Bell Island Sewage Treatment Plant
The Bell Island Sewage Treatment Plant is part of the Nelson Regional Sewage Scheme, which includes 15.5km of rising mains, 4 pump stations, the sewage treatment plant and biosolids application facility. It serves the communities of Nelson South, Richmond and Mapua.
The sewage treatment plant is located on Bell Island, Waimea Inlet. Treated effluent is discharged into the inlet on the outgoing tide. Stabilised sludge (biosolids) is beneficially applied to forests on Rabbit Island. The treatment plant consists of an aeration basin, clarifier, Dissolved Air Flotation System (DAF) and an autothermal thermophilic aerobic digestion (ATAD) plant that treats captured solids to produce biosolids. A system of pumps and pipework transfers biosolids to Rabbit Island.
The oxidation pond system of Bell Island consists of three facultative ponds in parallel and two maturation ponds in series. Effluent from the last maturation pond is discharged into the Waimea Inlet via an outfall pipeline and diffuser.
The treatment plant treats sewage equivalent to that generated by a domestic population of around 133,000 people. Peak flows and loads are highly variable due to the combined effects of stormwater infiltration and the seasonal nature of industrial food processing activities.