Assessing the Efficiency and Microbial Diversity of H2S-removing Biotrickling Filters at Various pH Conditions

Abstract

Reduced sulfur compounds such as H2S are extremely toxic and highly corrosive, produced in many industrial activities. The biological desulfurization process has been established to be a technically and economically effective alternative to traditional physicochemical processes. This study aimed to investigate the operation of three parallel biotrickling filters (BTFs) in removing H2S at different pH conditions (haloalkaliphilic, neutrophilic, and acidophilic) and their associated microbial population in the biodesulfurization process. BTF columns were inoculated with enriched inoculum and experiments were performed by gradually reducing Empty Bed Retention Time (EBRT) and increasing inlet concentration (Ci). The maximum Removal Efficiency (RE) and Maximum Elimination Capacity (EC) in EBRT 60s for haloalkaline, neutral and acidic conditions were, 91% and 179.5 g S-H2S m-3 h-1, 85.7%, and 141 g S-H2S m-3 h-1, 88% and 145 g S-H2S m-3 h-1 respectively. For visualizing the attached microbial biofilms on pall rings, Scanning Electron Microscopy (SEM) was used and microbial community structure analysis by NGS showed that the most abundant phyla in haBTF, nBTF, and aBTF belong to gammaproteobacteria, betaproteobacteria, and acidithiobacillia, respectively. The alpha analysis according to the Shannon and Simpson indexes showed a lower diversity of bacteria in the aBTF reactor than that of nBTF and haBTF and beta analysis indicated a different composition of bacteria in haBTF compared to the other two filters. These results indicated that the proper performance of BTF under haloalkaliphilic (natron) conditions is the most effective way for H2S removal from air pollutants of different industries.