Hu Qunhui: Industrialization of Reverse Osmosis Membrane Materials and Their Application in Industrial Wastewater Treatment

This article is reprinted from: Science China

On the afternoon of March 30, 2022, the Atmospheric Governance and Low-Carbon Development Committee of the China Biodiversity Conservation and Green Development Foundation (referred to as “China Green Development Foundation”) jointly organized with the Metallurgical Industry Planning & Research Institute an online seminar on green and low-carbon technologies for steel enterprises to achieve the dual carbon goals. Hu Qunhui, an engineer at Hunan Aowei Environmental Protection Technology Co., Ltd., delivered a technical presentation titled “Industrialization of Reverse Osmosis Membrane Materials and Their Application in Industrial Wastewater Treatment.” The key points of his remarks are summarized below for readers’ reference:

Distinguished experts and leaders, good afternoon. The topic of my presentation today is “Industrialization of Reverse Osmosis Membrane Materials and Their Application in Industrial Wastewater Treatment.” As we all know, China’s water resources and water quality are characterized by scarcity and uneven distribution. Issues of drinking‑water safety are becoming increasingly prominent, with significant disparities in water quality across regions: the northern and western areas suffer from excessively hard water, while the eastern regions face severe water pollution, leaving both surface and groundwater sources without adequate assurance of safety.

So, the status of drinking water safety and the application of membrane technologies in water treatment is roughly as follows: wastewater can typically be treated to a reuse‑grade quality using MBR; subsequent ultrafiltration and reverse osmosis steps can produce purified water and desalinated water, respectively; and further treatment with EDI can yield ultrapure water.

As public concern for health continues to grow, attention to drinking water safety is intensifying. Rising awareness of ecological and environmental protection has become a powerful driving force behind the rapid advancement of water‑treatment membrane technologies.

Thus, reverse osmosis membranes and nanofiltration membranes represent one of the key technologies for ensuring drinking water safety. In terms of market composition and the share of membrane‑separation technologies, the feedwater streams currently serving the desalination industry—primarily seawater, brackish water, river water, and wastewater—account for a significant portion. As for the industrialization of reverse osmosis membrane materials, by 2021 global production of RO and nanofiltration membrane sheets had reached approximately 240 million square meters, with foreign brands holding about two-thirds of the market and domestic brands accounting for the remaining one-third. To date, in the industrial membrane market, the installed base of 8‑inch industrial reverse osmosis membranes stands at roughly 6 million units, among which DuPont membrane elements comprise more than half, while domestically produced membranes collectively account for less than 15%. In 2021, the incremental supply of domestic anti‑fouling membranes was approximately 1.1 million units, yet their overall market share remained below 20%.

Regarding the Chinese market for 8-inch industrial membranes, their applications are primarily concentrated in desalination and ultrapure water production, as well as in textile dyeing, papermaking, petroleum, chemical processing, steel, metallurgy, and coal‑chemical industries. In this industrial‑scale treatment segment, affected by the COVID‑19 pandemic and related policies in 2021, the incremental demand for 8-inch reverse osmosis membranes in China reached approximately 1.0 to 1.1 million units, roughly on par with the previous year.

In the field of pure water membranes, demand is gradually declining as their application in advanced wastewater treatment across industries such as coal chemical engineering, steel, and petrochemicals continues to expand.

Thus, the development and industrialization of membrane materials hinge on three key issues: first, designing the molecular architecture of the functional layer to strike an optimal balance between selectivity and permeability; second, engineering and developing fouling‑resistant layers that ensure broad environmental applicability and extend product lifespan; and third, devising production‑scale manufacturing processes that enable defect‑free, controllable mass production and consistent performance. By enhancing the anti‑fouling properties of its membrane materials, Aowei Technology has successfully engineered a clean‑water‑compatible anti‑softening coating, while simultaneously improving water permeability, reducing surface roughness, and optimizing the membrane’s charge‑related performance.

Thus, regarding the fouling and cleaning‑recovery performance of this membrane material across different contaminants, it is evident that, thanks to our modified coating, both its fouling behavior and its cleaning‑recovery efficiency have been significantly enhanced.

