Field performance of an odour scrubber at a sewage treatment plant

Abstract

An activated carbon scrubber was constructed at a local municipal wastewater treatment plant to treat odorous air extracted from the headspace of an enclosure covering a primary sedimentation tank. The sewage air contained significant levels of hydrogen sulphide (H2S) in addition to other odorous constituents such as mercaptans, ammonia and volatile organics. The scrubber was monitored continuously over a period of 6 months to obtain data on its performance efficiency under the humid and hot field conditions that the scrubber was subjected to. Operating flow rates into the scrubber was also varied during the performance study. Data was obtained on the diurnal variation of toxic gases entering the scrubber as well as on the treatment efficiency of the scrubber for H2S and for odour removal under various operating conditions. Treatment efficiency of the carbon scrubber was high, in the region of 95%, although premature breakthrough of H2S was observed. Odour efficiency was however, found to be averaging about 60-70% indicating that other odorous constituents are probably not removed as efficiently by the activated carbon scrubber. The adsorption capacity of the carbon scrubber for H2S was estimated to be about 9.5% by weight of activated carbon.