Investigation of the effect of hydraulic retention time on anaerobic digestion of potato leachate in two-stage Mixed-UASB system

Abstract

In the present paper, potato leachate is introduced into the first reactor, converted to glucose through the hydrolysis process and then into the acetic acid during the acidogenic process and as a feed entered the second reactor, converting to methane and carbon dioxide based on the methanogenic process. For modeling, a kinetic model has been used to justify the two-stage system behavior using MATLAB software. In writing the equations for modeling in the first reactor, variations are taken with time, while in the second reactor, the equations are written in solid and liquid phase and in steady state. The relationship used in most cases to represent the kinetics of bacterial growth is the equation called Monod, which is used in modeling the system. The systems have been investigated at mesophilic temperature and the effect of the reaction's resistance on the boundary layer has been neglected in the concentrations around the granules. According to the modeling, by increasing the residence time and the concentration of input waste, the percentage of removal of organic compounds will increase and fluctuate between the oxygen content of 67–81% and the methane production efficiency will reduce (until less than 0.1 L CH4 g−1 CODremoved−1) that is agreement with laboratory model in 19th day. The results and studies have shown that the modeling performed for a two-stage system can be used in the mesophilic temperature conditions, and the internal mass transfer resistance in the granules is a controlling process.