Correct Answer: A
Explanation:
The objective of this study was to develop a treatment system that can effectively reduce the concentration of colloidal particles in raw water that can greatly reduce the cost of treatment and improvethe subsequent steps of treatment. Aluminum sulphate (alum) and ferric chloride as a coagulant and anionicpolymer as coagulant aid were used in the process that changed the scale of particles from nanoscale tomicroscale and larger by a physico-chemical process. The influence of PH, temperature, coagulant andcoagulant aid dosages on the coagulation process was studied and conditions were optimizedcorresponding to the best removal of organic matters, viruses, colloids, bacteria, color and decrease inturbidity. 85-98% reduction of turbidity from raw water can be achieved by using the optimum coagulantdosage (8ppm, ferric chloride/10 ppm, alum) in the optimum PH range (9.2, ferric chloride/8.5, alum) in theoptimum temperature (20°C, ferric chloride/24°C, alum). Ferric chloride produced better results than alum.Higher dosages did not significantly increase pollutant removal and were not economical. The resultsprovide useful information for raw water treatment