Potassium inhibition during sludge and biopulp co-digestion; experimental and model-based approaches

Process instability with consecutive low methane production are common challenges of the anaerobic digestion (AD) of municipal wastes. In the present study, the co-digestion of sewage sludge and municipal biopulp was investigated at batch and continuously fed digesters. At batch tests, the highest methane yield for co-digestion (467 +/- 17 mLCH(4)/gVS) was achieved when biopulp contributed to 80% of organic matter content and sludge the remaining 20%. At continuous mode operation, co-digestion achieved 0.91 +/- 0.11 L/(L.d) methane productivity, while mono-digestion of sludge achieved 0.62 +/- 0.05 L/(L.d). Potassium inhibition was investigated at the most efficient co-digestion scenario and was found that the half maximal inhibitory concentration (IC50) occurred at 8 g-K+/L. Subsequently, the effect of K+ was investigated at different scenarios at continuous operation. Simulations based on BioModel described the inhibitory effect of K+ by introducing non-competitive inhibition of methanogens. Simulation results confirmed the strongly inhibitory effect of potassium to the AD process. (C) 2020 Elsevier Ltd. All rights reserved.