Mesophilic, thermophilic and temperature phased anaerobic digestion of waste activated sludge

This paper deals with a two-year pilot scale experimental trial for the mesophilic (35°C), thermophilic (55°C) and temperature phased (70°C+55°C) anaerobic digestion of waste activated sludge at high rate (total solids 6% in the feed). The reactor operated at an organic loading rate of some 2,2 kgVS/m 3d and a hydraulic retention time of 20 days in the three different temperatures tested. The general conclusion of this study is that a two phase processes with a first hydrolytic phase at 70°C can be a convenient solution to improve the stabilisation capability of anaerobic digestion of waste activated sludge and can be easily implemented for the upgrade of full scale wastewater treatment plant