Issues‎ > ‎Vol19n2‎ > ‎

Removal of Water Turbidity Using Different Coagulants

Farouk Abdullah Rasheed

Irrigation Department, Faculty of Engineering, University of Sulaimani, Sulaimani, Kurdistan Region-Iraq,


Original: 24 August 2016, Revised: 27 November 2016, Accepted: 9 January 2017, Published online: 20 June 2017


Free Water turbid with high quality of potable water supply is the most important environmental issue. Surface water is usually rich in turbidity. Turbidity imparts a great problem in water treatment. In this present work, the performance and effectiveness of four different inorganic coagulant salts including alum, copper sulphate, ferric sulphate, and ferrous sulfate in water turbidity removal were investigated. No coagulant aids are used in the current study. Desired turbid samples with 100NTU (turbidity of surface water does not exceed 100NTU in no rain condition) are prepared in laboratory, mixing kaolin powder with tap water. The optimum conditions for maximum suspended solid removal are examined. A set of jar test experiments are conducted to find the optimum pH and coagulant dosage to reach appropriate operational conditions. The samples in jar apparatus underwent rapid mixing with speed of 100rpm for 1min. in order to attain uniform concentration of coagulants in water. Slow mixing with speed of 25rpm for 25 min. is used to give the colloidal particles favor to approach from each other to make flocs, and then allow the samples in the beakers to settle for 25 minutes to precipitate the agglomerates by gravity and sludge formation at the bottom of beakers. Results demonstrated that turbidity removal is dependent on pH and coagulant dosage. The highest turbidity removal efficiency was within % 97.9 for Alum when pH value is 6.5, %90.8 for copper sulphate when pH is 7, % 87 for ferric sulphate when pH is 4, and %72 for ferrous sulphate when pH is 4. Results indicated that alum has the best potential ability of water turbidity removal compared with other used coagulants.

Key Words:
Different coagulants, Optimum pH and dosage, Residual turbidity, Turbidity removal performance


[1] Ray, B. T., "Environmental Engineering", Southern Illinois University, PWS Publishing Company, (1993).

[2] HDR Engineering. "Handbook of Public Water System", John Wiley & Sons, pp. 251-283, (2001).

[3] Bratby, J., "Coagulants in Coagulation and Flocculation in Water and Wastewater Treatment", second ed., IWA Publishing, London, pp. 50-68, (2006).

[4] Water Research Commission, No: TT 181/02, First Edition, the Department of Water Affairs and Forestry, The Department of Health, Water Research Commission. (2002).

[5] Pernitsky, D. J., Edzwald, J.K., "Selection of alum and Polyaluminium coagulants: principles and applications", Journal of Water Supply: Research and Technology – AQUA, Vol. 55, No. 2, pp. 121-141, (2006).

[6] Bache, D. H., Johnson, C., Papavasilopoulos E., McGilligan F. J., "Sweep coagulation: structures, mechanisms, and practice", Journal of Water SRT-AQUA Vol. 48, No. 5, pp. 201–210, (1999).

[7] Gregory, J., "Particles in Water: Properties and Processes", London: IWA Pub.: Boca Raton, CRC Press Taylor & Francis (2006).

[8] Harif, T., Khai, M., & Adin, A. "Electrocoagulation versus chemical coagulation: Coagulation/flocculation mechanisms and resulting floc characteristics", Water Research, Vol. 46, pp. 3177-3188, (2012).

[9] Duan, J., Gregory, J., "Coagulation by hydrolysing metal salts", Advances in Colloid & Interface Science, Vol. 100-102, pp. 475-502, (2003).

[10] Pradyot Patnaik. "Handbook of Inorganic Chemicals", McGraw-Hill, (2002).

[11] Paul AB. "Electrolytic treatment of turbid water in package plant", 22nd WEDC Conference, pp. 286-88, (1996).

[12] J.C. Crittenden, R.R. Trussel, D.W. Hand, K.J. Howe, G. Tchobanoglous (eds), "Coagulation, mixing and flocculation, in: Water Treatment: Principles and Design", second ed., John Wiley & Sons, New Jersey, pp. 643-779, (2005).

[13] S. Sinha, Y. Yoon, G. Amy, J. Yoon, "Determining the effectiveness of conventional and alternative coagulants through effective characterization schemes", Chemosphere, Vol. 57, pp. 1115-1122, (2004).

[14] A. Mirwaiyi, A. Takdastan, N. Alavi and H. Mohamadian, "Removal of Turbidity, Organic Matter, Coliform and Heterotrophic Bacteria by Coagulants Poly Aluminum Chloride from Karoon River Water in Iran", Asian Journal of Chemistry; Vol. 24, No. 6, pp. 2389-2393, (2012).

[15] S. M. Moniruzzaman, M. H. Mishuk, Q. S. Sayeed, A. T. F. Rahman, "Study on the Performance of Different Coagulants for Turbidity and Color Removal", International Journal of Renewable Energy and Environmental Engineering ISSN 2348-0157, Vol. 02, No. 03, (July 2014).