPP) (State Government of Victoria, 2003). The conventional tertiary treatment technologies for nutrient removal comprising reverse osmosis followed by UV disinfection may not meet the policy objectives. Table 3 shows the performance of sewer mining plants using leading edge technology of microfiltration, reverse osmosis with UV disinfection and provides a comparison with the objectives in the SEPP. The practicality of treatment to meet these nutrient objectives is unknown and is an important issue when considering projects that discharge to waterways. The use of recycled water for environmental flows will need to occur via the risk assessment framework described in the SEPP, since current sewage treatment technologies have difficulties achieving the specified ambient nutrient levels. The discharge of high quality recycled water to local creeks and rivers in metropolitan Melbourne has the potential to provide an environmental and social benefit. Yarra Valley Water are currently determining the impact of reducing flows from the Craigieburn treatment plant on Merri Creek including the potential to maintain an environmental flow.
Table 3. Comparison of the performance of sewage mining plants with the SEPP objectives
Parameter Waters of Victoria Domain Gardens Sewer Albert Park Sewer Nutrient Objectives Mining Treatment Plant Mining Treatment Plant (mg/L) 2002 2003 (mg/L) (mg/L) Total Nitrogen <0.5 (75th percentile) 2.2 2.1 Total Phosphorus <0.025 (75th percentile) 0.2 0.13 48 Scenario Analysis
Scenario 11 – Thomson River Environmental Flows The Thomson River has been classified, as a priority stressed river downstream of the Cowwarr Weir. Treated water from the Eastern Treatment Plant would be further improved by polishing through a dual membrane treatment plant involving microfiltration, reverse osmosis and UV disinfection. Recycled water from this treatment plant would meet quality standards set for augmenting environmental flows, however, additional work would be required to demonstrate compliance. The plant sized at 400 ML/day would use a 150 kilometre pipeline to transport the treated water to a discharge location just below the Thomson Dam. Figure 19 is a diagrammatic representation of this scenario. There is precedence for using recycled water for replenishing environmental flows in rivers. Gwinnett County, Atlanta is one of the fastest growing areas in North America with population expected to be around 1 million by 2020. The Gwinnett County water reclamation project has been designed to augment environmental flows in the Chattahoochee River during low flow periods.
Figure 19 Diversion of recycled water to Thomson River (Source: MWC)
Yan Yean Reservoir Upper Maroondah Sugarloaf Yarra Reservoir Greenvale Reservoir Reservoir Reservoir Thomson Reservoir
Silvan Reservoir
Cardinia Thomson River Reservoir
ETP
Port Phillip Bay
Water supply catchment Water storage reservoirs Bass Water service reservoirs Strait Recycled water Water pipelines, aqueducts Western Port pipeline MWC drainage metro boundary Water Recycling Scenarios for Melbourne 49
TBL Assessment
Costs Comments Economic cost • The capital cost of the project is estimated to be around $830 million with annual operating costs around $40 million. The scheme is planned to use potable quality water to minimise risks to receiving waters. Environmental cost • Need to establish a pipeline route to minimise environmental damage. Potential to exacerbate flooding on the Thomson River in wet years. Social cost • None if floods are managed in the Thomson River.
Benefits Comments Economic benefit • Annual potable water saving of 45,000 ML stored in Thomson Reservoir is valued at $40 million. • Increased value from expanded agriculture in the Thomson Macalister Irrigation District. Environmental • Improving environmental flows in Thomson River. Nutrient dilution from increased benefit flows will benefit Gippsland Lakes. Social benefit • May provide increased recreational opportunities in the Thomson River and inject revenue to the Gippsland Region.
Discussion For this scenario to be developed further, refinements are required to develop the quality of water acceptable to the EPA as environmental flows. This could be achieved by the EPA working with other relevant organisations (such as DSE and Catchment Management Authorities) to develop detailed criteria for assessing beneficial 'recycling' to waterways. There may be reductions in the cost of treatment if water of lesser quality is acceptable for use as environmental flows. A proper TBL assessment also would have to consider the value of additional water flows to the Gippsland Lakes area. It should also examine opportunities to improve other rivers in the region such as the Tarago River and the La Trobe River, and service new urban growth in the region utilising the pipeline from the Eastern Treatment Plant to Thomson Reservoir. 50 Scenario Analysis
Scenario 12 – Werribee River Environmental Flows The Werribee River, classified as at risk of being stressed, is degraded downstream of Melton Reservoir requiring significant riparian works and environmental flows to improve its ecological health. Farmers in the Werribee Irrigation District use around 11 – 13,000 ML/year from the Werribee River primarily for agriculture and horticulture. This water is sourced from the Melton Reservoir and pumped from the river. If the river water used for agriculture could be substituted with recycled water from the WTP, additional flow could be made available benefiting the ecological health of the river, and/or used to supplement potable supplies to Western Water and/or Barwon Water. Figure 20 is a diagrammatic representation of this scenario.
