Evaluating controllability of pharmaceuticals and metabolites in biologically engineered processes, using corresponding octanol–water distribution coefficient

The efficiency of removing 9 different pharmaceuticals, 5 carbamazepine metabolites, and 1 personal care product through wastewater treatment plants and constructed wetlands was investigated. The compound concentrations were measured using solid phase extraction followed by liquid chromatography quadrupole tandem mass spectrometry. For extraction confirmation and better accuracy, isotopic dilution and standards addition methods were employed. The reporting limits for the investigated compounds were less than 10 ng/L except TCEP (24 ng/L). The removal efficiencies were found to be inversely proportional to the octanol–water partition coefficients (log Kow) after modification with ionizable functional groups (log Dow); compounds with a higher hydrophilicity were more efficiently removed in the engineered processes through biological treatment mechanisms. Carbamazepine metabolites that were formed in the early stages of certain metabolic reactions exhibited enhanced removal efficiencies due to a decreased log Dow values. However, the removal efficiency of those formed in later stages did not increase, but rather fluctuated with large standard deviations. The removal behaviors of metabolites in biologically operating engineered systems need to be more extensively examined.