Fate of dissolved odorous compounds in sewage treatment plants

The concentration of selected malodorous compounds dissolved in water in different unit processes of actual treatment plant, and in different location of small scale treatment plants (Jokasos) were identified in order to provide sufficient information to undertake proper action to solve the problems of malodor compounds in water environment and in wastewater reuse. Analytic methods to measure as low as mg/l level of 16 odorous compounds were developed. In total, four sewerage treatment plants, three sludge treatment plants and six Jokasos were surveyed. Treatment plants were chosen in a way so that most types of unit processes could be covered. Being exposed to anaerobic condition is the primary reason of production of odorous compounds. As far as the secondary treatment is operated properly, odorous compounds concentration in the effluent can be maintained below odor threshold concentration. Odorous compounds were produced during sludge treatment process while the sludge is sedimented, thickened and dewatered, or anaerobically digested. A new way to express the odor concentration is proposed to obtain quick and comprehensive visualization of odor intensity.