Modeling and Biokinetics in Anaerobic Acidogenesis of Starch-Processing Wastewater to Acetic Acid

Starch-processing wastewater was anaerobically treated to produce acetic acid in laboratory-scale, continuously stirred tank reactors. The optimal conditions, in which the maximum acetic acid production occurred, were 0.56 d hydraulic retention time, pH 5.9, and 36.1° C. Acetic acid production at the optimum conditions was 672 (plus-minus) 20 mg total organic carbonequivalent L^-1, which indicated a 75% conversion efficiency of influent total organic carbon into acetic acid. A fourth order Runge-Kutta approximation was used to determine the Monod kinetics of the acidogens by using unsteady-state data from continuous unsteady-state experiments at the optimum conditions. The model outputs and experimental data fit together satisfactorily, suggesting that the unsteady-state approach was appropriate for the evaluation of acidogenic biokinetics. These included (mu)m, Ks, Y, and kd, which were evaluated as being 0.13 h^-1, 25 mg total carbohydrate (TC) L^-1, 0.38 mg volatile suspended solid mg^-1 TC, and 0.002 h^-1, respectively.