Anaerobic digestion of pressed off leachate from the organic fraction of municipal solid waste

A highly polluted liquid (“press water”) was obtained from the pressing facility for the organic fraction of municipal solid waste in a composting plant. Methane productivity of the squeezed-off leachate was investigated in batch assays. To assess the technical feasibility of “press water” as a substrate for anaerobic digestion, a laboratory-scale glass column reactor was operated semi-continuously at 37 °C.A high methane productivity of 270 m−3 CH4 ton−1 CODadded or 490 m−3 CH4 ton−1 VSadded was achieved in the batch experiment. The semi-continuously run laboratory-scale reactor was initially operated at an organic loading rate of 10.7 kg COD m−3 d−1. The loading was increased to finally 27.7 kg COD m−3 d−1, corresponding to a reduction of the hydraulic retention time from initially 20 to finally 7.7 days. During the digestion, a stable elimination of organic material (measured as COD elimination) of approximately 60% was achieved. Linearly with the increment of the OLR, the volumetric methane production of the reactor increased from 2.6 m3 mreactor-3 d−1 to 7.1 m3 mreactor-3 d−1.The results indicated that “press water” from the organic fraction of municipal solid waste was a suitable substrate for anaerobic digestion which gave a high biogas yield even at very high loading rates.