Use of abstraction regime and knowledge of hydrogeological conditions to control high-fluoride concentration in abstracted groundwater: San Luis Potosi basin, Mexico

Significant amounts of fluoride are found in the abstracted groundwater of San Luis Potosi. This groundwater withdrawal induces a cold. low-fluoride flow as well as deeper thermal fluoride-rich flow in various proportions. Flow mixing takes place depending on the abstraction regime, local hydrogeology, and borehole construction design and operation, Fluoride concentrations (approximate to 3.7 mg l(-1)) could become higher still. in time and space, if the input of regional fluoride-rich water to the abstraction boreholes is enhanced. It is suggested that by controlling the abstraction well-head water temperature at 28-30 degreesC, a pumped water mixture with a fluoride content close to the maximum drinking water standard of 1.5 mg l(-1) will be produced. Further, new boreholes and those already operating could take advantage of fluoride solubility controls to reduce the F concentration in the abstracted water by considering lithology and borehole construction design in order to regulate groundwater flow conditions. (C) 2002 Elsevier Science B.V. All rights reserved.