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Nitto Denko Supplies “Reverse Osmosis Membrane” to Japan's Largest Seawater Desalination Plant
- Achieving boron rejection in a high-recovery-seawater desalination process -
1.6.2005
Nitto Denko Corporation (Ibaraki City, Osaka, CEO Masamichi Takemoto) has supplied a spiral-wound type reverse osmosis (RO) membrane module with enhanced boron rejection performance for a seawater desalination plant to be opened by the Fukuoka Area Waterworks Association in April 2005. Having already completed test operations during the summer season, Fukuoka Area Waterworks are currently in final-stage adjustments for full-scale operation this spring. This will be the largest-scale seawater desalination plant in Japan (with a capacity of 50,000 m3/day). The plant also features reduced costs through its high 60% recovery rate operation, and will realize improved demineralization through the use of a new system which effectively combines two types of RO membranes.
Product Development Background
Of the various methods for the desalination of seawater (e.g. distillation, electro dialysis, vapor compression, and RO process), RO is the mainstream method used due to its running cost, and in particular, its low energy cost. Seawater desalination plants using RO have been established in the Middle-East, the Mediterranean, Central America, and regions where fresh water is in short supply throughout the world.
In Japan, a 40,000 m3/day plant has been operating in Chatan, Okinawa since 1997 (a 15,000 m3/day part of RO supplied by Nitto Denko Group). In future, a great demand for RO is expected to continue, as more seawater desalination plants are planned, starting in isolated arid islands and regions needing improved water quality, and expanding throughout the world. Nitto Denko and the American company, Hydranautics. (California, 100%-owned subsidiary), supply the major, key device—RO modules—for the worlds water desalination plants.
Principals of Seawater Desalination Through RO
Product Features
Nitto Denko's low-pressure RO membrane achieves a stable high performance for removing boron. As boron is a small element, it can easily get through the RO membrane, so the membrane process is conducted in an alkali (pH 9.5) environment.
System Overview
The water processing system of Fukuoka Area Waterworks Association plant uses three different types of separation membranes. The pre-treatment section uses a clarifying ultrafiltration (UF) module from Nitto Denko, while the desalinating section uses a hollow fiber RO membrane from Toyobo Co., Ltd. The post-treatment section, which removes remaining boron from the desalinated water, uses Nitto Denko’s ultra-low-pressure RO membrane.
In the desalination process the permeate of high-pressure type RO is divided into high and low concentration parts. Only the high concentration-side RO permeate is processed by the second pass ultra-low-pressure RO, improving the efficiency of the double-pass RO desalination, and reducing the energy cost and a foot-print of facilities required.
Partial double-pass RO seawater desalination system
(The part of the RO permeate from the high-concentration side is sent to the boron-rejecting post-treatment) (Clarifying: Spiral UF Membrane) (Desalination: Hollow fiber high-pressure RO membrane)
Product Deliveries
| Clarification Membranes: | Spiral UF Membrane: | RS50-S8 | 3,060 Units |
| Boron rejecting Membrane: | Spiral super low-pressure RO Membrane: | ES20B | 1,200 Units |
| Sales size: | Approx. 1 billion yen |
Current Plant Overview
| Capacity: | 50,000 m3/day (estimated production) |
| Components: | Intake from seabed-sand-filtration, UF membrane, High-pressure RO, Low-pressure RO, Fresh water transport, Concentrate discharge, and Chemical injection equipment. |
| Location: | Aza-Kosenuki, Oh-aza-Nata, Higashi-ku, Fukuoka Prefecture |
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