2008/11 – Portarlington (Victoria) – E.coli, Turbidity, pH

January/February 2009: Portarlington – E.coli

29/1/2009 (15MPN/100mL) and 27/2/2009 (1 MPN/100mL) – On 29 January 2009, routine sampling of the Portarlington high level tank detected the presence of E.coli. The 15 metre high, 45kL tank is filled twice per day with 5 kL of fresh water dosed at 2.2mg/L of chlorine. The tank is manually checked for chlorine residual twice a week by coastal operators. Records indicate sufficient residual (0.56mg/L) within the tank prior to the detection. The laboratory was immediately engaged to conduct follow up sampling. Additionally, inspection of the tank failed to identify any signs of potential contamination. There were no faults or failures with the operation of the Portarlington disinfection plant prior to or post detection. Follow up samples were free from E.coli and contained a chlorine residual of 0.85 mg/L. The nature of suspected contamination is not known. A month after the initial detection a sample reported positive for E.coli. Follow up tests and investigations failed to detect E.coli or a cause of the detection. Since these detections, increased monitoring has failed to identify any further issues.https://www.barwonwater.vic.gov.au/vdl/A2034825/Annual%20Drinking%20Water%20Quality%20Report%202008-2009.pdf

January 7 2011: Portarlington – E.coli

Detection of Escherichia coli during commissioning of a new water main (3 MPN/100 ml). The offending sample was taken during the commissioning of a newly constructed feeder main. The pipeline was flushed and re-sampled. Follow up results were clear of Escherichia coli. Routine sampling within the Portarlington water quality sampling locality on the same day did not detect any Escherichia coli. A direct cause of the detection could not be identified.
January 24 2011: Portarlington – E.coli
Detection of Escherichia coli in storage tank (3 MPN/100 ml). Re-sampling was immediately conducted. The storage tank was filled with chlorinated water. Inspection of the storage tank was conducted and no cause was identified. Follow up results were clear of Escherichia coli.

A direct cause of the detection could not be identified.


March 9 2011: Portarlington – E.coli

Detection of Escherichia coli in drinking water Location #1 (14 MPN/100 ml) Location #2
(1 MPN/100 ml). Escherichia coli was detected in two locations on the same day. Flushing was immediately conducted, along with follow-up sampling in the surrounding area. Follow up results from all sites were clear of Escherichia coli. The following day, in order to reduce water age and increase turn over in the supply system, flushing of the major feeder main supplying

Indented Heads and St Leonards was conducted. The mobile disinfection unit was deployed to provide booster disinfection during this process.



Escherichia coli should not be detected in any 100 mL sample of drinking water. If detected
in drinking water, immediate action should be taken including investigation of potential
sources of faecal contamination.

“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

Portarlington – Victoria – Turbidity

2008/09: Portarlington (Victoria) – Turbidity 14 NTU (Maximum detection during year)

2009/10: Portarlington (Victoria) – Turbidity 6.6 NTU (Maximum detection during year)

2010/11: Portarlington (Victoria) – Turbidity 6.6 NTU (Maximum detection during year)

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.

Portarlington (Victoria) – pH (alkaline)

Average pH: 2008 July-2009 June: 8.67 pH units

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.