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Activated soil filters for removal of biocides from contaminated run-off and waste-waters |
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| Authors: | Bester Kai Banzhaf Stefan Burkhardt Michael Janzen Niklas Niederstrasser Bernd Scheytt Traugott |
| Affiliation: | a Department of Environmental Chemistry and -Microbiology, National Environmental Research Institute, Aarhus University, Frederiksborgsvej 399, 4000 Roskilde, Denmark b Institute for Environmental Analytical Chemistry, University Duisburg-Essen, Universitätsstr 15, 45145 Essen, Germany c University of Applied Science, Institute of Environmental and Process Engineering UMTEC Oberseestrasse 10, 8640 Rapperswil, Switzerland d Department of Applied Geosciences, Technische Universität Berlin, Ernst-Reuter-Platz 1, 10587 Berlin, Germany |
| Abstract: | Building facades can be equipped with biocides to prevent formation of algal, fungal and bacterial films. Thus run-off waters may contain these highly active compounds. In this study, the removal of several groups of biocides from contaminated waters by means of an activated soil filter was studied.A technical scale activated vertical soil filter (biofilter) with different layers (peat, sand and gravel), was planted with reed (Phragmites australis) and used to study the removal rates and fate of hydrophilic to moderate hydrophobic (log Kow 1.8-4.4) biocides and biocide metabolites such as: Terbutryn, Cybutryn (Irgarol® 1051), Descyclopropyl-Cybutryn (Cybutryn and Terbutryn metabolite), Isoproturon, Diuron, and its metabolite Diuron-desmonomethyl, Benzo-isothiazolinone, n-Octyl-isothiazolinone, Dichloro-n-octylisothiazolinone and Iodocarbamate (Iodocarb). Three experiments were performed: the first one (36 d) under low flow conditions (61 L m−2 d−1) reached removal rates between 82% and 100%. The second one was performed to study high flow conditions: During this experiment, water was added as a pulse to the filter system with a hydraulic load of 255 L m−2 within 5 min (retention time <1 h). During this experiment the removal rates of the compounds decreased drastically. For five compounds (Cybutryn, Descyclopropyl-Cybutryn, Diuron, Isoproturon, and Iodocarb) the removal dropped temporarily below 60%, while it was always above 70% for the others (Terbutryn, Benzo-isothiazolinone, n-Octyl-isothiazolinone, Dichloro-n-octylisothiazolinone). However, this removal is a considerable improvement compared to direct discharge into surface waters or infiltration into soil without appropriate removal. In the last experiment the removal efficiencies of the different layers were studied. Though the peat layer was responsible for most of the removal, the sand and gravel layers also contributed significantly for some compounds. All compounds are rather removed by degradation than by sorption. |
| Keywords: | Biocides Activated soil filter Storm water Triazines Phenylureas Isothiazolinones |
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