Organisationseinheit: Deutschland, Umweltbundesamt, Fachgebiet II.3.3 - Wasseraufbereitung
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Berlin
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Publikationen
Bromate formation potential during ozonation of wastewater treatment plant effluents
(2026) Seibel, Hannah Katharina; Sauter, Daniel; Gnirss, Regina; Ruhl, Aki Sebastian
Ozonation is an established advanced treatment process to transform organic micropollutants present in wastewater treatment plant effluents. In the presence of bromide, ozone treatment can cause formation of the oxidation byproduct bromate. Due to its potential carcinogenicity, its concentration in drinking water is regulated and limited to 10 μg/L in the European Union. Understanding relevant influences on bromate formation and potential control options is crucial to ensuring surface water quality and safe drinking water in case of semi-closed water cycles. This study investigates the bromate formation potential for four wastewater treatment plant effluents of the largest German city Berlin. Laboratory-scale ozonation experiments were conducted with varying ozone doses and bromide concentrations to determine bromate formation for different conditions that might occur during real operation. The results show native bromide concentrations of 0.14 to 0.32 mg/L and bromate concentrations of 0.3 to 1.3 μg/L for ozone consumptions around 0.7 mg/mg O3/DOC at pH values between 7 and 8. This corresponds to bromate yields of 0.2 to 0.6% (mg/mg bromate/bromide). Splitting the ozone dose into multiple smaller doses proved to be an efficient bromate control option for high specific ozone consumptions, with up to 48% less bromate formation. The results underline that the bromate formation potential in Berlin wastewater treatment plants does not limit ozonation as advanced wastewater treatment, since bromate concentrations of all plants were significantly below the drinking water limit of 10 μg/L for specific ozone consumptions around 0.7 mg/mg O3/DOC, even at artificially elevated bromide concentrations. © 2026 The Authors.
Hexavalent chromium (Cr(VI)) removal by reduction-coagulation-filtration (RCF) combined with deacidification in drinking water treatment
(2026) Dördelmann, Oliver; Hahn, Stefan; Al-Ameer Abadi, Mohammad; Panglisch, Stefan; Mahringer, Daniel
Excess dissolved carbon dioxide (CO2) is frequently encountered in natural groundwaters, originating from both geochemical and biological processes. In the investigated case, contamination of groundwater with toxic hexavalent chromium (Cr(VI)) occurred due to anthropogenic activities. The co-occurrence of CO2 and Cr(VI) posed a distinct challenge for water treatment, as multiple process steps need to be tailored to remove both substances at the same time. This study investigates an integrated treatment approach specifically developed for groundwater containing elevated levels of both Cr(VI) and CO2. The process combines reduction coagulation filtration (RCF) with ferrous iron (Fe(II)) dosage with limestone filtration for concurrent Cr(VI) removal and water deacidification. A pilot plant with two parallel filters—one filled with dense limestone and the other with porous limestone—was operated under varying Fe(II) dosages (Fe(II), 0.3–1.0 mg/L) and filtration velocities (4.4–15.5 m/h). Results demonstrate that the RCF process achieved efficient Cr(VI) removal at moderate Fe(II) concentrations (<1.0 mg/L), with no breakthrough or reoxidation observed. Limestone filtration efficiently increased pH, calcium concentration, and buffer capacity, thereby decarbonating the water. Porous limestone showed higher reactivity than the dense limestone commonly used. Analysis of backwash sludge confirmed stable chromium retention and low residual metal concentrations in the supernatant. These findings confirm that the integrated RCF–limestone process provides an effective and cost-efficient solution for treating groundwater impacted by anthropogenic Cr(VI) and naturally elevated CO2 concentration. © 2026 The Authors.
Complexity and challenges in agricultural water reuse monitoring from a German perspective
(2025) Hasselder, Pascal; Helmecke, Manuela; Tiehm, Andreas; Aumeier, Benedikt Maximilian; Förster, Christina; Zahn, Daniel; Ho, Johannes; Stapf, Michael; Zacharias, Nicole; Dockhorn, Thomas; Miehe, Ulf; Ruhl, Aki Sebastian
Agricultural water reuse is one approach to mitigate water stress. In addition to the minimum requirements, the European water-reuse regulation 2020/741 mandates a risk management approach for agricultural water reuse. In contrast to the microbiological monitoring, the extent of the chemical risk assessment and monitoring is not clearly defined. The resulting complexity of a typical agricultural water-reuse scheme was analyzed. Potentially relevant parameters were identified based on European and German regulatory frameworks, concerning key subjects of protection. An interdisciplinary assessment of efforts and challenges, regarding required analyses, was accomplished, using expertise from recent research investigating agricultural water reuse in Germany. Suggestions were provided for disinfection validation, microbiological monitoring parameters and analytical methods. Additionally, chemical indicator parameters were suggested to address relevant processes during monitoring. Both microbiological and chemical parameters presented analytical challenges, which were described with future needs to support water-reuse implementation. Costs for analyses were estimated using available price information, highlighting the high costs of certain analyses, especially for organic micropollutants. Therefore, analyses need to be further facilitated by the application of process indicators and the implementation of cost-effective, multi-target methods tailored to the requirements of risk management for agricultural water reuse.© Author(s) 2025
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