4 Material und Umwelt
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A new sewage sludge ordinance was set in force in Germany in 2017 that makes phosphorus recovery from sewage sludge mandatory. The technological possibilities for P-recovery from waste water, sewage sludge and sewage sludge ash were presented.
Wastewater contains a diverse array of organic and inorganic compounds and its complex composition strongly depends on the location and the connected dischargers. However, municipal wastewater as a carrier of feces and urine generally contains considerable amounts of the main nutrients nitrogen and phosphorus. The latter is in the focus of the discussions about the recovery potential of wastewater due to the relatively high mass flows of phosphorus in wastewater and the finite nature and decreasing quality of phosphate rock reserves. But due to the presence of the whole periodic table of elements, wastewater might contain further valuable components of interest for recovery including those defined as critical raw materials by the European Commission. Phosphorus and most of the other critical raw materials are fixed in the sewage sludge and after incineration in the sewage sludge ash (SSA). This is accompanied by high concentration factors from wastewater via sludge to ash. However, the mass fractions of the majority of elements in sewage sludge are comparable to those of the earth crust, indicating no relative enrichment. Nevertheless, enrichment factors of 100 or higher are given for phosphorus, copper, zinc, cadmium, silver, tin, lead and the platinum group elements indicating an anthropogenic input. An economic value of sewage sludge was estimated to $460,-/t calculated on the basis of the respective market prices for high purity elements – a theoretical value. A German survey of sewage sludge ashes showed that the mass fractions and the mass flows of most of the elements present in SSA are probably too low for an economic recovery. In most cases the mass flows are rather small compared to the imports and the chemical forms are not suitable for recovery. An exception is phosphorus that is present in high mass fractions up to 13% and that bears a high substitution potential. If the application of P-recovery technologies lead to a further concentration of valuable elements e.g. as by-products in side streams of the process, it would probably make also the recovery of other elements of economic interest.
Microbiologically influenced corrosion (MIC) is the deterioration of metals due to the metabolic activities of microorganisms. Microorganisms can take electrons directly from the metal surface (EMIC) thereby causing corrosion. Well known culprits of EMIC are: sulfate-reducing bacteria (SRB), acetogens and methanogens.
Our aims
- Develop a novel flow system to study MIC by methanogens to mimic industrial Environments
- Investigate the inhibitory concentrations of biocides targeting SRB on corrosive methanogenic strains
- Investigate the inhibitory effects of corrosion inhibitors on methanogens
- Compare the inhibitory concentrations to SRB
Microbiologically influenced corrosion (MIC) is an expensive but unpredictable problem for the industries. The most well-known culprit for MIC is the sulfate-reducing microorganisms (SRM), such as members from the genus Desulfovibrio. It has been widely accepted that SRM can contribute significantly to MIC through the production of hydrogen sulfide (HS-) or in some cases a direct electron uptake from the metal surface. However, in a real environmental system, SRM is not exclusive and often involved with other microorganisms that may also contribute to MIC, such as methanogens.
Methanogenic archaea can produce methane (CH4) using H2+CO2, formate, methylated amines or acetate. Methanogens are highly abundant in the environment and many are found in very extreme conditions, such as high temperature and high salinity. Previous researches have demonstrated that methanogens are capable of MIC, though the specific mechanisms are still under investigation. In the oil and gas industry, methanogens are not considered as the main contributor for MIC since the corrosion rates are often too low. However, the tests for methanogen-induced MIC are usually performed at static conditions, which cannot represent the system accurately. Here, we developed a novel anaerobic system to evaluate the corrosion potential of methanogens under flow conditions. We will use the Methanococcus maripaludis KA1 strain, which was isolated from a crude oil tank, as the organism of interest. A separate system for Desulfovibrio alaskensis will be established for corrosion rate comparisons. Furthermore, we will study the synergistic effects of M. maripaludis and D. alaskensis on MIC under flow.
Leachiing tests - a useful tool for the environmental impact assessment of construction products?
(2018)
Construction products and waste materials used for construction can be in contact with the environment and may release potential harmful compounds. Information on the total content of these substances in the product is not sufficient to assess its envrionmental impact since it does not consider realistic exposure conditions.The impact of these compounds is often assessed by using the total content in the product. This estimation lacks realistic exposure conditions.
Concerning the pathway to soil and groundwater by contact with rain or seepage water leaching tests, which were developed and standardized by the European Committee for Standardization, are available. While for secondary construction products and waste this investigation of the leaching behaviour is standard procedure and is already part of regulation in Germany (draft ordinance on reuse of mineral waste) and within Europe (landfill directive) the release from primary construction products got in the focus more recently. Several monitoring studies found unexpected high concentrations of substances used as herbicides and fungicides in surface water and stormwater originating from urban areas. As some of these compounds are even banned for the use in agricultural applications in Europe alternative sources as roof materials and façade coatings exposed to rain were suggested. Further field and laboratory tests confirmed construction products as sources of these substances in water.
The aim of this presentation is to show exemplary results of existing leaching methods and underline the strength and weaknesses of the test system with selected examples from our work. We especially draw the attention to the research which is still needed to close the gap between the results of leaching experiments and the subsequent risk assessment of the products.
The presentation gives an overview about the use of ecotoxicity testing in assessment of waste. Especially in cases with unknown composition this kind of test are useful. Recently, the assessment of the hazard property HP 14 "ecotoxicity" for the labelling of waste was published. The labelling procedure is explained in detail.
The presentation gives an overview about the use of ecotoxicity testing in assessment of waste. Especially in cases with unknown composition this kind of test are useful. Recently, the assessment of the hazard property HP 14 "ecotoxicity" for the labelling of waste was published. The labelling procedure is explained in detail.
The presentation gives an overview about the use of ecotoxicity testing in assessment of waste. Especially in cases with unknown composition this kind of test are useful. Recently, the assessment of the hazard property HP 14 "ecotoxicity" for the labelling of waste was published. The labelling procedure is explained in detail.