Reports within the environment research area

The results from this study indicates that aged MSWI bottom ash used mixed with planting soil (here 50 wt%>), e.g. in landfill cover purposes, do not give rise to significant elevated metal or metalloid levels in ryegrass during one growing season compared to conventional construction materials (here excavated soil and crushed stone). In addition, concentrations in leaves of shrubs and trees that self-established and grew in aged MSWI bottom ash where below tolerable daily intake for cattle (TDI) for cattle of all studieed metals and metalloids except Zn in aspen, birch and willow, In leaves from these trees the lefels of Zn were above that lower, but not upper, TDI value. The studyt also shows the importance of taking into account dusting and other particle spreading as an exposure route when evaluating the risks related to ash utilisation. Minimization of particle spreading should thus be an important component when designing risk mitigation measures if ashes are used in geotechnical constructions. Finally, the study also shows that the general accumulation factors used in Swedish Environmental Protection Agency Handbook 2010:1 would overestimate the plant uptake of all studied metals and metalloids except Cr from the studied ash materials to grass. These accumulation factors are thus not suitable when assessing risks related to ash utilization.

10-076.pdf

This report presents the needs and concerns of the environmental assessment authorities and operators in terms of screening of the ashes of plants.

The findings show an efficient and legally secure screening of ash in plants requires a greater clarity on the regulatory requirements, an increased quality of operators' base, and a common vision for content owners, operators and environmental review agencies.

09-277 Beslutsunderlag

This study considers application of tertiary treatment of effluent water in two Swedish pulp mills in a holistic perspective. Calculations of improved waste water quality and costs for membrane filtration, chemical treatment (precipitation) and sand filtration have been performed. The results differ considerably between the two plants as well as between treatment methods. Generally, nutrient discharges decrease more with chemical treatment than in other methods, while suspended solids are more effectively removed with filtration. Sand filtration is less expensive to install and operate than the other two methods.

The recipient to one of the mills is a large lake in central Sweden, while the other mill is located in a coastal area by the Bothnian Bay. Both recipients exhibit fairly good ecological status and the amounts of organic material and nutrients discharged by the mills are small compared to background loads. Simulations show no significant effects in the recipients of tertiary treatment of the pulp mill effluents. On the positive side, however, is the prospect of decreasing the totalt load on the environment of some substances. Against this should be considered the environmental effects of building and operating the treatment plants.

Our analysis of the combined environmental effects of the different treatment methods show that the total nutrient emissions decrease in all cases. In all other categories the environmental impact increases due to i.a. increased consumption of energy and chemicals during building and operating the treatment plants and due to increased sludge production. There is no established way of comparing different categories of environmental impact, but we have applied different methods to assess and normalize different environmental impacts. Numerical results from the different categories can be normalized against total emissions per year and per peson in a certain categories. This gives an indication about how much of the "available space" in a sustainable society that is consumed by the impact. The monetary value of increased CO2 emissions can also be estimated using abatement costs in other instances of using the price in emissions trading markets. In similar ways the monetary value of decreased nutrient emissions can be assessed and compared against the increased climate impact from the treatment plants.

In summary the results indicate that the environmental benefit of tertiary treatment in the pulp mills is ambiguous in a holistic perspective. None of the methods to compare different impact categories in this study definitely answers the question whether the benefit exceeds the costs. One reason for this is that primary and secondary treatment of the effluent waters are already installed in the mills and the present environmental impact is limited. There is also lack of data concerning the effect on potentially toxic substances by the tertiary treatment, which is a significant gap in the environmental balance account.

09-158 Reningssteg

Unburned carbon in combustion residues from biomass and wastes has been characterized using micro-Raman spectroscopy. These residues have been characterized with respect to LOI and TOC in previous investigations. The results have been evaluated using the height ratio I_D/I_G  between the two carbon peaks, disordered carbon (D) and graphitic carbon (G).

The samples appear to group themselves in three categories: bottom ashes with the lowest 

I_D/I_G   ratio, fly ashes and APC residues with a  I_D/I_G  ratio of approximately 1.5 and residues from

smaller furnaces using wood pellets as fuel with the largest 

I_D/I_G   ratio. This methods is recommended for use in investigations of unburned carbon in ash, as a

complement to methods based on the reactivity of the carbon and the ash.

09-384 Karakterisering av det oförbrända kolet i askor

Incineration of municipal solid waste has resulted in large quantities of residues which can be recycled in roads and landfill covers provided the environmental concerns related to leaching of salts and metals can be mitigated. The pollutant transport from these residues depends on quantify and variability of moisture at re-use sites. For realistic assessment of leaching rates and pollutant transport risks quantifying the moisture variability is important. Rapid and non-destructive measurement techniques are therefore necessary. The commonly available techniques (e.g. TDR, Time Domain Reflectometry) are not suitable due to high conductivity of waste materials. Even at moderate salinity levels the attenuation of TDR signal drastically  lowers its ability to determine the water content. The other alternative is to use dielectric measurements in frequency domain (FDR) which was used in the present project. A large amount of data was collected in several different ash materials over a wide range in water content (0-0.49 m³m^3-) and electrical conductivities (0-20 dS m^1-). Both TDR and FDR measurements were taken.

