Removing H2S in the Digester and Simultaneously Increasing Methane Production by Injecting Air
Thermophilic anaerobic digestion of food waste generates biogas with high concentrations of H2S,which needs to be removed before use.In a 230-day study,a thermophilic anaerobic digestion reactor was continuously operated.The study investigated the impact of varying organic loads,air injection flow,and biogas headspace recirculation on H2S removal.Additionally,the study analyzed the performance enhancement of anaerobic digestion after the introduction of air into the reactor headspace.The results obtained from this study found that 78%of the H2S could be removed by continuously injecting three times the theoretical air at a constant flow rate when the anaerobic reactor was operated under an HRT of 15 days and a biogas headspace residence time of 2.8 h.By recirculating the biogas to the headspace,the H2S content in biogas decreased from 0.2%to less than 0.01%,resulting in a 95%removal performance.Under the condition of air intake,the methane yield of thermophilic anaerobic digestion of food waste increased by 8.5%to 310 mL/g(measured by COD mass)and the volumetric biogas production reached 4.2 L/(L∙d),which is an increase of 10.5%compared to the control one.Acetic and propionic acid concentrations remained low and did not show significant differences.Conclusively,removing the H2S from inside the digester is a simple and low-cost method and has the feasibility to be used on an industrial scale for food digestion.
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