Biological removal of H2S gas in a semi-pilot scale biotrickling filter: Optimization of various parameters for efficient removal at high loading rates and low pH conditions

Abstract In this study, a semi-pilot scale biotrickling filter (BTF) was operated in a continuous co-current mode to remove high concentration of hydrogen sulfide (H 2 S) at optimum operational conditions. The early startup period of 6 days was needed, and then stable removal of H 2 S gas at inlet concentrations up to about 2000 ppm was successfully obtained at gas retention time (GRT) of 15 min and liquid recirculation rate (LRR) of 120 ml/min. The elimination capacities (ECs) increased linearly with increase in H 2 S loading rates (HLRs up to 38.5 g/m 3  h), but a gradual decrease in removal efficiency was observed from a volumetric HLR of 18.1 g/m 3  h. The LRR was further decreased from 120 to 30 ml/min, and the minimum liquid–gas ratio of 0.24 was found without decrease in removal efficiency. The MiSeq analysis revealed the presence of sulphur oxidizing bacteria (SOB) dominated by Acidithiobacillus caldus (>97%) at all portions of BTF.