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Paper des Monats
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Eingeladener Vortrag
- nein (35)
When reusing or disposing of contaminated granular waste materials there is a need to evaluate how the contaminants will interact on the pathway soil-groundwater and the effect this interaction will have on the surrounding environment. While column testing can provide a closer approximation to field percolation conditions than batch testing, there is still a need to develop column testing procedures that consider the requirements of practical testing time frames. This study evaluates the effect of different column contact times (2.5, 5, and 16 h) on the release of inorganic constituents from bottom ash and demolition waste, two commonly reused granular materials. Leaching data for representative constituents of concern, such as copper, chromium, sulfate and chloride, as well as pH and electrical conductivity was compared for all different contact times studied.
Results for the materials investigated in this study showed that variations in contact time have no significant effect on the release of the selected constituents and leaching parameters at low liquid to solid ratios. However, after a liquid to solid ratio of 1 L/kg, the effect is more noticeable, and higher contact times show lower pH values as well as a reduction in the release of constituents of concern from bottom ash. In the case of demolition waste, the variation of contact time did not have a strong effect on the leaching behavior.
This article presents a snapshot of key issues regarding characterization of granular waste materials with respect to their reuse as alternative construction materials, and the factors that need to be considered in their reutilization in order to comply with soil and groundwater protection regulations.
Thermische Bodenbehandlung
(2008)
A sustainable recycling of photovoltaic (PV) thin film modules gains in importance due to the considerable growing of the PV market and the increasing scarcity of the resources for semiconductor materials. The paper presents the development of two strategies for thin film PV recycling based on (wet) mechanical processing for broken modules, and combined thermal and mechanical methods for end-of-life modules. The feasibility of the processing steps was demonstrated in laboratory scale as well as in semi-technical scale using the example of CdTe and CIS modules. Pre-concentrated valuables In and Te from wet mechanical processing can be purified to the appropriate grade for the production of new modules.
An advantage of the wet mechanical processing in comparison to the conventional procedure might be the usage of no or a small amount of chemicals during the several steps.
Some measures are necessary in order to increase the efficiency of the wet mechanical processing regarding the improvement of the valuable yield and the related enrichment of the semiconductor material.
The investigation of the environmental impacts of both recycling strategies indicates that the strategy, which includes wet mechanical separation, has clear advantages in comparison to the thermal treatment or disposal on landfills.
Leaching experiments on the release of heavy metals and PAH from C&D waste and MSWI bottom ash
(2010)
Leaching tests are fundamental tools for the assessment of long-term impact of
contaminated waste materials on the soil-groundwater pathway. Waste materials should be
tested under conditions equal to their actual application in re-use scenarios to achieve reliable
results. Since the standards for leaching procedures available on international level so far are
either not validated or considered inadequate in respect to coarse grained materials, new
standards had to be developed. Therefore column percolation and batch test procedures have
been standardized and validated to enable their introduction to new German regulations
concerning waste management. Practical aspects of the test procedures as well as the
boundary conditions compared to the already existing standards will be described. Examples
including round robin test results will be given to justify the selection of the new
specifications.
Resource consumption is always accompanied by environmental impacts. In most cases, it is not possible to quantify the extent of such negative impacts. However, the external cost of uranium mining in Germany can be estimated at 30 Euro/kg U. The environmental impact can be reduced when waste materials are processed, so that their use as a secondary raw material, substituting for natural resources, is possible. The recyclability of waste materials depends on the price of a resource and the concentration of the component in the waste.
Permeable reactive barriers
(2005)
Behaviour of uranium in elemental iron and hydroxyapatite reactive barriers: column experiments
(2005)
Long-term performance of permeable reactive barriers has been investigated in laboratory experiments using elemental iron and hydroxyapatite as reactive materials and uranium as contaminant. Accelerated testing has been performed by applying elevated pollutant concentration and an increased flow velocity. The spatial distribution of uranium in the test columns has been investigated using a radioactive tracer. The results show that the migration pattern exhibits a linear behaviour.
