BOIL WATER ALERT
Gretna (Tasmania) – E.coli
July 2 2015: Gretna (Tasmania) – E.coli 1 MPN100/mL
July 8 2015: Gretna (Tasmania) – E.coli 5.2 MPN100/mL
July 16 2015: Gretna (Tasmania) – E.coli 1 MPN100/mL
July 22 2015: Gretna (Tasmania) – E.coli 6.3 MPN100/mL
August 5 2015: Gretna (Tasmania) – E.coli 6.4 MPN100/mL
August 13 2015: Gretna (Tasmania) – E.coli 10.9 MPN100/mL
August 20 2015: Gretna (Tasmania) – E.coli 5.2 MPN100/mL
August 26 2015: Gretna (Tasmania) – E.coli 2 MPN100/mL
September 2 2015: Gretna (Tasmania) – E.coli 1 MPN100/mL
September 10 2015: Gretna (Tasmania) – E.coli 4.1 MPN100/mL
September 17 2015: Gretna (Tasmania) – E.coli 2.5 MPN100/mL
September 23 2015: Gretna (Tasmania) – E.coli 1 MPN100/mL
September 30 2015: Gretna (Tasmania) – E.coli 8.6 MPN100/mL
October 7 2015: Gretna (Tasmania) – E.coli 6.3 MPN100/mL
October 15 2015: Gretna (Tasmania) – E.coli 2.6 MPN100/mL
October 23 2015: Gretna (Tasmania) – E.coli 8.5 MPN100/mL
October 30 2015: Gretna (Tasmania) – E.coli 8.6 MPN100/mL
October 7 2015: Gretna (Tasmania) – E.coli 6.3 MPN100/mL
October 15 2015: Gretna (Tasmania) – E.coli 2.6 MPN100/mL
October 23 2015: Gretna (Tasmania) – E.coli 8.5 MPN100/mL
October 28 2015: Gretna (Tasmania) – E.coli 13.4 MPN100/mL
November 4 2015: Gretna (Tasmania) – E.coli 26.5 MPN100/mL
November 12 2015: Gretna (Tasmania) – E.coli 3.6 MPN100/mL
November 19 2015: Gretna (Tasmania) – E.coli 1.5 MPN100/mL
November 25 2015: Gretna (Tasmania) – E.coli 17.5 MPN100/mL
December 10 2015: Gretna (Tasmania) – E.coli 3.1 MPN100/mL
December 17 2015: Gretna (Tasmania) – E.coli 3.1 MPN100/mL
December 22 2015: Gretna (Tasmania) – E.coli 4.1 MPN100/mL
December 30 2015: Gretna (Tasmania) – E.coli 5.2 MPN100/mL
January 6 2016: Gretna (Tasmania) – E.coli 18.5 MPN100/mL
January 14 2016: Gretna (Tasmania) – E.coli 2 MPN100/mL
January 21 2016: Gretna (Tasmania) – E.coli 1.1 MPN100/mL
January 27 2016: Gretna (Tasmania) – E.coli 6.3 MPN100/mL
February 3 2016: Gretna (Tasmania) – E.coli 18.9 MPN100/mL
February 11 2016: Gretna (Tasmania) – E.coli 1 MPN100/mL
February 18 2016: Gretna (Tasmania) – E.coli 1.5 MPN100/mL
February 26 2016: Gretna (Tasmania) – E.coli 9.2 MPN100/mL
March 2 2016: Gretna (Tasmania) – E.coli 83.3 MPN100/mL
March 9 2016: Gretna (Tasmania) – E.coli 12.2 MPN100/mL
March 17 2016: Gretna (Tasmania) – E.coli 7.5 MPN100/mL
March 23 2016: Gretna (Tasmania) – E.coli 7.5 MPN100/mL
March 30 2016: Gretna (Tasmania) – E.coli 6.3 MPN100/mL
April 6 2016: Gretna (Tasmania) – E.coli 7.4 MPN100/mL
April 14 2016: Gretna (Tasmania) – E.coli 6.3 MPN100/mL
April 21 2016: Gretna (Tasmania) – E.coli 1.5 MPN100/mL
April 27 2016: Gretna (Tasmania) – E.coli 4.7 MPN100/mL
May 4 2016: Gretna (Tasmania) – E.coli 24.6 MPN100/mL
May 12 2016: Gretna (Tasmania) – E.coli 4.1 MPN100/mL
May 19 2016: Gretna (Tasmania) – E.coli 3.1 MPN100/mL
May 25 2016: Gretna (Tasmania) – E.coli 12.1 MPN100/mL
June 9 2016: Gretna (Tasmania) – E.coli 248.5 MPN100/mL
2016/17: Gretna (Tasmania) – E.coli 11 E.coli exceedences. Poor microbiological performance can be attributed to a lack of barriers and the susceptibility to changes in quality from the Derwent River. The risk to public health is mitigated through the communication of the Permanent BWA to customers.
27/7/17: Gretna (Tasmania) – E.coli of 1 MPN/100mL in monthly compliance sample. System subject to PHA.
24/8/17: Gretna (Tasmania) – E.coli of 2 MPN/100mL in monthly compliance sample. System subject to PHA.
21/9/17: Gretna (Tasmania) – E.coli of 5.2 MPN/100mL in monthly compliance sample. System subject to PHA.
19/10/17: Gretna (Tasmania) – E.coli of 1 MPN/100mL in monthly compliance sample. System subject to PHA.
24/10/17: Gretna (Tasmania) – E.coli of 1 MPN/100mL in monthly compliance sample. System subject to PHA.
2017/18: E.coli detections occurred during the period the system was subject to a BWA. A newly constructed WTP provides treated water, after a rigorous testing program in consultation with DoH the BWA was lifted 23 November 2017 and met the microbiological compliance target when Potable.
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
Gretna (Tasmania) – Colour
August 6 2015: Gretna (Tasmania) – Colour Apparent 47 PCU
2016/17: Gretna (Tasmania) – Colour 41 HU (mean), 20.67 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…
Gretna – Tasmania – Turbidity
August 13 2015: Gretna (Tasmania) – Turbidity 6.15 NTU
January 14 2016: Gretna (Tasmania) – Turbidity 18.1 NTU
June 9 2016: Gretna (Tasmania) – Turbidity 10.6 NTU
2016/17: Gretna (Tasmania) – Turbidity 8.43 NTU (max), 2.43 NTU (mean)
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.