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Most plant operators do not take any action or install pre-treatment to protect their softening resin inventory from damage due to iron fouling or oxidative attack. In fact, it is not uncommon to find they fail to monitor or control the dosing of disinfection chemicals correctly or know the iron levels in their water supply.
Justifying the installation of a pre-treatment section is dependent on the anticipated additional life of the resin bed and improved performance. For many, it is cost-prohibitive to install special iron or activated carbon filters. The alternative is to accept a shortened resin life. This decision is probably dependent on the size of the plant.
The most effective methods to reduce oxidizing chemicals in the water supply before the water softener are to install activated carbon filtration or dose a reducing agent. Both activated carbon filtration and dosing a reducing agent such as sodium sulfite (less than two mg/l required to remove each mg/l of free chlorine) protect the resins from oxidative attack.
Higher cross-linked softening resins to help counter oxidative attack
While all synthetic ion exchange resins are affected by oxidation, some resins utilize a resin backbone with a higher cross-linking level. Hence this means the resin breakdown takes longer, increasing the resin life compared to lower cross-linked resins. This can be a cost-effective solution in reducing the frequency of resin changes, which can be a costly operation.
Resins with outstanding resistance to iron fouling
Purolite developed a range of Shallow Shell Technology (SST) softening resins, which employ a unique technology that distributes the ion exchange sites differently within the bead structure. This results in the iron being captured nearer to the beads’ surface, which means better reversible removal of iron on regeneration, and the resins are often slower in becoming fouled.
Consult your local Purolite sales office for further information regarding the best SST product for your manufacturing site.