Electrochemical CaCO3 scale removal with a bipolar membrane system

• Use of bipolar membranes for improving electrochemical calcium hardness removal.
• Bipolar membrane system shown to reduce energy requirement.
• Bipolar membrane system shown to enable chlorine free operation.

A recently developed electrochemical process for CaCO3 scale removal enables a major reduction in cathode area requirement. The basic concept of the improved system is separation of the anode and cathode compartments by a cationic ion exchange membrane and precipitation of the hardness in a separate crystallization vessel rather than by the conventional method of deposition on the cathode. This paper presents further improvements of the process by integration of bipolar membranes. Different arrangements of the membranes were explored (two cationic and one bipolar versus two bipolar and one cationic) with different flow schemes. Performance of the various configurations was characterized for hardness removal from both brackish and sea water feeds by measurement of current efficiencies, specific energy consumptions and specific precipitation rates. Results of this study indicate that integration of bipolar membranes enables significant improvement in current efficiencies and energy consumptions. Moreover, the integrated system enables complete prevention of the undesirable process of chlorine generation at the anode.