Evaluation and modelling of methane yield efficiency from co-digestion of waste activated sludge and olive mill wastewater

Abstract

This research aims to enhance the biodegradation efficiency of waste activated sludge co-digested with olive mill wastewater in a batch system at a laboratory scale in (600 ml) digester. The potential biomethane production was investigated. Different concentration ratios were tested out at a thermophilic temperature (55°C) for a retention period of 32 days. The results showed an increase in methane amount in the case of co-digestion. A height methane yield was obtained (71% of CH4) at a mixing ratio: 87.5/12.5 of waste activated sludge/olive mill wastewater. The kinetic modelling was done to analyze the digestion performance with two models: the modified Gompertz equation and the modified logistic equation. The kinetic data and the concentration ratio give a peak correlation, whose the Gauss amplitude equation is convenient to predict the optimum mixing ratio and the limited concentration to avoid the inhibition of process. The synergistic effect is limited if olive mill wastewater mixing ratio exceeds the limited ration (22%).