Figure 20 – Diversion of recycled water to Werribee River downstream of Melton Reservoir (Source: MWC)
Lerderderg Pykes Creek Gorge Djerriwarrh Reservoir State Park Reservoir Merrimn Water Reservoir available
Bacchus for other uses Marsh Melton
Melton Brisbane Ranges reservoir Ballan Road Balliang District Werribee Werribee River Irrigation District
Little River
Marsh Road Werribee Recycled Werribee water South You Market You Gardens Yangs Western
Geelong – Bacchus Treatment Plant
Princes Freeway Lara Port Phillip Bay
Geelong
Corio Bay Water Recycling Scenarios for Melbourne 51
TBL Assessment
Costs Comments Economic cost • The estimated cost of the infrastructure to transport recycled water from the Western Treatment Plant to Werribee irrigators is $5.2 million. The operating cost is around $100,000/year. If additional treatment is required project costs will increase to $35 million. Environmental cost • The impact of recycled water use on the salinity of the area will require further study. Social cost • There may be some irrigators unhappy to use recycled water in their market gardens due to a perception of the water as unclean.
Benefits Comments Economic benefit • The revenue earned will be around $400,000/year. There is little or no scope to increase the area farmed due to lack of suitable land. Environmental • Increased environmental flows in the Werribee River. benefit • Decreased treated sewage discharges to Port Phillip Bay. Social benefit • Potential to make water available for urban supply for Melton and Geelong.
Discussion Public consultation with farmers in the Werribee Irrigation District indicates that they are yet to embrace the concept of the use of recycled water for growing vegetables. Further treatment may be required before recycled water can be used for irrigating vegetables. In contrast to the Thomson River scenario, this scenario does not require releasing recycled water directly into the river and, hence, would avoid any additional treatment cost that would have been required to recycle water to a waterway. There would also be savings arising from potable water preserved in Pykes Creek Reservoir destined for the Werribee market gardens. This water could be diverted to improve the security of potable water supply for Barwon Water and Western Water. The provision of recycled water to the existing Werribee Irrigation District is potentially a viable scenario and is being considered as part of the business case for the Vision for Werribee Plains (Balliang) project. 52 Scenario Analysis
Scenario 13 – Pumping Melbourne’s recycled water north of the Divide – option 1
Scenario description This scenario involves recycling 100 percent of the suitably treated sewage from the ETP and WTP by pumping it across the Bay from ETP to combine the flow with the WTP. This combined flow of up to 270,000 ML/year (allowing for some continued environmental flow at WTP) would then be pumped north to the Great Dividing Range and discharged into existing irrigation channels (Figure 21). It would be used to supplement current irrigation schemes in regions to the north and west of the State. It would allow water currently used for irrigation to be used for environmental flows in the Goulburn River. It has the potential to eliminate the current treated sewage discharges into Port Phillip Bay and Bass Strait.
Figure 21. Map showing potential to pump Melbourne’s recycled water from ETP across bay and pump combined flows of ETP and WTP north of the Divide (Source: MWC)
Alexandra Yea
Healesville
Melbourne
WTP Dandenong ETP Parks and reserves State forest Freehold and other Pipeline Water Recycling Scenarios for Melbourne 53
TBL Assessment
Costs Comments Economic cost • Capital $1,500 million, Operating Cost $20 million/year. Note: lower costs have been estimated by an independent source. Environmental cost • Environmental impact of construction of the pipeline. • The scheme would have to be supported by a detailed environmental impact assessment prior to implementation with attention on the impact to the seasonal flow regime, nutrient loadings and salinity. • Potential to damage receiving waters if the recycled water is not treated to acceptable standard. Tertiary treatment to Class A with high nutrient removal would be required. • Potential for some environmental issues at the WTP if all treated sewage is pumped off site (eg. impact on existing wetlands and proposed on-site irrigation scheme). • Increased energy consumption and greenhouse gas emissions. • Potential negative impact on Port Phillip Bay and RAMSAR wetlands. Social cost • Significant concern is anticipated regarding the perception of sending Melbourne’s ‘waste’ inland to be managed by others.
Benefits Comments Economic benefit • The water could be utilised to increase the volume of irrigation water which is currently valued at up to $1,000/ML and a usage charge of approximately $30/ML. It also would provide security of supply. • If decision made today, it avoids need for the ETP outfall extension, a saving of $60 million capital cost. Environmental • Eliminates the current treated sewage discharges into the Bay at Werribee and into Bass benefit Strait at Boags Rocks. • Provides additional environmental flows of 270,000 ML/year in inland receiving waters. Social benefit • This innovative scenario would be a world leading, cutting edge demonstration of sustainable water resource planning. • It would create significant employment over three years. • Increased security of supply for irrigators.
