Water, Wastewater & Stormwater

Oral

394875 - Evaluating the Coagulation Potential of Different River Water Samples of Dhaka City

Wednesday, June 6
2:00 PM - 3:30 PM
Location: Greenway EF
Co-Authors: Abizer Kapadia, 74/A, Green Road, Dhaka, Bangladesh – University of Asia Pacific

The rivers surrounding Dhaka city are an advantage to it and essential for the survival of the megacity. Through continuous human accessibility & interventions in the rivers, the conditions of the rivers are deteriorating. However, even in a flood-prone country as Bangladesh, groundwater depletion occurs due to excess withdrawal and eventually surface water needs to be treated for drinking purpose. An important step in the treatment involves coagulation and flocculation that removes the colloidal particles from water that are difficult to settle. This study applies coagulation method on the samples collected from the three rivers surrounding Dhaka City namely, Buriganaga, Turag, and Shitalakkhya Rivers. The objective of this study was to find out the optimum doses of coagulants with which the most efficient removal of contaminants could be obtained. The samples were collected from the rivers and after settling, jar testing for coagulation was carried out on the samples utilizing alum and ferric chloride as the coagulants. The results were then analyzed for the dosages of both the coagulants for maximum removal of turbidity, color, and total suspended solids. Optimum dosage varied with coagulants for different river samples and also for different contaminant removal efficiencies. Over 90% removal of turbidity was possible with alum at a dose within 0.1 – 0.25 mg/L for the rivers. However, dosage of ferric chloride varied between 0.05-0.3 mg/L for removal of turbidity ranging from 54% to 98%. Total suspended solids and color were removed from the samples by over 90% by alum within 0.1-0.2 mg/L dosage range. With ferric chloride, over 50% removal of solids was possible, however, color removal varied from >30% - >90% among rivers with doses over 0.35 mg/L. These results indicate that effective treatment of surface water would necessitate characterizing the river water thoroughly to evaluate the treatment potential.

Nehreen Majed, PhD

Associate Professor
University of Asia Pacific

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394875 - Evaluating the Coagulation Potential of Different River Water Samples of Dhaka City



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