2015/18 – Herrick (Tasmania) – E.coli, Colour, Iron, pH, Temperature, Turbidity


Herrick (Tasmania) – E.coli

August 11 2015: Herrick (Tasmania) – E.coli 1 MPN100/mL

February 9 2016: Herrick (Tasmania) – E.coli 3 MPN100/mL

April 19 2016: Herrick (Tasmania) – E.coli 3 MPN100/mL

May 17 2016: Herrick (Tasmania) – E.coli 1 MPN100/mL

2016/17: Herrick (Tasmania) E.coli 5 exceedences. Poor microbiological performance can be attributed to a lack of barriers and the susceptibility to changes in quality from the Cascade Dam and Frome Dam. The risk to public health is mitigated through the communication of the Permanent BWA to customers.

11/7/17: E.coli of 1 MPN/100mL in monthly compliance sample. System subject to PHA.

16/1/18: E.coli of 178.5 MPN/100mL in monthly compliance sample. System subject to PHA.

14/2/18: E.coli of 6.2 MPN/100mL in monthly compliance sample. System subject to PHA.

13/3/18: E.coli of 4.1 MPN/100mL in monthly compliance sample. System subject to PHA.

9/4/18: E.coli of 2 MPN/100mL in monthly compliance sample. System subject to PHA.

15/5/18: E.coli of 2 MPN/100mL in monthly compliance sample. System subject to PHA.

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

Herrick (Tasmania) – Colour

August 25 2015: Herrick (Tasmania) – Colour Apparent 51 PCU

November 17 2015: Herrick (Tasmania) – Colour Apparent 48 PCU

March 22 2016: Herrick (Tasmania) – Colour Apparent 88 PCU

June 21 2016: Herrick (Tasmania) – Colour Apparent 75 PCU

2016/17: Herrick (Tasmania) – Colour 66 HU (max), 55.67 HU (mean)

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…

Herrick – Tasmania – Iron

March 22 2016: Herrick (Tasmania) – Iron 1070ug/L

March 22 2016: Herrick (Tasmania) – Iron (Dissolved) 318ug/L

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

Herrick (Tasmania) – pH (acidic)

Average pH: 2015 July-2016 June: 6.072 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.

Herrick – Tasmania – Temperature

February 9 2016: Herrick (Tasmania) – Temperature 21.4C


“No guideline is set due to the impracticality of controlling water temperature.
Drinking water temperatures above 20°C may result in an increase in the number of

Temperature is primarily an aesthetic criterion for drinking water. Generally, cool water is more palatable than warm or cold water. In general, consumers will react to a change in water temperature. Complaints are most frequent when the temperature suddenly increases.

The turbidity and colour of filtered water may be indirectly affected by temperature, as low water temperatures tend to decrease the efficiency of water treatment processes by, for instance, affecting floc formation rates and sedimentation efficiency.

Chemical reaction rates increase with temperature, and this can lead to greater corrosion of pipes and fittings in closed systems. Scale formation in hard waters will also be greater at higher temperatures…

Water temperatures in major Australian reticulated supplies range from 10°C to 30°C. In some long, above-ground pipelines, water temperatures up to 45°C may be experienced…

The effectiveness of chlorine as a disinfectant is influenced by the temperature of the water being dosed. Generally higher temperatures result in more effective disinfection at a particular chlorine dose, but this may be counterbalanced by a more rapid loss of chlorine to the atmosphere (AWWA 1990).

Herrick – Tasmania – Turbidity

December 12 2015: Herrick (Tasmania) – Turbidity 5.03 NTU

February 9 2016: Herrick (Tasmania) – Turbidity 19.4 NTU

April 19 2016: Herrick (Tasmania) – Turbidity 13.2 NTU

2016/17: Herrick (Tasmania) – Turbidity 20.5 NTU (max), 5.86 NTU (mean)

2017/18: Herrick (Tasmania) – Turbidity 8.29 NTU (max)

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.