Annual Review of the Microbiological Quality of Drinking-Water in New Zealand 2000
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Annual Review of the Microbiological Quality of Drinking-Water in New Zealand 2000 Prepared by the Institute of Environmental Science and Research Limited by Andrew Ball June 2001 Client Report FW0141 E12 Annual Review of the Microbiological Quality of Drinking-Water in New Zealand 2000 June 2001 Prepared as part of a Ministry of Health contract for scientific services by Andrew Ball Published with the permission of the Director-General of Health in October 2001 Ministry of Health PO Box 5013, Wellington, New Zealand ISBN 0-478-23959-9 (Booklet) ISBN 0-478-23960-2 (Internet) This document is available on the Ministry of Health’s web site http://www.moh.govt.nz Ministry of Health Disclaimer The data and analyses contained in the Annual Report on the Microbiological Quality of Drinking-Water in New Zealand 2000 have been supplied to the Ministry of Health by the Institute of Environmental Science and Research Limited (ESR). The Ministry of Health cannot confirm the accuracy of the data and the analyses and accepts no liability or responsibility for any acts or omissions, done or omitted in reliance, in whole or in part, on the data or the analyses. All local authorities and bulk water suppliers and relevant government agencies were given the opportunity to comment on and check this document for accuracy prior to publication. The Ministry of Health has endeavoured to ensure that the feedback has been included in this published report and would like to thank those who provided comments and corrections. ESR Disclaimer This report or document (the Report) is given by the Institute of Environmental Science and Research Limited (ESR) solely for the benefit of the Ministry of Health, Public Health Service Providers and other Third Party Beneficiaries as defined in the Contract between ESR and the Ministry of Health and is strictly subject to the conditions laid out in that Contract. Neither ESR nor any of its employees makes any warranty, express or implied, or assumes any legal liability or responsibility for use of the Report or its contents by any person or organisation. Draft Annual Report on the Microbiological Quality iii of Drinking-water in New Zealand 2000 Acknowledgements The author is very grateful for the efforts of the Health Protection Officers and local authority personnel who gathered the data and completed the questionnaire forms for this survey and, in particular, to those who took the time to provide useful feedback about the questionnaire. Thanks also to Alan Ferguson for assistance with water supply information systems. The care taken by Helen Davies, Chris Nokes and the staff of the Ministry of Health and of certain public health service providers in reviewing the report and providing valuable comment was also very much appreciated. iv Draft Annual Report on the Microbiological Quality of Drinking-water in New Zealand 2000 Contents Executive Summary ix Background ix Key findings ix Summary of data xi Recommendations xiv Consumer Feedback xvi 1 Introduction 1 1.1 Project specification 1 1.2 Previous surveys 1 1.3 Drinking-Water Standards for New Zealand: 1995 2 2 Methodology 4 2.1 The questionnaires 4 2.1.1 Water supplier monitoring–treatment plant and source water 4 2.1.2 PHSP surveillance of water treatment plant 4 2.1.3 Water supplier monitoring–distribution zone 4 2.1.4 PHSP surveillance of the distribution zone 5 2.1.5 Population information 5 2.2 Questionnaire distribution 5 2.3 Coverage of the survey 6 2.4 Quality control 6 2.5 Analysis 7 2.6 Shortcomings of the questionnaire 7 3 Overview of Drinking-water Supplies 9 4 Drinking-water Monitoring in the Distribution Zone 11 4.1 Adequacy of monitoring 11 4.1.1 Classification by health district 11 4.1.2 Classification by population band 14 4.2 Compliance 16 4.2.1 Classification by health district 16 4.2.2 Classification by population band 22 5 Drinking-water Monitoring at the Treatment Plant 24 5.1 The population distribution of treatment plants 24 5.2 Adequacy of treatment plant monitoring 25 Draft Annual Report on the Microbiological Quality v of Drinking-water in New Zealand 2000 6 Validity of Microbiological Monitoring 34 7 Water Supply Surveillance 36 7.1 PHSP surveillance of distribution zones 36 7.2 PHSP surveillance of treatment plants 39 7.3 Public health risk management plans 40 8 Monitoring and Surveillance in Schools 42 9 Private and Hospital Drinking-water Supplies 46 9.1 Private supplies 46 9.2 Hospital and health service supplies 47 10 Corrective Action 49 10.1 Responses to transgressions 49 10.2 ‘Boil Water’ notices 50 11 Disinfection 52 11.1 The effect of disinfection status on microbiological quality 52 11.2 Methods of disinfection 54 12 The Drinking-Water Standards for New Zealand: 2000 59 12.1 Some of the implications to microbiological compliance of the DWSNZ:2000 59 13 References 62 Appendix 1: Drinking-water microbiology questionnaires 