Feilding Wastewater Treatment Plant Upgrade
The Feilding wastewater scheme is the largest in the District and serves a number of large industries as well as 14,000 residents.
Parts of the Feilding wastewater network date back to 1905.
The treatment plant was upgraded in 1993/94 to improve effluent quality and cope with additional industrial loads. The upgrade included a second aerated lagoon, a solids contact tank and a clarifier. The sedimentation tank that was used for secondary settling became a second primary sedimentation tank.
The Feilding wastewater treatment plant, located on Kawakawa Road to the south of Feilding, was built in 1967. Prior to this plant being built, sewage was treated in a large septic tank.
A further upgrade is underway to improve effluent quality and Council is working closely with Horizons and to obtain a new resource consent which will allow Manawatu District Council to spray irrigate a significant proportion of the treated effluent onto land. This will provide an irrigation scheme which will increase the productivity of the land and produce a sustainable long term revenue stream. This revenue will be used to offset operational costs of the Feilding Waste Water Treatment Plant (WWTP). The shift to land disposal will also underpin Council's commitment to the Manawatu River Accord and local iwi by removing a significant volume of treated effluent which is currently discharged into the Oroua River.
In this upgrade there are several major projects and some smaller ones to increase the treatment capacity and create a more robust treatment system.
The anaerobic lagoon construction is complete and commissioning has begun. The lagoon has a minimum working level depth of 4 metres with a total overall volume of 25,000 m3. The purpose of the anaerobic lagoon is to create a buffer for the periodic high nutrient loads and improve the process and performance of the plant by partially treating the influent prior to entering the two existing aeration lagoons.
The two aeration lagoons are also being upgraded. Once drained of the partially treated wastewater and the sludge removed they are to be lined with plastic. Then a unique aeration system is to be installed to aid in the removal of nitrogen compounds. The first of the two ponds is to be lined this winter.
One of the main issues for the Feilding WWTP has been the inability to cope with large flows through the system due to stormwater infiltration during large rain events in town. This increased flow would reduce the time for the wastewater to be treated at the plant. To address this issue, a 27,000 m3 storm buffer pond is currently being constructed to store the wastewater that the plant is unable to treat effectively during storms. When the flow reduces, the stored wastewater will be directed back through the plant for treatment. During dry-weather periods the pond will hold the treated effluent for irrigation.