AWWA WQTC69293

Melbourne Water is the bulk water supplier for the City of Melbourne, Australia. Much of the city's drinking water supply is drawn from protected, uninhabited catchments and delivered to consumers disinfected but unfiltered. After many years of drought, severe storms in catchment areas in mid-2007 resulted in a water quality incident with high raw water turbidity levels from wash-off into reservoirs. A boil water notice was issued for small townships that received drinking water directly from the affected reservoir (Upper Yarra Reservoir). Melbourne Water has a certified risk management plan for drinking water quality (HACCP, ISO 9001, ISO14001) that requires research to be undertaken in areas of the water supply where risks are not fully understood or identified. Several years of research into the presence of Cryptosporidium in catchment animals, combined with detailed risk assessments and event-based sampling in catchment areas has shown that the risk of contamination of the water supply with human-infectious Cryptosporidium is low. Research results, combined with a quantitative microbial risk assessment and results of genotyping of Cryptosporidium in water samples during the incident was presented to the Victorian Department of Human Services, who determined that the risk of human infectious Cryptosporidium to the consumers of Melbourne's drinking water was acceptable. As a result, a boil water notice for Melbourne was not issued. This experience highlighted the importance of rigorous risk assessment and research to support water supply management decisions. Includes 7 references, tables, figures.