Abstract

SOLIS SILVAN, Rudy; LAINES CANEPA, José Ramón  and  HERNANDEZ BARAJAS, José Roberto. Mixtures with clotting potential to clarify superficial waters. Rev. Int. Contam. Ambient [online]. 2012, vol.28, n.3, pp.229-236. ISSN 0188-4999.

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 of85 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.

Keywords : coagulation; color; flocculation; jar test; suspended solids; turbidity.

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