Design of Polymer-Embedded Heterogeneous Fenton Catalysts for the Conversion of Organic Trace Compounds

Advanced oxidation processes are the main way to remove persistent organic trace compounds from water. For these processes, heterogeneous Fenton catalysts with low iron leaching and high catalytic activity are required. Here, the preparation of such catalysts consisting of silica-supported iron oxide (Fe2O3/SiOx) embedded in thermoplastic polymers is presented. The iron oxide catalysts are prepared by a facile sol–gel procedure followed by thermal annealing (calcination). These materials are mixed in a melt compounding process with modified polypropylenes to stabilize the Fe2O3 catalytic centers and to further reduce the iron leaching. The catalytic activity of the composites is analyzed by means of the Reactive Black 5 (RB5) assay, as well as by the conversion of phenol which is used as an example of an organic trace compound. It is demonstrated that embedding of silica-supported iron oxide in modified polypropylene turns the reaction order from pseudo-first order (found for Fe2O3/SiOx catalysts), which represents a mainly homogeneous Fenton reaction, to pseudo-zeroth order in the polymer composites, indicating a mainly heterogeneous, surface-diffusion-controlled process.

Analysing surface water-groundwater interactions on selected sites of the River Moselle: Identifying transport processes along an important inland waterway in Germany

<p>Hydraulic engineering structures like locks affect the natural hydraulic conditions and have a relevant impact on surface water – groundwater interactions due to enlarging the hydraulic gradient. For this, these sites are excellent areas to study associated flow paths, mass transport and their spatial and temporal variability in higher detail. However, no large-scale study at an inland waterway is available in Germany until now.</p><p>Our work aims to close this gap by applying a multiparameter approach for analyzing surface water-groundwater-interactions by using pH, electrical conductivity, major ions in combination with various other tracers like stable water isotopes, 222-Rn, and tritium. In this context, we also investigate the usability of organic trace compounds and their associated transformation products as potential new tracers.</p><p>The main study approach is based on the hypothesis that i) gaining stream sections show relatively high 222-Rn concentrations originating from discharging groundwater and ii) losing stream sections which are characterized by low 222-Rn concentrations as well as lower tritium and organic trace compounds inventories compared to unaffected areas.</p><p>During different flow-scenarios of the river Moselle, we test these hypotheses by means of a high-resolution longitudinal sampling at 2 km intervals of the main stream (along 242 km) and its major tributaries in combination with groundwater sampling at numerous wells.</p><p>Here, we present the first results of the longitudinal sampling campaign of the river Moselle in October 2020, which took place during intermediate flow conditions (Q=200 m³/s). We used on-site and in-situ 222-Rn measurements and electrical conductivity as a tracer to immediately identify zones along the Moselle with increased groundwater inflow.</p><p>With the use of these tracers, we will deepen the conceptual process understanding of surface water – groundwater interactions occurring at larger streams and during different flow conditions, which may lead to a general river characterization of losing and gaining stream reaches. Moreover, understanding the sources of water compounds and the processes involved during transportation and transformation is crucial for maintaining a good quality of the water body, which is key for proper water management. The findings obtained in the region of the Moselle river might be further transferred to other waterways and support decision making.</p>

Reduction of organic trace compounds and fresh water consumption by recovery of advanced oxidation processes treated industrial wastewater

Ozone (O3) has been used successfully in advanced wastewater treatment in paper mills, other sectors and municipalities. To solve the water problems of regions lacking fresh water, wastewater treated by advanced oxidation processes (AOPs) can substitute fresh water in highly water-consuming industries. Results of this study have shown that paper strength properties are not impaired and whiteness is slightly impaired only when reusing paper mill wastewater. Furthermore, organic trace compounds are becoming an issue in the German paper industry. The results of this study have shown that AOPs are capable of improving wastewater quality by reducing organic load, colour and organic trace compounds.

Characteristics and evaluation of natural attenuation processes for organic micropollutant removal during riverbank filtration

In industrialized and urban areas, surface waters are to a high level exposed to anthropogenic environmental impacts and are therefore often contaminated with a wide spectrum of organic trace compounds. Riverbank filtration is a well established technique in Europe and is most often used as an important component of the multiple-barrier system. During its underground passage, surface water undergoes a diversity of physical, biological and chemical processes, improving water quality significantly and adjusting it in ideal cases to the quality of natural groundwater. By means of examples taken from recent research projects and related to organic micropollutants currently under discussion, this contribution will report on characteristics of riverbank filtration with regard to its purification capacity for different classes of organic micropollutants.

Risk assessment for organic trace compounds in wastewater: comparison of conventional and advanced treatment

The elimination of organic trace compounds in municipal wastewater was analysed at three German wastewater treatment plants. Additionally, the effects of advanced treatment, membrane filtration, adsorption and oxidation processes were investigated. To assess the ecotoxicity of effluents, a number of tools were used: substance-specific evaluation, case studies for combined effects and risk assessment on the basis of cumulative parameters. The results of the research projects revealed that aquatic environmental risks can be reduced significantly using advanced treatment technologies for wastewater treatment plants.