December 2025
Water Management
Reclaiming industrial wastewater: Membrane solutions for oil separation
Industrial wastewater treatment remains a complex and evolving challenge, particularly when it comes to the removal of emulsified or free oil. With high contaminant concentrations, changing regulations and varying end-use requirements, selecting a wastewater treatment system can be challenging. Oil-contaminated wastewater is a byproduct of a wide variety of industrial processes—from food preparation to petroleum refining—that form oil-water emulsions through the use of surfactants or mechanical agitation through valves, pumps and pipelines. Once formed, these effluents are unsuitable for reuse within the manufacturing process and cannot be discharged into public waterways without significant remediation.
As companies seek to reduce water consumption and meet sustainability goals, the ability to reclaim process water and wastewater is critical. Effective treatment of oily wastewater is essential for improving water use efficiency across manufacturing sectors, enabling facilities to safely and economically reuse water and reduce dependence on freshwater resources. Water reuse also enables closed-loop systems that support circular production models and maximize resource efficiency.
While large particles of free-floating oils can typically be removed via gravitational separation, emulsified oils with particle sizes smaller than 0.02 mm require additional chemical, biological or physical separation processes. Conventional wastewater treatment methods, including flocculation, coagulation, chemical precipitation, centrifugation and electrodialysis, can have high energy requirements, rely on costly chemicals and result in incomplete contaminant removal.
Recent advances in polymeric membrane filtration technology have made water reuse a viable option for more facilities, including those with oil, grease and emulsified contaminants. These next-generation membranes enhance overall treatment efficiency, resulting in higher throughput, improved effluent quality and expanded opportunities for water reuse in industrial operations.
Benefits of membrane filtration. Membrane filtration relies on permeable membranes to separate solids, oil droplets and other contaminants from wastewater. Some membranes feature multilayer assemblies to control porosity and achieve filtration performance, often including hydrophilic polyacrylonitrile (PAN) material for the separation of oily water. Membrane filtration eliminates the need for heating and chemical reagents. With a compact facility footprint, membrane filtration systems are suitable for onsite and decentralized wastewater treatment settings such as manufacturing and offshore installations (FIG. 1).
FIG. 1. The author’s company’s innovations in composite membrane technology provide a high-performance solution that addresses the limitations of conventional filtration methods, offering superior oil and solids removal, higher flux rates and reduced fouling.
In the past, however, membrane technologies were particularly vulnerable to fouling, or the accumulation of oil and solids on the membrane surface. Fouling clogs the pores of the membrane, reducing flowrates and membrane performance. Filters had to be cleaned and replaced frequently, resulting in operational downtime and increased equipment costs. The latest membrane technology overcomes these challenges with a single-layer construction that enables the removal of oils and suspended solids from wastewater streams with low fouling and high flux rates.
Advances in composite membranes. Developed by researchers at the author’s company, the new membrane is a composite material formed by integrating a nanoporous, hydrophilic inorganic filler within a hydrophobic polymer matrix. The hydrophilic filler, with its high surface area, generates strong capillary forces that pull water through the membrane, while the nanoporous structure minimizes fouling by preventing the ingress of oil droplets and suspended solids. This unique morphology enables significantly higher flux rates and more effective oil-water separation with low energy consumption compared to conventional hydrophilic and oleophilic cast membranes, and can be used in both microfiltration (MF) and ultrafiltration (UF) processes.
To further enhance performance, the membrane is treated with a super-hydrophilic anti-fouling coating. This treatment inhibits the accumulation of oil, grease and other challenging emulsified materials on the membrane surface, extending operational life and reducing the frequency of maintenance and membrane replacement. The result is a more reliable and cost-effective filtration solution for industrial wastewater treatment (FIG. 2).
FIG. 2. The author’s company’s membrane filtration technology enables higher flux rates and more effective oil-water separation with low energy consumption compared to conventional hydrophilic and oleophilic cast membranes.
