Dynamic modeling and simulation of the impact of lipid inhibition on anaerobic digestion of desiccated coconut wastewater

Abstract

Desiccated Coconut Wastewater is categorized as a lipid-rich wastewater that can be treated using anaerobic digestion. Within the anaerobic digester, lipids are hydrolyzed into Long Chain Fatty Acids (LCFAs) and glycerol. LCFAs cause potential inhibitory effects significantly on acetoclastic methanogens and deteriorate digester performance. To study the impact of LCFA inhibition, the BioWin 6.2 integrated Anaerobic Sludge Digestion Model (ASDM) was extended with the lipid inhibition function. Out of all kinetic constants used in the rate equations, maximum specific growth rate of acetate degraders (µmax_acetate), half saturation rate of acetate degraders (Ks_acetate) and LCFA inhibition constant (Ki_LCFA) are the most sensitive parameters toward methane production. The calibrated model with lipid inhibition (Model 2) showed a higher negative impact on COD reduction, acetoclastic methanogen concentration, and methane production compared to model without lipid inhibition (Model 1), indicating a significant impact of lipid inhibition on anaerobic digestion. If Model 1 is used to simulate anaerobic digestion of lipid rich wastewater, deviations between the actual results and the model predicted results will be high. Thus, Model 2 can be used as a tool to predict the COD reduction, effect on the acetoclastic methanogens, and methane production in anaerobic digestion, which utilizes lipid-rich wastewater.