Diseño de un prototipo de uso doméstico para la remoción de arsénico en agua potable, basado en coagulación/floculación con cloruro de hierro (III)
Rojas-Chaves, Paola María
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In the North and in the North Pacific areas of Costa Rica, high concentrations of arsenic in drinking water have been found exceeding the guideline of 10 μg/L established by the Health Department of the country and also by the World Health Organization. Point of use systems based on coagulation/flocculation and filtration for arsenic removal was a solution for this problem. A prototype was developed using iron (III) chloride as a coagulant. Two flocculants were tested a synthetic one (cationic polymer KF-930-S) and natural one (“mozote” Triumfetta semitriloba). The optimum conditions were determined by jar tests with challenge water from the National Science Foundation and an initial arsenic concentration of 200 μg/L, these conditions were pH 6, iron (III) chloride dose of 12 mg/L and 14 mg/L for the cationic polymer and mozote, respectively, and cationic polymer dose of 1 mg/L and mozote of 250 mg/L. The time for the slow mix and settling were also determined: 1 and 20 min, respectively. A conventional treatment and a direct filtration were compared with jar tests with filters coupled; the first treatment and “mozote” as flocculant proved to be more convenient. The built prototype consists of two tanks, the first where the coagulation/flocculation/sedimentation happens and the second containing the sand filter with an effective size of 0,5 mm. The prototype provided a good performance using “mozote” as flocculant, reaching up to 99% removal, with initial concentrations of 200 μg/L, which results in a value less than 10 μg/L of arsenic in water. The efficiency of the protoype was also tested with water from the North Pacific of the area of Bagaces with an arsenic concentration of 10 μg/L, after the treatment the result was 3 μg/L of arsenic. This system is a very efficient, low cost and easy operation alternative for arsenic removal.
Proyecto de Graduación (Licenciatura en Ingeniería Ambiental) Instituto Tecnológico de Costa Rica, Escuela de Química, 2014