Rain delays plant upgrade

NATASHA THYNE
Last updated 05:00 11/08/2014
timaru district council wastewater treatment plant
JOHN BISSET/Fairfax NZ
WASTING AWAY: The layout of the new Timaru District Council wastewater treatment plant in Aorangi Rd. Waste travels through the plant in a figure-8 journey starting at the wetlands, 1, progressing to the oxidation ponds, 2, to maturation pond, 3, and finally the milliscreen building, domestic pump station, domestic screening plant and peak flow pump station, 4.

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Work on the Timaru District Council's wastewater treatment plant upgrade on Aorangi Rd is still in progress.

Timaru District Council drainage and water manager Grant Hall said that once completed, it will be significantly better than the current system.

The plant has yet to be fully commissioned due to rain and wet ground conditions.

Hall said it will be finished this year, but the ground in the second incomplete oxidation pond must dry before the silt lining could be finished.

The upgrade involves 48 hectares of land on both sides of Aorangi Rd. Two oxidation ponds take up 30ha. Eight hectares is used for a maturation pond and 10ha for the wetlands.

Included in the plant is a milliscreen building, a domestic pump station, a domestic screening plant and peak flow pump station.

The treatment will be tertiary level, with the wetlands providing more polishing of the water, Hall said.

The waste enters the plant and is separated into industrial and domestic flow. From there, it does a figure 8 journey through the different components.

Two pipes, next to the wetlands, transfer the industrial waste to the Milliscreen plant.

The domestic waste goes down the domestic pump station pipes to the domestic screen plant. Pipes transfer and split the waste between two oxidation ponds. The wastewater spends a month in the oxidation ponds, which provide biological treatment and improve its quality.

The islands in the ponds improve the circulation and insure the full retention period is completed.

Wastewater from inland towns Temuka, Geraldine and Pleasant Point is also transported to the oxidation ponds.

The water then runs along the pipes at the back of the ponds to the maturation pond.

It then goes back to the wetlands and exits into the peak flow pump station.

Finally, both the domestic and industrial waste is deposited three kilometres up the coast to the ocean discharge site.

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- The Timaru Herald

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