Mixtures with clotting potential to clarify superficial waters

The suspended particles cause both color and turbidity in surface waters. The use of chemical agents such as aluminum sulfate can remove a significant proportion of suspended solids, clarifying water in the first stage of purification. This study compared potential coagulant mixtures consisting of cassava starch (Manihot esculenta Crantz) and a commercial grade aluminum sulfate, which could reduce the amount of aluminum sulfate spent in water treatment plants. Using the jar test procedure, the optimal dose of aluminum sulfate (30 mg/L, treatment 1) to clarify a river water sample (a color of 85 CU, a turbidity of 70 NTU and a pH of 6.8) have been determined. This dose was the basis for the preparation of six mixtures with different compositions of starch and aluminum sulfate (treatments 2 to 7). In each treatment, three relevant physicochemical parameters in the coagulation-flocculation were measured: color, turbidity and pH. The results indicate that the best color removal (94% efficiency) was obtained with treatment 2 (2 mg/L of cassava over 28 mg/L of aluminum sulfate). The color removal for treatments 3 and 4 (4 mg/L of cassava over 26 mg/L of aluminum sulfate and 6 mg/L of cassava over 24 mg/L of aluminum sulfate, respectively) are statistically equal to those of treatment 1 according to the Dunnett's test for comparing means. With respect to turbidity removal, no significant difference between treatments 1 and 2 were observed, with a reduction of 98.7% and 97.9% respectively. Finally, the pH variation was insignificant in all treatments.Original Abstract: Las particulas suspendidas confieren color y turbiedad indeseables a las aguas superficiales. El uso de agentes quimicos como el sulfato de aluminio permite remover una proporcion significativa de los solidos suspendidos, clarificando el agua para su potabilizacion posterior. En este estudio se compararon mezclas con potencial coagulante compuestas por almidon de yuca (Manihot esculenta Crantz) y sulfato de aluminio grado comercial, que permitirian reducir la cantidad sulfato de aluminio usado en plantas de tratamiento de agua. Mediante prueba de jarras se determino la dosis optima del sulfato de aluminio (30 mg/L, tratamiento 1), en la clarification de una muestra de agua de rio (color de 85 CU, turbiedad de 70 NTU y pH de 6.8). Esta dosis, sirvio como base para la preparacion de seis mezclas con distintas composiciones de almidon y sulfato de aluminio (tratamientos 2 a 7). En cada tratamiento se m