As for our industrial membrane and reverse osmosis membrane product lines, we primarily offer four major series. One of these is the ultra‑low‑pressure composite reverse osmosis membrane, which operates at exceptionally low pressures while delivering high water production and high desalination rates comparable to conventional membranes, thereby significantly reducing operating costs.

The second series is low-pressure composite reverse osmosis membranes, designed for desalination of brackish and saline water. They operate primarily at low pressure and are characterized by high water production and superior salt rejection, making them ideal for use in systems producing purified and ultrapure water.

The third product series is an anti-fouling reverse osmosis membrane element line, primarily used in applications involving reclaimed water reuse and feedwater sourced from highly polluted surface water. Designed to withstand challenging water quality conditions, it offers robust fouling resistance and reduces the frequency of chemical cleaning.

The fourth product series comprises seawater desalination and high-pressure membrane solutions, designed for treating seawater, brackish water, and highly concentrated brine. These systems are suitable for desalinating high‑salinity brine, producing boiler feedwater for power plants, and enabling wastewater reuse, including applications such as leachate treatment.

In the anti-fouling series, a specialized surface treatment is applied to the membrane. Additionally, the membrane element’s structural design enhances its resistance to fouling and improves its cleanability and recoverability.

As for seawater desalination membranes, they are primarily used in wastewater reuse, leachate treatment, and zero‑liquid‑discharge applications, with very high consumption volumes.

In the field of industrial nanofiltration membrane elements, we primarily categorize our products into four major series based on the rejection rate for monovalent salts. The NF10, 30, 60, and 90 series correspond to sodium chloride rejection rates of approximately 10%, 30%, 60%, and 90%, respectively, with a rejection rate exceeding 90% for divalent ions.

In the field of nanofiltration membranes, the molecular weight cut-off typically ranges from 150 to 300 Da, and several product lines are available, primarily designed for the separation of specialized feed streams.

In terms of application scenarios for industrial membrane products, Aowei Technology’s solutions are currently deployed across a wide range of industries, including semiconductors, power generation, chemicals, automotive, metallurgy, textiles, as well as steel, coal chemical processing, textile dyeing, industrial wastewater treatment, leachate management, and aquaculture. Its permeate finds extensive use in applications such as ultrapure water for electronics, desalinated water reuse, boiler feedwater, specialized process waters, and reclaimed water reuse, with numerous proven case studies to support these uses.

Below are several typical application case studies. The first involves boiler feedwater, specifically its use at the self‑owned power plant of Shandong Weiqiao Aluminum & Electricity. The raw water source is Yellow River water, which undergoes integrated pretreatment, ultrafiltration, followed by two stages of reverse osmosis, and then a mixed‑bed ion exchange unit. The treated water ultimately serves as boiler feedwater. After two years of operation, the system has maintained a desalination rate exceeding 98%.

The second case is a water‑recycling project in the coal‑chemical industry, implemented at Zhongmei Yulin Energy & Chemical. The plant’s industrial wastewater undergoes advanced atomization treatment, followed by ultrafiltration, and then directly feeds into reverse osmosis to produce permeate for use as process water. Here are the on‑site conditions and actual operational data for the membrane system: the feedwater conductivity is approximately 1,800 µS/cm, while the permeate conductivity is around 50 µS/cm.

Finally, let me briefly introduce Aowei Technology. At present, the company’s core competencies are centered around four key technologies. The first is our capability in the design and development of membrane products—specifically, the R&D of membrane materials for reverse osmosis, nanofiltration, and ultrafiltration membranes.

The second component is the capability for analytical characterization, which encompasses our ability to perform various characterization and analytical assessments—covering water quality and other relevant parameters—throughout both the membrane product development process and its application.

The third key area is our capability for the independent design of critical equipment. At present, reverse osmosis technology remains dominated by foreign players, and China lacks standardized production facilities for membrane materials. Accordingly, we have independently designed the essential production equipment tailored to our proprietary membrane material formulation and processing technology.

The fourth area is our capability in the application‑oriented design of membrane products. We have a dedicated technical team and have also independently developed our own membrane system design software.

We are also conducting preliminary research in the areas of acid recovery, alkali recovery, solvent recovery, and vessel separation. That concludes my presentation for today. Thank you for your attention, and I welcome your comments and suggestions.