Lowering chloride levels
asked 26 January 2017 asked by Seef (360 points)
That is a high concentration. If you have a cheap energy source, you might consider distillation or osmosis. Otherwise, there is ion exchange with resin regeneration via caustic soda. All anions (not just Cl-) will be replaced by OH-, which will probably require correcting pH downstream. Why the need to treat at less than 10 mg/l?
Will activated carbon do, or what about a sodium metabisulfite injection?
No, neither activated carbon nor sodium metabisulphite are effective on chloride. The most economical solution remains, as stated previously, ion-exchange resins.
Be careful how you dispose of any chloride in the wastewater network after treatment (membranes or resins). Most regulations call for maintaining chloride levels around 0.5 g/l.