Sewage Treatment: Odour control

Sewage Treatment: Odour control

Odour control is an important aspect of the wastewater treatment process. Odorous air is collected at various stages of treatment by ventilation fans and ducted to booster fans, which pass it through earth filters (biofilters).

There are six earth filter beds covering the primary treatment stage. Each filter bed is 800 millimetre deep and divided in two sections. The filters cover a combined area of about 6,200 square metres.

Each filter has been upgraded with new media (designed by Watercare scientists) made up of scoria and bark insteadof scoria and soil. Bark has the advantage over soil in that its quality is more easily controlled and it allows for a less dense mixture, giving less resistence to airflow.

The new improved biofilter media is more effective and has a longer working life.

Odorous air is evenly distributed beneath the media by a system of header and distribution pipes. As it percolates upwards, the odorous compounds are treated by bacteria within the media. Odorous compounds are removed by physical and bacterial processes before being discharged to air.

Biofilters also treat air extracted from other areas of the treatment plant including the pre-treatment mixing chamber, gravity thickeners, the splitter boxes and the biosolids dewatering building .