Queanbeyan
Indicator: Drinking Water Quality
Results for this indicator are also available for [an error occurred while processing this directive]
Please note: Text or data highlighted in this colour represent an update to this indicator for the period 2008/09.
What the results tell us for Queanbeyan City Council
The Queanbeyan City Council area drinking water supply is of excellent and consistent quality.
Drinking water quality is monitored as part of the New South Wales (NSW) drinking water monitoring program and detailed results can be accessed through the website http://www3.health.nsw.gov.au/waterqual/samples/register.cfm.
This report on drinking water quality for 2004-2008 is prepared from examination of this data, to illustrate the quality aspects of the water supplied for domestic consumption in the City Council area. The City uses reticulated drinking water supplied by ACTEW Corporation, the supply utility for the Canberra area. The water is drawn from several supplies, depending on availability. The majority of the supply under normal rainfall conditions arises from the Cotter system, which consists of the Corin, Bendora and Cotter reservoirs. The other major storage is Googong reservoir, which during the recent drought has had low inflows from the rivers supplying the reservoir. To supplement the water availability in the Canberra/Queanbeyan supply, recent rebuilding of the Stromlo Water Treatment Plant has allowed water to be drawn directly from the Murrumbidgee River. Prior to the upgrading only water from the Cotter system was processed in this plant. This additional water can be used for the normal reticulated supply or pumped back into Googong reservoir to maintain storage levels. Googong reservoir water is processed at Googong water treatment plant, which is connected into the overall supply network. Both water treatment plants incorporate filtration, flocculation, sedimentation and chlorination. In addition the Stromlo plant now has Ultra Violet post-treatment sterilisation to destroy any residual Cryptosporidium cysts arising from the Murrumbidgee water. The supply is fluoridated.
Quality of the water supply systems
Queanbeyan system
This system provides water to a population of 29,000 people, in and around Queanbeyan City. This supply is an integral part of the Canberra supply network.
In the period 2004-08 a total of 782 samples from the Queanbeyan reticulation system were assessed for E. coli, and over the four years no samples showed the presence of the organisms. This indicates a consistently excellent quality drinking water supply.
In the same period, free chlorine was measured 744 times, and no sample exceeded the Guideline Value. pH was measured 48 times, with four samples exceeding the recommended range of 6.5-8.5. The maximum reported was 8.7 and the mean 7.7, indicating only slightly more alkaline water in these samples, of no health significance. One sample slightly exceeded the iron Guideline Value and another single sample the Value for aluminium. These have no health significance.
During 2008-09 a total of 183 samples from the Queanbeyan reticulation system were assessed for E. coli, and over the 2008-09 period no samples showed the presence of the organisms. This indicates a consistently excellent quality drinking water supply.
Free chlorine was measured 177 times, and no sample exceeded the Guideline Value. pH was measured 11 times, with no samples exceeding the recommended range of 6.5-8.5. The maximum reported was 8.3 and the mean 7.9. None of the samples tested were found to be outside the guideline values, confirming that the drinking water in Queanbeyan is of excellent quality.
Weetalabah supply
This provides 100 people with drinking water from the ACTEW reticulation network, which is chlorinated for disinfection and fluoridated.
In the period 2008-09 sixteen samples were assessed for E.coli, and none were detected. Two samples were assessed for inorganic components, one showed a pH of 8.9, just outside the recommended range of 6.5-8.5. This has no health significance. All other parameters were with the Guideline Values.
In the period 2008-09 all parameters were within the Guideline Values.
About the data
Interpreting the data
In 2004 the National Health and Medical Research Council (NHMRC) introduced the Australian Drinking Water Guidelines, which provide the basis for quality assessment. These Guidelines have not included Total Coliforms as a measure of water quality for health purposes, as the organisms are widely present in soil and untreated water and grow in water pipes, and do not reflect the content of pathogenic organisms. Monitoring for Escherichia coli is, by contrast, particularly informative, since this organism occurs in large numbers in faeces and hence is an effective indicator of faecal contamination. It is killed by standard drinking water treatment and therefore should not occur in domestic supplies. The drinking water Guideline Value is zero organisms per 100ml sample and any detected organisms present in the water therefore exceed the guideline, and should result in an increase in the disinfection of the supply.
This remedial action should be taken until the E. coli count returns to zero.
While there are many other pathogens present in faecal contamination of water, monitoring of E. coli has been shown to be an effective and straightforward method for public health. Where the data from a water supply for this period show E .coli present, it has been commented upon for each water supply reported.
Concentrations of inorganic components of water supplies do not have such a sharp impact on health as faecal contamination. The Guideline Values reflect safe concentrations for lifetime exposure, and minor exceedences, which briefly occur, are of negligible risk to public health. Inorganic constituents become a risk to public health when they consistently exceed the Guideline Values, with the risk increasing with the concentration in the supply. Where these have occurred, they are commented upon in the appropriate section of the report. Unless there is accidental contamination of the supply, it is unlikely that any substantial variations in concentration of inorganic components will occur throughout any year.
Continuing concentrations that significantly exceed the Guideline Values require investigation and rectification. The results included in the 2004-08 report are from 1 January 2005 to the time of writing, mid-November 2008.
The information assessed in this report is available on the NSW Health water database, and uses the current NHMCR Drinking Water guidelines as the reference for the analytical comparisons.
References
NSW Department of Health Drinking Water Database 2008 http://www3.health.nsw.gov.au/waterqual/samples/register.cfm.
NHMRC and NRMMC - see National Health and Medical Research Council and Natural Resource Management Ministerial Council
National Health and Medical Research Council and Natural Resource Management Ministerial Council 2004. Australian Drinking Water Guidelines. National Water Quality Management Strategy. http://www.nhmrc.gov.au/publications/synopses/eh19syn.htm
