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Veröffentlichung Pilot scale hexavalent chromium removal with reduction, coagulation, filtration and biological iron oxidation(2020) Dippon-Deissler, Urs; Mahringer, Daniel; Ruhl, Aki Sebastian; Zerelli, Sami SofieneCr(VI) is identified as highly toxic, therefore a far-reaching limitation of total chromium or Cr(VI) in drinking water was proposed by the Germany Environment Agency. There is a lack in efficient treatment processes to reach Cr(VI) concentrations below 1 (my)g L-1. In this study, the combination of chemical reduction, coagulation and filtration (RCF) was further developed by adding biological iron removal as filtration step (RCbF). The aim of this enhancement was to reach lower effluent concentrations and a higher robustness regarding process parameters. The effectiveness of Cr(VI) removal was investigated using two-stage pilot-scale waterworks. RCbF reaches Cr(VI) effluent concentrations below 0.5 (my)g L-1 despite variations of pH, filtration velocity, or Cr(VI) influent concentrations. Fe(II) dosage and hence molar excess of Fe(II) over Cr(VI) was identified as the key parameter for Cr(VI) removal. Low oxygen dosage for biological iron removal improved the efficiency of RCbF compared to RCF. The co-precipitation of Cr(III) and Fe(III) as solid solution in the supernatant of the filter bed was promoted by low oxygen concentrations making Cr(VI) the preferred oxidant. RCbF was shown to be a suitable treatment process for reaching a low limit value for total chromium or Cr(VI) concerning technical feasibility. © 2020 The Authors.Veröffentlichung Entfernung von Chrom (VI) mit Reduktion, Koagulation, Filtration und biologischer Eisenoxidation (RCbF) im Pilotmaßstab(2021) Dippon-Deissler, Urs; Mahringer, Daniel; Ruhl, Aki Sebastian; Zerelli, Sami SofieneVeröffentlichung In-situ fixed bed denitrification in sequential biofiltration: laboratory testing of solid substrates(2020) Filter, Josefine; Bosinsky, Christin; Kilinc, Sefine Oksal; Ruhl, Aki SebastianHigh nitrate concentrations in wastewater treatment plant effluents and aquifers can challenge sequential biofiltration systems in preventing nitrite and gas formation in the sand bed, as well as to achieve the regulated limit value for nitrate in potable water reuse applications. This study investigates the introduction of electron donors in the form of organic fixed bed materials as an in-situ anoxic zone into sequential biofiltration systems. Laboratory batch and column tests with straw, soft wood, peat, polylactic acid (PLA), and polycaprolacton (PCL) revealed incomplete denitrification with a hydraulic retention time below 10 h, high organic carbon leaching, especially during the first three months, and gas accumulation within the filter bed. Therefore, ex-situ denitrification prior to oxic biofilters or in a defined side-stream treatment is recommended. No enhanced transformation of trace organic chemicals was observed under nitrate reducing conditions. Peat revealed a sorption potential for 5-methyl-benzotriazole, carbamazepine, benzotriazole, and metoprolol. © 2020 The AuthorsVeröffentlichung Specific adsorption sites and conditions derived by thermal decomposition of activated carbons and adsorbed carbamazepine(2020) Eisentraut, Paul; Dittmann, Daniel; Goedecke, Caroline; Braun, Ulrike; Ruhl, Aki SebastianThe adsorption of organic micropollutants onto activated carbon is a favourable solution for the treatment of drinking water and wastewater. However, these adsorption processes are not sufficiently understood to allow for the appropriate prediction of removal processes. In this study, thermogravimetric analysis, alongside evolved gas analysis, is proposed for the characterisation of micropollutants adsorbed on activated carbon. Varying amounts of carbamazepine were adsorbed onto three different activated carbons, which were subsequently dried, and their thermal decomposition mechanisms examined. The discovery of 55 different pyrolysis products allowed differentiations to be made between specific adsorption sites and conditions. However, the same adsorption mechanisms were found for all samples, which were enhanced by inorganic constituents and oxygen containing surface groups. Furthermore, increasing the loadings led to the evolution of more hydrated decomposition products, whilst parts of the carbamazepine molecules were also integrated into the carbon structure. It was also found that the chemical composition, especially the degree of dehydration of the activated carbon, plays an important role in the adsorption of carbamazepine. Hence, it is thought that the adsorption sites may have a higher adsorption energy for specific adsorbates, when the activated carbon can then potentially increase its degree of graphitisation. © The Author(s) 2020Veröffentlichung Polystyrene microplastics do not affect juvenile brown trout (Salmo