The removal of arsenic from drinking water and associated costs: The Chilean case

Arsenic found in drinking water sources in northern Chile is mainly of natural origin due to the hydrological characteristics of the area, and the predominance of Quaternary volcanism. Water treatment plants in northern Chile remove arsenic by a coagulation process, bringing levels of this contaminant in the treated water down to around 0.04 mg l^-1. This value is considered high so there is an interest in reducing it significantly. In this paper, a technical and economic evaluation demonstrates that it is possible to reduce the residual arsenic in drinking water to values in the range 0.03-0.02 mg l^-1 at a very low cost, using the arsenic removal facilities currently operating in Chile. Consequently, exposure to arsenic could be reduced by 50%. To decrease arsenic levels below 0.02 mg l^-1, it would be necessary to use more advanced arsenic removal technologies, at a much higher cost. Reaching a standard at this lower level would lead to an estimated 83% increase in the price of water in Antofagasta. These results present the trade-off that the regulator faces between protecting health and the corresponding costs to society.