Abstract
Owing to the advantages of the natural coagulants under study, the present objective is to study the efficiency of blended coagulants: alum and chitin; alum and sago; and alum + chitin + sago. In this attempt, we have reduced the quantity of alum dose and added increasing quantities of the natural coagulants. The surface water samples collected from nearby sources were analyzed for the following parameters pre- and post-treatment with the coagulants. Coagulation and flocculation experiments were carried out using conventional jar test apparatus. Turbidity removal was observed to be nearly 99.29% at all pH ranges and doses. Removal of conductivity, solids and hardness was 58.83%, 32.03% and 33.33%, respectively. From the results obtained, it can be observed that the efficiency of blended coagulants in removal of various physicochemical parameters from the waters was better when compared to individual coagulants. The floc size in blend coagulants was larger than that of single coagulants. The data obtained in this study indicated the coagulation efficiency could be enhanced by using the blend coagulant.
Highlights
It has been understood that the efficiency of coagulation is influenced by certain factors, such as pH, temperature, alkalinity, coagulant type and mixing intensity (Camp and Root 1940; Kawamura 1976; Morris and Knocke 1984; Mhaisalkar et al 1991; Muyibi and Evison 1995; Rossini et al 1999)
Natural coagulants were blended with alum to obtain four ratios, keeping alum concentration standard and increasing the concentrations of the natural coagulants: Alum + chitin—1:1; 1:2; 1:3 and 1:4 Alum + sago—1:1; 1:2; 1:3 and 1:4 Alum + chitin + sago—1:1; 1:2; 1:3 and 1:4 Each ratio is again tested in four concentrations, i.e., 0.2, 0.4, 0.6 and 0.8 mg/l, which are coded with reference to the pH range as follows: Preparation of synthetic turbid water samples sample
Turbidity removal was observed to be highest with 99.29% at 6 pH and 0.15 mg/l dose
Summary
It has been understood that the efficiency of coagulation is influenced by certain factors, such as pH, temperature, alkalinity, coagulant type and mixing intensity (Camp and Root 1940; Kawamura 1976; Morris and Knocke 1984; Mhaisalkar et al 1991; Muyibi and Evison 1995; Rossini et al 1999). Many researchers have recommended a pH adjustment method to enhance the coagulation efficiency (Semmens and Field 1980; Gregor et al 1997; Myung et al 2001). Temperature is a critical factor in the removal of turbidity (Myung et al 2001; Vara 2012). Dharmappa et al 1993 focused on rapid mix parameters as a critical parameter for optimizing the coagulation process. Specific values were suggested for the optimal detention time and intensity of rapid mix by Mhaisalkar et al 1991. Sludge dewater ability is known as one economic factor in water treatment that affects the condition of pH, temperature, viscosity and so on
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