The membrane’s hybrid composite construction allows for precise control of pore size, separating emulsified oils and total suspended solids down to fewer than 10 parts per million (ppm). This membrane morphology removes contaminants with greater efficiency than conventional casting PAN and polyvinylidene fluoride (PVDF) membranes, as demonstrated by lower oil concentrations in the permeate and improved clarity in comparative testing.
The single-layer design also delivers flux rates two to four times higher than conventionally cast polymeric membranes. When cleaning is required, the membrane can be backwashed without risk of damage, a critical advantage for high-volume applications that use spiral wound filter configurations. Increased filtration efficiency can reduce the number of filtration units needed, helping facilities optimize floor space and enhance the sustainability of water treatment operations. Reduced fouling and extended cleaning intervals translate to potential savings in operational time, energy consumption and overall maintenance costs.
Staying ahead of PFAS legislation. New composite membranes also enable manufacturers to stay ahead of evolving regulations surrounding per- and polyfluoroalkyl substances (PFAS). In 2024, the U.S. Environmental Protection Agency (EPA) finalized a rule that designated perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), two common PFAS chemicals, as hazardous substances under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), and released the final National Primary Drinking Water Regulation, which sets maximum contaminant levels (MCLs) for six PFAS in drinking water. In Europe, the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) restriction proposal seeks to address the use of more than 10,000 PFAS chemicals and the European Chemicals Agency (ECHA) is expected to deliver its final opinions to the European Commission in 2026.
PFAS legislation not only affects effluent standards, but it could also have an impact on the manufacture of membrane filter materials. The durability of PFAS chemicals has made them a common component in some membranes, such as polytetrafluoroethylene (PTFE) and PVDF. The latest composite membranes are made without PFA chemicals, which can help manufacturers remain in compliance with possible restrictions and bans and also avoid service interruptions.
Filtration in the field. The new membrane has demonstrated its performance capabilities in laboratory testing and in real-world applications. The new polymeric membrane maintains durability in temperatures up to 155°F (68°C) and a wide range of pH levels from 1–10. With a standard spiral round configuration, the new membrane enables existing facilities that already utilize filtration separation to easily upgrade to the new composite membrane for higher flux rates and reduced maintenance costs.
In operations replacing chemical separation techniques, the new composite membrane has resulted in higher quality permeate and lower costs. In Texas (U.S.), a spiral wound membrane filter was used to treat oil contaminated water that contained 198,000 ppm oil. It resulted in a permeate with 3 ppm oil and lower turbidity than the previous chemical separation process. The membrane’s backwashing ability also creates opportunities to reclaim separated oil to minimize waste.
In manufacturing operations with very high quality permeate requirements, the composite membrane can also serve as a prefiltration stage ahead of reverse osmosis (RO) systems. While RO is highly selective and can remove a broad spectrum of contaminants that other technologies cannot, its membranes are particularly prone to fouling by oil. By efficiently removing oils and emulsified contaminants upstream, the advanced membrane reduces fouling potential and optimizes the performance and energy efficiency of the subsequent RO process.
Supporting efficient wastewater management. The treatment of industrial wastewater that contains oils and emulsified materials requires advanced, efficient and adaptable technologies that can meet evolving environmental regulations and industrial demands. Reclaiming and recycling wastewater has become a strategic priority for manufacturing companies seeking to enhance operational efficiency and advance sustainable practices.
Recent innovations in composite membrane technology provide a high-performance solution that addresses the limitations of conventional filtration methods, offering superior oil and solids removal, higher flux rates and reduced fouling. These membranes reduce maintenance, energy use and cost. By integrating high-flux polymeric membranes into wastewater treatment systems, industrial facilities can enhance water reuse, support circular production models and support responsible water management strategies.
The Author
Lisa Walters is PPG Product Manager, Specialty Products. In this role, she has guided the development of PPG’s membrane filtration technology. Throughout her 20 yrs at PPG, she has served in a variety of operational and commercial roles in the architectural and specialty materials industries. Walters earned her MS degree in chemical engineering from Lehigh University.
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