This study presents the latest results of the groundwater monitoring of a research project, which tested an innovative pump and treat method in combination with an in-situ remediation. This technique ...was assessed on an abandoned site in Austria, where two hot spots of hexavalent chromium (Cr(VI)) were located. For the in-situ remediation, a strong reducing agent (sodium dithionite) was injected into the underground to reduce Cr(VI) to Cr(III) by using different injection strategies. Throughout this treatment, part of the Cr(VI) is mobilized and not instantly reduced. To prevent a further spreading of the mobilized Cr(VI), the pump and treat method, which uses zero-valent iron to clean the groundwater, was installed downgradient of the hot spots. Based on the groundwater sample analyses, it was possible to distinguish different remediation phases, characterized by excess chromate and excess sulfite. During the excess sulfite conditions, Cr(VI) was successfully removed from the system, but after terminating the sodium dithionite injection, the Cr(VI) rebounded.
This study presents a detailed mineralogical and chemical characterization of a chromium contamination in alluvial deposits underlying a leather tannery in Austria. Drill cores revealed that the ...contamination is represented by a black layer that exhibits sharp boundaries with adjacent brown alluvial sediments. This black layer is located below the groundwater table and begins at the source of the contamination. The black layer thickens with increasing distance from the source and the depth of the upper boundary remains at the same level relative to the surface. Mineralogical and chemical investigations showed that the black layer contains reduced Cr phases, a Cr(III) hydroxide and a Cr(III)-Ca-containing hydrocalcite, which are present as discrete grains, in vein-like pore spaces and/or as a coating around mineral grains. Cr(VI) is nearly only present above the groundwater table. Our 2-D model predicts a longitudinal spread of the black layer of approximately 37 m downgradient from the source and a maximum transversal spread of approximately 10 m. This study shows that, if the source of the contamination is not eliminated, the plume will increase continuously farther downgradient.
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•A striking black layer contains Cr(III) hydroxide and Cr(III)-Ca-hydrocalcite.•Hexavalent chromium is found in alluvial sediments above the black layer.•The shape of the Cr(tot) plume reveals the source of the contamination: a soakaway.•A certain depth and associated reducing strength is needed to develop the black layer.•A 2-D model predicts lateral extents of ∼37 m (longitudinal) and ∼10 m (transversal) of the black layer.
This study presents the results of a research project dealing with the degradation of dissolved tetrachloroethene, MTBE and clopyralid by using a boron-doped diamond electrode, zero-valent iron in a ...fluidized bed reactor and ultraviolet radiation. These treatment methods were tested alone, in any combination of two as well as in combination of all three of them to identify emerging synergy effects. Additionally, the influence of adding H2O2 or H2O2 + H2SO4 is investigated. The experiments revealed that the treatment methods alone were able to decrease the organic contaminant concentrations, yet, the decomposition rate was not very sufficient. Applying the BDD yielded the highest decomposition rates, however, this degradation was accompanied by metabolite production. By combining two methods and adding H2O2, the decomposition was enhanced significantly for any combination. These removal rates were further increased by using the combination of the three treatment methods and adding H2O2 or H2O2 + H2SO4. These high removal rates were not achieved by solely using the combination of the three methods without further addition of chemicals. This research demonstrates the potential, but also the limitations of the investigated system.
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•Combining a boron-doped diamond electrode, zero-valent iron and ultraviolet radiation.•Combined three treatment methods for the degradation of dissolved organic compounds.•Tetrachloroethene, MTBE and clopyralid were successfully removed from the waters.•Treatment efficiency was significantly enhanced by adding H2O2 or H2O2 + H2SO4.•Given thresholds were reached by using the combination and H2O2 or H2O2 + H2SO4.
