Adsorption of Multi-heavy Metals Onto Water Treatment Residuals: Sorption Capacities and Applications

Inherently formed iron-based water treatment residuals (WTRs) were tested as alternative sorbents for multi-heavy metal removal from synthetic solutions, contaminated sediments, and surface waters. The WTRs were mainly composed of iron (hydr)oxides and had a high BET surface area (170.7 m2/g), due to the presence of micro- and mesopores. The sorption capacity of WTRs for As(V), Cd2+, Pb2+ and Zn2+ from synthetic solutions surpassed that of a commercially available goethite by 100-400% for single contaminant tests, and by 240% for total sorption in multi contaminant tests. The maximum sorption capacity of WTRs towards As(V), Pb2+ and Zn2+ was estimated by Langmuir equation fitting to range between 0.5 to 0.6 mmol/g, and their maximum sorption capacity for Cd was 0.19 mmol/g. WTRs performed significantly better than goethite for adsorption of cationic contaminants (Cd, Co, Ni, Pb, Zn) in the sediment tests, independent of the dosage or sediment sample. At the highest WTRs dosage (250 mg/g), concentrations of the cationic contaminants decreased by at least 80%, while approximately 40% removal was obtained with 50 mg/g dosage. Sorbent mixtures composed of WTRs with goethite, and with a clinoptilolite natural zeolite were used to reduce As leaching. The sorbent mixtures delivered the desired performance, with the natural zeolite performing better than the goethite as an amendment to WTRs. In addition, up to 90% removal of surface water contaminants was achieved with both fresh WTRs and the WTRs regenerated using 0.01 M EDTA

Strategic Selection of an Optimal Sorbent Mixture for In-Situ Remediation of Heavy Metal Contaminated Sediments: Framework and Case Study

Aquatic sediments contaminated with heavy metals originating from mining and metallurgical activities of aquatic sediments poses significant risk to the environment and human health due to the fact that these sediments not only act as a sink for heavy metals, but can also constitute a secondary source of heavy metal contamination. A variety of sorbent materials has demonstrated the potential to immobilize heavy metals. However, the complexity of multi-element contamination makes choosing the appropriate sorbent mixture and application dosage highly challenging. In this paper, a strategic framework is designed to systematically address the development of an in-situ sediment remediation solution through Assessment, Feasibility and Performance studies. The decision making tools and the experimental procedures needed to identify the optimum sorbent mixtures are detailed. Particular emphasis is given to the utilization and combination of commercially available, and waste-derived sorbents to enhance the sustainability of the solution. A specific case study for a contaminated sediment site in Northern Belgium with high levels of As, Cd, Pb and Zn originating from metallurgical activities is presented. The proposed framework is utilized to achieve the required remediation targets and to meet the imposed regulations on material application in natural environments

Inclusion of social indicators in decision support tools for the selection of sustainable site remediation options

Sustainable remediation requires a balanced decision-making process in which environmental, economic and social aspects of different remediation options are all considered together and the optimum remediation solution is selected. More attention has been paid to the evaluation of environmental and economic aspects, in particular to reduce the human and environmental risks and the remediation costs, to the exclusion of social aspects of remediation. This paper investigates how social aspects are currently considered in sustainability assessments of remediation projects. A selection of decision support tools (DSTs), used for the sustainability assessment of a remediation project, is analyzed to define how social aspects are considered in those tools. The social indicator categories of the Sustainable Remediation Forum – United Kingdom (SuRF-UK), are used as a basis for this evaluation. The consideration of social aspects in the investigated decision support tools is limited, but a clear increase is noticed in more recently developed tools. Among the five social indicator categories defined by SuRF-UK to facilitate a holistic consideration of social aspects of a remediation project only “Human health and safety” is systematically taken into account. “Neighbourhood and locality” is also often addressed, mostly emphasizing the potential disturbance caused by the remediation activities. However, the evaluation of ‘Ethics and Equality’, Communities and community involvement’, and ‘Uncertainty and evidence’ is often neglected. Nevertheless, concrete examples can be found in some of the investigated tools. Specific legislation, standard procedures, and guidelines that have to be followed in a region or country are mainly been set up in the context of protecting human and ecosystem health, safety and prevention of nuisance. However, they sometimes already include some of the aspects addressed by the social indicators. In this perspective the use of DST to evaluate the sustainability of a site remediation project, should be tuned to the legislation, guidelines and procedures that are in force in a specific country or regionpublisher: Elsevier articletitle: Inclusion of social indicators in decision support tools for the selection of sustainable site remediation options journaltitle: Journal of Environmental Management articlelink: http://dx.doi.org/10.1016/j.jenvman.2016.07.035 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved.status: publishe

