Modeling of the attached and suspended biomass fractions in a moving bed biofilm reactor

The performance, kinetics, and stoichiometry of three high-rate moving bed biofilm reactors (MBBRs) were evaluated. A constant surface area loading rate (SALR) and three different hydraulic retention times (HRTs) were utilized to create scenarios where the attached and suspended biomass fractions would differentiate, despite the main design parameter remaining constant. Performance was simulated using BioWin™ 6.0 software. The objective was to evaluate whether a calibrated/validated model could accurately predict experimental results. Initially, a sensitivity analysis was performed to determine influential parameters. The calibration/validation of influential parameters was then conducted via steady-state simulations for two base cases: 1) highest HRT; and 2) lowest HRT. Both sets of calibrated/validated parameters were substantiated using: 1) steady-state simulations at the other HRTs; and 2) dynamic simulations to evaluate the kinetic rates of attached and suspended biomass fractions at all HRTs. Results demonstrated that the model could be calibrated/validated for a single HRT, but could not accurately predict the performance, kinetics, or stoichiometry at other HRTs. •Influential parameters to activated sludge are different from those influencing MBBR.•Biofilm and suspended biomass parameters in modeling MBBR must be differentiated.•ASM lacks model flexibility in predicting carbon utilization pathways in MBBR.•Biofilm model could be calibrated/validated for a single HRT.•ASM does not accurately predict performance, kinetics, or stoichiometry at other HRT.