Discussion This scenario has very high capital and recurrent costs and public perception issues regarding sending Melbourne’s ‘waste’ inland. The recently released State environment protection policy (Waters of Victoria) (State Government of Victoria, 2003) acknowledges that discharge of recycled water for environmental flows or other uses is an acceptable form of reuse provided beneficial uses are protected. The EPA would therefore have to determine that a net positive environmental outcome and no impact on beneficial uses was achieved for a discharge of recycled water to be considered an acceptable form of reuse. The scenario should be further investigated. 54 Scenario Analysis
Scenario 14 – Pumping Melbourne’s recycled water north of the Divide – option 2
Scenario description This scenario considers diverting sewage from the northern parts of Melbourne’s sewerage system (rather than from Western and Eastern Treatment Plants in the previous scenario), treating the sewage to produce high quality recycled water and transferring this water into the Goulburn Valley. The recycled water would be used to supplement current irrigation schemes in the region to the north and west of the State. It would also allow water currently used for irrigation to be used for environmental flows in the Goulburn River. This scheme has the potential to reduce the volume of treated sewage discharged into Port Phillip Bay by 33,000ML/year or 12 percent and is shown schematically in Figure 22.
Figure 22. Schematic detailing potential to pump Melbourne’s recycled water north of divide (Source: YVW)
Goulburn River Proposed Pumping Station STP
Wandong
Wallan
Beveridge
Kalkallo Regional STP
Craigieburn
Epping North Cooper St
Bundoora Merri Ovoid
Coburg Lake
Bell St Water Recycling Scenarios for Melbourne 55
TBL Assessment
Costs Comments Economic cost • Capital cost of approximately $380 million. • Operating cost of approximately $10 million/year. • Net present cost of $215 million over 25 years. Environmental cost • Environmental impact of construction of the pipeline. • The scheme would have to be supported by a detailed environmental impact assessment prior to implementation with attention on the impact to the seasonal flow regime, nutrient loadings and salinity. • Potential to damage receiving waters if the recycled water is not treated to acceptable standard. Tertiary treatment to a minimum of Class A would be required. This includes the impact of nutrients on the Goulburn River and particularly Lake Nagambie. • Increased energy consumption and therefore increased greenhouse gas emissions. Social cost • Significant concern is anticipated regarding the perception of sending Melbourne’s ‘waste’ inland to be managed by others.
Benefits Comments Economic benefit • The water could be utilised to increase the volume of irrigation water, which is currently valued at up to $1,000/ML with a usage charge of approximately $30/ML. • Reduced spending on new sewers to cater for growth. • The recycled water would be used as a vital resource in an existing irrigation district with proven commercial returns and would provide increased security of supply. Environmental • Provide around 33,000 ML/year of recycled water for irrigation and/or to provide benefit much needed environmental flows in the Murray-Darling Basin. • Reduce discharges from the WTP to Port Phillip Bay by around 12 percent, so reducing the amount of nitrogen discharged to the Bay. • Reduce wet weather sewage spills. Social benefit • This innovative scenario would be a world leading, cutting edge demonstration of sustainable water resource planning project. • Create significant employment over a period of three years. • Help ensure the long-term viability of rural communities with economies supported by irrigated agriculture.
Discussion Similar to Scenario 13, Scenario 14 has high capital and recurrent costs and public perception issues regarding sending Melbourne’s ‘waste’ inland. The EPA would have to determine that a net positive environmental outcome and no impact on beneficial uses was achieved before the discharge of recycled water to the Goulburn River could be considered an acceptable form of reuse. The analysis suggests that the project is not as attractive as other projects for providing water savings and reducing treated sewage discharges to the environment. This conclusion would need to be reassessed once a standard TBL assessment framework has been developed. 56 Scenario Analysis
Other Potential Water Source Scenarios
Consideration of the role of stormwater in the urban water cycle The management of stormwater plays a vital part in contributing to the amenity of a modern society and the livability of the built environment. It is a vital component of the water cycle. Utilising stormwater in a proactive manner to supplement Melbourne’s water requirements is gaining increased interest as government and developers embrace water sensitive urban design. Potential options for increased stormwater use include: • stormwater harvesting and use to replace potable water; • increased utilisation of rainwater tanks; and • utilisation of stormwater to dilute salinity levels in sewage flows to the WTP. These options have been considered as Scenarios 15, 16 and 17 in this section of the report. Future planning of water recycling should give consideration to the enhanced role that stormwater could play in the overall water cycle.
