Hatea pump station and high rate storm treatment plant

This paper discusses the novel approach that Whangarei District Council is taking to address the problem of overflows at their Hatea Pump Station.

A 1000m3 storage tank was designed, which will also operate as a high rate clarifier and UV reactor to treat the effluent that overflows during high flow events. Since increased pump station capacity would overload the network downstream during high flow events, “off-loading” at this location is considered the preferred mitigation measure. The sewerage network model predicts eight events per annum when the capacity of the pump station is insufficient. The designed tank will reduce the quantity of discharges to approximately two events per year, and will also significantly increase the quality of the discharge.

The design includes screens and chemical dosing, but unlike conventional treatment and screening facilities, no sludge or screening handling facilities are required. All screenings are retained in the “day to day” pump station and all sludge is washed into the “day to day” pump station after the storage tank has been used. In this way both construction and operation costs of the treatment facility are low compared to a conventional treatment plant of similar capacity.