Applicability of osmotic bioreactor using potassium pyrophosphate as draw solution combined with reverse osmosis for removal of pharmaceuticals and production of high quality reused water

Osmotic membrane bioreactor (OMBR) has emerged as an alternative to the conventional membrane bioreactor (MBR) to precede reverse osmosis (RO) for wastewater treatment and reuse. However, it has not been fully demonstrated yet that technical improvements that may be obtained by OMBR-RO, when compared to MBR-RO, will be sufficient to support its application beyond laboratory scale. Therefore, this work addressed some key challenges to provide a general evaluation of the applicability of OMBR-RO for water reuse, focusing on the analysis of the combined process. Potassium pyrophosphate (K4P2O7) proved to be a promising draw solute to mitigate the prevalent problem of high reverse salt flux in OMBR, as the solute permeability obtained (0.05 LMH) is lower than those previously reported in literature using sodium chloride. The use of OMBR before RO allowed maintaining constant RO permeate flux. In terms of reused water quality (i.e. RO permeate), OMBR-RO process provided water of better quality: the concentrations of nitrite, nitrate, sulfamethoxazole, carbamazepine and diclofenac were 4, 10, 74, 6 and 4 times lower, respectively, in this process when compared to an MBR-RO. The only exception as 17-alpha-ethinylestradiol, whose concentration was higher in reused water obtained by OMBR-RO. The improvement in water quality for almost all PhACs and operational advantages due to double membrane barrier can support OMBR-RO implementation, particularly when very high removal of PhACs and nutrients is critical for the reuse option.