Reaction kinetics of degradation of natural hormones in activated sludge process

摘要

Natural hormones as well as artificial chemical compounds, found in wastewater and treated water, attract attention in terms of their possible disturbance of endocrine system of aquatic animals. A two-phase reaction kinetic model was proposed to describe the fate of estrogens in activated sludge process. Three parameters in the model, which are the water-sludge partition constant, the water-sludge transfer rate constant and the degradation rate constant, were identified experimentally for 17-beta-estradiol, estrone, 17-alpha-ethynylestradiol and bisphenol A. The fate of these compounds was simulated by using the obtained parameters for a conventional activated sludge reactor and the effect of operational conditions on the removal was examined. The simulation shows that the removal ratio of 17-beta-estradiol and of bisphenol A increased with the increase in HRT and MLSS, though the removal of 17-alpha-ethynylestradiol was less than 38% even at infinite SRT. The concentration ratio of the compounds transferred to the excess sludge to those in the influent was low, because the target solutes have a relatively hydrophilic nature and tend to remain in the water phase.