Anaerobic Sequencing Biofilter (AnSBio): A novel approach for high-quality biogas production from low-strength wastewaters at ambient temperature

The Anaerobic Sequencing Biofilter (AnSBio) treating municipal sewage was operated for 370-days at ambient temperature with an organic loading rate (OLR) of 0.4-0.7 kgCOD/m·d. Temperature did not affect soluble chemical oxygen demand (COD) removal efficiency (RE), which averaged 89 ± 3%, whereas, total COD (COD) RE, ranging 82 ± 5%, exhibited an unclear profile due to suspended solids (SS) loss under cooler temperatures. The inherent filtering capacity resulted in reduced bed porosity under psychrophilic temperatures, manifested as head loss increase (348 ± 34 and 314 ± 19 cm during first and second winter, respectively). Hydrolysis of particulate matter at mesophilic temperatures caused head loss decrease (271 ± 58 cm). Biogas yields were 124 and 315 NmL/gCOD at the lowest (14 °C) and the highest (35 °C) reactor operating temperature, respectively. Biogas methane content was 85 ± 4%. The AnSBio is a valid alternative for low-strength wastewater treatment at ambient temperature.