Drinking Water Quality
What the results tell us for Queanbeyan
The Queanbeyan Water Supply System delivered drinking water of a high quality throughout the current reporting period. Over that time, the 2004 national drinking water guidelines for microbiological quality—that no Escherichia coli or thermotolerant coliforms (both indicator bacteria) be found in any water sample—were met in 99% and 92% of the samples from across the council area. Organisms detected in early 2001 and thought to be thermotolerant coliforms were later shown to be environmental in origin. In those instances where bacteria were encountered, an appropriate response protocol was adopted to address the problem.
The drinking water quality requirements for 25 chemical parameters tested, under the 2004 national guidelines, were met in 100% of samples across the council area except for occasional, marginal exceedences of pH and aluminium. None of the exceedences is considered to have represented a health risk.
It is not possible to compare directly Queanbeyan City Council Area's water quality during the current reporting period with that in the previous period due to differences in the type of data used for each State of the Environment report.
Quality of the water supply systems
Drinking water for Queanbeyan City Council Area is provided by ActewAGL Corporation Ltd and reticulated by Queanbeyan City Council. The water is sourced normally from the Cotter/Bendora system, but if these reserves are low or unable to be used (such as after the January 2003 fires), water is also sourced from Googong Dam.
Queanbeyan's water supply system provided drinking water to 29,100 people located in Queanbeyan and Weetalabah within the city council area. Water for the latter residents is directed through pipes from Queanbeyan's supply system into storage tanks near Weetalabah. Additional chlorination of the stored water is undertaken periodically.
Two microbiological and 25 chemical parameters (see Interpreting the data) were monitored in the council area's drinking water as part of NSW Health's drinking water monitoring program (NSW Health 2000). The area's drinking water was not monitored for pesticides as, under current protocols (NSW Health 2000), the city council area was not considered to be at risk.
The majority of water quality parameters monitored from January 2001 to June 2004 met the relevant 2004 national guidelines for microbiological and chemical parameters. Those parameters that did not are shown in Table 1. No data were available for some years (see table).
Thirty-five occurrences of thermotolerant coliform bacteria and three occurrences of E. coli were recorded during the reporting period (see Table 1). Two of the instances of E. coli contamination were recorded in May 2001 and the other in April 2002. Most of the thermotolerant coliform contamination occurred during March–May 2001, with one instance each in December 2001 and April 2002.
Council's 2001 Supplementary State of the Environment Report indicated that council cleaned all reservoirs, flushed the mains, and increased the chlorine residuals throughout the system in response to the thermotolerant coliform occurrences to May 2001. Further investigation revealed that the organisms detected were not of a faecal nature but were environmental in origin and had multiplied under favourable conditions in the water supply reticulation system, presenting the impression of faecal contamination. They had no pathogenic (disease causing) qualities.
Chemical exceedences in the Queanbeyan supply system were confined to one instance each of pH (April 2004) and aluminium (April 2003). As these exceedences represented isolated incidents and were only marginally higher than relevant guidelines values, they were not considered to have posed a health risk.
E. coli and thermotolerant coliforms contamination were each recorded twice (February 2002) in the Weetalabah system (Table 1). As responses to these instances of bacterial contamination were successful there was no need for the Water Utility/Public Health Unit to recommend boiling water before using for human consumption.
The 2004 guideline values were met for all chemical parameters except pH on one occasion (December 2003). The exceedence was marginal and isolated, and thus not considered to be a health concern.
About the data
Queanbeyan City Council takes routine random water samples each fortnight to monitor the quality of the supply to ensure that the water supplied is of the best possible quality. Water samples are sent to relevant NSW Health laboratories for chemical and microbiological analyses, based on a schedule outlined in NSW Health (2000). Details of the monitoring program, including allocation of sample numbers based on the type of water supply system and population, and details of the response protocol when national standards are exceeded, can also be found in NSW Health (2000).
NSW Health provides analytical service through its Division of Analytical Laboratories in Sydney (microbiology and chemistry) and the Greater Murray Public Health Laboratory in Wagga Wagga (microbiology only). The results are owned by Queanbeyan City Council but maintained on the NSW Drinking Water Database (a statewide internet-based database) by NSW Health's Water Unit.
The data used for this report were sourced from the NSW Drinking Water Database. Results used only cover the period 1 January 2001 to 30 June 2004, as the database does not hold earlier data for any local government area. Further details of the database can be obtained from the NSW Health Water Unit.
Interpreting the data
The Australian Drinking Water Guidelines 2004 (NHMRC and NRMMC 2004)—here called the 2004 national guidelines—provide the standards for drinking water quality nationally. Although the 2004 national guidelines have superseded the 1996 national guidelines, they are yet to be ratified by the NSW Government. Consequently, the 1996 national guidelines are still being used in the NSW Drinking Water Database for determining exceedences. However, for this State of the Environment report, the 2004 national guidelines were adopted as the standards for analyses and interpretation of data to assess drinking water quality in the council area during the current reporting period.
The 27 drinking water quality parameters used for this report, their 2004 national guidelines values and notes on their interpretation are provided in Drinking Water Quality Parameters DrinkingWaterQualityParameters.htm.
E. coli and other thermotolerant coliforms are used as specific indicators of faecal contamination and hence the safety of water for drinking. When these organisms are detected in water samples, the water utility responds by raising the level of treatment with chlorine or other acceptable disinfectants to destroy potentially pathogenic coliforms.
The NSW Drinking Water Database contains instances of samples not meeting guideline requirements for total coliforms. This is because the database still uses the 1996 national guidelines which set a guideline value of 0 CFU/100 mL for total coliforms. However, since the 2004 national guidelines does not adopt a guideline value for coliforms (excluding E. coli) due to the lack of direct health significance, such exceptions in the data have been ignored for purposes of this report.
NHMRC and NRMMC (2004) Australian Drinking Water Guidelines 2004, National Water Quality Management Strategy, National Health and Medical Research Council and the Natural Resource Management Ministerial Council.
NSW Health (2000) Drinking Water Monitoring Program, October 2000, NSW Health Department, viewed 30 April 2005, http://www.health.nsw.gov.au/public-health/ehb/water/monitoring/DWMonitProgOct00.pdf.
|Microbiological3 / chemical parameter||January–June 2001||2001–02||2002–03||2003–04||January 2001–June 2004|
|No. of samples||No. of failures||Success rate (%)||No. of samples||No. of failures||Success rate (%)||No. of samples||No. of failures||Success rate (%)||No. of samples||No. of failures||Success rate (%)||Total no. of samples||Total no. of failures||Overall success rate (%)|
|Queanbeyan Water Supply System (supply population 29,000)|
|Weetalabah Water Supply System (supply population 100)|