2005/6 + 2010 + 2018/19 – Croydon (Victoria) – E.coli, Turbidity

Croydon – (Victoria) – E.coli

2005/6: Croydon (Victoria) – E.coli 3orgs/100mL
On 6 May 2010, E. coli of 1 org/100 mL was detected at two customer taps in the Croydon sampling locality. Both samples were taken by a Yarra Valley Water construction contractor from unapproved sampling locations: a hydrant in construction and a temporary
hose supply. It is believed that the sample was contaminated during the process of gathering the water. The area was block flushed and samples at official customer sampling taps in the
area returned negative results for E. coli. As a result of this incident, the process for testing and sampling for water quality at water mains associated with construction activities was modified
to ensure that sample collection is undertaken only by samplers from an accredited laboratory or by Yarra Valley Water approved personnel. These personnel will be appropriately trained
on sampling protocols. No subsequent action was required.
 (Yarra Water Valley Drinking Water Quality Report 2009-10)

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

Croydon (Victoria) – Turbidity

2018/19: Croydon (Victoria) – Turbidity. 21NTU (max), 1.2NTU (95th percentile)

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.