Dynamic modeling of nutrient removal by a MBR operated at elevated temperatures

The process performance of a MBR operated on municipal sewage at elevated temperatures was evaluated by dynamic modeling. The enhanced biological phosphorus removal (EBPR) performance varied from 40% to 95% with process temperature ranging from 24 to 38 °C. The respective maximum substrate uptake rate (q_PHA) was estimated at 1.5 gCOD_S/gCOD_X.day⁻¹ for Glycogen Accumulating Organisms (GAO) and 4.7 gCOD_S/gCOD_X.day⁻¹ for Phosphate Accumulating Organisms (PAO) with Arrhenius coefficients (θ) for GAOs and PAOs of 1.06 and 1.04 respectively. With these parameters the effluent PO₄ levels of the MBR operated for 450 days could be well described. In addition, the impact of mesophilic conditions and low influent P/VFA levels on GAO proliferation was evaluated under dynamic process conditions. Nitrification process was temporarily impaired at high temperatures around 38 °C. Simulations revealed that the contribution of the anoxic reactor to the total overall denitrification was limited to 40%The contribution of simultaneous nitrification and denitrification (SNdN) process to the denitrification was around 40–50% depending upon dissolved oxygen levels in aerobic and MBR tanks. The large contribution of SNdN was due to gas/liquid mass transfer limitation conditions mediated by high mixed liquor viscosities (20–35 mPa.S) in MBR system. The membrane flux was 43 L/m²/h corresponding to the specific permeability (K) of 413 L/m²/h/bar at 38 °C.