Te Puna scheme used for future wastewater planning

Thursday 20 April 2018

The new wastewater reticulation scheme in Te Puna West is being used in a trial that could save money and lead to more efficient wastewater operation in the Western Bay.

Western Bay of Plenty District Council is running a year-long trial with the Te Puna system that examines household water usage versus wastewater disposal.

The new community wastewater scheme installed in Te Puna West last year is a reticulated pressure sewer system (it connects to a wastewater treatment plant), and replaces traditional septic tanks.

Reticulation of wastewater, particularly for low-lying coastal communities, reduces the risk of inner harbour water contamination through septic tank seepage.

Due to the low-lying land at Te Puna West grinder pumps are installed at each individual household. These grind household wastewater and pump it to a wastewater treatment plant.

Typically wastewater is transported to the treatment plant through a gravity network. Gravity networks often experience large amounts of inflow and infiltration where stormwater gets into the wastewater network. This can overload Council's system and increases operation and maintenance costs.

The aim of the trial is to assess the amount of stormwater getting into the pressure network. Council will compare this to a typical gravity network to assess the pressures network's ability to reduce the amount of infiltration into the sewer system. This in turn could lower the operating costs of sewer systems in the future.

Council's Utilities Manager Kelvin Hill says the trial will enable Council to analyse in detail how to reduce infiltration issues and what long term financial benefits Council will gain by implementing them in other areas.

A smart water meter will be installed on each household which will measure the household's daily water use. In addition, Council has installed a `smart controller' on each wastewater grinder pump at the Te Puna properties. This can be used to measure the amount of wastewater leaving the house.

Kelvin says this will enable Council to compare water going in, versus water going out, and assess the percentage of disposed (waste) household water.

"This will ensure we are sizing our wastewater treatment plants and pipes appropriately in the future.

"We will also have a bulk flow meter picking up all wastewater from the Te Puna West community that will compare total water used by the house with total actual water being transported and treated. This will identify any stormwater infiltration.''

The trial is being conducted from May 2018 to May 2019. If successful, this could be used in future urban developments (e.g. Omokoroa, Katikati etc) to reduce pressure on current systems.