The pH adjustment is done in front of the second pass in such a case. An alternative for this process is a post treatment with IX. Although only a few plants are installed with this technique, this process has some clear advantages if the customer requests a low Boron concentration (0.3 mg/ liter). In a pilot test of a seawater desalination plant the Boron level could be reduced from 0.7 mg/l (after RO) to 0.2 mg/l (operating capacity of 2.6 g/l).
Since IX is a separation process with high selectivity, mainly Boron is removed and the capacity of the resin is not exhausted by other ions. Similar processes can be used to remove other critical compounds selectively after an RO process, like arsenic or heavy metals.
How to Use Engineering Software to Set–Up Water Treatment Systems
Most engineers use customized software from product manufacturers to design IX or RO systems. The company has designed new comprehensive software, designated LewaPlus. This software can calculate RO and IX arrays inside the same software. As a consequence, water treatment plants with a two pass system or hybrid processes using RO followed by IX can be compared, allowing the designer to quickly optimize the water treatment plant. Additionally, the effects of process variables, like temperature, can be calculated and assessed for a whole system.
When designing an RO plant, the software offers the possibility to get a recommended array based on the information which has been entered. Further updates are planned this year, for example the option for posttreatment with IX, and a detailed cost and energy calculation for the RO design.
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