|Siemens electrolyzer unit where brine is |
turned into sodium hypochlorite
Water softened to <17 mg/L hardness is used to produce a 2.8% w/w brine solution from stored salt. The brine solution is passed through an electrolyzer (image right) where a current is passed between two electrodes resulting in chlorine gas being produced at the positive electrode (anode) and sodium hydroxide and hydrogen gas at the negative electrode (cathode). The chlorine then reacts with the sodium hydroxide to produce a 0.8% sodium hypochlorite solution which is stored before added to the finished water for disinfection. Salt usage equates to 3.0-3.5 kg per kg chlorine equivalent. Fifty-seven liters of 0.8% sodium hypochlorite is equivalent to 0.45 kgs of chlorine gas or 3.79 liters of commercial sodium hypochlorite (12%). This results in a much safer and cost effective chlorination system. Further information on Siemens OSEC technology.