Hans van der Sloot Consultancy

Langedijk, Netherlands

Hans van der Sloot Consultancy

Langedijk, Netherlands
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Engelsen C.J.,Sintef | van der Sloot H.A.,Hans van der Sloot Consultancy | Petkovic G.,Norwegian Public Roads Administration
Science of the Total Environment | Year: 2017

In the present study, the metal leaching from recycled concrete aggregates (RCA) used in road sub-base is presented after > 10 years of exposure. The released levels of inorganic constituents, the effect of small variation of pH and the use of de-icing salt during winter season were studied. In addition, speciation modelling for the major elements has been provided. The pH varied from 7.5 to 8.5 for the sub-base constructed with RCA whereas the pH of around 8 was obtained for the test section not affected by the traffic and de-icing salts. Despite a small variation in pH, the leachability of Al, Ca and Mg was found to be strongly dependent on pH and fair agreement between the measured and predicted concentrations was obtained. The speciation modelling indicated that gibbsite, calcite and magnesite controlled the solubility of Al, Ca and Mg, respectively, which was in agreement with the expected carbonation products. Due to the larger pH fluctuations in the test sections exposed to the road traffic, increased concentrations were observed for the oxyanions. The same effect was not seen for the trace metal cations Cd, Cu, Ni, Pb and Zn. The distinct pH dependent leaching profile (solubility maximum in the mildly basic pH region) for vanadium could be seen after 10 years of exposure. The simplified risk assessment showed that the released quantities did not exceed the chosen acceptance criteria for groundwater and fresh water. The results obtained for the test section not influenced by road dust and de-icing salts, complied with these criteria even without considering any dilution effects caused by the mixing of pore water with groundwater. © 2017 Elsevier B.V.

Scharff H.,Afvalzorg Deponie BV | Van Zomeren A.,Energy Research Center of the Netherlands | Van Der Sloot H.A.,Hans Van der Sloot Consultancy
Waste Management and Research | Year: 2011

Although many countries are increasing their efforts to recycle and to re-use waste materials, landfilling will still be needed in order to dispose of wastes which cannot be recycled or treated in other ways. Since landfills will most probably be present for a long time, measures will have to be taken to reduce their (long-term) emissions. The European Commission has delegated the competent authorities to decide to end aftercare and several member states have provided regulations for this purpose. However, there is currently no guidance for long-term risk assessment to support an aftercare completion procedure for landfills. The aim of this study is to provide examples of current regulations and to demonstrate an alternative approach for a quantitative risk assessment of landfill leachate. The presented modelling approach clearly demonstrates the added value of site specific risk assessments of the long-term emissions from landfills and might provide a basis for application when the acceptance criteria for landfill will be revisited in the future. In addition, the modelling approach can be used as one of the toolboxes to perform assessments of the long-term emissions from landfill leachates and might help the competent authorities to decide whether the remaining emission potential is acceptable or not. Moreover, the results imply that local environmental conditions contribute to the acceptability of landfill emissions and are important factors in choosing a landfill location. © The Author(s) 2011.

Van der Sloot H.A.,Hans van der Sloot Consultancy | Kosson D.S.,Vanderbilt University
Journal of Hazardous Materials | Year: 2012

The evaluation of the hazardous nature of a waste is frequently based on total composition in many jurisdictions, while for most cases the chemical form of the constituents and the release pathways that may result in exposure of man and organisms under conditions of handling, transport, disposal or beneficial use are the most important factors controlling potential environmental impact. Thus, leaching assessment related to possible management scenarios rather than total content can provide a much more robust basis for evaluating health risks and environmental risks for waterborne pathways. Standardized characterisation leaching tests based on intrinsic characteristics of a material provide a new foundation for needed decisions. Chemical speciation modelling using characterisation testing results provides a means to identify mechanisms controlling constituent release, including mineral or sorptive phases, and thus insights into the long-term release behaviour of the material and approaches to reducing potential impacts. © 2011 Elsevier B.V..

Kosson D.S.,Vanderbilt University | Garrabrants A.C.,Vanderbilt University | DeLapp R.,Vanderbilt University | van der Sloot H.A.,Hans van der Sloot Consultancy
Chemosphere | Year: 2014

Current concerns about the environmental safety of coal combustion fly ash have motivated this evaluation of the impact of fly ash use as a cement replacement in concrete materials on the leaching of constituents of potential concern. The chemical effects of fly ash on leaching were determined through characterization of liquid-solid partitioning using EPA Method 1313 for four fly ash materials as well as concrete and microconcrete materials containing 0% (control materials), 25% and 45% replacement of portland cement with the fly ash source. All source materials, concrete formulations and replacement levels are representative of US concrete industry practices. Eluate concentrations as a function of pH were compared to a broader range of available testing results for international concretes and mortars for which the leaching characteristics of the component fly ashes were unknown. The chemistry of the hydrated cement fraction was found to dominate the liquid-solid partitioning resulting in reduced leaching concentrations of most trace metals compared to concentrations from fly ash materials alone. Compared to controls, eluate concentrations of Sb, As, B, Cr, Mo, Se, Tl and V from concrete products containing fly ash were essentially the same as the eluate concentrations from control materials produced without fly ash replacement indicating little to no significant impact on aqueous partitioning. © 2013 Elsevier Ltd.

