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Dit proefschrift heeft als doel om processen te ontwikkelen voor selectieve metaal herwinning uit afvalwater and processtromen die meerdere metalen bevatten, door gebruik te maken van sulfaat reductie onder zure omstandigheden

Lit.opg. en verklarende woordenlijst

Objectcode: NG-BH-08

Lit.opg.

In opdracht van: Gemeente Woerden.

Dit proefschrift heeft als doel om processen te ontwikkelen voor selectieve metaal herwinning uit afvalwater and processtromen die meerdere metalen bevatten, door gebruik te maken van sulfaat reductie onder zure omstandigheden

Met lit. opg

The objective of this research is the optimization of essential metal dosing in upflow anaerobic sludge bed (UASB) reactors used for methanogenic wastewater treatment. Optimization of essential metal dosing in UASB reactors is a compromise between achieving the maximal biological activity of the biomass present in the reactor, while minimizing the costs of the supplied metal and the metal losses into the environment. The fate of metals in the anaerobic granular sludge is studied. The boundary conditions to keep a stable reactor operation are evaluated: Nutrient deficiency due to lack of essential metals versus toxicity in case of their excess. Finally, metal dosing strategies are evaluated. It is shown that the metal addition to UASB reactors and the methanogenic activity are related and, more important, this relation can be quantified

Met lit. opg

Objectcode: NG-BH-08

This report describes levels of lead, mercury, cadmium and inorganic arsenic measured in 1997 in blood and urine of 300 Dutch adults. The aim of this study was to assess the body burden of non-occupationally adults exposed to these potentially toxic metals. Results demonstrate that lead levels in human blood have declined substantially since the late 1970s. No drop in cadmium concentrations in the urine could be detected in the last decade. A quarter of the research population have blood lead levels exceeding a level which might result in biochemical changes ( 50 ug/l). In about 2% of the population blood lead levels may induce a small rise in blood pressure ( 100 ug/l). The significance of both effects for public health is not yet clear. Metal concentrations as measured in this study were comparable with concentrations measured in other (European) countries. Age and sex are determining factors for both blood and urine levels of lead, mercury, cadmium and inorganic arsenic. Smoking causes a significant rise in the body burden from lead and cadmium. Moreover, alcohol consumption contributes to higher blood lead levels, the number of amalgam fillings to higher urine mercury levels and consumption of fish to higher urine inorganic arsenic levels. The research described here yields reference values for body burden of potentially toxic metals to the non-occupationally exposed adult Dutch population, and can be used as background levels in case of disasters to assess the exposure to groups at risk. Furthermore, the established reference values will make it possible to study future trends in exposure to toxic metals.

This report describes levels of lead, mercury, cadmium and inorganic arsenic measured in 1997 in blood and urine of 300 Dutch adults. The aim of this study was to assess the body burden of non-occupationally adults exposed to these potentially toxic metals. Results demonstrate that lead levels in human blood have declined substantially since the late 1970s. No drop in cadmium concentrations in the urine could be detected in the last decade. A quarter of the research population have blood lead levels exceeding a level which might result in biochemical changes ( 50 ug/l). In about 2% of the population blood lead levels may induce a small rise in blood pressure ( 100 ug/l). The significance of both effects for public health is not yet clear. Metal concentrations as measured in this study were comparable with concentrations measured in other (European) countries. Age and sex are determining factors for both blood and urine levels of lead, mercury, cadmium and inorganic arsenic. Smoking causes a significant rise in the body burden from lead and cadmium. Moreover, alcohol consumption contributes to higher blood lead levels, the number of amalgam fillings to higher urine mercury levels and consumption of fish to higher urine inorganic arsenic levels. The research described here yields reference values for body burden of potentially toxic metals to the non-occupationally exposed adult Dutch population, and can be used as background levels in case of disasters to assess the exposure to groups at risk. Furthermore, the established reference values will make it possible to study future trends in exposure to toxic metals.

