Abstract:
This study focuses on the treatment of the final non-oily wastewater stream originating from an oil refinery and processing site. Pre-treatment using electro-coagulation and main treatment/water recovery using forward osmosis (FO) is recommended. Firstly, the FO batch experiments were conducted with 0.75 M tetraethyl ammonium bromide (TEAB) as the surfactant draw solution and final non-oily stream as the feed solution. The feed solution cross flow velocity of 8 cm/s with operating temperature of 30 °C achieved the highest permeate flux of 7 L/m2/h, accompanied by a reverse solute flux of 0.19 g/m2/h. The FO membrane remained chemically stable against the contaminants. The key contaminants identified on the membrane surface were carbonates and sulfates of calcium and magnesium, so their pre-treatment with electro-coagulation (EC) was targeted. The EC process was systematically optimized for the electrode connection, electrode arrangement, current density, reaction time, and electrode material. Maximum removal observed were Mg 100%, Ca 38%, total hardness 68%, and SO42- 66% at an applied current of 1000 mA for 30 min using a bipolar series arrangement with Aluminum electrodes. The pre-treated stream produced a 35% higher flux in the FO process compared to the untreated stream. The findings of this study could serve a pivotal role in the scale-up applications of EC and FO for water and resource recovery from non-oily effluents from refineries.
