Biomethanization potential of sewage sludge and brewery wastewater under mesophilic and thermophilic conditions

This project was conducted at the laboratories of the Department of Environmental Technologies at Cádiz (Spain). The primary aim was to perform a biomethanation test to investigate anaerobic digestion of various wastes, including sludge from wastewater treatment plants and brewery wastewater. The study focused on a single-stage anaerobic co-digestion process of sewage sludge and brewery wastewater at two temperature ranges: mesophilic (35 °C) and thermophilic (55 °C), aiming to de-termine the more efficient mixture of both substrates and the best operational temperature range for both organic matter degradation and biogas production. Mesophilic conditions yielded more favourable results compared to thermophilic conditions. The 25BWW:75SS mixture achieved a production of 42.41 mLCH4/gVS, while the most favourable result was obtained for the reactor using only sewage sludge, reaching a production of 170.19 mLCH4/gVS. The results were less satisfactory under thermophilic conditions. Hence, the best mix-ing ratio was 25BWW:75SS, producing a yield of 32.75 mL CH4/gVS, while the highest result came from sewage sludge alone, with a yield of 36.85 mLCH4/gVS. These outcomes may be attributed to incomplete digestion, specifically blockage at the acetogenesis stage, leading to a significant accumulation of volatile fatty acids in the reactors. Hence, under mes-ophilic conditions, a yield of 0.64gVFA/gVS was obtained in 50BWW:50SS mixture and 0.66gVFA/gVS was obtained with the 25BWW:75SS mixture under thermophilic conditions.