Treatment of Shale Oil Produced Water with Zwitterion-modified Forward Osmosis Membrane

Abstract

Shale oil extraction with hydraulic fracturing consumes large volumes of 3 freshwaters and produces Produced Water (PW) with a high level of organic and 4 inorganic contaminants. This study applied a Forward Osmosis (FO) process to treat shale oil Produced Water (PW) obtained from a Permian Basin shale play in Texas. The FO membrane surface was modified with 3-(3,4-dihydroxyphenyl)-L-alanine (L-DOPA) coating to enhance membrane fouling resistance. The membranes were characterized before and after coating, with contact angle measurement and Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy. The L-DOPA coated FO membrane was utilized to treat PW in a Pressure Retarded Osmosis (PRO) mode, after preliminary filtration with 0.1, 0.2 or 0.45 μm filters. Optimum performance of water flux and flux recovery was observed when pre-treated with 0.1 μm. The coated membrane was further used to filter simulated PW, and diluted PW which was similar to Eagle Ford PW with TDS around 29,000 mg/L. Results showed that the zwitterionic coating reduced organic matter deposition on the membrane surface, and repelled salt ions to alleviate internal concentration polarization.