Drinking Water Quality
What the results tell us for Palerang
The quality of drinking water in Palerang Council Area was of a high overall standard during the reporting period. The 2004 national guidelines for microbiological quality—that no Escherichia coli or thermotolerant coliforms (both indicator bacteria) be found in any water sample—were met in 96% and 93% of the samples, respectively, from across the council area. In those instances where such bacteria were recorded the appropriate response protocol was adopted to address the problem. Consequently, at no time during the reporting period there was a need to recommend boiling water before using for human consumption.
The drinking water quality requirements for all chemical parameters tested, under the 2004 national guidelines, were met in 100% of samples across the council area except for iron, lead, pH and turbidity. The relevant national guideline values for iron, lead, pH and turbidity were exceeded in 12%, 6%, 12% and 5% of samples, respectively, from across the council area. None of the exceedences appears to have represented a health risk.
It is not possible to compare directly 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. However, the water supply systems at Bungendore and Captains Flat appear to have improved, although the quality of the Braidwood system appears to have declined.
Quality of the water supply systems
Three water supply systems provide drinking water in Palerang Council Area to just under 3,000 people living in Braidwood, Bungendore and Captains Flat (see Table 1). 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 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.
Water samples from the Braidwood Water Supply System did not meet the 2004 national guidelines for E. coli and thermotolerant coliforms on 17 and 15 occasions, respectively, during the reporting period.
E. coli were reported on five occasions during 2001 (February, March and December), 10 occasions during 2002 (February, March, July, August, October and November), once each during 2003 (January) and 2004 (April). Thermotolerant coliform occurrences followed a similar pattern, with five instances in 2001 (February, March and December) and 10 instances in 2002 (February, March, July, August, October and November). Responses to all the instances of bacterial contamination were successful and hence there was no need for the Water Utility/Public Health Unit to recommend boiling water before using for human consumption.
Lowered effectiveness of chlorine due to increased pH in off-stream storages is the most likely reason for the occurrence of bacterial contamination over an extended period. Off-stream storage increases the pH of water to greater than 8 or sometimes greater than 8.5. Such high pH levels significantly lower the effectiveness of chlorine as a disinfectant. Increased level of chlorine treatment was adopted to address the problem and subsequently the bacterial contamination was brought under control on these occasions. Council is currently planning for a new water treatment plant for adequately addressing the problem of bacterial contamination.
Exceptions in chemical parameters in the Braidwood system related to iron and pH. There were 10 pH exceedences during the reporting period, with one each occurring in February 2001, February 2003 and December 2003, and seven during 2004 (March, May and June). One isolated sample showed a marginally increased level of iron during 2003 (December). These exceedences were marginal, and are not considered to have posed a significant health risk (see Interpreting the data).
The overall quality of the Braidwood supply system appears to have declined in comparison with its performance during the last reporting period.
All samples tested during the reporting period for the Bungendore Water Supply System met all microbiological and chemical quality requirements specified in the 2004 national guidelines. This indicates that the quality of the water supplied by this system was of superior standard consistently throughout the reporting period. Bungendore supply system appears to have overcome its history of bacterial contamination problems since the installation of a chlorination plant during the last reporting period.
Captains Flat system
Water from the Captains Flat Water Supply System did not record any adverse microbiological results during the reporting period. A slightly elevated level of lead (0.024 mg/L) and turbidity (8.6 NTU) were recorded once (July 2002). These one-off increases were not considered to have posed any health risk. It may therefore be concluded that the water quality from this supply system was of a high quality for the reporting period.
Performance of the Captains Flat supply system appears to have improved in comparison with the last reporting period. This is attributable to the installation of a filtration system in October 20002.
About the data
Water samples were collected by Palerang Council and 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 Palerang 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.
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 zero CFU per 100 millilitres 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.
Reported exceedences of chemical parameters in the council area were not of health concern as they were only marginally above the 2004 national guideline values and/or these values are not health based:
- iron (national guideline not health based; reported exceedence of one milligram per litre was well below the three milligrams per litre level above which iron may be a health concern)
- pH (maximum exceedence value of 9 is marginal compared with guideline range of 6.5–8.5 and well within the range of 6–10.8 reported for major Australian reticulated water supplies)
- turbidity (national guideline not health based).
It was not feasible to make direct comparisons of water quality between results for this reporting period and the previous one. This is because the 2000 State of the Environment Report used aggregated data to report on three water quality issues (bacteriological tests, chemical tests and tests for pesticides), while the current report is based on a suite of individual chemical and microbiological parameters.
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.
|Parameter3||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 (%)|
|Braidwood Water Supply System (supplies Braidwood; supply population 1056)|
|Bungendore Water Supply System (supplies Bungendore; supply population 1,500)|
|All water samples tested during the reporting period met ADWG 2004 requirements.|
|Captains Flat Water Supply System (supplies Captains Flat; supply population 418)|
1 For an explanation of the 2004 national guidelines, see Interpreting the data; 2 No results available prior to 1 January 2001; 3 Does not include total coliforms