Sarkar S.,Vanderbilt University | Kosson D.S.,Vanderbilt University | Mahadevan S.,Vanderbilt University | Meeussen J.C.L.,Nuclear Research and Consultancy Group | And 3 more authors.
Cement and Concrete Research | Year: 2012

Chemical equilibrium modeling of cementitious materials requires aqueous-solid equilibrium constants of the controlling mineral phases (K sp) and the available concentrations of primary components. Inherent randomness of the input and model parameters, experimental measurement error, the assumptions and approximations required for numerical simulation, and inadequate knowledge of the chemical process contribute to uncertainty in model prediction. A numerical simulation framework is developed in this paper to assess uncertainty in K sp values used in geochemical speciation models. A Bayesian statistical method is used in combination with an efficient, adaptive Metropolis sampling technique to develop probability density functions for K sp values. One set of leaching experimental observations is used for calibration and another set is used for comparison to evaluate the applicability of the approach. The estimated probability distributions of K sp values can be used in Monte Carlo simulation to assess uncertainty in the behavior of aqueous-solid partitioning of constituents in cement-based materials. © 2012 Elsevier Ltd. All rights reserved.

Garrabrants A.C.,Vanderbilt University | Kosson D.S.,Vanderbilt University | DeLapp R.,Vanderbilt University | van der Sloot H.A.,Hans van der Sloot Consultancy
Chemosphere | Year: 2014

Concerns about the environmental safety of coal combustion fly ash use as a supplemental cementitious material have necessitated comprehensive evaluation of the potential for leaching concrete materials containing fly ash used as a cement replacement. Using concrete formulations representative of US residential and commercial applications, test monoliths were made without fly ash replacement (i.e., controls) and with 20% or 45% of the portland cement fraction replaced by fly ash from four coal combustion sources. In addition, microconcrete materials were created with 45% fly ash replacement based on the commercial concrete formulation but with no coarse aggregate and an increased fine aggregate fraction to maintain aggregate-paste interfacial area. All materials were cured for 3. months prior to mass transport-based leach testing of constituents of potential concern (i.e., Sb, As, B, Ba, Cd, Cr, Mo, Pb, Se, Tl and V) according to EPA Method 1315. The cumulative release results were consistent with previously tested samples of concretes and mortars from international sources. Of the 11 constituents tested, only Sb, Ba, B, Cr and V were measured in quantifiable amounts. Microconcretes without coarse aggregate were determined to be conservative surrogates for concrete in leaching assessment since cumulative release from microconcretes were only slightly greater than the associated concrete materials. Relative to control materials without fly ash, concretes and microconcretes with fly ash replacement of cement had increased 28-d and 63-d cumulative release for a limited number 10 comparison cases: 2 cases for Sb, 7 cases for Ba and 1 case for Cr. The overall results suggest minimal leaching impact from fly ash use as a replacement for up to 45% of the cement fraction in typical US concrete formulations; however, scenario-specific assessment based on this leaching evaluation should be used to determine if potential environmental impacts exist. © 2013 Elsevier Ltd.

Allegrini E.,Technical University of Denmark | Butera S.,Technical University of Denmark | Kosson D.S.,Vanderbilt University | Van Zomeren A.,Energy Research Center of the Netherlands | And 2 more authors.
Waste Management | Year: 2015

Residues from industrial processes and waste management systems (WMSs) have been increasingly reutilised, leading to landfilling rate reductions and the optimisation of mineral resource utilisation in society. Life cycle assessment (LCA) is a holistic methodology allowing for the analysis of systems and products and can be applied to waste management systems to identify environmental benefits and critical aspects thereof. From an LCA perspective, residue utilisation provides benefits such as avoiding the production and depletion of primary materials, but it can lead to environmental burdens, due to the potential leaching of toxic substances. In waste LCA studies where residue utilisation is included, leaching has generally been neglected. In this study, municipal solid waste incineration bottom ash (MSWI BA) was used as a case study into three LCA scenarios having different system boundaries. The importance of data quality and parameter selection in the overall LCA results was evaluated, and an innovative method to assess metal transport into the environment was applied, in order to determine emissions to the soil and water compartments for use in an LCA. It was found that toxic impacts as a result of leaching were dominant in systems including only MSWI BA utilisation, while leaching appeared negligible in larger scenarios including the entire waste system. However, leaching could not be disregarded a priori, due to large uncertainties characterising other activities in the scenario (e.g. electricity production). Based on the analysis of relevant parameters relative to leaching, and on general results of the study, recommendations are provided regarding the use of leaching data in LCA studies. © 2014 Elsevier Ltd.

