Study of the application of coagulants for the clarification of the water as substitute of the aluminum sulphate

Abstract

This study was carried out with the purpose of evaluating the efficiency of natural coagulants of vegetable origin moringa oleifera, cactus opuntia, seaweed and cassava starch, for the clarification of waters for human consumption, as a substitute for aluminum sulphate. This study analyzed samples of water from the Cesar River located in La Guajira, during the dry period and rainy season, representing low and high turbidity waters (40.8-800 NTU, 6.87-6, 90; 4.76-3.42mg / L; 101.30-71.10μ / cm; 4062.5-428.50mg / L; 224-64mg / L; 80-45 UC). Each of the biomass selected in this investigation was previously washed with some chemicals (Ca (OH) 2, CaCL 2, NaOH and NaCl), and analyzed with the absence of these substances. The bach system or jug ​​test simulated the coagulation and flocculation phases, where revolutions of 200 and 25 rpm respectively were established. For each of the biomasses several mixtures were prepared using dosages of 66, 83 and 1000 mg / L. In each treatment, physical and chemical parameters were measured in coagulation-flocculation assays: color, turbidity, OD, total solids, conductivity COD and PH. The results reveal greater efficiency with the application of the different chemicals called pre-treatment; while the only biomass that obtained better results with the absence of these was the cactus. The best pre-treatment was determined, and the moringa biomass reacts very efficiently using Ca (OH) 2 at an optimum dose of 66 mg / L, resulting in removals of 78.88 and 97.72%; cassava starch presented the best turbidity results with NaOH and with an optimal dose of 66 mg / L (18.33-79.73%); while the algae had the best efficiency with CaCL 2, obtaining the largest removals with dosages of 83 and 1000 mg / L (17.17-81.14%). Unlike all biomass, the cactus showed the best yield without the intervention of any of the pre-treatments evaluated, thus making the biomass more efficient, able to remove most of the particles present in the water (82.90-98.41%) with an optimal dose of 1000 mg / L ; demonstrating the efficiency of the natural coagulants studied.