Nyora (Victoria) – E.coli November 2014
A notification in accordance with section 22 of the Safe Drinking Water Act was forwarded to the Department following a low-level E. coli detection of 1 orgs/100mL for a site in Follet Drive, Nyora on the 17th November, 2014. Investigation found no evidence of related treatment or disinfection issues at the supplying Poowong water treatment plant, and total chlorine for the non- conforming site found to be a fairly typical 2.8 mg/L at the time of sampling. Additionally, there were no microbial detections recorded for other routine samples collected in connect ed localities of Poowong and Loch on the same day.
In response to the detection, the Follet Drive main was flushed and follow-up samples were collected from four customer tap sites in Nyora on the 18th November. While there were no microbial detections for the Follet Drive site resample, an E. coli detection of 3 orgs/100mL was recorded for a follow- up sample collected in Hewson Street. In response to this second detection, the entire Nyora reticulation system was flushed and the Nyora water tower was in
spected. There were no breaches of structural integrity observed for the tower, and no E. coli detections for samples collected subsequent to flu shing from seven sites in in the township on
the 19 th November.
While the source of the detected E. coli is unknown, the fact that a higher than usual volume of water was being withdrawn from the Nyora system for the purposes of pressure testing newly installed sewerage mains is noteworthy. It is possible that this change in the velocity of water flow caused dislodgement of biofilms from the walls of the water-mains.