63 Appendix 2: Notes to the 2000 annual survey of the microbiological quality of drinking-water 67 Appendix 3: Drinking-water standards for New Zealand:1995 80 Appendix 4: Ministry of Health register of laboratories approved for drinking-water compliance testing 83 Appendix 5: The use of non-approved laboratories for distribution zone compliance testing of local authority supplies 85 vi Draft Annual Report on the Microbiological Quality of Drinking-water in New Zealand 2000 Appendix 6: Distribution zone monitoring and surveillance 87 Northland 89 Auckland 94 Waikato 99 Tauranga 103 Whakatane 105 Rotorua 106 Tairawhiti 108 Hawkes Bay 110 Taranaki 113 Wanganui 115 Manawatu 117 Wairarapa 119 Hutt Valley 120 Nelson 122 Marlborough 124 West Coast 126 Canterbury 128 South Canterbury 133 Otago 135 Southland 138 Appendix 7: Anomalies between microbiological quality and grading 140 Appendix 8: Anomalies between monitoring and surveillance results 142 Appendix 9: Distribution zones on permanent ‘boil water’ notice 144 Appendix 10: School drinking-water supplies 145 Appendix 11: School drinking-water supplies that have yet to be registered 157 Appendix 12: List of health districts and public health service providers 158 Appendix 13: Ministry of Education circular to schools 159 Appendix 14: Grading 165 Draft Annual Report on the Microbiological Quality vii of Drinking-water in New Zealand 2000 List of tables Table 3.1: Numbers and populations of distribution zones and treatment plants 9 Table 3.2: Number of distribution zones and populations supplied in the health districts 9 Table 4.1: Summary of the adequacy of monitoring in distribution zones 12 Table 4.2: Adequacy of zone monitoring expressed as percentages 13 Table 4.3: Distribution zone monitoring expressed in terms of population 13 Table 4.4: Adequacy of distribution zone monitoring data by population band 15 Table 4.5: Summary of 2000 distribution zone monitoring compliance data 17 Table 4.6: Reasons for non-compliance in the distribution zone 22 Table 4.7: Compliance monitoring in the distribution zone by population band 22 Table 5.1: Water sources for different population bands 25 Table 5.2: Treatment plant compliance by population band 26 Table 5.3: Treatment plant compliance by health district 27 Table 5.4: Causes of faecal coliform non-compliance of treatment plants by population 27 Table 5.5: Causes of non-compliance at the treatment plant by health district 29 Table 5.6: Cryptosporidium compliance in treatment plant by population band 30 Table 5.7: Demonstration of the secure status of groundwater by health district 32 Table 7.1: Distribution zone surveillance in each health district 37 Table 7.2: Summary of distribution zone surveillance by population band 38 Table 7.3: Methods used for distribution zone surveillance 39 Table 7.4: Summary of treatment plant surveillance by population band 40 Table 7.5: Methods used for treatment plant surveillance 40 Table 8.1: Monitoring and surveillance in distribution zones of school supplies 42 Table 9.1: Compliance of private supplies 46 Table 9.2: Supplies to hospitals / health services 47 Table 10.1: Corrective action following distribution zone transgressions 49 Table 11.1: Disinfection status 52 Table 11.2: Compliance of treatment plants with disinfection 53 Table 11.3: Compliance of treatment plants without disinfection 54 Table 11.4: Disinfection methods used for different population bands 55 Table 11.5: Effectiveness of disinfection methods 56 Table 11.6: Disinfection methods by population band in complying treatment plants 57 viii Draft Annual Report on the Microbiological Quality of Drinking-water in New Zealand 2000 Executive Summary Background The report covers the fourth year when microbiological quality was assessed using the Drinking-Water Standards for New Zealand: 1995 (DWSNZ:1995). The information on the microbiological quality of drinking-water was obtained through public health service providers (PHSPs) using questionnaires that sought data concerning surveillance and monitoring programmes carried out by PHSPs and water suppliers respectively. Water suppliers fall into two groups: local authorities, including commercial water supply companies contracted by local authorities, and private organisations or communities responsible for the operation of their own drinking-water supplies. The water suppliers are responsible for water quality monitoring, whereas the PHSP carries out surveillance of the management of drinking-water quality in the health district. The survey sought information about both distribution zones and water treatment plants. In addition to microbiological quality information, the questionnaire sought information about the water treatment processes in use and the means used to demonstrate compliance with the DWSNZ:1995. Key findings The 2000 Register of Community Drinking-water Supplies in New Zealand contained 1968 water treatment plants and 2054 distribution zones and covered an estimated 87% of the New Zealand population.