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Electrochemical precipitation has obtained great attentions for water softening in recent years. In order to avoid cathode deactivation, periodical scale detachment is essential. In general, the scale adhered to the cathode is detached by mechanical scraping. Although mechanical scraping is easy operated, elastic scraper must be installed between electrodes, leading to the low softening efficiency and high energy consumption. To overcome such a problem, a new current pulsated electrochemical precipitation process was proposed in this paper. Scale detachment was accomplished by increasing the current density significantly. Experimental results showed that the both high softening and detachment performance were achieved. The precipitation rate was as high as 40.47 g/h/m2. The energy consumption and the total hardness removal efficiency were 8.9–13.2 kWh/kg CaCO3 and 17.8–22.8%, respectively. Repetitive experimental results indicated the current pulsated electrochemical precipitation process could run steadily without any performance decay detected after repetitive operation.

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Electrochemical precipitation is an attractive method in recirculated cooling water treatment. However, the currently available single electrochemical precipitation reactors are usually poor in softening performance. In this paper, we presented a multistage electrochemical precipitation reactor with eight series-wound cells for water softening. Hydraulic characterization showed that the new reactor proposed had less back mixing, short circuit, and dead zone. Softening investigation further demonstrated that the new reactor had better performance. The precipitation rate, energy consumption, and current efficiency were 71.1 g/h/m2, 3.17 kWh/kg CaCO3, and 37.6%, respectively. It was also found that the multistage reactor could run steadily, with almost no deterioration in softening efficiency detected after long-term operation.