Colin Roxburgh, Waimakariri District Council
A key lesson learnt following the Havelock North Drinking Water Contamination Event is the importance that total coliforms can play in understanding the health and integrity of a public water supply. A drinking water quality parameter previously given little focus has now become a key metric in guiding responses and targeting attention in the management of drinking water systems.
This paper presents case studies in how total coliform detections have been used in practice to address issues of biofilm development, and reservoir integrity improvements that otherwise may have either gone unnoticed for years, or become pre-cursors to more serious contamination events.
Two normally unchlorinated supplies were monitored for coliforms, and through analysis of results changes in the systems were detected. With guidance from recently developed Incident Response Plans, and with expert external input, responses to the events were put in place. This included the implementation of emergency chlorination systems, trouble shooting and diagnostics of the root causes, communication with the affected communities, elected members and Taumata Arowai. Regular meetings were held with a core team of asset managers, operational staff, contractors, and senior management representatives throughout the process, until the issues had been resolved.
This approach has highlighted the benefits of applying an “elimination strategy”towards coliforms, as targeting a baseline of no non-zero detections allows any deviations from this to be easily identified and promptly acted upon.
There were many lessons learnt through these events, which are reflected on throughout this paper. This includes the importance of having sound monitoring, alerting, and response systems, a contractor with a good understanding of their supplies, and the ability to quickly and easily adapt systems to different modes of operation to help optimise the response.