Stormwater flows Urbanisation has led to increased volumes of stormwater being discharged to waterways. Studies have shown that the peak flow from an urbanised catchment can be as much as 35 times the peak flow from the same catchment in a rural condition as rural land is relatively pervious to rainfall and its uneven surface retards and stores surface flow. It is estimated that in residential areas, 40 percent of the surface area (roofs, driveways, roads, paving, etc.) is impervious to the penetration of rainwater, and in industrial areas the figure is 80 percent. In addition, drainage pipelines provide efficient paths for stormwater to travel quickly down the catchment. These factors lead to an increase in peak flows and flow quantities. Understanding the management of stormwater in an urban environment requires an understanding that: • rainfall is not a consistent or predictable event; • on average a very high percentage of Melbourne’s water falls in very few storm events; and • the drainage system has to always be in a state of readiness to receive the extreme storm event (usually defined as the one in 100 years event) to prevent flooding The Government will continue to increase the focus on sustainability and water-sensitive urban design, which will lead to continued improvements in the management of stormwater. Initiatives aimed at decreasing the amount of stormwater run-off from the built environment, such as decreasing the percentage of impervious surfaces in new developments and improving the treatment of storm water via constructed wetlands, are becoming common features of modern urban design. Innovative methods, such as diverting the ‘first flush’ of the stormwater drainage (which contains the bulk of the pollution load) into the sewerage system rather than into waterways, are under investigation by MWC. These initiatives should see a continual improvement in the built environment of Melbourne. The stormwater system is shown diagrammatically in Figure 23. Water Recycling Scenarios for Melbourne 57
Figure 23. The drainage system (Source: MWC)
Regional Local (MWC) (Councils)
Channels Waterways 677 km 5,087 km
Underground drains 1,088 km Retarding basins – 119 Wetlands – 25 Litter traps – 15
Tidal Levee banks gates – 3 193 km
Pumping stations – 22 58 Scenario Analysis
Scenario 15 – Stormwater harvesting
Scenario description In this scenario, stormwater harvesting involves increasing the use of retarding basins as a source of storage of stormwater and ‘harvesting’ the stormwater for use. Stormwater would be treated through combinations of pollution traps, settling ponds and constructed wetlands and where appropriate, more sophisticated processes would be utilised. Aquifer storage and recovery (ASR) can be considered within a modern urban stormwater design system. This involves pumping winter flows into the groundwater table, then pumping it out in summer months when it is required. The complex hydrology and potential consequential environmental impacts of ASR are not well understood and require further investigation. Potential uses of the treated stormwater would include: • suburban agriculture; • water substitution for large irrigators such as golf courses, race courses and public open space; and • domestic applications for gardens through a third pipe system. It is anticipated that increased focus and utilisation of stormwater harvesting in new urban developments will be a natural consequence of the Government’s desire to develop sustainable water management systems and the move to increase water sensitive urban design. It should be noted that this scenario is analogous to the processes that provide our existing potable water supply system. The difference is that the catchment for this scenario is the built urban environment rather than the pristine natural environment currently used to supply water for much of the potable system.
Figure 24. Schematic of stormwater system (Source: MWC)
Stormwater enters waterway Weir diverts some flow into wetland while maintaining sustaining flow in waterway
Spillway and Sedimentation pond bypass channel removes larger protect wetland suspended particles from higher flows Inlet structure controls flow into wetland Flat, planted area removes leaf litter Treated water is returned to Fine particles stick to waterway and plant stems in marshes flows to Bay Outlet structure detains water for the required period (usually 72 hours) Port Phillip Bay Water Recycling Scenarios for Melbourne 59
TBL Assessment
Costs Comments Economic cost • The financial cost of this scenario has not been assessed. It would have to be assessed against each individual scheme proposal. • It should be noted that the existing drainage network and retarding basins have been designed and built to retard extreme weather events, usually 1 in 100 year storms. Alternative use of retarding basins as dams will require a dramatic operational change, possibly resulting in large capital expenditure and the system being less effective in retarding major storm events. Environmental cost • Increased harvesting and use of stormwater reduces the amount of water discharged to the environment – to wetlands, streams, rivers and ultimately into the bays. However, due to the large increase of stormwater discharge volumes resulting from urbanisation, it is considered that increased harvesting is unlikely to result in serious problems. Social cost • Waterways and related stormwater basins are considered a valuable community asset. Increased harvesting of stormwater has the potential to denigrate the public value of retarding basins which are currently highly valued public open space regions when not in flood.