This study was undertaken to investigate the long-term performance of elemental iron as reactive material for the removal of uranium in passive groundwater remediation systems. By using 237U as a radioindicator it was possible to track the movement of the contamination front through a test column without taking samples or dismantling the apparatus. The stoichiometric ratio between uranium and iron was found to be 1:(1390±62). The reaction between iron and uranium is of pseudo first-order kinetics and the rate constant was measured to be (1.1±0.09)×10-3 s-1. These data enable the calculation of ideal lifetime for permeable reactive barriers (PRB) using iron for uranium removal neglecting hydrological factors that may impair the function of PRBs.
Langzeitbeständigkeit von permeablen reaktiven Wänden zur Sanierung kontaminierter Grundwässer
(2003)
The recycling of refractory materials in the chemical, metallurgical and glass industry has only had minor relevance until now because of the high performance required from these materials (stability against corrosion, inert when coming into contact with the glass melt, etc.). Refractory lifetimes are limited because of corrosion at higher temperatures. The best furnace lifetimes has been achieved with chromium oxide and chromium oxide corund refractories. Waste from the production and use of refractory material is generated in three main forms: as residues from cutting and grinding, as refractories which have limited or no contact with glass melts, and as refractories with infiltration of sublimation residues or condensates. The waste material is classified as hazardous waste due to its chromium content. In this study, arc furnace technology was used for thermal treatment of the waste materials to enable recycling of refractory materials. (author abst.)
Municipal sewage sludge is a carrier of nutrients most important phosphorus (P) but also contains organic pollutants and heavy metals. A two steps thermal treatment based on 1. mono-incineration of sewage sludge under destruction of organic pollutants and 2. thermochemical treatment of the resulting ashes to remove heavy metals and increase P-bioavailability is suggested by the authors. The process aims at P-fertilisers production from sewage sludge. Seven sewage sludge ashes of different origin and composition and one residue from gasification of sewage sludge were thermochemically treated. The raw ashes were mixed with a chlorine donor (e.g. MgCl2) and thermally treated in a gas tight lab-scale rotary furnace. The distributions of the heavy metals between solid and gas phase were determined. The heavy metals concentrations of the treated ashes matched the legislative limits in most cases. The products from thermochemical treatment are suited raw materials for P-fertiliser production. Relevant process parameters such as temperature, type and concentration of Cl-donor and retention time were optimised for the thermochemical treatment step.
Leaching tests are fundamental tools for the assessment of long-term impact of contaminated waste materials on the soil-groundwater pathway. Experiments were carried out in the framework of standardization and validation of column percolation and batch test procedures, in particular concerning the stipulation of the experimental setup. The colloid release of column and batch experiments was compared and the influence of different column filling heights (12.5–50 cm) on the release of polycyclic aromatic hydrocarbons (PAH) from soil was studied, as well as the effect of varying contact times (2.5–16 h) on the release of chromium from construction and demolition (C&D) waste and municipal solid waste incineration (MSWI) bottom ash. The results indicate that filtration of the eluate, which is required for batch tests, does not always allow the simulation of the actual colloid amount in soil pore water. Medium column heights four times the inner diameter of the column seemed to provide reasonable equilibrium adjustment conditions and avoid major biodegradation. The release of chromium was only marginally affected by the contact time, varied between 0.115 and 0.150 mg/kg for demolition waste eluate at a liquid-to-solid ratio of approximately 5 L/kg.
Kreislauf von Ressourcen
(2013)
Die Materialflüsse in Industriegesellschaften sind von enormer Größe. Im Jahr 2008 betrug der direkte Materialeinsatz (direct material input, DMI) (Czichos et al., 2008) in Deutschland 1687 Millionen Tonnen (Daten von destatis, 2010). Dazu gehören Energieträger (Kohle, Öl, Gas), Erze, Baumaterialien, Industrieminerale und Biomasse. Knapp 36 % davon (605 Millionen t) werden importiert. Mit zu berücksichtigen sind bei den Materialflüssen auch die nicht verwerteten Rohstoffentnahmen (z.B. Abraum im Bergbau, Bodenaushub, Bergematerial, Verbleib von Holzabfallen im Wald), die sich für die inländische Rohstoflentnahme auf 2229 Millionen Tonnen beliefen. Die nicht verwerteten Rohstoffentnahmen bei den Importen sind mehr als der Faktor 4 höher (2543 Millionen t) (Buyny et al., 2009).
