Potential tertiary treatment of produced water using highly hydrophilic nanofiltration and reverse osmosis membranes

Abstract

This study characterized the potential of new, highly hydrophilic nanofiltration (NF) and reverse osmosis (RO) membranes for the beneficial reuse of produced water. It was found that both NF and RO membranes were hydrophilic at 23°±0.90 and 37°±0.49, respectively. The findings of the permeation tests revealed that the NF membrane exhibited a higher permeability (7.3Lm−2h−1) in pure water than the RO membrane (3.4Lm−2h−1). The NF membrane was effective at rejecting certain monovalent salt ions (in 2000mg/L, 97% Na2SO4, 95% MgSO4, 94.8% CaSO4, 94% K2SO4, and 87% Na2CO3), whereas the RO membrane was more effective at rejecting hard salts (96% Na2CO3, 88% NaCl, 85% KCl, 85.4% BaCl2, 83% NaHCO3, and 80–81% for Na2SO4, MgCl2, SrCl2, and K2SO4). A primary assessment of the post-treatment potential of the NF and RO membranes for produced water showed that the critical component in produced water was characterized mainly by TDS and TOC at 854 and 26.3mg/L, respectively. The RO membrane was more efficient at rejecting these components, in quantities of 244mg/L of TDS and 6.7mg/L of TOC, whereas the NF membrane attained 520mg/L of TDS and 22.9mg/L of TOC. Both membranes reduced the initial oil concentrations (2mg/L), turbidity (21 NTU) and TSS (10mg/L) to less than 1mg/L. Conclusively, the findings on the treated water quality substantiated the possibility of utilizing RO-treated water as a future source of water.