An integrated hydrodynamic-biokinetic model to optimize the treatment processes in a laboratory-scale, pilot-scale, and full-scale bioreactor

Abstract

One major disadvantage of membrane bioreactors (MBRs) is the high operating and aeration costs, and optimizing the process to attain economic efficiency is essential. In this study, a hydrodynamic - biokinetic integrated model was developed by combining a multiphase computational fluid dynamics (CFD) model with a population balance (PBM) submodel, an activated sludge (ASM1) submodel, and a combined (EPS – SMP) CES submodel. The developed integrated model was used to investigate the efficiency of treatment of bioreactors on three different scales (case 1- laboratory, case 2 – pilot, and case 3- full-scale system). The simulated values of bubble size count, total chemical oxygen demand (TCOD), total nitrogen (TN), ammonical nitrogen (SNH), nitrate‑nitrogen (SNO), EPS, and SMP concentrations were well validated with the experimental results, with an error percentage of 2.8 %, 6.32 %, 2.25 %, 0.53 %, 1.19 %, 4.62 %, and 2.05 %, respectively. The validated model is then extended for sensitivity analysis to identify optimum conditions (H/B ratio, H/S ratio, and bubble size) to reduce TCOD and TN concentration. The maximum percentage reduction in TCOD and TN concentrations in the most optimum scenario was 20 and 23 %, respectively, for case 3. Also, a reduction of 32 % in the cost of aeration was observed (for case 3) when the bubble size was reduced to 5 mm (from the current value of 7 mm). The preceding results suggest that the integrated model successfully optimized the treatment processes.