India generates 0.15 million metric tons (MT) of solid waste per day out of which more than 80% is organic fraction. Apart from this, 38% of the households use septic tanks where proper disposal of faecal sludge is also need of the hour. Anaerobic co-digestion (ACD) of two different substrates has positive potential towards solving this problem. In the present study, ACD of organic fraction of municipal solid waste (OFMSW) and septage solids (SS) was studied at three different levels, i.e., lab-scale, pilot-scale (1 m3), and full scale- capacity (325 m3). A loading rate of 1.5 kg VS/m3 was selected. The bio-methanation potential (BMP) assay showed a maximum biogas generation, i.e., 120±20.6 mL/gmVS with 68% maximum methane concentration at a 5:1 OFMSW and SS ratio. Cumulative biogas production after 30 days was 1.6 L/gmVS. The ultimate biogas production in the pilot-scale plant was 1000±100.5 L/day with 71% methane. The plant was also efficient in removing 87% of COD and 61% of VS. The full-scale anaerobic digester was set up at Mormugao Municpal Council, Goa India wherein the objective was to co-digest OFMSW and SS. This digester showed a similar removal pattern like earlier studies i.e., 94% and 45% COD and VS removal, respectively. The average methane content of the biogas was 68%. Full-scale operation of the anaerobic digester did not show any operational problems at the chosen co-digestion conditions.
Anaerobic co-digestion in a liquid recirculation pilot-scale reactor: Thermal and hydraulic study
