ION EXCHANGE Update 5 July 2010

Limits of oxidants

The table shows the maximum acceptable concentration of chlorine, chlorine dioxide or ozone in water, for conventional water treatment applications. It is not valid for UPW, CPP etc.
Excess oxidants can be neutralised with sulphite or dithionite salts or sulphur dioxide. Excess chlorine can be removed by an activated carbon filter.

The dosage of chlorine or chlorine dioxide has a "persistent" effect, i.e. the oxidant remains in water for a long time. Ozone, on the other hand, tends to disappear rapidly.

Resin type Maximum
WAC gel 1.0 0.5 0.8
WAC macro 0.05 0.02 0.04
SAC gel 0.20 0.10 0.15
SAC macroporous 0.30 0.15 0.30
WBA (all) 0.05 0.02 0.04
SBA styrenic gel 0.10 0.02 0.04
SBA acrylic gel 0.10 0.05 0.04
SBA styrenic macroporous 0.10 0.05 0.04
SBA acrylic macroporous 0.10 0.02 0.04
SBA nitrate selective 0.10 0.05 0.04

The above values are not guarantee numbers, but only "believed to be safe" in the present state of our knowledge.

Sometimes, chloramines are used instead of chlorine for disinfection. Because the dosage is much higher (expressed as Cl2) and chloramines are not removed well by activated carbon (only 50 % removal compared to about 90 % for free chlorine), chloramines have a strong degradation effect on the resin.

© François de Dardel