Poowong – (Victoria) – E.coli (Boil Water Alert February 2013)
2012 Nov: An E. coli detection was recorded for the Poowong water tower inlet/outlet site on the 27th November 2012. The chloramine disinfection residual was also found to be lower than normal at the time of sampling. There were no detections for samples taken the same day from the clear water storage outlet at the water treatment plant or a customer tap sample in the
Poowong township. The tower roof and structure were inspected but no obvious sites for ingress of external contaminants could be found. The low chloramine level suggested that water within the tower was ageing and losing its protective disinfection residual. The chloramine dosage at the treatment plant was increased accordingly and flushing was carried out to replace aged water within the tower. The operating volume of the tower was also lowered to increase the rate of water turnover. As the volume of water in the Poowong water tower cannot be reduced significantly without causing a total loss of pressure to some customers, and the level of mixing within the tower, at the time, was minimal, some ageing of water within the upper section of the tower was unavoidable. A new tap was installed and routine sampling of the upper section of the water column in the tower was commenced from the 4th December 2012 so that the ageing water could be monitored. The tower was resampled on the 29th November and additional samples were taken from six different sites in the Poowong distribution system; there were no further detections of E. coli or coliforms.
2012 Dec: E. coli was again detected at the Poowong water tower inlet/ outlet site on the 4th December 2012. Partial draining and refilling of the tower was carried out in response to the detection. Follow-up samples from the tower and three customer taps sites in Poowong were collected on the 5th December, with all results indicating there was no detectable E. coli. As it was possible that sediment and biofilm accumulations within the tower were exerting a demand on the available chloramine, a diving contractor was engaged, and the walls and floor of the tower we re cleaned onthe 19th December 2012.
2013 Feb: An E. coli detection was recorded for a routine sample taken from the upper section monitoring site(representing water approximately three metres from the roof) of the Poowong water tower on the 26thFebruary 2013. As a resample collected from the same site on the 28th February also recorded a positive E.coli result, a precautionary boil water advisory was issued for the northern section of Poowong.
2013 April: E. coli was again detected in the upper section of the Poowong water tower on the 9th April 2013. There were no microbial detections for the inlet/outlet of the tower or for a registered customer tap sample in Poowong. Pumps were operated to overflow the tower and remove contaminated water. Follow-up samples were taken from the tower and three customer tap sites in the northern section of the reticulation system on the 11th April; E. coli was not detected in any of the samples.
2013 June: A low-level E. coli result was recorded for a sample taken from the Poowong water tower on the 4th June 2013. There was no E. coli detected for samples collected from the inlet/outlet site or a registered customer tap site in the township. The chloramine residual at the time of sampling was at a level normally adequate for rapid disinfection so the newly-
reinforced tower roof was inspected closely for possible sites of ingress. No obvious gaps or holes could be found, however. In response to the detection, the tower was taken offline
(changes to valve set-up carried out during riser pipe works enabled capacity for tower to be isolated from the distribution system), partially drained and refilled with freshly
-treated water from the plant.
2013 Aug: Follow-up samples collected from the tower and eight customer tap sites on the 6th June all recorded results of no detectable E. coli. On the 6th August 2013, the tower was completely drained, inspected and professionally cleaned by an external contractor. The possibility of
amphibians or rodents gaining entry to the tower via the 11-metre high internal overflow riser pipe was also investigated. No direct evidence of such access could be found but a wire
cage was fitted to the inlet of the overflow pipe to remove any potential for this to occur.
2014 July: A notification under section 22 of the Act was sent to the Department on the15th July 2014 in relation to E. coli detection for the Poowong water tower (internal site). Despite having a total chlorine concentration of 2.7mg/L, a sample taken on the 14th July 2014 was found to contain coliforms at a level of 10 orgs/100mL, with 4 orgs/100mL being E. coli. In response to the detection, the tower was partially drained and refilled with freshly treated water.
Investigation confirmed that the Poowong water treatment plant was operating within specifications and there were no treatment or disinfection issues. Follow-up samples collected at the tower and five customer tap sites in Poowong on the 15th July were found to contain no
E. coli or coliforms.
2019 April: The Department of Health and Human Services was notified in accordance with section 22 of the Safe Drinking Water Act of Escherichia coli (E. coli) detection at the Poowong water tower outlet. The detection of the bacterium at a level of 2 orgs/100 ml was recorded for a routine weekly sample collected on the 23rd April 2019. Immediate corrective actions involved flushing 20,000 litres of water in the tower to waste for replacement with water from the Poowong clear water storage basin. There were no other detections for routine samples collected at two sites in Poowong on the same day as the nonconforming sample, nor were there any for investigative samples collected at four sites (including the tower outlet) in the town the following day. While this suggested the presence of E. coli was isolated in terms of duration and location, and no treatment failures at the supplying Lance Creek water treatment plant were indicated, the incident was recorded as a noncompliance with the water quality standard for Poowong. A notification under section 18 of the Act was submitted to the department accordingly. It was determined from investigation that the presence of E. coli could most likely be attributed to low water turnover in the tower, consequent loss of disinfection residual, and possible ingress of contaminants through a small hole in the tank roof. With the hole now repaired, close monitoring and management of disinfection residual with proactive flushing is in place while longer term options for hydraulics improvement are investigated.
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
Poowong (Victoria) – Colour
2018 February: Korumburra (Victoria) – Colour 16HU (highest level)
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…