title: Short and long term biosorption of silica-coated iron oxide nanoparticles in heterotrophic biofilms.
abstract: The increased application of engineered nanoparticles (ENP) in industrial processes and consumer products has raised concerns about their impact on health and environmental safety. When ENP enter the global water cycle by e.g. wastewater streams, wastewater treatment plants (WWTP) represent potential sinks for ENP. During biological WWT, the attachment of ENP to biofilms is responsible for the desired removal of ENP from the water phase avoiding their release into the aquatic environment. However, the fundamental mechanisms guiding the interactions between ENP and biofilms are not yet fully understood. Therefore, this study investigates the behavior and biosorption of inorganic ENP, here magnetic iron oxide nanoparticles coated with silica (scFe3O4-NP), with heterotrophic biofilms at different time scales. Their magnetic properties enable to follow scFe3O4-NP in the biofilm system by a magnetic susceptibility balance and magnetic resonance imaging. Biofilms were exposed to scFe3O4-NP at short contact times (5 min) in flow cells and complementary, scFe3O4-NP were introduced into a moving bed biofilm reactor (MBBR) to be observed for 27 d. Mass balances revealed that scFe3O4-NP sorbed to the biofilm within a few minutes, but that the total biosorption was rather low (3.2 μg Fe/mg TSS). scFe3O4-NP mainly sorbed to the biofilm surface inducing the detachment of outer biofilm parts starting after an exposure time of 3h in the MBBR. The biosorption depended on the exposure concentration of scFe3O4-NP, but less on the contact time. Most scFe3O4-NP exited the flow cell (up to 65%) and the MBBR (57%) via the effluent. This effect was favored by the stabilization of scFe3O4-NP in the bulk liquid by organic matter leading to a low retention capacity of the MBBR system. The results contribute to improve our understanding about the fate of ENP in environmental and in technical biofilm systems and give indications for future investigations needed.
authors.affiliation: Engler-Bunte-Institut, Chair of Water Chemistry and Water Technology, Karlsruhe Institute of Technology (KIT), Engler-Bunte-Ring 1, 76131 Karlsruhe, Germany.
authors.forename: Maria P
authors.initials: MP
authors.lastname: Herrling
authors.affiliation: Engler-Bunte-Institut, Chair of Water Chemistry and Water Technology, Karlsruhe Institute of Technology (KIT), Engler-Bunte-Ring 1, 76131 Karlsruhe, Germany; Urban Bioengineering for Resource Recovery, Bauhaus-Institute for Infrastructure Solutions, Bauhaus-Universität Weimar, Coudraystraße 7, 99423 Weimar, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Lackner
authors.affiliation: Engler-Bunte-Institut, Chair of Water Chemistry and Water Technology, Karlsruhe Institute of Technology (KIT), Engler-Bunte-Ring 1, 76131 Karlsruhe, Germany.
authors.forename: Oleg
authors.initials: O
authors.lastname: Tatti
authors.affiliation: Pro(2)NMR, Institute for Biological Interfaces 4 and Institute for Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology, Adenauerring 20b, 76131 Karlsruhe, Germany.
authors.forename: Gisela
authors.initials: G
authors.lastname: Guthausen
authors.affiliation: Engler-Bunte-Institut, Chair of Water Chemistry and Water Technology, Karlsruhe Institute of Technology (KIT), Engler-Bunte-Ring 1, 76131 Karlsruhe, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Delay
authors.affiliation: Institute of Functional Interfaces, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Franzreb
authors.affiliation: Engler-Bunte-Institut, Chair of Water Chemistry and Water Technology, Karlsruhe Institute of Technology (KIT), Engler-Bunte-Ring 1, 76131 Karlsruhe, Germany; DVGW Research Laboratories for Water Chemistry and Water Technology, Engler-Bunte-Ring 1, 76131 Karlsruhe, Germany. Electronic address: harald.horn@kit.edu.
authors.forename: Harald
authors.initials: H
authors.lastname: Horn
mesh_terms: D001673:Biodegradation, Environmental; D018441:Biofilms; D005290:Ferric Compounds / Q000378:metabolism*; D053758:Nanoparticles / Q000032:analysis / Q000378:metabolism*; D012822:Silicon Dioxide / Q000737:chemistry; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism*
chemical_list: D005290:Ferric Compounds; D014874:Water Pollutants, Chemical; C000499:ferric oxide; D012822:Silicon Dioxide
keywords: Biomass; Magnetic nanoparticles; Magnetic susceptibility; Mass balance; Wastewater treatment