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Measurements and modeling of the adsorption of natural organic matter (NOM) on oxide surfaces are presented and compared. Agreement is good and supports the view that the adsorption of NOM on oxides depends significantly on complex formation reactions between specific sites on oxide surfaces and functional groups on the NOM. Coagulant requirements can and often are set by the total organic carbon (TOC) concentration in a water source. Frequently there is a stoichiometric relationship between the required coagulant dosage and the TOC of the water to be treated. Other important factors include pH and the concentration of divalent cations. Ozone may benefit or retard coagulation, depending on coagulant type and the water quality characteristic that is dominant in setting the optimum coagulant dose.

A hybrid SC/SF model to describe the adsorption of weak polyelectrolytes on metal oxide surfaces is presented. This model couples the surface complexation (SC) model for the effects of surface and solute speciation on the adsorption of monomers on oxides with the Scheutjens-Fleer (SF) model for the effects of macromolecular properties on the adsorption of polymers and polyelectrolytes on surfaces. The average magnitude of the specific interactions between polyelectrolyte functional groups and surface sites, expressed by the parameter χ s (hyb), varies systematically with surface and polyelectrolyte speciation and hence with solution chemistry. Measurements of the adsorption of polygalacturonic acid (PGUA) on hematite over wide ranges of pH and ionic strength are used to test the hybrid model. Good agreement of model simulations and adsorption measurements is achieved. A reaction represented by >MeOH + L -) >MeOHLprovides the best representation of the experimental data.

The efficiency of humic acid removal by coagulation and 2-hour sedimentation was studied. The investigations also included determination of optimum pH for removing humic and fulvic acids from aqueous solutions (pH = 6.0 or > 10.0). The experiments show that 1) ferric sulphate is less efficient than alum, and 2) Al3ł and Fes+ act as coagulants and coordinating ions for metal-organic complexes and are removed together with humic acids. NOTATION А1residual concentration of aluminium ions, -coloured matter [g Pt/m3],Bk -residual coloured matter (colour of water after treatment) [g Pt/m3],coagulant dose [g/m3],ЕСС -effective consumption of coagulant, Fet+residual concentration of ferric ions, FA -fulvic acids, HA -humic acids, ifp -isolated from peat, pa -pure for analysis,HAkresidual concentration of humic acids.

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