Numerical modeling of an integrated OMBR-NF hybrid system for simultaneous wastewater reclamation and brine management

The osmotic membrane bioreactor (OMBR) is an energy-efficient wastewater purification technique that integrates a membrane bioreactor (MBR), a forward osmosis (FO) membrane, and a draw solution. The main objective of this study was to develop a hybrid model that combines an OMBR with nanofiltration (NF) for simultaneous wastewater reclamation and brine management. In this model, reverse osmosis (RO) reject brine and wastewater were used as draw and feed solutions, respectively. The results from the model suggested that a stable pure water flux of 2.10 dm/d can be obtained with a water salinity of 352.62 mg/L at an effective osmotic pressure of 11.42 bar. To further investigate the model, sensitivity analysis of five main system inputs of the hybrid OMBR-NF system was carried out. The results showed that the water flux can be improved by enhancing the mass diffusion coefficient on the draw solution side (K_d) and the salt concentration of the final draw solution (X_di). In addition, the water flux can be improved by reducing the internal concentration polarization (ICP) effect. For instance, the water flux increased from around 1.90 to 2.33 dm/d when K_ICP was decreased from 0.56 to 0.36 d/dm. Lastly, it was found that X_di was the main influence on the permeate water quality; increasing it from 20,000 to 70,000 mg/L caused the water salinity to increase from 100 to 352 mg/L. Overall, this novel hybrid system can be used to achieve better water quality and reduce environmental pollution from highly concentrated brines.