Treatment of automotive industry wastewater using anaerobic batch reactors: The influence of substrate/inoculum and molasses/wastewater

A study of the anaerobic treatment of an automotive-industry wastewater was conducted at mesophilic temperature in batch mode. In this study, molasses was used as a co-substrate. The experiments were carried out with samples prepared in 500 ml bottles using a shaker at 35 °C. The concentration of inoculum was prepared to be 5000 mg/L VSS. Substrate–inoculum ratios (SIR) were 0.75 and 1.0. Molasses–wastewater ratios (MWR) were 0.3, 1, and 3. All tests were carried out against controls of inoculum without substrate. A speed of 150 rpm was used for the sample bottles and they were examined daily for chemical oxygen demand (COD), pH, total solids, and total gas. The highest COD removal efficiency, 47%, was at SIR = 0.75 and MWR = 3. The highest total solid material removal efficiency was at SIR = 1 and MWR = 0.3. The best result in biogas production was at SIR = 1 and MWR = 0.3 and SIR = 0.75 and MWR = 3. Monod-, zero-, first-, and second-order kinetic models were used to calculate and define model constants for organic removal rates. Data show a close fit to the Monod kinetic model based on the verification constants (R2) and other parameters (Ks, Umax, k0, k1, and k2).