Prise winners list

Development of high-performance reverse osmotic membrane elements for desalination of seawater

Chuo-ward, Tokyo (Ehime Factory: Matsumae-town, Ehime Prefecture)
Toray Industries Corporation
Other award winners
Tsutomu Arai, Katsufumi Oone, Atsushi Ogiwara, Tomomasa Katayama, Hiromitsu Kanamori, Takasi Seki, Hiroki Tomioka, Teijiro Hatano, Masaki Azuma
Recommended by
Suido Kiko Kaisya, Ltd.

Inoue, Takeharu  (40)
Water Treatment Engineering Dept., Membrane Technology Section, Manager

Any phenomenon has a cause. However difficult a problem may be, we can solve it by studying it scientifically

Along with the energy and food problems, the "water problem" such as depleted water resources and deterioration of water quality is becoming more serious in many countries in the world. The amount of water used in the world is increasing rapidly at a rate two times the population growth, and it is expected that 3.5 billion people will face the problem of water shortage fifteen years later. Using its technologies for polymer chemistry and permeable membrane to solve the global water problem, Toray Industrial Corporation has developed "reverse osmosis membrane elements for desalination of seawater". Water treatment plants using those new elements, which not only desalinates seawater but also purifies wastewater up to the drinking water level, are being constructed in Middle East, Africa and other many countries in the world. Currently those plants recycle 14 million m3 of water a day (in conversion to produced water quantity) and help 60 million people have a pleasant daily life.


Can't we remove boron without changing the basic structure of RO membrane? We started to review our basic research

We have many water problems worldwide today due to the rapid population growth, development of industry and global warming. The 21st century is said to be the "Century of Water", and serious water shortage may affect people's daily life and even cause a conflict. Many companies are developing technologies for desalination of seawater and purification of wastewater so that the water can be used as drinking water or for a similar purpose. Toray Industries Corporation, who developed a reverse osmosis membrane (RO membrane) for the first time in Japan, is one of the major companies in this business field. "Companies in many countries started research of RO membrane in the 1960s and we started our research in 1968. At first, we used 'cellulose acetate' as material of membrane, but started to use 'cross-linked aromatic polyamide' to produce RO membrane elements around 1990. This new product reduced energy cost because the operating pressure of membrane was low, and its salt rejection rate was high. Therefore this membrane element became a major hit product in the first half of 1990 and shipment amount of it increased significantly." Mr. Inoue, the responsible person for development, talked about the history of RO membrane development.
A RO membrane consists of three layers, namely the polyester nonwoven fabric, polysulfone substrate and cross-linked aromatic polyamide. The feed water such as seawater is flowed into the membrane and pressure higher than the osmotic pressure is applied to filter it and produce clean water. By separating the low-molecular organic matters and ions, seawater is desalinated and safe drinking water can be produced.
However, people began to call for removal of boron in 2000, and the World Health Organization (WHO) declared a guideline in 2004, "The content of boron in safe drinking water should be 0.5mg / L or less."
"We asked ourselves, 'How can we remove boron without changing the basic structure of RO membrane, which our seniors have struggled to produce?' We judged that we had to review our basic research. We adjusted the polymer molecular composition of several hundred types of cross-linked aromatic polyamide sheet surface and conducted membrane permeation tests every day."

We conducted tests repeatedly at our factory to manufacture a commercial product based on our research results in our laboratory

As a result, by using a nondestructive analysis technology in nanometer level called "positron annihilation lifetime technique", Mr. Inoue's group measured the pore diameters of sheets precisely and verified the relation between the removal rate of boron and the pore diameter distribution for the first time in the world. Based on this knowledge, his group succeeded in development of "high-performance boron removal RO membrane", the pores of which were controlled in accuracy of nanometer.
"At first, however, we successfully developed a sheet of about only A4 size. It was necessary for us to produce membranes of 1m width and several thousand meter length in the same quality to commercialize them. Therefore by using the production lines in our Ehime factory, together with factory staff, we produced test products repeatedly."
At the same time, jointly with their production and engineering departments, they started development of automatic assembling machine for the elements. So far tens of workers had to lay membranes manually and assemble cylindrical elements, and so the assembly work was time-consuming and troublesome. In addition, the quality of adhesion layers among the membranes was not always the same because the work was performed manually.
"We had to manufacture an automatic assembly machine by all means to reduce the cost and time and improve the product quality. Finally we completed it and achieved production efficiency six times higher than that in manual work and improved the product quality drastically. This production process was also highly evaluated."
It took about ten years for them to commercialize a new high-performance RO membrane after they started research. The new membrane can remove boron very effectively and can produce clean water in the quantity 1.5 times larger than the conventional one. Before 2000, the removal rate of boron was 85 to 90%, but it is now about 93% and they will achieve the removal rate of 95% sooner or later. They have already cleared the value set by the WHO. In addition, compared with the evaporation method used for desalination of seawater, this new membrane can produce high-quality water at about 1/5 of normal energy usage. 
"We found answers for problems with painstaking efforts for ourselves, and it is our utmost pleasure that our research results are contributing to our society. We had to make a hypothesis, verify it and repeat this practice patiently, but we believed that we would be able to find a solution because science always follows the natural rules."
The RO membrane technology of this company can also remove arsenic and persistent organic matters that causes problems these days. Toray Industries Corporation handles its water treatment business as strategically important one and started to invest heavily in it. Mr. Inoue will have more chances for using his ability.

Toray Industries Corporation

Jan. 1926
96.9 billion yen
7348 (as of Mar. 2009)
Brief information:
By making use of its polymer chemistry technology for various membrane products, the company handles its water treatment business as a strategically important one and aims to be the number-one company in the business field.

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A cut model of RO membrane element manufactured with an automatic assembling machine (left), and cross section of element interior (right). Flowing through the membranes that are wound spirally, water is separated into concentrated water and permeated water.


RO membrane elements that can produce water suited for various purposes. Their brand name is "ROMEMBRA".


The RO membrane elements of this company are used by the Singapore desalination plant, the greatest plant in the Pacific Rim, and other plants in Middle East and Africa. The photo shows the large desalination plant in Hamma, Algeria.