van der Sloot H.A.,Hans van der Sloot Consultancy | Kosson D.S.,Vanderbilt University | van Zomeren A.,Energy Research Center of the Netherlands
Waste Management | Year: 2016

In spite of the known heterogeneity, wastes destined for landfilling can be characterised for their leaching behaviour by the same protocols as soil, contaminated soil, sediments, sludge, compost, wood, waste and construction products. Characterisation leaching tests used in conjunction with chemical speciation modelling results in much more detailed insights into release controlling processes and factors than single step batch leaching tests like TCLP (USEPA) and EN12457 (EU Landfill Directive). Characterisation testing also can provide the potential for mechanistic impact assessments by making use of a chemical speciation fingerprint (CSF) derived from pH dependence leaching test results. This CSF then forms the basis for subsequent chemical equilibrium and reactive transport modelling to assess environmental impact in a landfill scenario under relevant exposure conditions, including conditions not readily evaluated through direct laboratory testing. This approach has been applied to municipal solid waste (MSW) and predominantly non-degradable waste (PNW) that is representative of a significant part of waste currently being landfilled. This work has shown that a multi-element modelling approach provides a useful description of the release from each of these matrices because relevant release controlling properties and parameters (mineral dissolution/precipitation, sorption on Fe and Al oxides, clay interaction, interaction with dissolved and particulate organic carbon and incorporation in solid solutions) are taken into consideration. Inclusion of dissolved and particulate organic matter in the model is important to properly describe release of the low concentration trace constituents observed in the leachate. The CSF allows the prediction of release under different redox and degradation conditions in the landfill by modifying the redox status and level of dissolved and particulate organic matter in the model runs. The CSF for MSW provides a useful starting point for comparing leachate data from other MSW landfills. © 2016 Elsevier Ltd.

Hjelmar O.,Wageningen University | Van Der Sloot H.A.,Hans van der Sloot Consultancy | Comans R.N.J.,Energy Research Center of the Netherlands | Wahlstrom M.,VTT Technical Research Center of Finland
Waste and Biomass Valorization | Year: 2013

Waste-derived aggregates are being considered as possible candidates for development of End-of-Waste (EoW) criteria at European Union (EU) level in accordance with Article 6 (1) of the EU Waste Framework Directive (2008/98/EC) as a means of increasing the recovery of resources from waste. If a waste-derived aggregate achieves EoW status, it will become a (construction) product and hence be regulated by the Construction Products Regulation (CPR) which means that in most EU Member States there will be no applicable environmental protection regulation. It is therefore important that the criteria a waste-derived aggregate must fulfil to achieve and maintain EoW status ensure sufficient protection of the environment and human health. It is shown that EoW criteria that do not include restrictions on the conditions of the use of waste-derived aggregates for specific construction purposes will result in leaching limit values that are so stringent that very few, if any, waste-derived aggregates can meet them. It is therefore roposed to impose restrictions and conditions on the use aspart of possible future EoW criteria for waste-derived aggregates, and a step-wise methodology for development of more realistic leaching limit values for EoWis outlined. The methodology incorporates the mitigating effects of various measures that reduce the potential environmental impact of construction applications with waste-derived aggregates. Recommendations are also made of the practical testing and documentation procedures for aggregates with EoW status within the framework of the CPR. © The Author(s) 2013.

van der Sloot H.A.,Hans van der Sloot Consultancy | van Zomeren A.,Energy Research Center of the Netherlands
Mine Water and the Environment | Year: 2012

A pH dependent leaching test (CEN/TS 14429) and a percolation leaching test (CEN/TS 14405) developed in CEN/TC 292 have been used for the first time to characterise the release behaviour of different sulphidic mining wastes. Geochemical speciation modeling using LeachXS Orchestra provides another type of partitioning between mineral and sorptive phases than is currently practised in the mining industry. Comparing new leaching test data for seven tailings and two waste rock samples with model predictions gives new insights into release behaviour. In leaching, mineral transformations on the surface of waste rock or tailings particles, rather than bulk mineral composition, dictate release, which implies that mineralogical examinations are not necessarily relevant from a leaching perspective. Kinetic aspects of release from sulphidic waste can be addressed by testing material in different stages of oxidation or exposure to atmospheric conditions. © 2012 Springer-Verlag.

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