The reason that the company undertook the big step in adding RO membrane technology to its separation products portfolio is that reverse osmosis is a complementary technology to the ion exchange (IX) resins.
The ion exchange resins have been produced for more than 70 years under the brand name Lewatit. As a general rule, reverse osmosis can efficiently desalinate water with high salinity, but ion exchange can selectively remove certain ions from the water. Table 1 shows that depending on the requested permeate quality, which separation technique could be used.
RO Treatment for Water Desalination
In modern separation applications, combined RO and IX processes are not only used in applications like the desalination of boiler feed water, but in other process applications like the removal of boron from sea water, or the treatment of produced water from unconventional gas resources. These applications have recently been under much discussion because of increasing public concern for water quality and environmental considerations.
Treating Water in Gas Production
The production of gas from unconventional sources is growing rapidly worldwide. Water that comes up along with the gas is not only challenging to treat, but must often meet strict regulatory standards prior to release into the environment. Such regulations pose challenges to water treatment system designers. While varying significantly, typical waters may have a TDS range of 2,500 – 10,000 mg/l, total alkalinity of 1,000 – 3,000 ppm as CaCO3, and a pH in the order of 8-9.
Since most inland areas are sensitive to the discharge of salts, the concentrate from a water treatment process will require specialized disposal. Therefore, minimizing the volume of waste concentrate is paramount to the success of the application. RO processes with a high recovery rate and low usage of chemicals are one solution.
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