Biokinetic coefficients of anaerobic immersed membrane bioreactor (AnIMBR) treating dairy wastewater

In order to determine biokinetic coefficients, namely, cell yield (Y), maximum specific growth (μ_m), endogenous decay coefficient (k_d), and saturation constant (K_s), a lab-scale anaerobic immersed membrane bioreactor (AnIMBR) was used. The AnIMBR was performed at different values of mixed liquor suspended solids (mixed liquor suspended solids (MLSS) values of 5,000, 10,000, and 15,000 mg/L) and influent chemical oxygen demand (chemical oxygen demand (COD) values of 2,000, 4,000, 6,000, and 8,000 mg/L). The results showed that Y, μ_m, k_d, and K_s were in the ranges of 0.2022–0.427 mg/mg, 0.0334–0.1095 (1/d), 0.0009–0.0022 (1/d), and 4612–6663 (mg COD/L), respectively. Values of Y, μ_m, and k_d were in the range of those reported in the published literature for various anaerobic processes using different substrates. However, values of K_s, obtained from the current investigation, were higher than those reported in the published literature. This can be attributed to the fact that by increasing the influent COD and decreasing the MLSS concentrations, the process removal efficiency will decrease and in turn, K_s will increase. Effluent COD at different values of MLSS was simulated and sensitivity analysis showed that the process performance was more sensitive to K_s than other biokinetic coefficients.