Which of the following is the optimum coagulation conditions

Which of the following is the optimum coagulation conditions of pH and alum dose?

1. pH 5.5 and dose of 0.1 mg/L

2. pH 5.0-6.5 and dose of 0.3-3 mg/L

3. pH 7-8 and dose of 20-50 mg/L

4. pH 7-8 and dose of 3-10 mg/L

5. pH 6-9 and dose of 15-100 mg/L

Solution

In Jar testing the pH of the sample is to be maintained at 6 to 8.5

and the optimum value of coagulant generally lies between 8 to 10 for general water.

hence (option 4 )

pH 7-8 and dose of 3-10 mg/L is the optimum coditions of pH and alum