Odour possible as the Christchurch Wastewater Treatment Plant is upgraded

13 March 2006

Residents may notice some odour from the Christchurch Wastewater Treatment Plant during the two weeks following the shut down next Monday (20 March) of one of the main trickling filters, integral to the treatment process, for a planned upgrade.

Christchurch City Council’s City Water and Waste Unit Manager Mark Christison says the filter, the second to be upgraded, is being shut down as part of an eight week operation to repair corroded concrete walls and install new distributing arms in the 52m diameter tank. The new arms provide increased capacity to further improve the quality of the city’s wastewater.  

“With one of the trickling filters out of commission there is a risk of some odour as the biomass on the filter dies off and is removed from the filter,” Mr Christison says.

Although the work is planned to take eight weeks to completed, it is expected that only the initial drying and flushing of the filter during the first two weeks will cause any odour.

“During the last three months we have operated the plant in a way to reduce the amount of solids held in the filter so there are less solids to be removed in the shut down process,” Mr Christison says.  

“When the first filter was upgraded, early last year, there was a large amount of solids in that filter which caused significant odour over a long period.  This is not expected to be the case this time due to the efforts over the last three months.”

The work on the second trickling filter is one of the last major items in the upgrade of the city’s treatment plant which started in 1998 and is part of work by the Council to improve the quality of final effluent discharged from the treatment plant. It is integral to improving the Estuary and coastal environment.

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