Metals are naturally occurring compounds and some of them are essential for survival of organisms. These aspects are directly related to the effects of metals in ecosystems, and should explicitly be taken into account in risk assessment procedures for metals that usually operate through total concentrations. Thereupon, the aspect of bioavailability has insufficiently been taken into account in current methodologies for risk assessment. Recently, the insight has increased in the chemical and biological processes that jointly deter-mine the availability of metals for the biota that comprise the eco-systems. In this report a review is given of the current scientific possibilities for taking differences in bioavailability of heavy metals into account in future risk assessment and standard setting. It is concluded that there are indeed such possibilities. Currently, however, lack of suited data and insights hinder the development of a modified system for risk assessment and standard setting that is 'better' capable of predicting actual effects in soil ecosystems than current methodologies. A general concept is being presented that might serve as a basis for the modified system. Within the concept it is assumed that adverse effects will occur only when a species-, soil- and metal-specific critical value is exceeded. A new system of risk assessment could be based upon two sets of toxicity data: one data-set for species that are exposed via the pore water, and one set for species for which uptake via the solid phase is the dominant uptake route. Nevertheless, both risk assessment and standard setting could in the new system still primarily be based upon total metal concentrations in the soil solid phase. At present, there appear to be insufficient data and well-defined conceptual frameworks to allow for implementation of a modified system. In the report a prioritization of additional research needs is therefore included.

Metals are naturally occurring compounds and some of them are essential for survival of organisms. These aspects are directly related to the effects of metals in ecosystems, and should explicitly be taken into account in risk assessment procedures for metals that usually operate through total concentrations. Thereupon, the aspect of bioavailability has insufficiently been taken into account in current methodologies for risk assessment. Recently, the insight has increased in the chemical and biological processes that jointly deter-mine the availability of metals for the biota that comprise the eco-systems. In this report a review is given of the current scientific possibilities for taking differences in bioavailability of heavy metals into account in future risk assessment and standard setting. It is concluded that there are indeed such possibilities. Currently, however, lack of suited data and insights hinder the development of a modified system for risk assessment and standard setting that is 'better' capable of predicting actual effects in soil ecosystems than current methodologies. A general concept is being presented that might serve as a basis for the modified system. Within the concept it is assumed that adverse effects will occur only when a species-, soil- and metal-specific critical value is exceeded. A new system of risk assessment could be based upon two sets of toxicity data: one data-set for species that are exposed via the pore water, and one set for species for which uptake via the solid phase is the dominant uptake route. Nevertheless, both risk assessment and standard setting could in the new system still primarily be based upon total metal concentrations in the soil solid phase. At present, there appear to be insufficient data and well-defined conceptual frameworks to allow for implementation of a modified system. In the report a prioritization of additional research needs is therefore included.

Bioavailability of chemicals in the environment has been the topic of scientific research for a number of years. Following up on requests from within the field of risk assessment and standard setting, the Stearing Group "Integral Standard Setting" (INS) asked for an advice on the future role of biological availability in standard setting and risk assessment. A workshop was organised in response to this request. In this report the main recommendations of the workshop are given. In addition, a number of policyrelated advises are incorporated, including an assessment of the time frames needed. The aim of the report is to review the utility of bioavailability-related research for standard setting and risk assessment and to put the expected applicability of the results of this research in a realistic time frame. It is foreseen that implementation of the topics with potential for future implementation in risk assessment or standard setting, will result in a more realistic risk assessment. The reliability of the present policy on chemical substances will benefit without defecting the environment. An active attitude from regulating bodies is essential for implementing the potentially favourable options and to stimulate researchers to focus their research activities on those topics that are most relevant from a policy making point of make. In addition to these general conclusions, detailed information on all options dealing with bioavailability of metals and organic substances in water, sediment and soil is given in the report.

Bioavailability of chemicals in the environment has been the topic of scientific research for a number of years. Following up on requests from within the field of risk assessment and standard setting, the Stearing Group "Integral Standard Setting" (INS) asked for an advice on the future role of biological availability in standard setting and risk assessment. A workshop was organised in response to this request. In this report the main recommendations of the workshop are given. In addition, a number of policyrelated advises are incorporated, including an assessment of the time frames needed. The aim of the report is to review the utility of bioavailability-related research for standard setting and risk assessment and to put the expected applicability of the results of this research in a realistic time frame. It is foreseen that implementation of the topics with potential for future implementation in risk assessment or standard setting, will result in a more realistic risk assessment. The reliability of the present policy on chemical substances will benefit without defecting the environment. An active attitude from regulating bodies is essential for implementing the potentially favourable options and to stimulate researchers to focus their research activities on those topics that are most relevant from a policy making point of make. In addition to these general conclusions, detailed information on all options dealing with bioavailability of metals and organic substances in water, sediment and soil is given in the report.

