Fate of inert cod fractions in two-stage biological treatment of a strong wastewater

In this study, the effluent of an alcohol distillery after passing through a chemical treatment is characterized in terms of its inert COD fractions and the changes likely to be induced by two-stage biological treatment on the magnitude of these fractions are observed. The experimentally obtained results indicated that the anaerobic treatment gives lower soluble inert COD fractions than a corresponding aerobic treatment for the investigated wastewater. Therefore, the preference of anaerobic treatment instead of an aerobic one as the first stage is ascertained. The anaerobic first stage has a COD removal efficiency of 96%, whereas with a subsequent aerobic treatment 79% removal can be achieved on the basis of the stoichiometry of the inert COD. The anaerobic full-scale plant performance of 80% can be improved up to 96%.