Arsenic concentrations in floodplain soils

Arsenic concentrations in a Belgian floodplain affected by industrial activities were compared with As concentrations in European floodplain soils from the FOREGS database. The upper 30 cm of the Belgian floodplain soil showed a clear enrichment with As, related to anthropogenic activities, while single extractions indicated that the mobility of As was significantly higher in the upper 12 cm of the soil. Fe was the independent variable that most significantly explained the total content of As in floodplain soils in the FOREGS database. A regression equation with major elements as independent variables allowed to predict As concentrations in the floodplain soils, and enable d to detect potential anomaliesstatus: publishe

Excavated soil as a secondary resource

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Environmental impact of soil remediation activities: evaluation of quantitative and qualitative tools

When evaluating remediation technologies for contaminated soil and groundwater, the beneficial effect of the remediation, namely cleaner soil and groundwater, are mostly emphasized without consideration of the environmental impact of the remediation activities themselves. Nevertheless, different qualitative, semi-quantitative and quantitative methods to estimate the environmental impact of soil remediation activities are available. Within the framework of contaminated site management, an environmental impact assessment can be performed for two main reasons: to guide a user in his choice for a potential (future) soil remediation technique, or to evaluate the environmental performance a soil remediation technology after the remediation has been carried out. In the present study, different tools which can be used to estimate or quantify the environmental impact of a soil remediation process were critically evaluated. Therefore, 3 case studies were worked out, in which several remediation options were evaluated for each case, based on data of the soil remediation project itself or on data from pilot projects. The evaluation tools that were used consisted of a BATNEEC (Best available Technique not Entailing Excessive costs) analysis, different types of CO2 calculators and two more detailed LCA (life cycle analysis)-based evaluation methods. A life cycle management (LCM) approach structuring environmental activities, combined with life cycle analysis (LCA) for a quantitative examination, can be helpful for the selection of site remediation options with minimum impact on the ecosystem, human health and the environment in general. However, LCA-based evaluation methods are rather complex and require much more data than a classical BATNEEC analysis or the calculation of the carbon footprint. The case studies worked out in this papers highlight the most important parameters to take into account for the evaluation of the environmental footprint of soil remediation activities and provide a guidance for environmental impact assessment within the framework of contaminated site management.status: publishe

Soil and circular Economy: state of the art on the reuse of excavated soil in Europe

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A Critical Evaluation of Single Extractions from the SMT Program to Determine Trace Element Mobility in Sediments

Two commonly applied single extractions procedures, namely extractions with ammonium-EDTA and acetic acid, were evaluated based on the analysis of 72 samples from alluvial sediments. For most trace elements (Cu, Zn, Cd, Ni, As, and Pb), a significant linear relationship could be established between their ammonium-EDTA or acetic acid extractable concentrations and their total concentrations, the organic carbon content, pH, and Fe , Al, and/or Ca content in the sediments. The scientific understanding of trace element partitioning in the complex soil-water system with these simple models is rather limited, but they offer the opportunity to use data from single extractions in a more comprehensive way. Despite the fact that these extractions cannot directly be related to the bioavailability of elements, they can provide input data for use in risk assessment models. Additionally, they also offer possibilities to perform a fast screening of the mobilizable pool of elements in soils and/or sediments

'Possibilities and limitations of LCA for the evaluation of soil remediation and cleanup

