1,4-dioxane in German drinking water: Origin, occurrence, and open questions

The persistent, mobile, and toxic ether 1,4-dioxane poses a risk to German drinking water production. Even though groundwater provides the largest share of German drinking water supply, regionally, these resources have to be complemented by surface waters, which are locally exceeding the German drinking water guidance value of 5 μg/L. Contamination predominantly originates from wastewater treatment plant (WWTP) effluents as major point sources. Case studies show that commonly applied raw water extraction methods such as river bank filtration (RBF) do not act as sufficient barriers against source water contamination with 1,4-dioxane, consequently, drinking water concentrations of up to > 2 μg/L were determined. Emission mitigation measures as advanced oxidation processes (AOPs) were assessed and resulted in a reduction of surface and drinking water concentrations. Since 1,4-dioxane has also been proven to be a contaminant in German groundwater in concentrations of up to 152 μg/L at selected sites, drinking water relevant groundwater should be increasingly monitored. •1,4-dioxane in focus of authorities due to advances in REACH regulation.•Surface water contamination translates to occurrence in associated drinking water.•Groundwater occurrence scarcely studied despite high relevance for drinking water.•Maximum 1,4-dioxane concentration in German drinking water: 2.0 μg/L.•Mitigation: Interplay between treatment approaches and preventive measures.