Benefits Comments Economic benefits • Has the potential to supply water at lower cost than other sources in selected locations. Environmental • Has the potential to significantly improve the treatment of stormwater and improve the benefits health of our streams, rivers and bays. • Stormwater utilised under this scenario will be a direct substitute for potable supply leading to increased security of our water supply. Social benefits • Has the potential to significantly improve the water assets of the community in the urban environment.
Discussion Stormwater harvesting will have an increased role in the water cycle management of Melbourne as sustainable, water sensitive, urban designs are implemented. Government policy should be proactive and lead and precede this increase in demand for increased stormwater harvesting. Stormwater harvesting should be considered as an alternative water resource option and be integrated into future planning processes of MWC, local government and retail water businesses. MWC (responsible for regional drainage), in liaison with local government (responsible for local drainage) and retail water businesses (providers of reticulated third pipe systems for recycled water and potentially stormwater recycling services to customers), should examine opportunities for increased stormwater harvesting in the Melbourne region with a TBL assessment of its viability. 60 Scenario Analysis
Scenario 16 – Increased utilisation of rainwater tanks
Scenario description Rainwater tanks are a traditional source of domestic water supply for isolated properties and small communities, but they are not commonly used in urban areas. Rainwater tanks have the potential to provide substitutes for potable water where water is used for garden watering and/or toilet flushing. Currently they are used primarily for garden watering due to the additional plumbing cost and complexity of connecting them to toilets. The yield of the most common residential tanks sold in the market is shown in Figure 25. The price ranges from $900 (0.6 kL) to $1,300 (4.5 kL) with an additional $800 to $1,000 for connection to the toilet.
Figure 25. Yield from typical domestic rainwater tank (50 percent of the roof area contributing to supply) (Source: South East Water)
60
50
40
30
20 Yield (kL/year) Yield
10
0 0.6 1.0 2.2 4.5 Capacity (kL)
Yield (kL/year) – garden only Yield kL/year – garden and toilet
Tank size 0.6 kL 1 kL 2.2 kL 4.5 kL Cost – garden only ($/ML) 8,200 8,300 7,300 7,200 Cost – garden and toilet ($/ML) 5,400 5,000 4,700 4,700
It should be noted that rainfall is not uniform across the Melbourne region with variations ranging from 350 mm/year in the west to 650 mm/year at Mornington Peninsula. The viability is therefore dependent upon geographic location. The most effective arrangement for Melbourne is for the tank to be also connected to the toilet. This provides a threefold increase in yield over the garden only use. The most efficient option of capturing the additional yield is to connect the toilet to the tank when constructing a new house rather than retrofitting an existing house. In a new house where the total roof area contributes to supply, the cost could be as low as $3,600/ML if supply is connected to both the garden and the toilet. Water Recycling Scenarios for Melbourne 61
Based on the average household use of approximately 75 kL/year for garden use, a tank to meet all garden and toilet flushing needs would be quite large. Most urban rainwater tanks are between 1,000 and 2,000 litres 1 which provides between one and two hours of garden watering time. These tanks play only a limited role in reducing potable consumption when it is considered that the majority of garden watering is required between December- March when the tanks are likely to receive the lowest incidence of rainfall. Greater use of rainwater tanks can be anticipated for non-residential water use across the Melbourne region in the future, including supply for public buildings and industrial uses. The increased runoff from the large roof area of these buildings, coupled with potentially larger tank sizes, makes the installation for such uses a more commercial proposition. Installation of a rainwater tank is best undertaken if it can be designed into a new building rather than expensive retrofitting. These opportunities will continue to be assessed on a case-by-case basis, however as an example, a 31,500 L tank was recently installed at the Whitehorse Civic Centre as the primary flushing source for public toilets. Current Government policy does not support the use of rainwater tanks for drinking water within the urban environment. Water quality can be a problem with all roof water systems, especially in urban and industrial areas. Potential water quality problems include: • atmospheric pollution, particularly in industrial areas; • bird and possum droppings, which can pollute the water with bacteria and gastro-intestinal parasites; • small animals which can get into a tank and may die there; and • pollutants associated with roofing materials, such as paints, detergents and other chemicals which can dissolve in the run off. VicUrban’s Aurora development in Epping North is currently assessing the viability of utilising rainwater for all domestic hot water uses. A rainwater harvesting system is composed of a rainwater tank, a first flush device, a pump and ultra violet (UV) disinfection. It is proposed to test whether appropriate disinfection can be achieved from just the hot water service which will remove the cost and ongoing operational and maintenance costs associated with UV disinfection. This development is expected to commence in 2004 and will ultimately service 8,500 properties over 15 years. In 2003, the Government introduced a rebate of $150 to encourage home owners to install rainwater tanks of a minimum size of 600 litres. The retail water businesses implement the scheme on behalf of the Government.
