Treatment characteristics of two different substrates were investigated by two-phase anaerobic digestion at 20 °C. One substrate contained 87 percent carbohydrates and proteins and the other 94 percent carbohydrates and lipids. The anaerobic system consisted of a completely mixed reactor for hydrolysis and acidogenesis reactions, and an upflow filter for methanogeneous conversions. The experiments showed that the best phase separation occurs with 4 to 8 hours of detention times within the acid reactor. A single anaerobic system with upflow anaerobic filter alone for the same total detention times at the same substrate concentrations was operated for comparison. The results proved that two-phase digestion systems have higher digestion efficiencies than corresponding single-phase digestion systems. For substrates with more lipids the digestion efficiencies were very much greater.

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