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Savings made after reviews of the way the Oamaru water and sewage treatment plants are managed by the Waitaki District Council will be passed on to ratepayers, who will benefit by about $25 a year each from next year.
The Oamaru water supply's membrane technology - which along with ozonisation and chlorination ensured the water was clean and safe - had survived well beyond what was originally planned.
After seven years, the membrane needed to be replaced, council assets group manager Neil Jorgensen said this week.
''We've taken great care to regularly maintain the original membrane and this has meant it has had a much longer life than anticipated [by about 15%],'' he said.
The new membrane had the capacity to clean and filter 25% more water and was expected to last 10 years, as opposed to seven years.
It would save $100,000 a year in operating costs, reducing the Oamaru water rate by $10 from next year.
''The increase in amount of water the plant can produce is important - it means that the treatment plant will be able to supply water to Oamaru and surrounding areas for many years to come,'' Mr Jorgensen said.
A review of the Oamaru wastewater and sewage treatment system resulted in savings by treating wastewater more efficiently without compromising the environmental impact.
The purpose-built treatment plant required significant input and costs to ensure wastewater was treated adequately before being discharged. The improvements identified in the review had resulted in new management practices being adopted.
That was likely to result in annual savings of $120,000, resulting in about a $15 reduction per ratepayer.