A comparative study of coagulants used in water treatment

Abstract

Turbidity is one of the of drinking water treatment problems. Turbid water contains molecules, plankton and colloids, is dealt with through the addition of coagulation chemicals in a process called coagulation and flocculation. In this research, three of the most commonly used coagulants used in water treatment process were examined for their efficiency in reducing turbidity. Those are Aluminum sulfate (alum), Ferric chloride and Poly aluminum chloride (PACl). Experiments were conducted using synthetically prepared turbid water by adding kaolin and using a Jar test instrument to define the optimum dosage from each chemical. The tests were conducted for two turbidity levels; 52 and 580 NTU. The results showed that Poly aluminum chloride is more efficient than both alum and ferric chloride. A dosage of 75 mg/l from PACl reduces the turbidity of the water from 580 to 4.55 NTU (99.2%), and from 52 to 1.5 NTU (97.1%). Applying the same operating conditions, Alum and FeCl3 should be a lower efficiency for turbidity removal. The efficiency of Alum and Ferric were 98.5% and 93.8% for water with 580 NTU, and 98.8% and 86.1% for water with 52 NTU.