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 degrees C. Acetic acid production at the optimum conditions was 672 +/- 20 mg total organic carbon(equivalent) 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 micro(m), K(s), Y, and k(d), 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.