Zwitterionic surfactant stabilised oil-water separation using composite PES membranes with particular reference to the Atyrau Refinery in Kazakhstan

Abstract

Water scarcity is an escalating global concern, necessitating wastewater reuse as a sustainable strategy to reduce pressure on natural resources. This thesis presents a comprehensive approach to water management using pinch analysis, emphasizing that cooling water demand is as critical as energy demand, particularly in inland regions where water availability is limited. This issue is especially pressing for Kazakhstan, a dry, landlocked country facing worsening water shortages due to climate change. A striking example is the recent severe reduction in the Zhayik River’s flow in the Atyrau region, which has intensified water shortages and driven urgent policy revisions.
This research analyses water consumption at the Atyrau Oil Refinery in comparison to other national refineries, revealing a significant performance gap. Modernization efforts have transitioned the refinery from an open-loop to a closed-loop wastewater treatment system, substantially reducing water intake from the Zhayik River and achieving zero liquid discharge to evaporation ponds. While these upgrades under the “Tazalyq” modernization project have improved wastewater treatment efficiency, conventional methods remain ineffective in removing small, stable oil droplets (<5 µm).
To address this limitation, membrane technology was explored as an advanced treatment solution. Membrane processes effectively concentrate small stable oil droplets without additional chemical usage, yielding high-quality permeate suitable for reuse. This study investigates novel composite polyethersulfone (PES) membranes, evaluated alongside phase-inverted PES membranes, commercial polyvinylidene fluoride (PVDF) membranes, and commercial hollow fibre membranes. A synthetic oil-water emulsion was developed to simulate produced water, stabilized using zwitterionic surfactants, which exhibit both cationic and anionic charges, enhancing antifouling performance crucial for oil-water separation. Extensive membrane characterization confirmed the superior properties and filtration performance of the proposed membranes in treating synthetic oil-water emulsions, offering a promising solution for wastewater reuse in water-scarce regions.