Remoción de arsénico (as) y fluoruros (f-) en aguas subterráneas mediante coagulación, adsorción y doble filtración

The presence of arsenic (As) in drinking water has caused the spread of Chronic Regional Endemic Hydroarseni-cism (HACRE), this is a disease that causes skin lesions and different types of cancers. Regarding the presence of fluoride (F-) in drinking water, lower concentrations to 1.5 mg/L protect the dentures of children who use them, but it has been shown that higher concentrations of F- to 2 mg/L generate dental fluorosis (stained teeth) and deseases affecting the bones such as skeletal fluorosis. At the Center for Sanitary Engineering (CIS) thas been developed a process for the removal of As and F- in groundwater which has low total salinity. The ArCIS-UNR® process con-sists of a coagulation-adsorption process on aluminum hydroxide flocs, initial pH correction and two filtration stages: a first coarse upflow gravel prefiltration then rapid filtration. This process achieves As concentrations less than 0.05 mg/L in treated water (with a more controlled operation 0.02 mg/L), and 1.5 mg/L of F-, and is being applied to real scale in populations up to 10000 inhabitants. However, ArCIS-UNR® process is requested for cities with larger population and with higher concentrations of F- in the water to be treated. Therefore it was proposed to modify the original process, on the one hand to work with a initial pH of 6, because according on previous re-search, the F- removes better at low pH, and on the other hand to replace the coarse prefiltration stage by an stage of upflow rapid filtration so it could be possible to work with higher flow rates with lower filter surface. Prelimi-nary tests indicate that this new scheme can achieve good results in terms of removal of As and F-. For concentra-tions of As in the raw water between 0.08 and 0.12 mg/L, outlet concentrations were obtained in the treated water < 0.02 mg/L. While initial concentrations of F- to between 2.7 and 3.0 mg/L, outlet concentrations between 1.4 and 1.6 mg/L were achieved. La presencia del Arsénico (As) en aguas destinadas a bebida ha ocasionado la diseminación del Hidroarsenicismo Crónico Regional Endémico (HACRE), enfermedad que se manifiesta principalmente por alteraciones dermatológicas, pudiendo evolucionar hacia distintos tipos de cáncer. Con respecto a la presencia de los Fluoruros en aguas de bebida, concentraciones menores a 1.5 mg/L protegen las dentaduras de los niños que hagan uso de las mismas, pero se ha demostrado que concentraciones de F-superiores a los 2 mg/L generan fluorosis den