Application of hollow fibre membrane reactor for biological removal of H2S

Hydrogen sulfide (H₂S) is a toxic pollutant and harmful to human health. Industries such as pulp and paper manufacturing, rayon production, natural gas extraction and refining, and crude petroleum refineries generate waste gas streams with high H₂S concentrations. Both physico-chemical and biological methods are used for H₂S removal from the gas stream. Biological methods offer several advantages such as environmental friendly, less expensive and require simple operation and maintenance compared to physico-chemical methods. In this study, a hydrophilic hollow fibre membrane (HFM) based bioreactor configuration has been tested for biological H₂S removal. Three reactors were fabricated and operated for ~ 3 months where two reactors were used for biological conversion process and the third reactor was used for abiotic process. The effective membrane area of a HFM module used in each reactor was 0.0138 m². The bioreactors demonstrated efficient gas-liquid mass transfer through the HFM module and achieved ~ 99% removal efficiency with an elimination capacity of ~ 17.0 g m^-3 h^-1. The H₂S flux of the bioreactor was ~ 0.20 g m^-2 day^-1 which was ~ 9 times higher than the abiotic reactor for an inlet H₂S concentration of ~ 0.90 g m^-3. The overall mass transfer coefficient value for the biotic process was 17.2 µm s^-1 which was ~ 25 times higher than the abiotic process. The bioreactors demonstrated both microbial attached growth on the membrane surface and suspended growth in the liquid phase. Microbial community analysis confirmed the presence of diverse sulfur-oxidizing bacteria at genus level including Acinetobacter, Dechloromonas, Hydrogenophaga, Rhodopseudomonas and Sulfurospirillum. Moreover, the enrichment of other bacterial genera such as ammonia-oxidizing (e.g. Nitrosospira), organic matter degrading (e.g. Trichococcus) and methanogenic (e.g. Methanosaeta) microorganisms demonstrate the diverse microbial ecology of the sludge growing in the bioreactor.