Background: Global produced water generation is about 120,000 MGD which contains hydrocarbons, salts, and other contaminants in huge quantities. Different process-dependent produced water streams are generated at an oil exploration site. The water-oil separator (WOSEP) recovers any remaining oil and generates WOSEP outlet stream with total dissolved solids (TDS) concentration of 92 g/L. The separated oil is desalted, producing another stream termed desalter effluent with a TDS around 6.3 g/L. Untreated discharge of produced water in abandoned reservoirs or sea can cause significant environmental and aquatic life deterioration. However, after suitable treatment, it can be reused for re-injection or other onsite applications. Forward osmosis (FO) and membrane distillation (MD) are two emerging membrane-based low-pressure water treatment technologies. FO-MD hybrid systems is proven efficient and stable in produced water treatment with identification of some key foulants like oil nd grease, sulfate, silicates and calcium. Removing these key contaminants through pre-treatment can improve the performance of the FO-D hybrid system.

Aim of the study: To experimentally identify which technique is the most suitable for the pre-treatment of WOSEP outlet and desalter effluent streams in terms of increased and stable flux, membrane chemical stability and reduced reverse salt flux.

Materials and methods: Five different pre-treatment technologies were studied including polymeric micro-filtration, polymeric ultra-filtration, ceramic ultra-filtration, electro-coagulation and ion-exchange through resins. Figure 1 shows...