Effects of dissolved organic matter on adsorption of hydrophobic organic compounds by river- and sewage-borne particles

Adsorption of cholesterol and 2,2',5,5'-tetrachlorohiphenyl by particles from river water and treated sewage was studied in distilled water, sewage and river water and was compared to adsorption in solutions of organic matter concentrated from sewage and river water by ultrafiltration. Partition coefficients and standard free energies of adsorption are reported. Results indicate that sewage particulate matter is a more effective adsorbent than river particulates. Adsorption from samples of concentrated dissolved organic matter was less efficient than from unconcentrated samples and from distilled water. Chemical equilibrium considerations indicate that this is due either to formation of associations between the study compounds and other dissolved organic matter, thus stabilizing them in the dissolved phase, or to competitive adsorption.