title: Removal of naproxen and bezafibrate by activated sludge under aerobic conditions: kinetics and effect of substrates.
abstract: Naproxen and bezafibrate fall into the category of pharmaceuticals that have been widely detected in the aquatic environment, and one of the major sources is the effluent discharge from wastewater treatment plants. This study investigated the sorption and degradation kinetics of naproxen and bezafibrate in the presence of activated sludge under aerobic conditions. Experimental results indicated that the adsorption of pharmaceuticals by activated sludge was rapid, and the relative adsorbabilities of the two-target compounds were based on their log Kow and pKa values. The adsorption data could be well interpreted by the pseudo-second-order kinetic model. The degradation process could be described by the pseudo-first-order kinetic model, whereas the pseudo-second-order kinetics were also well suited to describe the degradation process of the selected compounds at low concentrations. Bezafibrate was more easily degraded by activated sludge compared with naproxen. The spiked concentration of the two-target compounds was negatively correlated with k1 and k2s , indicating that the substrate inhibition effect occurred at the range of studied concentrations. Chemical oxygen demand (COD) did not associate with naproxen degradation; thus, COD is not an alternative method that could be applied to investigate natural organic matter's impact on degradation of pharmaceuticals by activated sludge.
authors.affiliation: College of Environmental Science and Engineering, Hunan University, Changsha, People's Republic of China; Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha, People's Republic of China; South China Institute of Environment Sciences, MEP, Guangzhou, People's Republic of China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Tang
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Li
authors.forename: Zhen-Cheng
authors.initials: ZC
authors.lastname: Xu
authors.forename: Qing-Wei
authors.initials: QW
authors.lastname: Guo
authors.forename: Cheng-Yang
authors.initials: CY
authors.lastname: Hong
authors.forename: Yong-Xin
authors.initials: YX
authors.lastname: Bing
mesh_terms: D000332:Aerobiosis; D001629:Bezafibrate / Q000302:isolation & purification* / Q000378:metabolism; D007700:Kinetics; D009288:Naproxen / Q000302:isolation & purification* / Q000378:metabolism; D012722:Sewage / Q000382:microbiology*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D012722:Sewage; D014874:Water Pollutants, Chemical; D009288:Naproxen; D001629:Bezafibrate
keywords: activated sludge; bezafibrate; kinetics; naproxen