Avaliação da qualidade de mistura de águas de salinidades diferentes com e sem dessalinização solar para a região do semiárido da Paraíba.

Abstract

In the Semi-Arid region of Paraiba State the majority of the superficial waters and groundwaters not only has a small yield hut also shows a high salinity concentration (chloride - CI- > 800 mg/1). Such waters of high salinity and high ionic strength are inadequate for human use and/or for other uses. In order to help to minimize this problem, this work shows a deep study on the quality of blended waters concerning its salinity and saturation degree. From the preparation of synthetic high salinity waters and low salinity waters and with the aid of a solar distiller, built in reduced scale and of the conventional type, it were analized the following types of blend, (i) blend MB or high salinity water with dessalinized water and (ii) blend MB or high salinity water with Lou salinity water. The synthetic high salinity waters were prepared with chemical composition similar to those of the Semi-Arid region of Paraiba and it was included a carbonic species in order to simulate a natural water. Two types of waters were used, i.e.: (I> MaHC03 + MaCl + CaSGU2HK0 and (II) MaHC03 i MaCl f MgC'ls: + CaCla + H3O. The degree of salinity was prepared from the chloride - Cl~ concentration; i.e.; from C1 - (mg/1) 1500 to 3000 for high 'salinity waters of the system I, from C1 - (mg/1) 1000 to 3500 for those of the system II and finally, from Cl~ (mg/1) 100 to 200 for low salinity waters. All simulations of the waters - and experimental determinations were made at the Laboratório of Water Quality of the Water and Wastewater Agency of Paraiba CAGEPA, in Alto Branco township, Campina Grande, PB. The experimental results indicate that both blending processes are efficient for minimizing the salinity of natural waters and produce a greater water volume. The theory of the carbonated system of Loewenthal & Marais (1976 and 1986) was applied to evaluate the saturation degree of the waters (potencial of precipitation/dissolution of calcium carbonate - CaCDs). The results showed that the final waters of both blending types although showing a slight subsaturation tendence, are practically stable.