1 This compares with between 50,000 – 100,000 litres for a farm tank supplying all water requirements for a household 62 Scenario Analysis
TBL Assessment
Costs Comments Economic cost • For an average size tank (2.2 kL) the cost ranges from $7,300/ML (garden only) to $4,700/ML (garden and toilet). • If 10 percent of Melbourne households had tanks (130,000) the cost would range from $130 million (garden only) to $260 million (garden and toilet) based on an average 2.2 kL size. Environmental cost • Increased harvesting and use of rainwater reduces the amount of water discharged to the environment – to wetlands, streams, rivers and ultimately into the bays. This issue requires additional investigation. Social cost • Rainwater tanks of a size greater than 4.5 kL have generally been regarded as detracting from the amenity of the built environment.
Benefits Comments Economic benefit • Ranges from $1.6 million to $4.7 million. Environmental • Rainwater utilised under this scenario will be a direct substitute for potable supply benefit leading to increased security of our water supply. Social benefit • Has the potential to significantly improve the water awareness of the community in the urban environment. • Water tanks are embraced as a symbol of water conservation awareness and ‘doing the right thing’.
Discussion Widespread adoption of water tanks could lead to increased pressure on Government to consider tank water for drinking purposes. Increased use of rainwater tanks for domestic garden applications and toilet flushing will provide a reasonably small and quite expensive contribution to future potable water substitution. It is anticipated that if tank water was used as a supply of potable water (as currently occurs across much of rural Australia), in addition to garden and toilet use, an increase in consumption of tank water by 5 – 10 times would result. This would create a saving of between 0.3 – 0.6 ML/year of potable water within five years. A detailed risk analysis should be conducted to determine the risk to public health arising from increased consumption of tank water. In addition, a detailed TBL assessment should be conducted regarding the impact of changing government policy regarding the usage of tankwater throughout Melbourne. Water Recycling Scenarios for Melbourne 63
Scenario 17 – Utilisation of storm water to reduce salinity in sewage flows to WTP
Description Sewage entering the WTP at Werribee contains high salt levels. The treated water leaving the WTP also has high salinity (>1,000 mg/L) and hence has the potential to be environmentally harmful if not managed in a sustainable manner. A TBL assessment of the costs and benefits to dilute the sewage with stormwater is considered under this scenario.
TBL Assessment
Costs Comments Economic cost • Under investigation: costs associated with the additional infrastructure to collect and transfer the stormwater via the sewerage system to the WTP, and additional costs of treatment. Environmental cost • Increased harvesting and use of rainwater reduces the amount of water discharged to the environment– to wetlands, streams, rivers and ultimately into the bays. • Likely to result in increased sewage spills to the environment. Social cost • Nil.
Benefits Comments Economic benefit • A financial benefit from this scenario will arise if, (1) increased recycling of water from WTP demands a TBL–justified, lower salinity water; and (2) this scenario proves to be the most commercial method of reducing salinity. Environmental • Lower salt levels in recycled water, therefore reduced impact on the environment. Benefits • Reduced environmental impact of polluted stormwater discharges to the environment through transfer and treatment at WTP. Social benefit • Nil.
Discussion High levels of salt in the treated water from WTP poses significant risk to the viability of future recycled water schemes. It is likely that existing salt levels will need to be reduced if widespread water recycling is to be adopted due to: • the impact on receiving soils and groundwater; and • the impact on agricultural produce (many crops require salinity of less than 1,000 mg/L). This scenario presents one method for reducing salinity however it must be considered in the context of the overall feasibility of recycling from WTP. MWC is currently preparing a business case for the Balliang Recycled Water Project, which is a large-scale, water recycling project from WTP. The business case will include a detailed risk assessment of salinity and the potential for this scenario to be integrated into the long-term management of salinity. MWC, in partnership with City West Water, is developing a salinity reduction strategy for sewage entering WTP. The strategy will be complete by June 2004. The business plan for the Werribee Plains Vision, expected to be released during 2003, identifies a range of initiatives that will support the further development of these scenarios including salt reduction. It is anticipated that Scenario 17 will be considered further within these two projects. 64 Scenario Analysis
Scenario 18 – Desalination The growth in desalination plants has increased markedly over the last 10 years with reverse osmosis becoming the generally accepted process. Until the last few years, the largest seawater reverse osmosis plants were limited to 38ML/day (14,000 ML/year). With the improvement in membrane technology, the largest contracted plant under construction has a capacity of 166 ML/day (60,000 ML/year). Major environmental issues with desalination plants are the disposal of brine, which is often discharged back to the ocean via an outfall, and the greenhouse gases associated with the very high energy requirements. The overall treatment cost is now reported to be as low as $1,000/ML for large plants (greater than 100 ML/day) and the transfer and delivery is estimated to be $500/ML, resulting in a total cost of $1,500/ML. With regard to Melbourne, a suitable site would require water storage, and access to the reticulation system. The only feasible sites appear to be on the Mornington Peninsula where there are local water storages near both Port Phillip Bay and Western Port. At these sites the plant size would be relatively small (less than 5 ML/day) and make a minor contribution to substituting potable supplies. A large plant supplying Cardinia from Western Port (28 kilometres away) would offer a more feasible solution.
