Improvement of Double-pass Reverse Osmosis System in the Demineralized Water Production

Abstract

The following results were obtained in the experiments to improve the treated water quality at a combination system with two reverse osmosis systems, called “Double-pass Reverse Osmosis System”. (1) The installation of degasifier to reduce CO₂ gas in raw water, gave a remarkable improvement of product water. (2) H₂SO₄ and Ca(OH)₂ were used as the alternates of HCl and NaOH, respectively, to reduce pH value for preventing scaling and to convert CO₂ to HCO₃ or CO₃ ion. (3) The electrolized cathode water was used instead of injecting alkali reagent such as NaOH for CO₂ convertion, and resulted in the reduction of ion increace, which was expected to improve product water quality.