Adsorption of Natural Estrogens and Their Conjugates by Activated Sludge

Adsorption to biomass is a key mechanism which results in the elimination of natural estrogens and their conjugates from sewage. Freundlich model showed that the adsorption capacities of estrone and 17β-estradiol to activated sludge were the highest at neutral pH. The lower capacities at pH 2 and 11.5 could be due to the competition of sludge adsorption sites by cations or electrostatic repulsion from particles of similar charges. The lowest adsorption capacity at pH 11.5 was attributable to electrostatic repulsion, and the highest capacity at pH 2 might be due to the increased sulfate adsorbability. For estrogen conjugates such as estrone-3-sulfate and 17β-estradiol-3-sulfate, adsorption performances were similar at pH 5, 7, and 9. It was observed that mean values of log K _D were 2.78, 2.61, 1.67, and 1.94 l kg TSS^?1; log K _OM were 2.96, 2.79, 1.77, and 2.04 l kg VSS^?1 and those of log K _OC were 3.31, 3.12, 2.21, and 2.46 l kg OC^?1 for estrone, 17β-estradiol, estrone-3-sulfate, and 17β-estradiol-3-sulfate, respectively.