Zero-valent iron (ZVI) has been used for water treatment for more than 160 years. However, passivation of its surface often constituted a problem which could only be tackled recently by the ...innovative Ferrodecont process using a fluidized bed reactor. In this study, pilot scale experiments for the removal of Mo, Cr, W, Cu, Ag and Zn from two industrial waste water samples and lab-scale experiments for the beneficiation of the abrasion products are presented to integrate the Ferrodecont process into a complete recycling process chain. Firstly, 38.5 % of Cu was removed from sample A, yielding abrasion products containing 33.1 wt% Cu as metallic copper (Cu) and various Cu compounds. The treatment of sample B removed 99.8 % of Mo, yielding abrasion products containing 17.8 wt% of Mo as amorphous phases or adsorbed species. Thermal treatment (1300 °C) of the abrasion product A indicated a reduction of delafossite to metallic Cu according to differential scanning calorimetry (DSC), thermogravimetry (TG) and X-ray diffraction (XRD), which was successfully separated from the magnetic iron phases. Hydrometallurgical treatment (1.5 M NaOH, 3 d, liquid:solid ratio (L:S) = 15:1) of sample B yielded aqueous extracts with Mo concentrations of 5820 to 6300 mgL−1. In conclusion, this corresponds to an up to 53-fold enrichment of Mo during the entire process chain.
Zusammenfassung
Im Bereich der Altlastensanierung wird das Verfahren, das sich bei der Behandlung der ungesättigten Bodenzone bewährt hat, nun auf die gesättigte Bodenzone übertragen. ...Hydrogeologisch-hydrogeochemische Modellierungen der zeitlichen und räumlichen Entwicklung der Konzentration der Cr-Spezies sollen eine Abschätzung des zeitlichen Rahmens einer Sanierung ermöglichen. Langfristig scheint auch im Bereich der Altlastensanierung die Anwendung der Technologie auf andere Elemente als Chrom, z. B. Arsen, möglich.
Das ferroDECONT-Verfahren basiert auf der Fixierung gelöster Metalle mittels Reduktion und/oder Adsorption und/oder Fällung an nullwertigem Eisen in einer Wirbelschicht. Aufgrund der Vielzahl der fixierbaren Metalle bietet sich ein weites Spektrum von Anwendungsfeldern, sowohl in der Altlastensanierung als auch in der recyclingorientierten Abwasserbehandlung.
Im Bereich der Abwasserbehandlung zeigen erste Ergebnisse aus Laborversuchen, dass die meisten kritischen und potenziell kritischen Metalle mit dem ferroDECONT-Verfahren aus dem Wasser entfernt werden können.
Background: The prognostic performance of the residual cancer burden (RCB) score is a promising tool for breast cancer patients undergoing neoadjuvant therapy. We independently evaluated the ...prognostic value of RCB scores in an extended validation cohort. Additionally, we analyzed the association between chemotherapy dose reduction and RCB scores. Methods: In this extended validation study, 367 breast cancer patients with available RCB scores were followed up for recurrence-free survival (RFS), distant disease-free survival (DDFS), and overall survival (OS). We also computed standardized cumulative doses of anthracyclines and taxanes (A/Ts) to investigate a potential interaction between neoadjuvant chemotherapy dose reduction and RCB scores. Results: Higher RCB scores were consistently associated with adverse clinical outcomes across different molecular subtypes (HR for RFS = 1.60, 95% CI 1.33–1.93, p < 0.0001; HR for DDFS = 1.70, 95% CI 1.39–2.05, p < 0.0001; HR for OS = 1.67, 95% CI 1.34–2.08, p < 0.0001). The adverse impact prevailed throughout 5 years of follow-up, with a peak for relapse risk between 1–2 years after surgery. Clinical outcomes of patients with RCB class 1 did not differ substantially at 5 years compared to RCB class 0. A total of 180 patients (49.1%) underwent dose reduction of neoadjuvant A/T chemotherapy. We observed a statistically significant interaction between dose reduction and higher RCB scores (interaction p-value = 0.042). Conclusion: Our results confirm RCB score as a prognostic marker for RFS, DDFS, and OS independent of the molecular subtype. Importantly, we show that lower doses of cumulative neoadjuvant A/T were associated with higher RCB scores in patients who required a dose reduction.
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