Quality standards for heavy metals are based on the total amount of the metal present in the solid phase. In some cases risk limits are derived which are almost equal to the natural background concentration. Thereupon, it is insufficiently taken into account that some metals are essential for living organisms. These observations were ground for developing a conceptual framework for an improved risk assessment methodology that does take these aspects into account. As a first step towards implementation of the framework, toxicity tests were performed with natural substrates and biota that actually reside in these substrates. Thereupon, the bioavailability of the metals for the species tested is explicitly taken into account. It is concluded that integration of knowledge on soil chemistry (speciation and competition), the ecological characteristics of the test species, and the underlying mechanisms of toxicity do indeed enable future implementation of an improved methodology for risk assessment of heavy metals. It is shown that the dominant uptake routes for metals by specific classes of organisms as well as the presence of competing cations (especially H+) need to be specifically taken into account. The strategies employed by biota to detoxify accumulated metals could be used for developing improved risk assessment methodologies based upon internal metal levels as being the ultimate expression of bioavailability.

Quality standards for heavy metals are based on the total amount of the metal present in the solid phase. In some cases risk limits are derived which are almost equal to the natural background concentration. Thereupon, it is insufficiently taken into account that some metals are essential for living organisms. These observations were ground for developing a conceptual framework for an improved risk assessment methodology that does take these aspects into account. As a first step towards implementation of the framework, toxicity tests were performed with natural substrates and biota that actually reside in these substrates. Thereupon, the bioavailability of the metals for the species tested is explicitly taken into account. It is concluded that integration of knowledge on soil chemistry (speciation and competition), the ecological characteristics of the test species, and the underlying mechanisms of toxicity do indeed enable future implementation of an improved methodology for risk assessment of heavy metals. It is shown that the dominant uptake routes for metals by specific classes of organisms as well as the presence of competing cations (especially H+) need to be specifically taken into account. The strategies employed by biota to detoxify accumulated metals could be used for developing improved risk assessment methodologies based upon internal metal levels as being the ultimate expression of bioavailability.

Lit.opg.

Lit.opg.

Lit.opg.

Lit.opg.

This thesis addresses the geochemical aspects of AVS (Acid Volatile Sulfide) and SEM (Simultaneously Extracted Metals) in floodplain lake sediment, its spatial distribution in floodplain lakes and dynamics over time, the link with effects on single species (bioassays), as well as the impact of excess SEM on the in situ benthic community, in one consistent methodological approach. Using this approach the SEM-AVS concept is thus evaluated on various levels from geochemical through ecotoxicology towards ecology. Furthermore, the aspect of spatial and temporal variability is addressed. For the case studies in the field, several floodplain lakes located in the floodplain area Afferdensche and Deestsche Waarden along the Waal branche of the Rhine were selected. Occasionally, this selection was extended towards other floodplain lakes along the Rhine branches. The main goal of this research is a) to explore the actual risks of trace metals to benthic communities in floodplain systems and b) to evaluate the SEM-AVS concept as a tool to assess bioavailable concentrations of trace metals in dynamic floodplain sediment

Projectnr.: 1256, projectcode: w-pa. - Opdrachtgever: gemeente Woerden

Lit.opg. en verklarende woordenlijst.

