2006/12 – Cranbourne (Victoria) – E.coli, Iron, Colour, Turbidity

Cranbourne – Victoria – E.coli
The seventh E.coli detection was from a routine sample taken at Centreville Tank Cranbourne, in the Cranbourne locality, on 17 April 2009 (two E.coli organisms per 100mL) with a free chlorine residual of 0.01 mg/L. The tank is supplied by Cardinia Reservoir. The tank was
immediately isolated, inspected and dosed to a free chlorine residual of 0.5mg/L. All system checks were clear and the re-sample was clear of E.coli . The tank remained off-line for the winter months due to low turnover, and will be put back into the system in summer
when demands on the system increase. This occurrence was thought to be due to windblown contamination. This tank has since been fully sealed.

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

Cranbourne – Victoria – Iron

2006/7: Cranbourne (Victoria)  – Iron 430ug/L (Highest level only)

2007/8: Cranbourne (Victoria)  – Iron 720ug/L (Highest level only)

2011/12: Cranbourne (Victoria)  – Iron 840ug/L (Highest level only)

Based on aesthetic considerations (precipitation of iron from solution and taste),
the concentration of iron in drinking water should not exceed 0.3 mg/L.
No health-based guideline value has been set for iron.

Iron has a taste threshold of about 0.3 mg/L in water, and becomes objectionable above 3 mg/L. High iron concentrations give water an undesirable rust-brown appearance and can cause staining of laundry and plumbing fittings, fouling of ion-exchange softeners, and blockages in irrigation systems. Growths of iron bacteria, which concentrate iron, may cause taste and odour problems and lead to pipe restrictions, blockages and corrosion. ADWG 2011

Cranbourne (Victoria) – Colour

2006/7: Cranbourne (Victoria) – Colour Apparent 20 HU (Highest Level Only)

2007/8: Cranbourne (Victoria) – Colour Apparent 32 HU (Highest Level Only)

2011/12: Cranbourne (Victoria) – Colour Apparent 80 HU (Highest Level Only)

Based on aesthetic considerations, true colour in drinking water should not exceed 15 HU.

“… Colour is generally related to organic content, and while colour derived from natural sources such as humic and fulvic acids is not a health consideration, chlorination of such water can produce a variety of chlorinated organic compounds as by-products (see Section 6.3.2 on disinfection by-products). If the colour is high at the time of disinfection, then the water should be checked for disinfection by-products. It should be noted, however, that low colour at the time of disinfection does not necessarily mean that the concentration of disinfection by-products will be low…

Cranbourne – Victoria – Turbidity

2006/7: Cranbourne (Victoria) – Turbidity 17 NTU (Maximum detection during year)

2007/8: Cranbourne (Victoria) – Turbidity 46 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.