Timaru  District Council commissioned a team lead by Geoff Mills to carry out a strategic review of its six urban and rural water supply assets and accepted the report recommendations that improvements to the Timaru City water supply ( Population  30,000) be first priority so that it could meet the  Drinking-water standards for NZ  particularly the rigorous requirements for prozozoan ( Giardia and Cryptosporidium) compliance.

Timaru has two main water sources; the upland Pareora River run of the river source and the lowland Opihi infiltration gallery source. Generally the water sources have low turbidity and low colour with the main potential health risk associated with  the possible presence of protozoans sourced from localised agricultural development in the generally untouched catchments.

A number of  potential treatment options were investigated and after life-cycle costing,  turbidity control at the inlet of one existing raw water reservoir, ozone oxidation of the raw water with post-treatment distribution system chlorine disinfection together with conversion of  the second existing raw water reservoir to treated water storage and covering this reservoir  with an HDPE floating cover was selected as the preferred process.

Extensive ozone pilot studies confirmed the viability of the option . Bulk water samples were sent to an overseas laboratory for confirmation of the pilot plant results, to provide data on the optimisation of  the ozone dose rate the design of the ozone contact tank and the ozone diffuser array.  The concept was reviewed by Ministry of Health to ensure compliance with the then being developed Drinking -water standards for New Zealand and the final conclusions were then peer reviewed.

The constructed treatment system has performed to specification so enabling the Timaru City water supply to meet the Drinking-water Standards for NZ at an estimated capital cost saving at the time of $2.5-3million