A research study submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development

Thesis (M.Sc.) - Asian Institute of Technology, 1986

The efficiency or a pilot water treatment plant consisting of mixing unit, Flocculation and sedimentation units, rapid sand filtration and chlorination stage was assessed in removing coliphages from raw water containing artificially high levels of coliphages. The individual processes achieved removal to different degrees. The flocculation and sedimentation units yielded the highest removal of 93% at an alum dose of 320 mg/L. In addition with the batch study, coliphage removal by the flocculation process was independent of changes in turbidity of the raw water, the extended detention time of flocculation time; but, it was affected by the types and doses of coagulant used. Alum, ferric chloride and cationic polyelectrolyte were satisfactory coagulants to remove coliphage and turbidity from the water, Increased dosages increased both removals to some extent. The efficiency of coliphage removal in rapid sand filtration was low, ranging from 2.3 to 38.6 % The final chlorination stage was the most effective in removing coliphages and effluent coliphage could not be detected by plaque-assay method when residual chlorine was maintained at 0.4-0.6 mg/L. The total removal of the plant resulting from these subsequent units was considered 100 %.