Modeling an Anaerobic Reactor with an Outside Recycling Line for Municipal Wastewater Treatment by Modified Anaerobic Digestion Model No. 1 (ADM1)

In this study, we developed a mathematical model based on anaerobic digestion model No.1 (ADM1) for municipal wastewater treatment. The model classified the microbes in an anaerobic system as two genera: acidogens and methanogens. According to their growth and decay processes, the model simplified the anaerobic digestion of municipal wastewater into two sub-processes: transforming sugar, protein and lipid into VFA and then producing CH₄ and CO₂ from VFA. Also, chemical equilibriums were introduced. The dynamic process involved in the anaerobic system was solved by Matlab to calculate the effluent quality of the reactor such as COD, the VFA concentration, pH, and alkalinity variation. Based upon the ADM1 and dynamic constants in the literature, the stable operational data obtained from a pilot reactor was used for parameter sensitivity analysis, estimation, adjustment and calibration of the anaerobic digestion dynamic model. The dynamic model was then used to simulate the performance of the same OCAR reactor under the condition of an upward flow velocity of 2.0, 3.67, 5.0, 7.0, and 10.3 m/h as well as the residence time of 6, 4, 2, and 1 h during 165 days. The average relative error of estimated effluent COD, alkalinity, VFA is less than 10% as compared with the actual operation results.