Capacitive deionization (CDI) represents a new approach to the treatment of a variety of water/wastewater streams contaminated with inorganic compounds. ENPAR Technologies Inc. of Canada has developed its DesEL System, which combines high water recoveries with high ion removal efficiencies. The system operates on the principle of capacitive deionization to remove ionic compounds referred to as total dissolved solids (TDS). The results of several bench and pilot tests of capacitive deionization systems are presented. In addition to the removal of general TDS, the system can be configured to preferentially remove monovalent ions. This alternative approach has been used to selectively remove nitrate from groundwater with only minor reductions in overall TDS. Pilot testing of the DesEL system has been conducted on groundwater containing high arsenic levels (0.210 to 0.820 mg/L). The DesEL system was effective at removing the As from the groundwater stream to less than the detection limit of 0.005 mg/L. The DesEL system has proven to be an effective technology for a variety of water and wastewater treatment applications.
Abstract:A series oflaboratory experiments were conducted to evaluate the effectiveness of an electrochemical approach to ameliorate AMD. An electrochemical cell was constructed using a block of massive sulfide-graphite rock from the Sherman Iron Ore Mine ofTemagami, Ont., Canada as the cathode, scrap iron as the sacrificial anode, and acidic leachate collected from the mine site as the electrolyte. The cell raised the pH of -41.0 L ofleachate from 3.0 to a maintenance value of -5.5. This result was accompanied by a significant decrease in redox potential from >550 to <300 mv. Furthermore, iron sulphate precipitate formed, with a concomitant lowering of Al, Ca, and Mg solution concentrations. The study clearly demonstrated the electrochemical approach to be a technically feasible and practical method of ameliorating AMD.
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