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Organic Trace Substances Relevant for Drinking Water

Author(s): Assessing their Elimination through Bank Filtration
Congress: 2008
Author(s): Gabriele Wessel, Gesche Grützmacher, Ingrid Chorus

Keyword(s): trace contaminants, water supply, bank filtration, complexing agents, perfluorinated compounds, pesticides, metabolites
AbstractThe project “Organic Trace Substances Relevant for Drinking Water – Assessing their Elimination through Bank Filtration (TRACE)” aims at giving an up-to-date overview of the potential risk resulting from the occurrence of chelating agents, perfluorinated compounds (PFCs) and selected pesticides in surface waters and to show if there is a potential for the substances to persist during bank filtration and artificial recharge. During the first phase of the project which is subject of the presentation, a literature study was conducted addressing their occurrence (in the Berlin region and elsewhere), amounts produced as well as data on their persistence in the subsurface. This was the basis for a decision on the substance applied in the field scale experiments at the UBAs experimental field during the following project phase. Using freely available databases (e.g. ULIDAT, DIMDI, Tiborder) 1148 references were screened for their relevance to these topics, and 450 of these were classified as relevant. Of these, so far the 223 most important references have been compiled in an ACCESS database which comprises data on the data origin as well as on specific values (e.g. measured concentrations, amounts produced, use, main metabolites, sources, pathways in the environment). The database links this information so that output forms (“fact sheets”) can be created that summarize all data for one specific substance. The regarded substances were subsequently classified according to the criteria: usage / production, occurrence in surface water (if possible also in groundwater and bank filtrate), degradation potential, biological degradability, production of relevant metabolites and toxicity. For the chelating agents three substance groups were examined closely: aminocarboxylates, hydrocarboxylates and phosphonates (all other substance groups were found to be irrelevant due to total biodegradability). The aminocarboxylates were found to be produced in highest numbers and to occur most frequently (especially EDTA, PDTA, NTA and DTPA). There are, however, already extensive investigations on this field so that few knowledge gaps were identified. Hydrocarboxylates are produced in lesser amounts and for some ready biological degradability has been shown. For these reasons further investigations are not a priority. Phosphonates produce relevant metabolites (phosphates that enhance eutrophication) and are produced in high amounts (> 1000 t/a). This substance group is therefore recommended for further investigations. Currently a variety of research projects cover the field of perfluorinated compounds (PFCs) that occur in aquatic environments world wide and whose toxicity and persistence is not yet clearly determined. Most investigations aim at the main substances of this group: PFOA and PFOS. These are, however, currently being replaced by shorter chained PFCs on which investigations are lacking. This substance group is therefore also of interest for further investigations. For the pesticides glyphosate and isoproturone high production rates and frequent occurrence in surface and groundwater world wide were determined. Due to this fact and to the presence of relevant metabolites (e.g. AMPA) as well as to limited knowledge on their fate during underground passage these substances were classified as highly interesting for further investigations. Therefore glyphosate was selected for the field scale studies in the second phase of the project.
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