History and Current Status of Reverse Osmosis Technology

Pure Water Preparation Industry

Marked by the entry of Hydranautics' reverse osmosis membrane products into the mainland China market eight years ago, domestic reverse osmosis pure water preparation technology has entered a stage of rapid development. It has been widely applied in industrial sectors such as power, petroleum, chemical, metallurgy, electronics, pharmaceuticals, and food, as well as in civilian applications such as municipal water supply and direct drinking water. Compared with traditional ion exchange and electrodialysis methods, reverse osmosis membrane technology occupies the vast majority of the pure water preparation market share. Reverse osmosis technology was first applied in China to the production of flushing water in the microelectronics industry. In recent years, the technological and consumer wave generated by reverse osmosis technology for direct drinking water has swept across the country from south to north and east to west, greatly promoting the popularization of RO technology.

In recent years, stable exchange rates, tariff reductions, fierce price competition from foreign membrane manufacturers in the domestic market, continuous price reductions by domestic distributors, and the gradual localization of supporting products have all contributed to a continuous decline in the market price of membranes and their supporting products, as well as the engineering cost of reverse osmosis systems. Meanwhile, the overall national strength and purchasing power of enterprises have increased, and personal consumption levels have risen. This, in turn, has promoted the widespread adoption of reverse osmosis technology. It has facilitated the acceptance of reverse osmosis technology and its products by various industries, including direct drinking water, municipal water supply, and various industrial sectors, forming a crucial link in their respective technological advancements. This, in turn, has played a certain role in promoting the overall progress of domestic industry.

Reverse Osmosis Membrane Products

Regarding the structural forms of reverse osmosis membranes, the market for hollow fiber membranes, tubular membranes, and plate membranes is relatively narrow. As a result, DuPont has ceased production of its hollow fiber membranes, and Toyobo's hollow fiber membranes have extremely limited sales in China. However, due to the low pretreatment requirements, wide range of water sources that can be treated, extensive application range, and huge market, spiral wound membranes have become almost synonymous with reverse osmosis membranes. In terms of membrane materials, cellulose acetate membranes, due to their high operating pressure and low desalination rate, have basically withdrawn from the market. Low-pressure and ultra-low-pressure aromatic polyamide composite membranes have become the absolute mainstream in the market. The development trend of membrane products is towards a wider variety and more versatile approach, including low-fouling membranes, positively charged membranes, and sodium filtration membranes.

Hydranautics' low-fouling membranes (LFC1 and LFC3 series) possess strong chemical antifouling properties. They are made by adding an antifouling material layer to the original polyamide composite membrane, making the originally negatively charged membrane surface electrically neutral and simultaneously increasing its hydrophilicity, thereby effectively improving the membrane's resistance to organic fouling. Dow Chemical's low-fouling membranes (BW30-FR series) possess strong physical antifouling properties. They improve the smoothness of the membrane surface and increase the thickness of the feed screen layer, reducing turbulence and increasing flow velocity on the membrane surface, thus effectively improving the membrane's resistance to microbial fouling. Low-fouling membranes have unique advantages in surface water, reclaimed water, wastewater treatment, and the concentration and purification of other solutions. Since entering the domestic market in 1998, they have received increasing attention and have been rapidly adopted. In recent years, positively charged membranes have emerged, with positively charged membrane surfaces that can more effectively remove cations. When used in the second stage of reverse osmosis, they can effectively improve the overall system desalination rate, achieving the system's permeate water quality requirements with a conductivity below 1 μS/cm. Nanofiltration membranes, strictly speaking, do not belong to the category of reverse osmosis membranes. Their membrane materials are diverse and not limited to aromatic polyamides. Membrane quality assessment can consider multiple indicators such as viruses, bacteria, amine nitrogen, and BOD, not just low desalination rates. Therefore, nanofiltration membranes have a wide range of applications and deserve significant development.

