Removal of multiple drinking water contaminants by combined ion exchange resin in a completely mixed flow reactor

This research evaluated the combined ion exchange (CIX) process to give drinking water treatment plants a new option for multiple contaminants removal. The CIX process uses anion exchange resin and cation exchange resin in a single vessel, which enables simultaneous removal of anionic and cationic contaminants. The novel aspect of the CIX process investigated in this research was its application in a small pilot, completely mixed flow reactor (CMFR) with resin recycle and resin regeneration thereby providing realistic performance data. A wide range of contaminants was tested for removal including dissolved organic carbon (DOC), calcium, strontium, nitrate, sulfate, sodium, and chloride, and sodium chloride (NaCl) and potassium bicarbonate (KHCO₃) were compared in terms of regeneration efficiency. The key results showed 50 to 80% removal of DOC, calcium, strontium, and sulfate, and less than 30% removal of nitrate, sodium, and chloride. In general, NaCl and KHCO₃ showed similar regeneration efficiency. Removal of sodium and chloride by CIX was only possible when KHCO₃ was used for regeneration due to the potassium and bicarbonate counterions.