Materials have been used throughout history for their structural properties, e.g. ductility, elasticity, hardness etc., and later also for their physical properties, i.e., for their characteristic response to external perturbances. These last properties have been investigated in this thesis by using quatumechanics. The mutual interactions of the many-particles which constitute matter complicate its theoretical description enormously. Time-dependent density-functional theory provides a powerful tool to investigate these dynamic properties in atoms, molecules, and clusters. Indeed this theory maps the many-particle problem of interacting electrons in a time-dependent external field onto an auxiliary system of noninteracting particles in an effective field. The many-particle effects enter through so-called exchange-correlation contributions to the effective potentials describing this field. These effective potentials are uniquely determined by the time-dependent density for a given initial state. Essential in this formulation is that the time-dependent density is exactly the same in the real and auxiliary system. The time-dependent density can thus be obtained from the auxiliary system once we know the effective potentials, which in turn are functionals of the time-dependent density. This requires a self-consistent procedure in which one updates the approximate densities and potentials in an iterative way. In this thesis we have only considered systems, initially in the ground state, which are perturbed only weakly by an external electromagnetic field. In this so-called linear response regime the induced density is proportional to the applied field. The exchange-correlation potentials depend on the density in a nontrivial way: the potentials at time t and position r depend in general on the density at all earlier times t' and at all positions r'. In the linear response regime this relation is expressed through a so-called exchange-correlation response kernel. The most common approximation for the exchange-correlation potentials is the adiabatic local density approximation (ALDA), in which these potentials are instantaneous and local functionals of the density. The scenario becomes more complicated for solids, which can be treated as 'open' systems, i.e., systems without boundary. To fully describe these systems, the density is replaced by the current-density leading to time-dependent current-density-functional theory (TDCDFT). In this thesis we have formulated the linear response of metallic crystalline systems to an electric field within this theoretical framework. The method gives already reasonable results for the dielectric and electron energy-loss functions within the ALDA. Although this approximation describes well the interband region of the spectra, it is less satisfying in the intraband region, where relaxation processes, such as electron-electron and electron-phonon scattering, become more important. Indeed the ALDA fails to reproduce the Drude-like tail in the absorption spectra. Approximations to the exchange-correlation potentials which are local-functionals of the current-density and hence nonlocal-functionals of the density can be included in a natural way in our formulation. In these approximations the exchange-correlation kernels can have memory, and thus relaxation processes due to electron-electron scattering can be taken into account. Other types of deviations from experiments can be observed in systems containing heavy elements, if relativistic corrections are neglected. Our method can treat scalar relativistic effects and spin-orbit coupling both in the ground-state and response calculations by using the zeroth-order regular approximation (ZORA). The spin-dependent formulation of the method, which allows to treat spin-orbit coupling, represents a first step to describe the linear response to an external magnetic field.

Lit.opg. en verklarende woordenlijst.

Objectcode: GLM-MH-03.

Materials have been used throughout history for their structural properties, e.g. ductility, elasticity, hardness etc., and later also for their physical properties, i.e., for their characteristic response to external perturbances. These last properties have been investigated in this thesis by using quatumechanics. The mutual interactions of the many-particles which constitute matter complicate its theoretical description enormously. Time-dependent density-functional theory provides a powerful tool to investigate these dynamic properties in atoms, molecules, and clusters. Indeed this theory maps the many-particle problem of interacting electrons in a time-dependent external field onto an auxiliary system of noninteracting particles in an effective field. The many-particle effects enter through so-called exchange-correlation contributions to the effective potentials describing this field. These effective potentials are uniquely determined by the time-dependent density for a given initial state. Essential in this formulation is that the time-dependent density is exactly the same in the real and auxiliary system. The time-dependent density can thus be obtained from the auxiliary system once we know the effective potentials, which in turn are functionals of the time-dependent density. This requires a self-consistent procedure in which one updates the approximate densities and potentials in an iterative way. In this thesis we have only considered systems, initially in the ground state, which are perturbed only weakly by an external electromagnetic field. In this so-called linear response regime the induced density is proportional to the applied field. The exchange-correlation potentials depend on the density in a nontrivial way: the potentials at time t and position r depend in general on the density at all earlier times t' and at all positions r'. In the linear response regime this relation is expressed through a so-called exchange-correlation response kernel. The most common approximation for the exchange-correlation potentials is the adiabatic local density approximation (ALDA), in which these potentials are instantaneous and local functionals of the density. The scenario becomes more complicated for solids, which can be treated as 'open' systems, i.e., systems without boundary. To fully describe these systems, the density is replaced by the current-density leading to time-dependent current-density-functional theory (TDCDFT). In this thesis we have formulated the linear response of metallic crystalline systems to an electric field within this theoretical framework. The method gives already reasonable results for the dielectric and electron energy-loss functions within the ALDA. Although this approximation describes well the interband region of the spectra, it is less satisfying in the intraband region, where relaxation processes, such as electron-electron and electron-phonon scattering, become more important. Indeed the ALDA fails to reproduce the Drude-like tail in the absorption spectra. Approximations to the exchange-correlation potentials which are local-functionals of the current-density and hence nonlocal-functionals of the density can be included in a natural way in our formulation. In these approximations the exchange-correlation kernels can have memory, and thus relaxation processes due to electron-electron scattering can be taken into account. Other types of deviations from experiments can be observed in systems containing heavy elements, if relativistic corrections are neglected. Our method can treat scalar relativistic effects and spin-orbit coupling both in the ground-state and response calculations by using the zeroth-order regular approximation (ZORA). The spin-dependent formulation of the method, which allows to treat spin-orbit coupling, represents a first step to describe the linear response to an external magnetic field.

