The Potential of Biogas Recovery from Anaerobic Co-digestion of Fecal Sludge and Organic Waste

Abstract

According to some reports, the amount of fecal sludge (FS) that is also known as septic tank sludge or septage in urban areas of Vietnam is relatively high. It can be up to hundreds of tons per year in some big cities (Hanoi Urban Environment. The situation and solutions of management, collection and treatment of fecal sludge, International Conference on Management of sludge from the drainage system and sanitation (FS3 – 2015) – Proceedings sludge management in Vietnam opportunity to improve, pp 25–27, 2015). Therefore, the management and treatment of septic tank are an urgent problem currently. Ingredients of fecal sludge such as total nitrogen (TN), total phosphorus (TP), and alkalinity are high, but the ratio of C/N is often lower (Montangero A, Strauss M, Fecal sludge treatment, Eawag/Sandec, 2004; Klingel F et al, Fecal Sludge Management in Developing Countries, Eawag/Sandec, 2002; Thai et al, Fecal sludge management from the sanitation, Science and Technology Publishing, Hanoi, 2013). So, the anaerobic co-digestion fecal sludge with other organic wastes with C/N higher can recover biogas. This study was conducted with experiment model in mesophilic fermentation conditions during 40 days in the solid waste laboratory of National University of Civil Engineering. Fecal sludge (FS) and organic waste (OW) have mixed with the ratios of 4:1, 3:1, and 2:1 by weight in three parallel models. Experimental results showed that at ratio of 3:1, it yielded higher biogas production with 514.33 Nl/kgVS of feed. Also the ratio and parameters of process such as the change of its height, temperature, pH, and COD are consistent with anaerobic digestion process, and the amount of fecal sludge treated is high relatively.