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Background & Aims of the Study: Hydrogen sulfide (H₂S) is a colorless and highly toxic, easily dissolved in water, flammable and explosive gas. Hydrogen sulfide gas is the main cause of odor emissions from municipal sewage plants. One method for removal of hydrogen sulfide gas is the use of biological systems, biofilter. The aim of this study was to survey removal hydrogen sulfide provide in septic tank by vermicomposting biofilter.

Materials and Methods: In this study pilot-scale biofilter has been made of bed vermicompost and wood trash. To survey biofilter performance under real condition, the pilot installed in one wastewater pumping station of Ahwaz city, Iran. The study was carried out over 80 days. Inlet and outlet H₂S concentration were measured on regular basis. To provide an optimal condition for bacterial growth, moisture was adjusted between 40% and 60% throughout the experiment.

Results: Results showed that H₂S concentration emitted from the pumping station during the study varied greatly between 33 and 54ppm .The maximum adsorption capacity of the biological bedding was recorded at 22.4 g/m³.hr and the mean efficiency of H₂S removal account the startup time was 89.31% .The mean performance efficiency during the biological activity after the startup was recorded at 96.88%.

Conclusion: use up biofilter with vermicompost bed and woodchip is an economic method for H₂S removal of septic tanks. Removal efficiency of more than 96% is expected with this method.