Sometimes, either as a result of accidental over chlorination, it is necessary to lower the chlorine level of pool water. This is achieved by treatment with either Sodium Thiosulphate or Hydrogen Peroxide. As an example for each 1 p.p.m. (mg.l)chlorine in 45,000 litres there will be 450gm chlorine. For each gram of chlorine add 2gm Sodium Thiosulphate or 1.5gm 30% Hydrogen Peroxide.

the process of removing residual chlorine from wastewater treatment plant effluent that has been disinfected with chlorine.

The removal of chlorine from the effluent of a treatment plant. Sodium bisulfite solution is primarily used for this purpose.