Abstract
The current study examines the impact of mixing methods in enhancing the coagulation – flocculation process. Two types of coagulants: Aluminum Sulfate Hydrate {Al2(SO4)3.16H2O} and Magnesium Chloride {MgCl2}) were used. The polyacrylamide {(C3H5)n} utilized as flocculent aid. A fully baffled mixing tank agitated with retreat curve impellers rotates in range of 60-105 rpm with 15 rpm as increment step and mixing time for 600 sec was used in present study. The present investigation includes two methodologies: first one based on numerical solution using MIXSIM 2.0, ANSYS Fluent, while the second based on experimental work. The Kaolin particles were utilized to represent the suspensions collides in natural raw water. The image analysis technique was involved to determine the surface area of producing flocs. The results establish that the most appropriate impeller rotational speed for flocculation process is in the range of 90 and 105 rpm for alum coagulant. The maximum surface area of floc is 3.252 mm2 produced at 60 rpm with 240 sec of mixing time. The maximum final floc surface area is 1.91mm2 at 90 rpm and 600 sec of mixing time. For magnesium chloride coagulant the max surface area of floce was 1.19 mm2 produced at 75 rpm and 360 sec of mixing time, the best impeller rotation speed was 75 rpm that produced the final surface area of floc which is 0.783 after 600 sec of mixing tank. These types of floc is appropriate for sedimentation process to be followed by normal procedure of drinking water treatment.
