Avaliação da qualidade e tratamento das águas subterrâneas para irrigação em Jaíba e Janaúba - precipitação e corrosão

Abstract

The lower quality of groundwater and the adoption of micro irrigation systems make chemical obstructions of systems possible. Water quality evaluation regarding precipitation and corrosion is crucial for its use and management. The objective of this work was to evaluate groundwater quality in the towns of Janaúba and Jaíba using water analysis database from CTNM/EPAMIG from 1993 to 2006. The following physical and chemical characteristics were analyzed: pH, EC, Ca2+, Mg2+, Na+, HCO3- and CO32 calcium carbonate saturation index (SR), stability index (SI) and corrected calcium (Caº). The volume of phosphoric and hydrochloric acid necessary for neutralization of water alkalinity through systematic chemigation was estimated to avoid calcium carbonate precipitation. High levels of severely restrictive bicarbonate were found in more than 63% of the sampled wells. This, added to high Ca2+/Mg2+ relation, indicates the precipitate in the form of calcium carbonate. SR values a little over 0.3and 6.0 for SI show the precipitating potential in more than 85% of the analyzed water samples, but close to neutrality. Incrustations can be avoided through application of phosphoric and hydrochloric acid through continuous injection in amounts varying from 1.0 to 0.3 L.m-3, respectively, for the towns of Janaúba and Jaíba. KEYWORDS: calcium carbonate, pH, well, irrigation, clogging.