Modeling full-scale osmotic membrane bioreactor systems with high sludge retention and low salt concentration factor for wastewater reclamation

• OMBR with sludge concentrator exhibits high retention and low concentration factor.
• The full-scale OMBR model simulates hollow-fiber and flat-sheet FO modules.
• The model helps to find optimal design parameters for OMBR–RO hybrid system.
• The appropriate water recovery ensures high flux and less adverse effect on microbes.
• FO cost decreases and RO cost increases at higher DS flow rates and concentrations.

A full-scale model was developed to find optimal design parameters for osmotic membrane bioreactor (OMBR) and reverse osmosis (RO) hybrid system for wastewater reclamation. The model simulates salt accumulation, draw solution dilution and water flux in OMBR with sludge concentrator for high retention and low salt concentration factor. The full-scale OMBR simulation results reveal that flat-sheet module with spacers exhibits slightly higher flux than hollow-fiber; forward osmosis (FO) membrane with high water permeability, low salt permeability, and low resistance to salt diffusion shows high water flux; an optimal water recovery around 50% ensures high flux and no adverse effect on microbial activity; and FO membrane cost decreases and RO energy consumption and product water concentration increases at higher DS flow rates and concentrations. The simulated FO water flux and RO energy consumption ranges from 3.03 to 13.76 LMH and 0.35 to 1.39 kWh/m3, respectively.