When evaluating remediation technologies for contaminated soil and groundwater, the beneficial effect of the remediation, namely cleaner soil and groundwater, are mostly emphasized without consideration of the environmental impact of the remediation activities themselves. Nevertheless, practitioners and decision makers can rely on a broad range of decision tools that can help them to achieve a better balance between economic, social and environmental health aspects of contaminated land remediation. A holistic approach for the management of contaminated land should ideally include an assessment of the environmental risk of the contamination, an assessment of the environmental, social and health impact of the remediation process and a cost-benefit analysis of the remediation project. A life cycle framework, including a life cycle management (LCM) approach structuring environmental activities and life cycle analysis (LCA) for a quantitative examination, can be helpful for the selection of site remediation options with minimum impact on the ecosystem and human health. During the last 10 years, several instances have emerged in which a life cycle approach has been applied to the remediation of contaminated sites. Besides addressing the environmental impact of the remediation activities for a specific site, attention should also be paid to the consequence of reintroducing a remediate site into the economy. From a legal point of view, there should be ways to encourage the use of sustainable remediation technologies, together with a disconnection of treated soils from the definition of waste. Finally, the focus should move from remediation, whether sustainable or not, to prevention of soil contamination.edition: 1ststatus: publishe

Release of Vanadium from soils by conventional leaching procedures and extractions

1. Introduction Despite the fact that vanadium (V) is among the 20 most abundant elements in the earth's crust5, with average concentrations between 50 and 150 µg g-1, this element receives relatively few attention in the scientific literature on soil and sediment geochemistry. However, the last few years, the attention for this potentially harmful element is growing. Some countries adopted threshold values for vanadium in soils, sediments, ground- or surface water, but in general vanadium is of little importance in environmental legislation. In the present study, the release of vanadium from soils and from certified reference materials was investigated by means of several types of leaching tests and extractions that are frequently use for soil and sediment characterization. The data of the physico-chemical soil characterization, extractions and leaching tests can be used estimate the actual and potential risk for vanadium release into the environment. 2. Methodology Dredged sediment derived soils and alluvial soils from the northern part of Belgium were subjected to a physico-chemical (grainsize, pH, CEC, and total element concentrations) and mineralogical (XRD) characterization. Single extractions with CaCl2 (0.01 M), acetic acid (0.43 M) and ammonium-EDTA (0.05 M) were performed to estimate the actual and potential mobilization of V from the sediments. The SMT sequential extraction scheme was applied on a selection of samples. pHstat leaching tests were applied according to the method described by Van Herreweghe et al.8 3. Results and discussion Ammonium-EDTA was used to estimate the mobilizable element concentrations. The average EDTA-extractable V concentration in the dredged sediment derived soils was 2.46 mg/kg which is 2 comparable with average EDTA-extractable V-concentrations (3.40 mg/kg) reported by Gäbler et al.4 In the alluvial soil samples, the average ammonium-EDTA-extractable V concentration was 11.2 mg/kg. These soils are contaminated with V (with V-concentrations up to 301 mg kg-1), which can also explain for the higher potentially mobile V-content in these soils. Acetic acid only released very low V-concentrations, (between 0.5 and 6 mg/kg), accounting for less than 5% of the total V-content in the samples. The maximum CaCl2-extractable V concentration, which can be considered representative for porewater composition was 12 mg kg-1 with an average concentration of 4 mg kg-1, which is far below the value of 3 mg mg kg-1, which is proposed by Edwards et al. and would cause significant toxic effects to plants. In the sequential extractions, the residual fraction of V was dominant for all samples, which together with the reducible fraction accounted for 90% of the total V concentration in the samples. The acid extractable fraction of V was very low (below 5%), whereas between 5 and 10 % of the total V content was recovered in the oxidisable fraction. Leaching of V as a function of pH was generally characterized by a typical V-shaped pattern, with maximum release at very low (pH 2) and very high pH (pH 10). At pH 2, The release of V as a function of time followed the similar pattern as described before for heavy metals. Geochemical speciation modeling indicates that V occurs as VO2+ species at pH 2, whereas at more neutral and alkaline pH values (pH 6 tot 10), VO2(OH)2- and VO3OH2-are the prevailing V-species1. 4. Conclusion The leaching tests and extractions applied in this study show that vanadium generally displays a very limited actual and potential mobility in soil. Mobile V concentrations, as estimated by the amount of V released by a single extraction with CaCl2 0.01 mol L-1, were low, even in the most contaminated soil samples. Reducing conditions may initially cause a release of V into the environment, but under reducing, saturated conditions, V is immobile9.status: publishe