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.
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 .