THE REMOVAL OF H₂S FROM PROCESS AIR BY DIFFUSION INTO ACTIVATED SLUDGE

Abstract

Emissions of H₂S from publicly owned treatment works is a serious problem, therefore collection and treatment of these emissions is essential. In this work, the performance of a bench scale activated sludge system used for the removal of H₂S from foul air was investigated, and the effects of H₂S concentration (5 to 50 ppm_v) on COD reduction and biomass settleability were studied. After biomass acclimation, the reactor was operated in a continuous mode at a hydraulic retention time of 5 h and a mean cell residence time of 6 days. Results showed that COD and H₂S removal were 93.5 and 94.5%, respectively. Furthermore, H₂S concentration up to 50 ppm_v did not significantly affect the COD reduction. H₂S loading rates of up to 7.5 mg_H2S g^-1 _MLSS d^-1 were treated with greater than 94% efficiency. The only adverse effect of H₂S that was observed was an increase in the sludge volume index at loading rates over 4.5 mg_H2S g^-1 _MLSS d^-1, at which bulking of the sludge occurred. Overall, the results indicate that H₂S at concentrations usually emitted from wastewater treatment processes (lower than 50 ppm_v), can be efficiently treated by diffusion into activated sludge without compromising the performance of the activated sludge process.

Keywords:

• ACTIVATED SLUDGE DIFFUSION
• HYDROGEN SULFIDE
• ODOR EMISSION
• WASTEWATER TREATMENT