An overview of principles of odor production, emission, and control methods in wastewater collection and treatment systems.

Odorous gases are the most important reason that people register complaints with organizations responsible for wastewater collection and treatment systems (WCTS). Although several studies have been conducted for prevention and control of odorous gases, no comprehensive research exists about recent achievements in this area. The aim of the present study is to collect and categorize the new achievements in preventing and controlling odorous gases in WCTS. Two strategies for controlling odor emissions from WCTS are (1) prevention of odor production and (2) removal of odorous compounds from emissions of WCTS. Between the two, priority goes to preventing odorous compounds' production. Several methods have been developed to prevent odor production, such as increasing oxidation reduction potential; inhibiting the activity of sulfide reducing bacteria; chemical removal of hydrogen sulfide; applying formaldehyde and paraformaldehyde to prevent hydrogen sulfide production; and using fuel cells in hydrogen sulfide inhibition and gradual release of oxygen in gas phase by using MgO2 or CaO2. In addition to preventing odorous compounds in WCTS, many other methods have been introduced to remove odorous compounds from emissions of WCTS, such as biofilters; bioscrubbers; biotrickling filters; suspended growth reactors; and membrane bioreactors and scrubbers. Through this review, responsible organizations can find new, effective, and economical strategies to prevent and control odorous gases in WCTS.