Odour-minimising measures continue at wastewater treatment plant

Christchurch City Council staff continue to undertake a range of measures to try and reduce any offensive odours from the fire-damaged Christchurch wastewater treatment plant.

 Head of Three Waters Helen Beaumont says the on-site team continues to add polymer dosing to the primary sedimentation tanks to reduce the organic loading on the oxidation ponds.

“Polymer dosing helps to ensure that we divert between 65 and 70 per cent of solids to the digesters, which eases the pressure on ponds,” she says.

“Dissolved oxygen level is one of the fastest indicators of pond health and we’re monitoring these levels daily and adjusting the wastewater flow paths to make sure the effluent is spread out across the ponds. This improves water quality, reduces the odour and minimises the sludge rising to the surface.

“When surface sludge appears on the ponds, we use a boat to quickly break it up,’’ Ms Beaumont says.

The Council has also borrowed two aerators to use on the oxidation ponds. These are being serviced and are planned to be installed later this month.

“These will help to aerate the ponds and prevent surface sludge, which, in turn, will reduce the odour,” says Ms Beaumont.

In the meantime the damage assessment of the two trickling filters that were at the centre of the fire is still being done.

Until the damage assessment is completed, it’s not known if the concrete housing can be repaired and the trickling filter media replaced. If the concrete housing is badly damaged, the Council will look at options for rebuilding the trickling filters alongside alternative technology.

More information can be found at ccc.govt.nz/wastewaterfire.