Reverse Osmosis Membrane Market

In the RO membrane product market, Hydranautics/Nitto Denko (USA) and Dow Chemical/Filmtec (USA) currently hold approximately 80% of the domestic market share. Other foreign membrane manufacturers, such as Koch/Fluid Systems (USA), Osmonics/Desal (USA), Trisep, CSM/Saehan (Korea), and Toray (Japan), collectively hold approximately 20% of the market. This situation indicates that all international spiral-wound membrane manufacturers with large-scale production capacity have entered the domestic market and secured a place. China began developing RO membranes (hollow core and spiral wound) in the 1960s, with technological development almost in sync with the world at that time. In the following years, domestic levels gradually lagged behind international levels, and foreign membrane production lines were introduced starting in the 1980s. Currently, represented by Huludao Yuchai Northern Membrane Industry Co., Ltd., there are still 4-5 companies with certain production capacity, but their market share in the domestic membrane market is less than 2%.

Domestic sales of various types of spiral-wound membranes were approximately US$200 million, US$500 million, US$800 million, US$1000 million, US$1500 million, and US$25 million from 1996 to 2001, respectively, with an estimated sales of US$30 million in 2002. Global RO membrane sales in 2001 were approximately US$500 million. Excluding regional and product price differences, domestic membrane sales volume accounted for approximately 10% of global sales volume. In 2001, Hydranautics took the lead by investing in and building a factory in Shanghai (Songjiang) to produce spiral wound membranes, and the products entered the domestic market in May 2002. It is believed that other foreign membrane manufacturers will also follow suit and build factories in China. Some emerging domestic membrane manufacturers are also accelerating the construction of factories in Hangzhou, Guiyang, and other places, and their products will soon be available on the market. At that time, the domestic membrane market will further expand, and competition will become more intense, with related downstream industries of domestic membrane technology being the biggest beneficiaries.

Reverse Osmosis Membrane Applications

In the application of RO membranes, the YUMA Water Plant in the United States (which treats canal water), put into operation in the 1980s, still maintains its position as the world's largest reverse osmosis membrane water treatment project with a daily treatment capacity of 280,000 tons. Seawater desalination is one of the important application areas of reverse osmosis technology. Globally, the three largest seawater desalination projects with a production scale exceeding 100,000 tons/day are located in the UAE, Saudi Arabia, and Spain, respectively. Among them, the Fujairah Water Plant in the UAE, which just started operation in 2002, has a treatment capacity of 140,000 tons/day. According to incomplete statistics, the world currently produces over 12 million tons of pure water per day using reverse osmosis technology. In comparison, while my country's total production and the scale of individual projects are still at a relatively early stage, its development is rapid and its market potential is enormous. Conservative estimates suggest that there are currently over 200 reverse osmosis systems in China with a production capacity exceeding 100 m³/h for industrial use. The largest completed project is the 750 m³/h, 14,000 ppm sub-seawater desalination project at the Cangzhou Chemical Plant, using domestically produced membranes from Yuchai Northern Membrane Company. The largest projects under construction in 2002 were two 2,000 m³/hr rolling mill water systems at the Shanghai Baoshan Steel Plant and Taiyuan Steel Plant. The largest projects in the power industry are the 100 m³/h power plant water projects in Yantai and Dalian. There are already over a dozen reverse osmosis production lines for bottled and packaged water with a production capacity exceeding 500 m³/h, with the largest reaching 1,000 m³/h. It is expected that drinking water production systems with a daily production capacity of 10,000 tons will appear in Shandong and Dalian within the next two years. Due to economic and geographical factors, reverse osmosis projects are concentrated in Shandong Province and Dalian. With the increasing aridity in northern my country and the rising demands for water quantity and quality from industrial and residential sectors, membrane-based seawater desalination will inevitably shift from its current focus on marine and island applications to industrial and municipal sectors, representing a huge market potential.

Reverse Osmosis Supporting Products

The supporting product market is developing in tandem with the membrane product market. Many foreign supporting products, such as ARGO's scale inhibitors, GRUNDFOS and DP's vertical multistage centrifugal pumps, PROCON and NOCCHI's vane pumps, CODELINE's membrane pressure vessels, AUTOTROL and FLACK's multi-way valves for water softeners, PARK and STRUCTURE's fiberglass filter cartridges, and BLUEWHITE and KING's panel flow meters, once dominated the membrane supporting product market. However, thanks to the concerted and unremitting efforts of domestic membrane distributors and similar supporting product manufacturers, these membrane supporting products are gradually being localized. Currently, product quality is generally up to standard, and market prices have fallen significantly. Some products are also sold to the United States and other countries of origin, opening up a brand new field for the development of this industry.