Anaerobic Co-digestion of Sewage Sludge with Cheese Whey under Thermophilic and Mesophilic Conditions

Anaerobic digestion of sewage sludge (SS) and co-digestion with cheese whey (CW) was evaluated in batch conditions under mesophilic and thermophilic regimens. Results indicated that the co-digestion can be successfully attained despite some inhibitory stages that may be initially present due to the accumulation of volatile fatty acids. Degradation of the mixture SS-CW followed a similar pattern without influence of the temperature. Tests in thermophilic conditions performed better, with the absence of inhibitory stages associated with fatty acids accumulation. Moreover, a significant increase in the rate of biogas production was obtained along with a great reduction of the time necessary for digestion. However, lower methane yields were obtained under thermophilic temperatures.