Isolation and application of indigenous microorganisms for hydrogen sulfide removal from biogas via biofiltration

BACKGROUND AND OBJECTIVES: Hydrogen sulfide is a major contaminant in biogas that leads to corrosion of equipment, unpleasant odors, and reduced energy efficiency. Conventional methods for hydrogen sulfide removal, such as chemical scrubbing and adsorption, are often costly and environmentally unfriendly. In contrast, biological removal using microorganisms has emerged as a sustainable and cost-effective alternative. Therefore, the study objectives were to isolate and evaluate efficient microorganisms for hydrogen sulfide removal from biogas and to assess their performance in a biofiltration system.METHODS: Soil samples were collected from a swine farm and enriched in sulfur-based selective media to isolate hydrogen sulfide -degrading microorganisms. Two strains, Sphingomonas paucimobilis and Enterobacter cloacae, were selected based on their growth and hydrogen sulfide removal capability. The strains were immobilized on coconut husk and applied in a laboratory-scale biofilter. Biogas composition was analyzed before treatment, and hydrogen sulfide removal efficiency was evaluated at gas flow rates of ۰.۳–۰.۵ liters per minute, corresponding to empty bed residence times of ۴.۰–۶.۶ minutes.FINDINGS: The initial hydrogen sulfide concentration in untreated biogas was ۴,۲۸۱ (±۲۶) part per million. Both strains demonstrated the ability to reduce hydrogen sulfide, with removal efficiency improving progressively over the operational period, indicating microbial adaptation and biofilm development on the coconut husk support. The biofilter inoculated with Sphingomonas paucimobilis showed a rapid increase in performance, achieving ۳۶.۵ percent removal on day ۱, increasing to over ۸۰ percent within the first week, and reaching a maximum efficiency of ۸۴.۸ percent on day ۱۳. During the stable phase of operation, the system maintained relatively high removal efficiencies before showing a slight decline toward the end of the experiment, possibly due to substrate limitation or accumulation of metabolic by-products. In contrast, the biofilter containing Enterobacter cloacae exhibited a lower maximum removal efficiency of ۷۶.۷ percent and demonstrated less stability over time under similar operating conditions.CONCLUSION: Overall, Sphingomonas paucimobilis exhibited superior performance in hydrogen sulfide removal compared to Enterobacter cloacae. The findings suggest that this strain has strong potential for application in biofiltration systems for biogas purification, offering an environmentally friendly and sustainable approach for hydrogen sulfide mitigation.

کلیدواژه ها:

Biofiltration ، Biogas purification ، Hydrogen sulfide (H۲S) removal ، Sphingomonas paucimobilis (A۲۱) ، Sulfur oxidizing bacteria.