Yass Valley
Indicator: Drinking Water Quality
Results for this indicator are also available for [an error occurred while processing this directive]
What the results tell us for Yass Valley
The Yass Valley drinking water supply from the Yass River is treated extensively. It is therefore surprising that any samples showed E. coli present, particularly the sample for the 5th November this year that showed 8 organisms per 100mL of drinking water. The samples before and after showed no organisms.
Almost all the concentrations of inorganic constituents showed concentrations below Guideline Values. Exceptions were hardness, which is not related to health, and aluminium. On one occasion in 2007 the concentration of aluminium reached 1.18mg/L, compared to advice from the National Health and Medical Research Council (NHMRC) that water supply authorities are ‘strongly encouraged to keep acid soluble aluminium concentrations as low as possible, preferably below 0.1 mg/L’.
Murrumbateman water is drawn from a bore, with no treatment. On 26th June 2007 there were 16 E. coli organisms per 100 mL of water, which coincided with a very high concentration of total coliforms, indicating contamination of the bore water.
The water shows hardness, which is frequent in underground water. There were no concentrations of inorganic components of health concern.
Quality of the water supplied
Yass
Yass town drinking water supply is sourced from the Yass River and provides drinking water for a population of 6,311 in the Yass town and communities at Binalong and Bowning. The supply is fully treated, including a powdered activated carbon facility, fluoridated and disinfected with chlorine.
Overall 34 parameters of water quality were assessed. A total of 320 samples were assessed for E. coli, and seven samples showed organisms. The highest count was eight organisms per 100mL of water on 5th November 2008. In January 2008, three organisms per 100mL water were recorded. In 2007 only one sample showed one organism, in 2006 none were found, however in 2005, four samples showed organisms, the highest being 5 E .coli per 100 mL.
Forty five samples were assessed for inorganic components. Hardness and total dissolved solids exceeded the recommended concentration, in the case of hardness in about half the samples, but this does not have any health significance.
Aluminium exceeded the Guideline Value of 0.2 mg/L in 5 cases. The highest concentration of aluminium was 1.18 mg/L on 3rd April 2007, with a second high sample on 29th May 2007 of 0.59 mg/L. A high concentration of 0.88 mg/L was recorded on 8th August 2006. While it was not possible for the NHMRC to set a health-based guideline value for aluminium, water supply authorities are ‘strongly encouraged to keep acid soluble aluminium concentrations as low as possible, preferably below 0.1 mg/L’.
Iodine was slightly above the guideline value three times in 2006, which has no health significance. All other parameters were within the guideline values.
Murrumbateman
Drinking water for the 330 people living in Murrumbateman is drawn from the Murrumbateman Bore. There is no treatment of the water, and no disinfection.
One hundred water samples were assessed for quality, with measurement of 34 water quality parameters.
There were three reports of E.coli in the water supply, two of which were one organism per 100mL of water, occurring on 24th January 2006 and on 12th February 2008. On 26th June 2007 there were 16 organisms per 100 mL of water, which coincided with a very high concentration of total coliforms. This indicates faecal contamination of the supply, possibly due to heavy rain, washing surface material into the bore.
Inorganic components were measured in ten samples over the four years. Total dissolved solids and hardness exceeded the guidelines in most samples, but this has no health significance. The guidelines were aimed at the lime scaling of pipes, which increases with hardness. Iodine exceeded the guideline values in six of the ten samples, but the mean value was equal to the guideline and the maximum was 0.12, compared to the guideline of 0.1mg/L. This has no health significance. Lead exceeded the guideline in two samples, but the mean was well below the guideline, which also has no health significance. All other parameters were within the guideline values.
About the data
Drinking water quality is monitored as part of the NSW drinking water monitoring programme, 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 Council. The Council uses both public and private water supplies, but only those supplies recorded on the health database are available for comment in this report.
Interpreting the data
In 2004 the 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 this report are from 1st 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 NHMRCl 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 (National Health and Medical Research Council) and NRMMC (Natural Resource Management Ministerial Council) (2004). Australian Drinking Water Guidelines. National Water Quality Management Strategy. http://www.nhmrc.gov.au/publications/synopses/eh19syn.htm
