Changing Horses Midstream: The Dollars and Sense of the Waiohine WTP Upgrade

In the 1990s South Wairarapa District Council installed one of the first membrane water treatment plants in New Zealand. By 2010, demonstrating compliance with the DWSNZ was difficult and the plant had some operational issues. After the assessment of a number of upgrade options, Council decided that rather than installing further equipment to make the existing plant comply with the standards it would take a different approach and develop a new groundwater source and treatment system that would have a lower DWSNZ log credit requirement. Three Ministry of Health (MoH) subsidy applications followed and three shallow bores were installed with an 880 metre pipeline to the existing plant. The second stage of the project involves extension of the existing treatment plant building and installation of UV disinfection and pH adjustment equipment. The good quality ground water allows treatment with UV disinfection alone, reducing operational costs and simplifying standards compliance. This project demonstrated how an in-depth understanding of the DWSNZ can identify the simplest and most cost effective path to compliance and the importance of the MoH subsidy programme in achieving that goal.