trutta f. fario) or modulate effects of the pesticide methiocarb(2020) Schmieg, Hannah; Huppertsberg, Sven; Knepper, Thomas P.; Ruhl, Aki SebastianBackground There has been a rising interest within the scientific community and the public about the environmental risk related to the abundance of microplastics in aquatic environments. Up to now, however, scientific knowledge in this context has been scarce and insufficient for a reliable risk assessment. To remedy this scarcity of data, we investigated possible adverse effects of polystyrene particles (104 particles/L) and the pesticide methiocarb (1 mg/L) in juvenile brown trout (Salmo trutta f. fario) both by themselves as well as in combination after a 96 h laboratory exposure. PS beads (density 1.05 g/mL) were cryogenically milled and fractionated resulting in irregular-shaped particles (<50 (micro)m). Besides body weight of the animals, biomarkers for proteotoxicity (stress protein family Hsp70), oxidative stress (superoxide dismutase, lipid peroxidation), and neurotoxicity (acetylcholinesterase, carboxylesterases) were analyzed. As an indicator of overall health, histopathological effects were studied in liver and gills of exposed fish. Results Polystyrene particles by themselves did not influence any of the investigated biomarkers. In contrast, the exposure to methiocarb led to a significant reduction of the activity of acetylcholinesterase and the two carboxylesterases. Moreover, the tissue integrity of liver and gills was impaired by the pesticide. Body weight, the oxidative stress and the stress protein levels were not influenced by methiocarb. Effects caused by co-exposure of polystyrene microplastics and methiocarb were the same as those caused by methiocarb alone. Conclusions Overall, methiocarb led to negative effects in juvenile brown trout. In contrast, polystyrene microplastics in the tested concentration did not affect the health of juvenile brown trout and did not modulate the toxicity of methiocarb in this fish species. © The Author(s) 2020Veröffentlichung Perfluoroalkyl substances (PFAS) adsorption in drinking water by granular activated carbon: Influence of activated carbon and PFAS characteristics(2021) Cantoni, Beatrice; Turolla, Andrea; Ruhl, Aki Sebastian; Wellmitz, JörgPerfluoroalkyl substances (PFAS) persistence in the environment leads to their presence in drinking water, that is of high concern due to their potential human health risk. Adsorption onto activated carbon (AC) has been identified as an effective technique to remove PFAS. Adsorption isotherms and breakthrough curves, determined by rapid small-scale column tests (RSSCTs), were studied for eight PFAS and four granular ACs, characterized by different origins, porosities and numbers of reactivation cycles. Both batch and RSSCT results highlighted the strong interaction of AC and PFAS characteristics in adsorption capacity. The most important factor affecting AC performance is the surface charge: a positively-charged AC showed higher adsorption capacities with greater Freundlich constants (KF) and later 50% breakthroughs compared to the AC with neutral surface. Among the positively-charged ACs, a microporous AC demonstrated higher adsorption capacities for hydrophilic and marginally hydrophobic PFAS, while the mesoporous AC performed better for more hydrophobic PFAS, possibly due to lower pore blockage by organic matter. These results were confirmed at full-scale through a one-year monitoring campaign, in which samples were collected at the inlets and outlets of GAC systems in 17 drinking water treatment plants spread in a wide urban area, where the four analyzed ACs are used. © 2021 Elsevier B.V.Veröffentlichung Varying attenuation of trace organic chemicals in natural treatment - a review of key influential factors(2021) Filter, Josefine; Zhiteneva, Veronika; Ruhl, Aki Sebastian; Vick, CarstenThe removal of trace organic chemicals (TOrCs) from treated wastewater and impacted surface water through managed aquifer recharge (MAR) has been extensively studied under a variety of water quality and operating conditions and at various experimental scales. The primary mechanism thought to dictate removal over the long term is biodegradation by microorganisms present in the system. This review of removal percentages observed in biologically active filtration systems reported in the peer-reviewed literature may serve as the basis to identify future indicators for persistence, as well as variable and efficient removal in MAR systems. A noticeable variation in reported removal percentages (standard deviation above 30%) was observed for 24 of the 49 most commonly studied TOrCs. Such variations suggest a rather inconsistent capacity of biologically active filter systems to remove these TOrCs. Therefore, operational parameters such as the change in dissolved organic carbon ((Delta)DOC) during treatment, hydraulic retention time (HRT), filter material, and redox conditions were correlated to the associated TOrC removal percentages to determine whether a data-based relationship could be elucidated. Interestingly, 11 out of the 24 compounds demonstrated increased removal with increasing (Delta)DOC concentrations. Furthermore, 10 compounds exhibited a positive correlation with HRT. Based on the evaluated data, a minimum HRT of 0.5-1 day is recommended for removal of most compounds. © 2021 Elsevier Ltd.Veröffentlichung System zur Untersuchung der Sedimentation von Mikroplastik (10-300 (micro)m)(2021) Dittmar, Stefan; Pries, J.; Ruhl, Aki SebastianIm Vergleich zu gelösten Stoffen unterliegen partikuläre Substanzen wie Mikroplastik (MP) in aquatischen Systemen anderen Dynamiken. Die wirksamen Transportmechanismen wie Deposition und Resuspendierung sowie Flotation und Sedimentation sind dabei nicht nur von Charakteristiken des betrachteten Gewässers, sondern in höherem Maß auch von Eigenschaften der Partikel selbst abhängig. Da gängige Polymere sowohl geringere (zum Beispiel PE, PP) als auch höhere Dichten (zum Beispiel PS, PET, PVC) als Wasser aufweisen, flotieren einige MP-Partikel, wohingegen andere sedimentieren. Partikeldichte, -größe und -form können potenziell wiederum durch Agglomeration, Fragmentierung sowie biologischen Bewuchs verändert werden. Quelle: https://onlinelibrary.wiley.com/Veröffentlichung Characterization of activated carbons for water treatment using TGA-FTIR for analysis of oxygen-containing functional groups(2022) Dittmann, Daniel; Zietzschmann, Frederik; Ruhl, Aki Sebastian; Schumann, Pia; Saal, Leon; Braun, UlrikeWater treatment with activated carbon (AC) is an established method for the removal of organic micropollutants and natural organic matter. However, it is not yet possible to predict the removal of individual pollutants. An appropriate material characterization, matching adsorption processes in water, might be the missing piece in the puzzle. To this end, this study examined 25 different commercially available ACs to evaluate their material properties. Frequently reported analyses, including N2 adsorption/desorption, CHNS(O), point of zero charge (PZC) analysis, and X-ray photoelectron spectroscopy (XPS) were conducted on a selected subset of powdered ACs. Inorganic elements examined using X-ray fluorescence (XRF) and X-ray iffraction spectroscopy (XRD) revealed that relative elemental contents were distinctive to the individual AC's raw material and activation procedure. This study also is the first to use thermogravimetric analysis (TGA) coupled to Fourier-transform infrared spectroscopy (FTIR) to conduct quantitative analyses of functional surface oxygen groups (SOGs: carboxylic acid, anhydride, lactone, phenol, carbonyl, and pyrone groups) on such a large number of ACs. The comparably economical TGA provides a surrogate for the PZC, the oxygen and carbon content, as well as mass loss profiles that depict the AC's chemistry. Furthermore, we found that SOG contents determined by TGA-FTIR covered a wide individual range and depended on the raw material of the AC. Surface chemistry might therefore provide an indication of the suitability of a particular AC for a variety of target substances in different target waters. TGA and TGA-FTIR can help practitioners to control AC use in waterworks or wastewater treatment plants.Veröffentlichung Indications of recent warm and dry summers' impact on private wells for drinking-water supply in Germany: a review of press articles(2022) Görnt, Annika; Rickert, Bettina; Vogelsang, L.; Ruhl, Aki SebastianClimatic changes lead to seasonal droughts with declining groundwater levels, and - especially in rural regions - private wells in the upper aquifer might fall dry. However, only limited information and no systematic administrative reporting of the extent are available for Germany yet. Therefore, a systematic analysis of newspaper articles as a promising source of information was conducted for the extraordinarily hot summers of 2018, 2019 and 2020. The results of the database searches were analysed with respect to frequency and local and regional hotspots, relations to climatic data, extent of the reported dry-fallings and emergency water supply. The analysis indicates hotspots particularly for the federal states of Saxony, where a subsidy programme for connecting to the public water supply was reissued in 2019, for Bavaria and North Rhine-Westphalia. Emergency supply was realised through various approaches. It was partly required until the winter months and did not always have drinking-water quality. As private wells are particularly vulnerable to the effects of climate change, their operators should be involved as a stakeholder group in future discussions about allocating water resources to increasingly competing uses in periods of scarcity. © 2022 The Authors
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