Comprehensive model of anaerobic digestion of swine manure slurry in a sequencing batch reactor

An improved mathematical model of anaerobic digestion in a sequencing batch reactor (SBR) process is developed. The model simulates the interactions b etween the biological, liquid (physicochemical) and gas phases. These pheno mena are supported by experimental data. The advanced model assumes: (1) si x populations of bacteria, including two populations of acetoclastic bacter ia, are present in the bioreactor; (2) hydrogen in the gaseous phase is not in equilibrium with dissolved hydrogen; (3) production of volatile fatty a cids (VFA) is regulated by the concentration of hydrogen in the liquid phas e; and (4) the process is not affected by large concentrations of VFA and a mmonia. The model contains a large number of kinetic constants and has the capability to predict the pH and methane production, as well as the concent rations of acetic (Ac), propionic (Pr) and butyric (Bu) acids; dissolved an d gaseous hydrogen and soluble chemical oxygen demand (SCOD) in the SBR as a function of time. The model coefficients were determined for data, gather ed from pilot scale digesters operated under psychrophilic conditions. The calibrated model was able to simulate methane production, SCOD, Ac and Pr a cid concentrations in the dynamic conditions of an SBR, operated over a ran ge of operating conditions. (C) 2000 Elsevier Science Ltd. All rights reser ved.