Advancing Towards Zero Liquid Discharge: Hybrid Membrane and Electro-Oxidation Processes for Petrochemical Wastewater Reuse

Petrochemical industries consume substantial volumes of water and generate complex wastewaters that require advanced treatment to enable sustainable reuse. This study developed and evaluated a hybrid treatment system integrating ultrafiltration (UF), reverse osmosis (RO), electrodeionization (EDI), membrane distillation (MD), and electro-oxidation (EO) for tertiary petrochemical wastewater recovery and reuse. Pilot-scale UF achieved 91.5% water recovery, effectively removing suspended solids, turbidity, and iron, thereby producing suitable feedwater for downstream RO treatment. The RO system operated at 50.5% water recovery, generating permeate, with conductivity below 40 μS/cm for EDI polishing, and concentrate streams for MD treatment. EDI achieved 95.3% water recovery and produced high-purity demineralized water with conductivity below 0.30 μS/cm. MD treatment of RO concentrate and ultra-concentrate achieved recoveries of 82% and 60%, respectively, producing permeate suitable for clarified water reuse. Additionally, MD permeate from RO concentrate showed adequate quality for further demineralized water production via EDI. EO treatment of MD concentrates reduced chemical oxygen demand (COD) to values below 30 mg/L, corresponding to removals greater than 63% and 91% for the RO concentrate-derived and ultra-concentrated RO-derived streams, respectively. Chloride removal reached 52.3% and 56.1%, respectively, although the removal of other inorganic constituents remained limited. Overall, the integrated system enabled 96 to 98% wastewater reuse, demonstrating strong potential for circular water management and zero liquid discharge strategies in petrochemical industries.