EQUILIBRIUM-MODEL OF ANAEROBIC REACTORS

An equilibrium model was developed to study the physical and chemical aspects of anaerobic fixed-bed biofilm reactors. Development of the equilibrium model was based on the fact that the total carbon dioxide production during an anaerobic process is distributed between the liquid and gaseous phase according to Henry's Law. Similarly, the same relationship holds for methane production. By assuming that the carbonate system is the only source of alkalinity in the anaerobic system, the equilibrium model was developed. The equilibrium model described well the behavior of anaerobic fixed-bed biofilm reactors, which was verified by the experimental results. An anaerobic fixed-bed biofilm reactor with 15 L of packing material was the subject of this study. The reactor was fed with synthetic leachate solution made from a mixture of organic acids to an organic loading of 3.33 kg COD/m(3).day. The reactor was operated to test the effects of two operational parameters, namely, alkalinity and hydraulic retention time (HRT). The results demonstrated that equilibrium conditions exist for all operational conditions and, as a result, can be accurately modeled by an equilibrium model.