Influence of Hydraulic Retention Time in the Methanogenic Stage on Biohythane Production and Dissolved Sulfide Removal From Acidogenic Effluent

This study investigates the optimal operational parameters for biohythane production and dissolved sulfide removal during the two‐stage anaerobic digestion across various hydraulic retention times. Biohythane, composed of hydrogen and methane, is a promising source of clean energy. However, the presence of dissolved sulfide, which can oxidize into toxic and corrosive hydrogen sulfide (H 2 S), poses a challenge to its quality and application in energy conversion equipment. A two‐stage bioreactor was constructed, with the first stage, known as the acidogenesis phase, dedicated to biohydrogen production using mixed fruit waste (MFW) (initial glucose concentration 5 g/L, 60°C, pH 6.0) and the second stage (methanogenesis phase) to biomethane production using acidogenic effluent (∼4.87 g/L initial VFA concentration, 37°C, pH 8.5) with the addition of shredded tire (100 g) and an initial dissolved sulfide concentration of approximately 640 mg S 2− /L (37°C, pH 8.5). Experiments were conducted at various HRTs (2, 1.5, and 1 day) to optimize biomethane yield and dissolved sulfide removal. The results indicated that the modified Gompertz equation accurately fitted biohydrogen production, yielding 2.48 mol H 2 /mol glucose. The optimal HRT for biomethane production was 1.5 days, yielding 0.96 mol CH 4 /mol VFA, with butyric acid dominancy. The optimal HRT for dissolved sulfide removal was 24 h, achieving a removal efficiency of 78.13%, an adsorption capacity of 1.50 mg/g, and a final H 2 S concentration of 150 ppm. The present study demonstrated the efficacy of two‐stage anaerobic digestion for the production of biohythane with removal of dissolved sulfide, thereby enhancing energy recovery from MFW.