Reduction of odors from a facultative pond using two different operating practices

This paper presents the results of a proposed intervention to deal with the odor problems of a sewage treatment works (STW), which is located near a populated area. The STW consists of a facultative pond. Since this pond functions under close to anaerobic conditions, unpleasant odors are emitted. In this respect, two possible ways to deodorize the pond were evaluated. Firstly, the recirculation of effluent using 1/6 of the flow stream followed by aeration of the pond with a reduced power aerator. In order to study the efficiencies of the deodorization methodologies chemical analyses of the gases NH3 and H2S, olfactometric analyses and evaluation of the environmental perception of the population in relation to the odors originating from the STW, were carried out for each experimental situation. The results showed a significant reduction in odors when aeration with reduced power equipment was utilized in combination with recirculation of effluent in the pond. Reductions in emissions of H2S from 0.1345 mg/m3 to 0.0083 mg/m3 and of NH3 from 0.021 mg/m3 to 0.0073 mg/m3 were obtained. To analyze the behavior of the pond, its planktonic community was investigated, with a difference in species for the situations with and without odor being observed.