Natural Organic Matter and Humic Substances Interactions

(color removal ≥ 90%) is defined by the pH ranging from 4.4 to 6.2 and aluminum dosages of
> 1.9mg L -1 Al.
Figures 2b and 2c show similar results, but for water sample IV (Figure 2d), indicating only
one zone for ≥ 95% removal efficiency, which was defined by the pH ranging from 4.9 to 5.5
and aluminum dosages of > 4.2mg L -1 Al; Zone 2 (≥ 90% removal efficiency) was defined by
the pH ranging from 4.5 to 5.6 and aluminum dosages of > 2.7mg L -1 Al.
4. Conclusions
15th IHSS Meeting- Vol. 3
To achieve the same degree of color removal, the water samples with lower apparent
molecular sizes required higher doses of aluminum sulfate. The coagulation probably
occurred as a result of charge neutralization through a positively charged hydrolyzed
aluminum species at lower pH values, while at higher pH values it probably occurred due to
the adsorption of humic and fulvic acids on the Al(OH)3(s) precipitate.
References
1. G.R. Aiken, in G.R. Aiken et al. (Eds.), John Wiley and Sons, New York, 1985, p. 363–385.
2. L.D. Bernardo and A.D.B. Dantas (2005). Methods and Techniques for Water Treatment, RiMa,
São Carlos, 2005.
3. P.N. Johnson and A. Amirtharajah, Res. and Techn. J. AWWA., 75 (1983), 239.
4. G. A. Edwards and A. Amirtharajah, J. AWWA., 77 (1985), 57.
5. http://www.ihss.gatech.edu, acessed in jun 2008.
6. Standards Methods for the Examination of Water and Wastewater 1998 20th Edition, APHA,
AWWA, AWPCF, Washington, DC, USA.
7. R.L. Malcolm and P. MacCarthy, Environ. Intern., 18(1992), 607.
8. E.M. Thurman and R.L. Malcolm, Environ. Sci. Technol., 15 (1981), 466.
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