Water Improvements for Cambridge


Waipa District Council



$2.1 Million

Project type:
Water Treatment

Plant Capacity:

Customer Need

Cambridge is growing – and fast. The current population of around 19,000 is expected to be home to an additional 14,000 by 2050 putting the existing Karapiro water treatment plant (WTP) under enormous pressure and in need of an upgrade. In August 2018, FILTEC completed a two year project involving the design, manufacture and installation of new processing equipment – a plate settler plant followed by gravity multimedia and sand filtration to handle coagulation, flocculation, clarification, filtration and disinfection.

What We Did

The plate settler plant has a very small footprint compared to conventional clarifier techniques. In order to achieve the small footprint, a high-rise rate is required and therefore a dense floc must be formed. Due to low solids in Lake Karapiro a sludge seeding process was installed to provide sufficient supply of solids for floc formation.

The coagulation and flocculation steps were critical and significant emphasis was placed on this by FILTEC’s process engineers. This resulted in the inclusion of a delay tank with gentle mixing followed by rapid / flash mixers then individual flocculation tanks with gentle agitation.

The Results

The filters and change of polymer provide water of a quality that has enabled the plant to achieve an additional log credit for enhanced filtration. In turn, this enabled the entire plant to achieve 4 log protozoa compliance in line with the New Zealand Drinking Water Standards exceeding the requirement for this source water.

Bringing the plant online has nearly doubled the capacity of the Karapiro treatment facilities and reduced the reliance of supply being solely on the old plant, providing additional redundancy in case of an outage in the original plant. For the residents of Cambridge, it’s also secured high quality water capacity well into the future.