Objectcode: GLM-MH-03.

ARC-Projectcode 2006/37

Met lit. opg

Projectnr.: 1256, projectcode: w-pa. - Opdrachtgever: gemeente Woerden

ARC-Projectcode 2006/37

Lit.opg.

This thesis addresses the geochemical aspects of AVS (Acid Volatile Sulfide) and SEM (Simultaneously Extracted Metals) in floodplain lake sediment, its spatial distribution in floodplain lakes and dynamics over time, the link with effects on single species (bioassays), as well as the impact of excess SEM on the in situ benthic community, in one consistent methodological approach. Using this approach the SEM-AVS concept is thus evaluated on various levels from geochemical through ecotoxicology towards ecology. Furthermore, the aspect of spatial and temporal variability is addressed. For the case studies in the field, several floodplain lakes located in the floodplain area Afferdensche and Deestsche Waarden along the Waal branche of the Rhine were selected. Occasionally, this selection was extended towards other floodplain lakes along the Rhine branches. The main goal of this research is a) to explore the actual risks of trace metals to benthic communities in floodplain systems and b) to evaluate the SEM-AVS concept as a tool to assess bioavailable concentrations of trace metals in dynamic floodplain sediment

Lit.opg. en verklarende woordenlijst.

Lit.opg.

Trace metals are essential for anaerobic microorganisms, because they are present as cofactor in many of their enzymes. Therefore anaerobic wastewater treatment systems using these microorganisms to perform biological conversions are dependent on these metals for their (optimal) performance. In practice these metals are supplied to the influent when they are absent or insufficiently present in the wastewater. This supply is generally not very rational. However, such a rational metal supply is desired in order to reduce the costs, to minimize the introduction into the environment and to maximize the biological activity. To achieve this insight, in the trace metal dynamics in anaerobic granular sludge bed reactors is required. This thesis therefore focuses on the retention, accumulation and release of trace metals in anaerobic granular sludge and the factors affecting these processes. Further the impact of metal presence/absence and dosing on the anaerobic conversion of methanol was addressed

Lit.opg. en verklarende woordenlijst.

Dynamic metal speciation analysis in aquatic ecosystems is emerging as a powerful basis for development of predictions of bioavailability and reliable risk assessment strategies. A given speciation sensor is characterized by an effective time scale or kinetic window that defines the measurable metal species via their labilities. Here we review the current state of the art for the theory and application of dynamic speciation sensors. We show that a common dynamic interpretation framework, based on rigorous flux expressions incorporating the relevant diffusion and reaction steps, is applicable for a suite of sensors that span a range of time scales. Interpolation from a kinetic spectrum of speciation data is proposed as a practical strategy for addressing questions of bioavailability. Case studies illustrate the practical significance of knowledge on the dynamic features of metal complex species in relation to biouptake, and highlight the limitations of equilibrium-based models.

Trace metals are essential for anaerobic microorganisms, because they are present as cofactor in many of their enzymes. Therefore anaerobic wastewater treatment systems using these microorganisms to perform biological conversions are dependent on these metals for their (optimal) performance. In practice these metals are supplied to the influent when they are absent or insufficiently present in the wastewater. This supply is generally not very rational. However, such a rational metal supply is desired in order to reduce the costs, to minimize the introduction into the environment and to maximize the biological activity. To achieve this insight, in the trace metal dynamics in anaerobic granular sludge bed reactors is required. This thesis therefore focuses on the retention, accumulation and release of trace metals in anaerobic granular sludge and the factors affecting these processes. Further the impact of metal presence/absence and dosing on the anaerobic conversion of methanol was addressed