Efficiency of a coagulation/flocculation–membrane filtration hybrid process for the treatment of vegetable oil refinery wastewater for safe reuse and recovery

Abstract

Treatment of real (RVORW) and synthetic (SVORW) vegetable oil refinery wastewaters using membrane filtration system was experimentally studied. Experimental runs with SVORW were used to identify the best conditions to perform with RVORW treatment. The bench-scale experiment was carried out using a commercial ceramic 0.245m2 ultrafiltration (UF) membrane (150kDa) in cross-flow filtration (CFF) mode at a flow rate of 3000 L⋅h−1 and a trans-membrane pressure (TMP) of 1.2bars. However, such membrane is vulnerable to fouling and it is insufficient to give water of good quality suitable for reuse. This investigation, aims to improve the purification performances of UF by exploring its combination with other treatment options, i.e. optimized coagulation/flocculation (CF) as pre-treatment and dead-end filtration (DEF) as post-treatment for better treated-water quality. According to the results, when using CF as pre-treatment under optimal conditions (2.4 g⋅L-1of aluminium sulfate, 60.05 mg⋅L-1 of CHT flocculant, under initial pH of 9.23), the hybrid CF/UF process allows to achieve the best treated RVORW water quality with turbidity, COD and TOC removals reaching 100 %, 98 % and 97 % respectively compared to those of CF and UF used separately, with membrane permeability of 135 L⋅h−1⋅m-2⋅bar−1 which is in agreement with an industrial application.