2007/17 – Pirlangimpi (Northern Territory) – E.coli, Turbidity, pH

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Pirlangimpi (Northern Territory) – E.coli

13 – 16 April 2007.  Pirlangimpi. High counts of both total coliforms and E. coli from all samples taken in the reticulation system.

2006/07: Pirlangimpi E.coli 4 samples exceeding trigger levels. 91.1% samples within trigger levels

2008/09: Pirlangimpi E.coli 3 Number of detections. 3 – 5 September , 2008 Incident: Significant levels of E. coli were detected in the surface water source and throughout the distribution system. This water supply relies on a single surface water source and has been identifi ed as having a high risk of contamination.

2008/9: Pirlangimpi (Northern Territory) – 3 E.coli detections.

“Coliforms are Gram-negative, non-spore-forming, rod-shaped bacteria that are capable of aerobic and facultative anaerobic growth in the presence of bile salts or other surface active agents with similar growth-inhibiting properties. They are found in large numbers in the faeces of humans and other warm-blooded animals, but many species also occur in the environment.

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 2011

Pirlangimpi (Northern Territory) – Turbidity

2009/10: Pirlangimpi Turbidity 6.6NTU

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.

Aesthetic: Based on aesthetic considerations, the turbidity should not exceed 5 NTU at the
consumer’s tap.

Pirlangimpi (Northern Territory) – pH (acidic)

2007/08: Pirlangimpi pH 6.3

2008/09: Pirlangimpi pH 6.2

2009/10: Pirlangimpi pH 6.2

2010/11: Pirlangimpi pH 6

2015/16: Pirlangimpi pH 6.1

2016/17: Pirlangimpi pH 6.4

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.