Discussion In summary, it is envisaged that the environmental issues will prevent the adoption of large scale desalination at this stage. However, continually evolving technology makes developments in the area of desalination worthy of ongoing consideration. Further investigation of world’s best practice is required to fully understand the experience and technologies that are being utilised in countries such as Israel. Water Recycling Scenarios for Melbourne 65
Scenario 19 – Aquifer storage and recovery
Description This scenario considers the temporary storage of recycled water in aquifers for future use. Aquifer Storage and Recovery (ASR) of recycled water is being utilised worldwide with several long-term examples, including 26 years experience at Orange County, California, USA. In 1997, research commenced on reclaimed water ASR at Bolivar, South Australia, providing local information on this option (Peter Dillon, pers. com.). Stormwater harvested from wetlands may also be stored in aquifers for subsequent recycling. Figure 26 is a schematic diagram of the process using stormwater. Recycled water can be stored within an aquifer with little mixing with the existing groundwater. This effectively acts as a subsurface storage distinguished by the different characteristics (such as salinity) of the recycled water and the groundwater. The inactivation of pathogenic micro-organisms in recycled water is of great importance with respect to protecting human health. A significant aspect of ASR is the potential impact on the groundwater quality, particularly the fate of contaminants. To ensure that recovered water meets targets for beneficial use, and that groundwater quality is protected in the long term, it is essential to consider aquifers as reactive rather than inert storages. As the survival of pathogens in groundwater diminishes with time, recycled water recovered from aquifers usually has improved microbiological quality. Studies are currently examining changes in other contaminants in recycled water whilst contained in an aquifer (Peter Dillon, pers. com.). Clogging is one of the key operational problems in ASR. It is generally entirely or partly attributed to microbial growth and biofilm development around the injection well. Studies at Bolivar with irrigation quality reclaimed water reveal that clogging can be managed by appropriate pre-treatment and by customised and inexpensive well maintenance programs. Laboratory column studies and geochemical modelling can indicate the quality of water and the level of management required for sustainable utilisation of an ASR program. Pilot studies, however, are essential for establishing operating procedures and the choice of treatment method prior to designing the network of injecting wells and the optimum recovery points.
Figure 26. Diagrammatic representation of process of ASR (Source: CSIRO Land and Water)
Runoff Irrigation Injection well Wetland
Groundwater level
Confining layer Natural recharge Aquifer 66 Scenario Analysis
Case Studies Seville Wandin Melbourne Metropolitan Study Yarra Valley Water recently conducted a feasibility study of using recycled water primarily from its Upper MWC has carried out a preliminary study examining the Yarra and Healesville Sewage Treatment Plants for opportunities for ASR in the Melbourne metropolitan aquifer recharge in the Seville Wandin area. The study area. Aquifers with potential for injection rates greater examined the geological, geophysical and than 5 ML/day/bore have an annual capacity between hydrogeological data within the Seville Wandin area 15,000 to 50,000 ML. These aquifers cover: with a view to characterising the aquifer and its • Western Province (Werribee Formation) suitability for injection of recycled water. • Nepean Province (Werribee Formation and The study found that there is potential for recharge Bridgewater Formation); and because the main aquifer in the area, the Older Volcanics aquifer, is currently over-committed for • Western Port Province (combined tertiary aquifers) extraction purposes. The EPA, however, requires recycled water injected into the aquifer to meet a very Although ASR is technically feasible in a number of high standard of quality to protect beneficial uses of the aquifers in the study area, the Werribee Formation the aquifer. Consequently, the sewage treatment plants aquifer was ranked first and second in the Western would need to be upgraded at a significant cost to and Nepean Provinces respectively. Due to potential for ensure the recycled water from these plants meets the surface discharge, the Bridgewater Formation was ranked required EPA injection standard. significantly below some of the Western Port aquifers in the Werribee Formation in the Nepean Province. Discussion The study identified the Werribee Formation in the Use of ASR for storage and additional treatment of Western Province as the best option to undertake a recycled water is considered to be technically feasible. pilot ASR study with a system of 50 GL capacity. The retail water businesses are continuing to look at Aurora Development potential ASR opportunities around Melbourne. Prior to embarking on a pilot study, a number of key activities The proposed VicUrban Aurora Development in Epping require further consideration. These include: North is currently assessing the suitability of aquifer storage and recovery for recycled water. In order to (1) assessing the fraction of organic matter in recycled support the strategy of extensive use of recycled water, water identified for injection bores; significant storage is required on or near the site. The (2) assessing the nature of aquifers, their hydraulic and use of aquifer storage and recovery is currently being geochemical properties, the groundwater quality in investigated as an alternative to conventional surface relation to environmental values, the degree of storage, such as in dams. Preliminary findings suggest confinement and existing uses; that it may be possible to utilise ASR for the development but it is likely to be more costly than (3) assessing areas of demand for recycled water in conventional storage methods. relation to prospective aquifers and the availability of water infrastructure, power and land over prospective aquifers; (4) assessing the requirements for water quality and maintenance procedures for aquifer materials at the most prospective sites to avoid clogging; (5) working with the EPA on issues linked to aquifer exclusion zones and the aquifer treatment function to meet groundwater quality protection requirements; and (6) refining pilot study costs including pre-treatments, drilling costs for observation and extraction wells and SCADA monitoring and control systems. Water Recycling Scenarios for Melbourne 67
References
DOI (2002). Melbourne 2030: Planning for Sustainable Growth. Department of Infrastructure, Victoria, October 2002.
