Formation, Breakage and Reformation of Humic Flocs by Inorganic and Organic Coagulants

  • Kam, Sang-Kyu ;
  • Lee, Min-Gyu ;
  • Kang, Kyung-Ho ;
  • Xu, Mei-Lan
  • Published : 2008.03.31


The floc formation, breakage and reformation of humic acid by inorganic (alum and PAC) and organic coagulants (cationic polyelectrolytes) at several conditions (pH, ionic strength and floc breakage time) were examined and compared among the coagulants at different conditions using a continuous optical monitoring method, with controlled mixing and stirring conditions. For alum, the shapes of formation, breakage and reformation curves at different pH (5 and 7) were different, but the shapes and the sizes of initial floc and reformed floc were nearly the same in the absence and presence of electrolytes at pH 7. For PAC, similar shapes of the curves were obtained at different pH and ionic strength, but the sizes were different, except for those of reformed flocs at different pH. However, for these coagulants, reformed flocs after floc breakage, occurred irreversibly for all the conditions used in this study. For organic coagulants, the time to attain the initial plateau floc size, the extent of floc strength at high shear rate and reversibility of reformed floes were different, depending floc formation mechanism. Especially, for the cationic polyelectrolyte forming humic flocs by charge neutralization or electrostatic patch effect mechanism, reformed flocs occurred reversibly, regardless of pH and floc breakage time, but occurred irreversibly in the presence of electrolytes.


Floc breakage;Floc strength;Floc recovery;Humic acid;Inorganic and organic coagulants;Monitoring


  1. Spicer P. T., Pratsinis S. E., Raper J., Amal R., Bushell G., Meesters G., 1998, Effect of shear schedule on particle size, density, and structure during flocculation in stirred tanks, Power Technol., 97, 26-34
  2. Francois R. J., 1987, Strength of aluminium hydroxide flocs, Water Res., 21, 1023-1030
  3. Gregory J., Li G., 1991, Effects of dosing and mixing conditions on polymer flocculation of concentrated suspensions, Chem. Eng. Comm., 18, 3-21
  4. Nobukawa T., Sanukida S., 2000, Genotoxicity of halogenated by-products in the disinfected waters, Text of Posters of 1st IWA World Water Congress, Paris, France, Np-049
  5. Rebhun M., Lurie M., 1993, Control of organic matter by coagulation and floc separation, Water Sci. Technol., 27(11), 1-20
  6. Tipping E., 1993, Modelling ion binding by humic acids, Colloids & Surfaces A, 73, 117-131
  7. Smeds A., Franzen R., Kronberg L., 1995, Occurrence of some chlorinated enol lactones and cyclopentane-1,3-diones in chlorine-treated waters, Environ. Sci. Technol., 29(7), 1839-1844
  8. Serra T., Colomer J., Casamitjana X., 1997, Aggregation and breakup of particles in a shear flow, J. Colloid Interface Sci., 187, 466-473
  9. Gregory J., Rossi L., 2001, Dynamic testing of water treatment coagulants, Water Sci. Technol.: Water Supply, 1(4), 65-72
  10. Matsuo T., Unno H., 1981, Forces acting on floc and strength of floc, J. Enviion. Eng. ASCE, 107, 527-545
  11. Brakalov L. B., 1987, A connection between orthokinetic coagulation capture efficiency of aggregates and their maximum size, Chem. Eng. Sci., 42, 2373-2383
  12. Muhle K., 1993, Floc stability in laminar and turbulent flow, In Dobias, B. (Ed.), Coagulation and Flocculation. Dekker, New York, pp. 355-390
  13. Bache D. H., Johnson C., McGilligan J. F., Rasool E., 1997, A conceptual review of floc structure in the sweep floc domain, Water Sci. Technol., 36(4), 49-56
  14. Duan J., Gregory J., 2003, Coagulation by hydrolysing metal salts, Adv. Colloid Interface Sci., 100-102, 475-502
  15. Gregory J., 1996, Polymer adsorption and flocculation, In Finch, C. A. (ed.), Industrial Water Soluble Polymers, Royal Society of Chemistry, Cambridge, UK, pp. 62-75
  16. Yukselen M. A., Gregory J., 2004, The reversibility of floc breakage, Int. J. Miner. Process, 73, 251-259
  17. Gregory J., Chung H. J., 1995, Continuous monitoring of floc properties in stirred suspensions, J. Water Supply: Res. Technol., AQUA, 44, 125-131
  18. Durand-Piana G., Lafuma F., Audebert R., 1987, Flocculation and adsorption properties of cationic polyelectrolytes toward Na-montmorillonite dilute suspensions, J. Colloid Interf. Sci., 119, 474-480
  19. Kretzschmar R., Holthoff H., Sticher H., 1998, Influence of pH and humic acid on coagulation kinetics of kaolinite: a dynamic light scattering study, J. Colloid Interface Sci., 202, 95-103
  20. Leentvaar J., Rehbun M., 1983, Strength of ferric hydroxide flocs, Water Res., 17, 895-902
  21. Clark M. M., Flora J. R., 1991, Floc restructuring in varied turbulent mixing, J. Colloid Interface Sci., 147, 407-421
  22. Ray D. T., Hogg R., 1987, Aggregate breakage in polymer-flocculated suspensions, J. Colloid Interface Sci., 116(1), 256-268
  23. Bolto G. A., 1995, Soluble polymers in water purification, Prog. Polym. Sci., 20, 987-1041
  24. Xu M. L., Lee M. G., Kam S. K., 2005, Comparison of flocculation characteristics of humic acid by inorganic and organic coagulants: effects of pH and ionic strength, J. Environ. Sci., 14(8), 723-737
  25. Lee M. G., Kam S. K., 2005, Charge determination of cationic polyelectrolytes by visual titrimetry and spectrophotometry, J. Environ. Sci., 14(6), 525-532
  26. Griebel T., Kulicke W. M., 1992, Molecular characterization of water-soluble cationic polyelectrolytes, Makromol. Chem., 193, 811-821
  27. Kam S. K., Kim D. K., Lee M. G., 2003, Effects of polyelectrolyte dosage, kaoline particles and pH on flocculation of humic acid by cationic polyelectrolytes, J. Environ. Sci., 12(8), 861-870
  28. Gray S. R., Ritchie C. B., 2006, Effect of organic polyelectolyte characteristics on floc strength, Colloids and Surfaces A: Physicochem. Eng. Aspects, 273, 184-188
  29. Horn A. F., Merrill E. W., 1984, Midpoint scission of macromolecules in dilute solution in turbulent flow, Nature, 312, 140-141
  30. Zhou J. L., Rowland S., Mantoura R. F. C., Braven J., 1994, The formation of humic coatings on mineral particles under simulated estuarine conditions- a mechnistic study, Water Res., 28(3), 571-579
  31. Yukselen M. A., Gregory J., 2002, Breakage and re-formation of alum flocs, Environ. Eng. Sci., 19, 229-236