A comparative study of different coagulants used in treatment of turbid water

Turbidity is one of the major problems in the treatment of drinking water. Turbid water contains molecules, plankton, and colloids, and is dealt with through the addition of coagulation chemicals in processes called coagulation and flocculation. In this research, three of the most commonly used coagulants utilized in the process of turbid water treatment are examined for their efficiency in reducing turbidity. The three types of different coagulants that have been employed are aluminum sulfate (alum), ferric chloride, and poly aluminum chloride (PACl). The samples are taken from the Tigris River at various levels from the water’s surface (60, 120, 180, 240, and 300 cm). The results showed that PACl is more efficient in removing turbidity than alum and ferric chloride. Ferric chloride is a more efficient coagulant than alum at different ranges of turbid water. In this study, the effects of employing a natural coagulant such as “Walnut coat” with PACl and synthetic polyacrylamide with PACl for removing turbidity are compared to using PACl alone. When compared to PACl alone, polyacrylamide with PACl was effective in removing turbidities of 22.8 and 25.7 NTU. Walnut coat was also proven to be more effective when combined with PACl for lower turbidities (20.7 and 21 NTU). Within the first 5 min of slow mixing with polyacrylamide, large, transparent, and readily settled flocs formed, whereas the same flocs formed after 30 min of slow mixing with PACl and walnut coat as flocculant. With both polyacrylamide and walnut coat as coagulants, better sludge properties were obtained, with low water content and high density that can be readily dried and disposed of.