The result demonstrate that the FDR measurements are less affected by salinity than TDR which reduces the effective frequency as salinity level increases. This results in over estimation of the water content. The FDR measurements were converted to water content using both an empirical approcah and dielectric relaxation modelling. Results show that the FDR technique can give highly accurate water content measurements over a wide range of salinity levels. 

08-193.pdf

This report presents lab testing results from a water cleaning device that may have a future role for the marine environmental to reduce the amount of dead sea bottoms in coastal areas. This problem is due to lack of water circulation and an excess of nutrients that still cause eutrophication, a high sedimentation rate and the sulfur cycle itself. The fish productivity may recover in the Baltic and fiords again if the bottom water returns from anoxic to oxic state again. To solve the eutrophication in the Baltic is one of the EU strategies before 2021.

The technical advantages from this device that clean the sea water from toxic H2S by no consumption of energy or toxic substances and the construction is made by sustainable material and with a simplicity that make it possible to enlarge the device to a big scale. Other techniques that can be complementary solutions. Prevention of emission (nutrients mainly) is also still important to prevent eutrophication but the problem has not been solved yet and the majority of the amount of phosphate is stored in the bottom sediment due to the phosphorous biogeochemical cycle.

During this validation test the lab scale prototype was tested in a 10m3 basin for cleaning toxic H2S from sea water by oxidation to harmless sulfate. The focus in this report is to quantify cleaning time and cleaning capacity (% of start H2S concentration) during  four separate experiments. This construction has got a "battery like" principle for the water cleaning. During discharging this "battery" the H2S get oxidized back to sulfate again (like in the oxic water state). To verify the cleaning time the electrode potential (mV) has been logged and water samples for analyzing concentration of H2S have been taken. During two experiment the cleaning capacity of 100% was reached. Different cleaning times has noticed from 15 minutes, 1 hour to 1 day - using different size of electrodes etc. Water samples were also taken to check the biological impact before and after cleaning (pH, alkalinity, salinity, nutrients and oxygen etc). No negative biological impact is shown because the values are close to detection limits mainly and no toxic products were expected.

09-127 Validating a lab prototype..

Although there are few occasions during a year that the wind is calm, calculations on smoke ventilation rarely, or never, consider its effects. The wind creates a pressure on the surrounding walls of a building and can affect the internal air movements through leakages or openings in the facade. This project concern wind effects on natural smoke ventilation and the possibilities to make predictions using CFD applications of different complexity.

Although using fairly rough computational grids, all the programs show good predictions of wind pressure on the sides of a building. The separation effect on the building roof is more complex and therefore more difficult to predict. In order to follow good practice, the mesh should be fine enough to include the boundary layer (small y+). However, in several calculations it was shown that good, mesh independent, results could be obtained using large grids withouth resolving the boundary layer. This is important since it opens up for industrial size calculations.

The applications found in the open-source package OpenFOAM did not excel in simulation of fire and buoyancy driven flows and cannot be recommended in design calculations. The RANS-based code Sofie as well as the LES-based code FDS are both recommended for such exercises.

07-231 CFD-based design of natural smoke ventilation

There are considerable incentives in Sweden - from environmental, conservation and economic points of view - to utilize ash and activated sewage sludge in covers for landfills. The Tveta Recycling Plant thus uses mixtures of these residues in the protecing layer and ash in the seal. Others, however, use mixtures of ash and sewage sludge for the latter, and this has prompted questions as to whether the Tveta recycling Plant is actually complying with the requirements on best available technology. Times of hundres and thousands of years are not accessible to ordinary  experiements. Therefore, aleration of organic material over time has been studied in to historical sources (anthropogenic analogue) and in marine sediments according to moderns sources (natural analogue). For the case of the Tveta Recycling Plant, neither alkalinity nor salinity was identified to protect a seal of ash and activaded sewage sludge in the long term, and results on availability of oxygen were inconsluvie. The antropogenic analogues of Roman cements and similar supports the selection of solely ash as the best alternative for the seal.

07_148-langtidsegenskaper-hos-tatskikt.pdf

Money was funded to Lisa Lundin, Department of Chemistry, Umeå University to buy equipment to sample fly ash from the flue gas in combustion plants. An APEX Instrument cyclone PM10, PM2.5 kit was purchased with a source sampling kit following the USEPA Method 5. This equipment allows simultaneously sampling of PM10 and PM2.5. The cyclones were used to sample fly ash before a textile filter in a combustion plant in Sweden which has trouble with PCDD/F in flue gases that are released to the air after a modification of the plant. The results show that formation of PCDD/F occurs in the textile filter. The contribution of the PCDD increased when comparing ashes taken before the textile filter and ash from the filter. However, the contribution of PCDD and PCDF to the WHO-TEQ is approximately the same in the ashes it suggests that other PCDD congeners than the 2,3,7,8 substituted are formed in the textile filter. Further investigations are needed to elucidate the reason for the formation of PCDD/F in the textile filter.

