In sewage treatment plants, the sludge treatment lines generate odor nuisances. Odors are mainly caused by sulfurous compounds (H2S, mercaptans, organic sulfides), nitrous compounds (ammonia and organic nitrogen) and acid, aldehyde and ketone type organic compounds. A survey was undertaken during which air was sampled near the treatment units of 12 sewage works. According to the analytical results, the reasons for the formation of odor-generating compounds are explained for each facility. The main sources of bad smells are the thickeners (H2S, CH3SH, NH3), thermal processing (H2S, acetaldehyde), dewatering (H2S, NH3), storage (NH3 if final stabilization with lime is applied). Preventive techniques that make it possible to reduce odorous emissions are described, as well as curative methods consisting of roofing the structures and treating the air extracted. Comparative statements have been drawn up on odor control systems already in service, two special cases being described: chemical scrubbing and biodeodorization. The results obtained stress the good performance levels of these two methods, the use of which is becoming generalized in France for industrial applications.
