The Water Quality Study


Prof Christopher Fairley
Dr Martha Sinclair
Dr Margaret Hellard
Assoc Prof Andrew Forbes 

Funded by: Cooperative Research Centre for Water Quality and Treatment, The Water Services Association of Australia, Melbourne Water Corporation, South East Water Limited, Yarra Valley Water Limited, City West Water Limited, Department of Human Services Victoria

The Water Quality Study was a randomised double blinded controlled trial to determine whether microorganisms in drinking water were contributing to community gastroenteritis in the city of Melbourne.

Melbourne's primary water supply originates from highly protected forest catchments, and is chlorinated but not filtered prior to distribution to consumers. Most large cities have less well-protected water sources but a higher degree of water treatment including filtration. The study area consisted of several suburbs on the southeast of the city which were chosen for their combination of demographic and water supply characteristics (new homes, high rate of home ownership, young families, unfiltered water).

Six hundred families were recruited and randomly allocated to receive a real or sham water treatment unit. Real units consisted of a 1 micron absolute filter cartridge and a UV treatment chamber, and greatly reduced the microbiological content of the water. Sham units were identical in outward appearance and normal use characteristics but were altered internally so that they had no microbiocidal effect.

Participating families recorded details of gastrointestinal illness, medical treatment, travel, recreational water activities and other relevant information in weekly Health Diaries. Additional questionnaires were administered at intervals to assess water intake and food consumption. Adult participants provided blood samples for serological testing, and both adults and children provided faecal specimens for pathogen analysis at baseline and following episodes of gastroenteritis.

Conventional water quality parameters in the study area were monitored by the water supply utility, and composite mains samples were tested weekly for a range of pathogens including protozoa.

A successful 6 week Pilot study of 50 families was conducted in June /July 1997, and the Main study commenced in September 1997. Data was collected for 15 months (68 weeks) with a 4 week break over each Christmas holiday period. The data collection phase was completed in March 1999, and the results of the study were announced in April 2000.

No difference in the rate of gastroenteritis was detected between the two groups of families, demonstrating that waterborne pathogens do not make a significant contribution to community gastroenteritis in Melbourne. This result is likely to apply to other water supplies with similar characteristics. The same methodology is now being used to assess waterborne disease risks in the US.

Hellard ME, Sinclair MI, Forbes AB and Fairley CK. A randomized blinded controlled trial investigating the gastrointestinal health effects of drinking water quality. Environmental Health Perspectives 109 (8) August 2001.

This paper can be downloaded as a PDF file from the Environmental Health Perspectives journal (

The Water Quality Study Team received the 2000 Department of Human Services Award for Excellence for Public Health Research for its work on the study.