06-166-flygaska.pdf

Model development for the flow structure in the flotation process

Dissolved Air Flotation (DAF) is a process for the separation of minute floc/particles in water and wastewater treatment. The method is based on the use of microscopic air bubbles which should attach to the floc and lift it to the water surface for subsequent removal. The flow structure in the flotation tank is of utmost importance to the separation efficiency and previous experimental studies had indicated the importance of the density effects of the bubbles on the flow structure. The project has investigated the possibility to simulate, at least in a qualitative way, the important features of the flow pattern in a DAF pilot plant tank using numerical flow models based on Navier-Stokes' equations and a continuity equation for the bubble distribution and contents. A two-dimensional, laminar approach was used. Two different cases were tested. The first one dealt with the situation without bubbles and it was possible to simulate the occurrence of the large scale eddy which occurred according to measurements of the flow structure. The second case dealt with the addition of bubbles of a fixed size and an assumption of the validity of the Boussinesq approximation on the effect of bubbles on the bulk water density. Initial computations indicated that a stratified flow structure could be obtained. However, numerical stability problems occurred which limited the use of realistic, low viscosity values. Further efforts are required in order to minimize stability problems as well as to use simultaneously a range of bubble sizes.

06-058_modellutveckling.doc

Modern mass spectrometers that can be used on-line to monitor emissions of gaseous organic pollutants offer the possibility to investigate in more detail their occurrence in flue gases. This information is needed for the development of means to abate these emissions.

The REMPI-TOF mass spectrometer at GSF in Germany has been modified in order to:
o Increase the selectivity of the instrument for PAH compounds
o Shorten the interval between two samplings to lower than a minute, while keeping the sensitivity to PAH at the ppb level

The instrument has then been used in a research project financed by Värmeforsk (The Swedish Thermal Engineering Research Institute) where the relation between PAH and carbon monoxide concentrations was studied. The impact of sulphur additives was the main topic of this project. The performance of the mass spectrometer fulfilled all expectations.

06-133_rokgaser.pdf

The overall objective of the project was to find out if toxic, non-radioactive chemical waste can be safely stored underground with due respect to: 1) present EC safety regulations and possible future  stricter rules for environmental protection, 2) technical feasibility, and 3) cost efficiency. These goals were reached and the worked-out concept for isolating hazardous waste is available for practical application. Deep abandoned mines appear to be suitable for the disposal because of low cost and suitable chemical conditions.

A major issue has been to develop techniques for isolation of hazardous waste, primarily mercury, in solid or solidified form, for which a couple of techniques have been identified and tested. The best isolating medium turns out to be dense clay material applied in the form of pre-compacted blocks of clay powder or as on-site compacted clay layers. The project has involved lab experiments and theoretical modelling for assessing the performance of clay components as engineered barriers. Solidification of liquid waste is needed and a suitable clay type for this purpose has been identified. The techniques for preparation and application of the clay-based materials have been tested and found to be very effective as “near-field” isolation of solid waste represented by mercury batteries. The overall conclusion is that such waste and other solidified hazardous waste can be isolated from the biosphere for hundreds of thousands of years and that subsequent groundwater contamination will be lower than stipulated by the EU. The study has included, in addition to the major issue of isolating waste, estimation of the rock mechanical stability of drifts and rooms suitable for disposal of such waste.

The major scientific achievements are 1) Selection principles of data for release of toxic inorganic and organic elements from clay-embedded solid and solidified liquid waste. 2) Understanding of the mechanisms of diffusive transport of toxic elements through clay embedment to the rock surrounding underground disposal rooms, and ways of modelling them, 3) Development of numerical tools for calculating long-term mechanical stability of disposal rooms and examples of applying them, and 4) Validation of numerical tools for calculating transport of toxic contaminants in large rock masses using relevant rock structure systems.

Lund 2007-12-03

Roland Pusch

Geodevelopment International AB

01-067_kvicksilveravfall.pdf.pdf

Studies suggest that airborne particles cause health effects at concentrations normally found in cities. In a recent study our research group showed that particles generated by combustion of pellets damage the gene pool in cultivated human lung cells in the same degree as particles generated by combustion of wood in an old non-environmentally approved steam boiler. In order to further develop steam boilers and fuels, more knowledge about particles that are dangerous to human health is needed.

In recent years, nanoparticles have been in focus since they are suspected to be particularly harmful to human health. In order to examine these particles, without exposing humans or animals, new types of test systems are required.

We are currently developing an integrated system (a so called CULTEX system) for nanoparticles and cell exposure. The principle of the CULTEX system is that cells are cultivated on a specific membrane, where the cells get nourishment from cell media beneath the membrane and are exposed to a freshly generated particle aerosol from above.

The CULTEX system is a new method set up at the Department of Biosciences and Nutrition at the Karolinska Institutet financially supported by AF’s (Ångpanneföreningens) Foundation for Research and Development. The CULTEX system is up and running and are currently being optimised for nanoparticles.

Future applications of the CULTEX system are to evaluate the toxicity of nanoparticles with different chemical compositions. In addition, it will be possible to evaluate the importance of particle size for the toxicity. Such information will help the industry to develop better steam boilers, particle filters etc.

06-142_nano-partiklar.pdf