Aerobic, Anaerobic Treatability and Biogas Production Potential of a Wastewater from a Biodiesel Industry

The purpose was to investigate the treatability of a wastewater from a biodiesel production industry under (1) aerobic conditions, using domestic activated sludge as inoculum; (2) anaerobic conditions, using sludge from an anaerobic domestic wastewater treatment digester; (3) utilization of wastewater for biogas production. The aerobic biodegradation batch tests were conducted in reactors with a working volume of 1.0 L, according to Zahn Wellens's methodology proposed by the Organization for Economic Co-operation and Development. The anaerobic treatability was determined by the methodology proposed by Field et al. (4A(0) Seminario de Depuracin anaerobia de aguas residuales, Valladolid Universidad, Secretariado de Publicaciones, Valladolid, 1988). Based on the results of anaerobic biodegradation, four new reactors with a working volume of 1.0 L were inoculated to evaluate the biogas production potential. The experiments showed that wastewater can be degraded under aerobic conditions with no lag-phase. COD maximum concentration of 780 mg L-1 could be metabolized aerobically. The anaerobic biodegradation only started after the adaptation phase (3 days). After 28 days, it was possible to achieve removal efficiencies above 90 % for the conditions applied in anaerobic tests. It was possible to obtain 114 mL of biogas for the highest influent COD concentration of 800 mg L-1 and F/M ratio = 0.25.