DSE (2003). Securing Our Water Future. Department of Sustainability and Environment, Victoria, August 2003.
EPA Victoria (2001). Reuse Options for Household Wastewater. Domestic Wastewater Management Series, Publication 812, November 2001. EPA Victoria.
EPA Victoria (2003). Guidelines for Environmental Management: Use of Reclaimed Water. Publication 464.2, EPA Victoria, July, 2003.
NRE (2002a). Healthy Rivers, Healthy Communities & Regional Growth – Victorian River Health Strategy. Department of Natural Resources and Environment, August 2002.
NRE (2002b). New Water for Victoria: Victoria’s Water Recycling Action Plan. Department of Natural Resources and Environment, Victoria, October 2002.
State Government of Victoria (2003). Variation to State environment protection policy (Waters of Victoria) No. S 107. Victoria Government Gazette, 4 June 2003.
Water Resources Strategy Committee (2002). 21st Century Melbourne: a WaterSmart City – Final Report. Water Resources Strategy Committee for the Melbourne Area, October 2002. 68 Glossary
Glossary
Beneficial use Means a use of the environment or Sewerage system The pipes, pumps and treatment any element or segment of the plants used to transfer or treat environment that is conducive to sewage. public benefit, welfare safety, Sewer mining Tapping into and pumping sewage health or aesthetic enjoyment and out of a sewer for treatment and which requires protection from the recycling. effects of waste discharges, emissions or deposits. SEW South East Water Limited. CBD Central business district. Stormwater Rain water which runs off the urban area and flows into gutters, CWW City West Water Limited. the drainage system and Class A As defined in Guidelines for waterways. Environmental Management: Use of South Eastern The 56km outfall from the Eastern Reclaimed Water (EPA Victoria, July Outfall Treatment Plant at Carrum to 2003). Boags Rocks on Bass Strait. DSE Department of Sustainability and TDS Total Dissolved Solids. Environment. Treated sewage Treated water that is discharged Effluent Commonly used term for treated from a sewage treatment plant. sewage. Wastewater Water that, following capture or EPA Environment Protection Authority. use by the community, currently ETP The Eastern Treatment Plant which does not have a form of beneficial is owned and operated by MWC. reuse. Includes greywater, sewage and stormwater. Gigalitre Also GL = 1,000,000,000 litres. Water Recycling A recycled water plan produced by Greywater Household water which has not the Department of Natural been contaminated by toilet Resources and Environment in discharge and includes water from October 2002. bathtubs, dish washing machines, clothes washing machines and Watertable The surface plane of the saturated kitchen sinks. soil is called the watertable, which rises and falls as groundwater Groundwater Water is found within the pores, levels change. cracks and other space between soil particles. When these spaces WHO World Health Organisation. are saturated with water, the zone WTP The Western Treatment Plant which is referred to as containing is owned and operated by MWC. groundwater. YVW Yarra Valley Water Limited. Kilolitre Also kL = 1,000 litres. Megalitre Also ML = 1,000,000 litres. MWC Melbourne Water Corporation. Potable water Water of drinking quality. Recycled water Also referred to as reclaimed water, it is water that has been derived from sewerage systems or industry processes and treated to a standard that is appropriate for its intended use. Sewage Any liquid that is sent through the sewerage system to a treatment plant.
DSE customer service centre 136 186
www.dse.gov.vic.au