Auf der Outputseite geht von diesen riesigen Mengen der größere Anteil in den Bestand (net addition to stock, 637 Millionen t), der nächst größere Anteil in den Export (388 Mt). Immerhin 256 Millionen Tonnen werden durch dissipative Nutzung in der Umwelt verteilt. Die Bilanz geht auf, wenn man Gase auf der Inputseite und Emissionen in die Atmosphäre auf der Outputseite (Verbrennung von fossilen Rohstoffen zu CO2 und Wasser) berücksichtigt. An diesen Zahlen erkennt man, dass Ressourcen nur in beschränkten Maß im Kreislauf geführt werden, sonst wäre der Zuwachs zum urbanen Lager nicht so groß.
Glossary Biomineralization A process by which living organisms produce minerals. - Chernobyl Ukrainian city site of the largest nuclear power plant accident in history. - Cut-off-wall Underground structure designed to prevent the flow of water. - DART Deep aquifer remediation tool. - Diffusion Movement of ions and molecules from places of higher concentration to places of lower concentration. - Electrochemical remediation Remediation technologies comprising electrochemical transport and transformation methods. - Electrokinetic screens Structures used to prevent radionuclides from diffusing from the polluted area into the environment. - Electromigration Transport of charged ions or ion complexes in solution. - Electroosmosis Movement of liquid relative to a charged stationary surface, - Electrophoresis Movement of charged particles relative to a stationary fluid. - Enhanced electrochemical remediation Use of pH control and additives to improve removal efficiency. - EURT East Urals Radioactive Trail area contaminated due to a nuclear accident. - Natural attenuation (NA) Remediation relying entirely on natural processes. - Permeable reactive barriers Passive in situ treatment zones of reactive material that degrades or immobilizes contaminants as groundwater flows through it. - Phytoremediation Soil remediation using living plants and their associated microorganisms. - Radionuclide or radioisotope An atom with an unstable nucleus whose excess energy is available to be imparted to a newly-created radiation particle within the nucleus or to an atomic electron. - Total material requirement (TMR) Sum of domestic and imported primary natural resources and their hidden flows.
Sewage sludge and sewage sludge ashes (SSA) are produced in huge amounts at municipal waste water treatment plants (WWTP) all around the world and have become an issue for many urbanized areas. To deal with this unceasing mass flow in an ecologically and economically responsible way a comprehensive chemical and structural characterization of all types of SSA is needed. X-ray powder diffraction (XRD) is one of the most promising analytical methods for this task. Although, there has been ample chemical evidence showing that many SSA contain aluminium phosphate as a major component up to now no aluminium phosphate or aluminium-rich mixed phosphate phase has been reported to be identified by XRD in a SSA produced at a mono-incineration facility. The outcome of the present com-bined XRD and Mossbauer spectroscopy investigation provides comprehensive evidence closing this gap for the first time.
Ressourcen aus Abfall
(2012)
Die Beseitigung unbehandelter Abfälle auf Deponien gehört der Vergangenheit an, nicht nur weil Verordnungen diese Praxis verbieten, sondern auch, weil wegen steigender Preise für Rohstoffe und sinkender Gehalte in Erzen auch in Abfällen nach Alternativen gesucht wird. In den Aschen aus Hausmüllverbrennungsanlagen können mit einfachen Verfahren Metalle zurückgewonnen werden. Mit dem Phosphor aus Klärschlammaschen können Düngemittel hergestellt und so natürliche Ressourcen geschont werden. In beiden Fällen ist die Anreicherung der Wertstoffe durch den Verbrennungsprozess vorteilhaft, da die Effizienz von Recyclingprozessen stark von der Konzentration im Ausgangsgut abhängig ist.--------------------------------------------------------------------------------------------------------------------------------
Disposal of untreated waste has come to end due to new legislation in this field. Furthermore as a response to increasing prices for primary raw materials and decreasing ore concentrations products from waste treatment display a source for secondary raw materials. Elemental metals can be easily separated from municipal solid waste incineration bottom ash. Fertilizers can be produced using phosphate from sewage sludge ashes thus preserving natural resources. In both cases the enrichment taking place in the incineration process facilitates the resource recovery, because the efficiency of recycling processes is dependent on the concentration of the input material.
