title: Factors influencing sorption of ciprofloxacin onto activated sludge: experimental assessment and modelling implications.
abstract: Many of the pharmaceuticals and personal care products occurring in municipal sewage are ionizing substances, and their partitioning behaviour is affected by ionic interactions with solid matrices. In activated sludge systems, such interactions have currently not been adequately understood and described, particularly for zwitterionic chemicals. Here we present an assessment of the effects of pH and iron salt dosing on the sorption of ciprofloxacin onto activated sludge using laboratory experiments and full-scale fate modelling. Experimental results were described with Freundlich isotherms and showed that non-linear sorption occurred under all the conditions tested. The greatest sorption potential was measured at pH=7.4, at which ciprofloxacin is speciated mostly as zwitterion. Iron salt dosing increased sorption under aerobic and, to a lesser extent, anoxic conditions, whereas no effect was registered under anaerobic conditions. The activated sludge model for xenobiotics (ASM-X) was extended with Freundlich-based sorption kinetics and used to predict the fate of ciprofloxacin in a wastewater treatment plant (WWTP). Scenario simulations, using experimental Freundlich parameters, were used to identify whether the assessed factors caused a significant increase of aqueous ciprofloxacin concentration in full-scale bioreactors. Simulation results suggest that a pH increase, rather than a reduction in iron salt dosing, could be responsible for a systematic deterioration of sorption of ciprofloxacin in the WWTP.
authors: Department of Environmental Engineering, Technical University of Denmark (DTU), Kongens Lyngby, Denmark. Electronic address: fabp@env.dtu.dk.
authors: Fabio
authors: F
authors: Polesel
authors: Institute of Hygiene and Environmental Medicine, RWTH Aachen University, Aachen, Germany.
authors: Kai
authors: K
authors: Lehnberg
authors: Institute of Hygiene and Environmental Medicine, RWTH Aachen University, Aachen, Germany.
authors: Wolfgang
authors: W
authors: Dott
authors: Department of Environmental Engineering, Technical University of Denmark (DTU), Kongens Lyngby, Denmark.
authors: Stefan
authors: S
authors: Trapp
authors: Department of Ecotoxicology and Risk Assessment, Norwegian Institute for Water Research (NIVA), Oslo, Norway.
authors: Kevin V
authors: KV
authors: Thomas
authors: Department of Environmental Engineering, Technical University of Denmark (DTU), Kongens Lyngby, Denmark.
authors: Benedek Gy
authors: BG
authors: Plósz
mesh_terms: D000327:Adsorption; D000900:Anti-Bacterial Agents / Q000737:chemistry*; D019149:Bioreactors; D002712:Chlorides / Q000737:chemistry; D002939:Ciprofloxacin / Q000737:chemistry*; D003198:Computer Simulation; D005290:Ferric Compounds / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008962:Models, Theoretical; D012722:Sewage / Q000737:chemistry*; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D002712:Chlorides; D005290:Ferric Compounds; D005296:Ferrous Compounds; D012722:Sewage; D014874:Water Pollutants, Chemical; C020748:ferrous sulfate; D002939:Ciprofloxacin; C024555:ferric chloride
keywords: Activated sludge; Ciprofloxacin; Fate modelling; Sorption; Wastewater treatment; Xenobiotic trace chemicals