Assessment of the energy needs for the arsenic remediation of drinking water by electrodialysis

Abstract

In this work, three different arsenic-rich well waters from the territory of Viterbo (Italy) were processed via electrodialysis (ED) to remove arsenic. These waters having different chemico-physical parameters (i.e. pH, electric conductivity, main anion and cation, as well as arsenic, concentrations) were preliminarily submitted to limiting current tests to determine the electric current to be applied in constant-current batch desalination trials by using a laboratory-scale electrodialyzer. Arsenic removal was non-selective, its percentage removal (ρAs) being about 71% of the desalination degree (DD) achieved (i.e. 80–85%) at the end of any batch desalination. The specific energy consumption (w) was found to be linearly related to DD in the range of 71–75 W h m−3. Thus, contrary to generally accepted belief, arsenic removal by ED resulted to be by far less energy intensive than reverse osmosis, its specific energy consumption being almost of the same order of magnitude as that associated with the ED removal of nitrates from drinking water. Two empirical relationships (ρAs and w against DD) were developed to assess firstly the DD associated with prefixed arsenic removal and then to estimate the corresponding specific electric energy consumption.