Field tests of drinking water disinfection by direct electrolysis

Summary

The results of studying direct electrolysis of natural underground water with the purpose of determining possible production of low concentration sodium hypochlorite for drinking water disinfection before supplying it to the residents of Grushevskaia village of the Aksaisk District, Rostov Area are presented. The use of natural surface or underground water as electrolyte provides for eliminating the stage of artificial chloride solution making; that will simplify the technology of disinfectant production at the point of application and reduce the operation expenses. The studies were carried out in a full-scale plant in two directions: determination of the optimal parameters of the flow-through electrolyzer; determination of the lifetime of electrodes. The results of the full-scale studies confirmed possible disinfection of chloride-containing natural water (chloride concentrations 200–233 mg/dm3) by direct electrolysis. The process parameters of the electrolyzer operation with underground fresh water were determined: current density; water flow to the electrolyzer (flow rate); the time of electrode operation as an anode and as a cathode. The optimal composition of electrode coating was determined: in ruthenium –iridium oxide coating the weight ratio of Ru to Ir was 20:80. The use of iridium in the coating effects the formation of active chlorine and the electrode lifetime. The presence of ruthenium in the oxide layer in 20:80 weight ratio to iridium increases the anode lifetime tenfold (up to 4000 hours) compared to the anode without iridium.

Key words

potable water , disinfection , water treatment , direct electrolysis , electrolyzer , low-concentrated sodium hypochlorite