2014 – Walhallow (NSW) – E.coli, Hardness
Rainwater tests at Walhallow indicated that half of the rainwater tested had E. coli. Of the samples tested, 30/58 (52 %) had E. coli with a mean of 18 colony-forming units per sample (Table 3). Overall, 3/5 rainwater tanks had more than 50% E. coli detection rate 2 over the sampling period.
The ADWG recommends no E. coli in every 100ml of a drinking water sample. There is no guideline value for total coliforms as they are not recommended for use as an indicator of faecal contamination. Total coliforms are an indicator of disinfection efficiency. Rainwater at Walhallow is not disinfected…
Thermotolerant coliforms are a sub-group of coliforms that are able to grow at 44.5 ± 0.2°C. E. coli is the most common thermotolerant coliform present in faeces and is regarded as the most specific indicator of recent faecal contamination because generally it is not capable of growth in the environment. In contrast, some other thermotolerant coliforms (including strains of Klebsiella, Citrobacter and Enterobacter) are able to grow in the environment and their presence is not necessarily related to faecal contamination. While tests for thermotolerant coliforms can be simpler than for E. coli, E. coli is considered a superior indicator for detecting faecal contamination…” ADWG
Town Water Hardness
During the period 2006 to 2015, routine town water monitoring data for Walhallow showed that the mean total hardness measured as calcium carbonate (CaCO3) was 268 mg/L compared to the ADWG value of 200 mg/L (NSW Health, n.d.). Participants often referred to town water as “hard water” that caused “itchy and scaly” skin after bathing. Consequently, the community disliked the town water and this may lead to perceived water insecurity. When hard water is heated, the calcium hydrogen carbonate (Ca(HCO3)2 that causes the hardness is converted into CaCO3, which is deposited as a whitish scale. Hence “hard water” is the qualitative description that people use for the scaling actions of water, while water hardness is a quantitative measure of metal ions that are dissolved in the water usually measured as CaCO3 (McMell on, 2010).
“To minimise undesirable build‑up of scale in hot water systems, total hardness (as calcium
carbonate) in drinking water should not exceed 200 mg/L.
Hard water requires more soap than soft water to obtain a lather. It can also cause scale to form on hot water pipes and fittings. Hardness is caused primarily by the presence of calcium and magnesium ions, although other cations such as strontium, iron, manganese and barium can also contribute.” Australian Drinking Water Guidelines 2011