High solid mono-digestion and co-digestion performance of food waste and sewage sludge by a thermophilic anaerobic membrane bioreactor

Abstract The performance of co-digestion of food waste (FW) and sewage sludge (sludge) by a thermophilic anaerobic membrane bioreactor (ThAnMBR) was firstly investigated. The long-term stable operation showed the feasibility of the utilization of ThAnMBR for mono- and co-digestion of FW and sludge at a high solid condition. Good permeate quality was obtained at all sludge ratios while the addition of sludge restricted the methane generation. For a sludge substitution with a 25% TS-based substrate, the biogas yield of 0.812 L/g-VSfed was at 91% and 158% that of the mono-digestion of FW and sludge, respectively. Membrane performance indicated that the ThAnMBR operated stably at a high flux of 5 LMH under the high solid (∼27 g/L) condition. Furthermore, membrane filtration with a 0.1 μm pore size of hollow fiber not only completely removed suspended solids but also rejected about 70% of soluble COD, 80% of soluble carbohydrates and 17% of soluble proteins.