Separate estimation of adsorption and degradation of pharmaceutical substances and estrogens in the activated sludge process.

The removal of three estrogens such as 17beta-estradiol, two endocrine disruptors like bisphenol A, and 10 pharmaceutical substances like ibuprofen (IBP) by activated sludge was experimentally examined. The contribution of adsorption and degradation to the overall removal was estimated separately and successfully. At the neutral pH condition, the target pharmaceutical substances showed little tendency of adsorption to the sludge and their water-sludge partition coefficients were lower than those of the target estrogens. On the other hand, the increasing tendency of adsorption was observed in the lower pH condition. A linear relationship between the log of the partitioning coefficient and logK(ow) was observed when pH was lowered to keep the pharmaceuticals neutral solutes. The acidic operational condition was preferable for the removal of acidic pharmaceutical substances because the limiting stage for the removal was not biodegradation but the transfer of substances from the water phase to the sludge phase.