Designing biological filters to eliminate odors in septic tank based on the amount of hydrogen sulfide

Introduction: Odor emission is a common environmental problem in septic tank. The feasibility of using trickling filter to eliminate the malodorous gases from the septic tank was studied. Methods and Material: A trickling filter is set up at the outlet of the waste gases of the septic tank, which was attached to the universityʹs cafeteria. In this investigation, the trickling filter system was used, measuring the hydrogen sulfide and ammonia concentration to control the odor and to determine the elimination capacity (EC) of filtration. Results: The obtained results showed insignificant amount of ammonia, while the concentration of H2S was recorded at 90 ppm. Empty Bed Residence Time (EBRT) in the filter represented a significant relevance with the inlet concentration and the elimination rate of H2S. There is a significant linear relationship between the mass flow rate of H2S and the amount of cooked food as well as temperature. Also a significant relationship between EC and inlet concentration of H2S was observed. The trickling filter in an optimum condition with an EBRT of 200 seconds was able to remove H2S up to 99.9%. An empirical equation is developed to design a trickling filter. Conclusions: Trickling filter is an affordable and cost-effective method to remove hydrogen sulfide from the septic tank.