2008/11 + 2016/17 – Angurugu (Northern Territory) – E.coli, pH, Turbidity

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Angurugu (Northern Territory) – E.coli

24/12/09: Significant levels of E. coli were detected in Angurugu’s water supply. As Alyangula’s water supply comes from the same source as Angurugu’s, the water boil alert was extended to Alyangula as a precaution. Power and Water in conjunction with GEMCO, who manage the water treatment system undertook an inspection to identify the source of contamination and increased chlorine disinfection levels. The system was then comprehensively flushed to remove the potentially contaminated water. Analyses of additional water samples confirmed that the water was clear from E. coli and other indicator bacteria and the Department of Health lifted the Precautionary Notice on Friday 25 December. 97% E.coli performance over year.

“E.coli

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

Angurugu (Northern Territory) – pH (acidic)

2007/08: Angurugu pH 6.2

2008/09: Angurugu pH 6

2016/17: Angurugu pH 5.4

Based on the need to reduce corrosion and encrustation in pipes and fittings, the pH of
drinking water should be between 6.5 and 8.5.

New concrete tanks and cement-mortar lined pipes can significantly increase pH and
a value up to 9.2 may be tolerated, provided monitoring indicates no deterioration in
microbiological quality.

pH is a measure of the hydrogen ion concentration of water. It is measured on a logarithmic scale from 0 to 14. A pH of 7 is neutral, greater than 7 is alkaline, and less than 7 is acidic.

One of the major objectives in controlling pH is to minimise corrosion and encrustation in pipes and fittings. Corrosion can be reduced by the formation of a protective layer of calcium carbonate on the inside of the pipe or fitting, and the formation of this layer is affected by pH, temperature, the availability of calcium (hardness) and carbon dioxide. If the water is too alkaline (above pH 8.5), the rapid deposition and build-up of calcium carbonate that can result may eventually block the pipe.

Angurugu (Northern Territory) – Turbidity

2010/11: Angurugu Turbidity 11.6 NTU

Chlorine-resistant pathogen reduction: Where filtration alone is used as the water treatment
process to address identified risks from Cryptosporidium and Giardia, it is essential
that filtration is optimised and consequently the target for the turbidity of water leaving
individual filters should be less than 0.2 NTU, and should not exceed 0.5 NTU at any time
Disinfection: A turbidity of less than 1 NTU is desirable at the time of disinfection with
chlorine unless a higher value can be validated in a specific context.