Die Abfallwirtschaft in Deutschland behandelt eine Menge von 359 Mio. Tonnen. Den größten Anteil haben Bau- und Abbruchabfälle mit 54%. Die Behandlungsverfahren dafür unterscheiden sich stark von denen für Siedlungsabfälle. Gemäß Europäischer Abfallrichtlinie ist Recycling gegenüber einer energetischen Verwertung in der Hierarchie der Abfallbehandlungsverfahren höher bewertet. Bei der thermischen Behandlung entscheidet die Energieeffizienz des Verfahrens, ob eine Behandlung als Verwertung oder Beseitigung gilt. Nach dieser Richtlinie erfolgt die Berechnung der Energieeffizienz stark vereinfacht mit der sogenannten R1-Formel. Veröffentlichte Daten zu Wärme- und Stromproduktion verschiedener thermischer Abfallbehandlungsanlagen werden mit der R1-Formel und Daten aus der Literatur verglichen. Mengen und Entsorgungswege sowie Möglichkeiten zur Bewertung von Abfallbehandlungsverfahren werden diskutiert. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Waste management in Germany covers an amount of 359 million tons. The largest fraction is construction and demolition waste (C&D waste) with some 54%. The treatment processes for C&D waste differ from those for municipal solid waste. According to the European Directive on Waste a waste hierarchy shall apply where recycling has a higher priority than energy recovery. A thermal treatment is regarded as recovery operation only if the energy efficiency is above a certain limit. Under the terms of the directive a simplified calculation of the energy efficiency is perfomed using the so-called R1 formula. Published data on heat and power production of several thermal waste treatment plants are compared to the R1 formula and data from literature. Amount and waste management options for different waste fractions and how to evaluate different waste management processes are discussed.
In den Rückständen thermischer Verfahren sind bedingt durch den Verbrennungsprozess Metalle sowohl in elementarer wie auch in chemisch gebundener Form enthalten. Früher wurde Eisenschrott vor allem deshalb mit Magneten abgetrennt, weil sonst die Verwertung als Baustoff erschwert war. Nichteisen-Metalle, bei Rostasche aus einer Müllverbrennungsanlage (MVA) sind dies hauptsächlich Kupfer und Aluminium, können mit der Wirbelstromtechnik abgetrennt werden. Auf diese Weise sinken auch die Gehalte an umweltrelevanten Schwermetallen. Allerdings werden die kleinen Korngrößen und die chemische gebundenen Metallen (z.B. Oxide oder Carbonate) bisher in der Aufbereitung nicht erfasst. Der Beitrag befasst sich mit den verfahrenstechnischen Potenzialen zur Erhöhung der Metallausbeute.
Werkstoffe
(2012)
Raw material supply is essential for all industrial activities. The use of secondary raw material gains more importance since ore grade in primary production is decreasing. Meanwhile urban stock contains considerable amounts of various elements. Photovoltaic (PV) generating systems are part of the urban stock and recycling technologies for PV thin film modules with CdTe as semiconductor are needed because cadmium could cause hazardous environmental impact and tellurium is a scarce element where future supply might be constrained. The paper describes a sequence of mechanical processing techniques for end-of-life PV thin film modules consisting of sandblasting and flotation. Separation of the semiconductor material from the glass surface was possible, however, enrichment and yield of valuables in the flotation step were non-satisfying. Nevertheless, recovery of valuable metals from urban stock is a viable method for the extension of the availability of limited natural resources.
In den Rückständen thermischer Verfahren sind als Folge des Verbrennungsprozesses Metalle sowohl in elementarer wie auch in chemisch gebundener Form enthalten. Früher wurde Eisenschrott vor allem deshalb mit Magneten abgetrennt, weil sonst die Verwertung als Baustoff erschwert war. Nichteisen-Metalle – bei Rostasche aus einer Müllverbrennungsanlage (MVA) sind dies hauptsächlich Kupfer und Aluminium – können mit der Wirbelstromtechnik abgetrennt werden. Auf diese Weise sinken auch die Gehalte an umweltrelevanten Schwermetallen. Allerdings werden die kleinen Korngrößen und die chemisch gebundenen Metallen (etwa Oxide oder Carbonate) bisher in der Aufbereitung nicht erfasst. Im vorliegenden Beitrag werden die verfahrenstechnische Potenziale aufgezeigt, mit denen die Metallausbeute erhöht werden kann.