New Kerikeri-Waipapa water clarifiers commissioned

If you’ve travelled Kerikeri Road recently, you may have noticed two truck-sized metal containers now located next to the town’s water reservoir.

Despite speculation on social media, these imposing-looking containers have nothing to do with fluoridation of the water supply. Instead, they are state-of-the-art clarifiers designed to remove suspended particles from the two raw water sources that supply Kerikeri and Waipapa - Waingaro Reservoir and Puketotara Stream.

The units replace an existing concrete clarifier tank that was deteriorating and needed to be retired. Due to the limited size of the site and little available flat land, the council opted to install two lamella clarifying units. These contain a series of angled plates inside each container. Water flows between the plates and the solids settle onto these before eventually falling to the bottom of the clarifier. The accumulated solids are periodically removed. The angled plate system gives lamella clarifiers a footprint that is about 30 per cent less than other types of clarifier.

The two units at Kerikeri Road can produce 220 cubic metres of clarified water an hour. This is a significant increase in volume when compared to the previous system and will help the council achieve its goal of increasing the capacity of the water treatment plant to 4000 cubic metres a day within the next five years. 

The units were commissioned over four weeks in January and February when a range of water quality tests were undertaken. These showed that the clarifiers meet New Zealand water safety standards. They consistently reduce raw water turbidity by 70 per cent, achieving a turbidity of less than 1 NTU. The World Health Organisation (WHO) recommends a turbidity level of less than 1 NTU (nephelometric turbidity units) for drinking water. 

Image: The two lamella clarifiers have a smaller footprint than traditional clarifying units making them suitable for the Kerikeri Rd site.