Biological odour control by diffusion into activated sludge basins

Abstract

Diffusion of odourous air into activated sludge basins is an effective and economical approach for odour control at wastewater treatment plants. Over 30 facilities in North America practice this technique. Most of these applications are for dilute or moderate strength air streams with relatively low hydrogen sulfide (H2S) levels. Unfortunately, the lack of data documenting the effectiveness of the process and concerns for blower corrosion have limited its acceptance as a method for controlling odour emissions. This paper presents a compilation and review of wastewater treatment facilities that are currently using activated sludge diffusion. Performance data are tabulated, and information on operation and maintenance of the blower/diffuser systems are summarized. New data are presented that compare the effectiveness of coarse vs. fine bubble diffusers for treatment of a high strength, high-H2S air stream from sludge holding tanks at Concord, NH. Designand performance information is presented on a dedicated odour control system installed at Phoenixville, Pennsylvania in 1996 that collects high-H2S air streams from an influent chamber and primary clarifiers and diffuses it into a mechanically-aerated activated sludge basin. A cost-effectiveness analysis is presented for a blower/diffuser system installed exclusively for odour control. Methods used to overcome initial operational problems are discussed.