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Finzgar N.,Envit Ltd | Jez E.,University of Ljubljana | Voglar D.,University of Ljubljana | Lestan D.,University of Ljubljana
Geoderma | Year: 2014

Geostatistical technique was used to predicted spatial reduction of metal contamination after applying EDTA-based soil remediation. Soil samples from 268 locations in the Meza Valley, Slovenia with Pb and Zn concentrations up to 8955 and 15518mgkg-1 were extracted with the chelating agent ethylenediamine tetraacetate (EDTA). On average, 63 and 22% of Pb and Zn, respectively, were removed with washing solution containing 60mmol EDTA per kg of soil and 75 and 34% of Pb and Zn with 120mmol EDTA kg-1 soil. Spatial structure analysis revealed a good spatial structure and little spatial variation of data, which were further interpolated using Empirical Bayesian kriging to produce a continuous surface of Pb and Zn concentrations before and after remediation. Geostatistical simulations showed that the contaminated area covers 19.4km2 and that soil remediation (60mmol EDTA kg-1) has the potential to reduce the area with Pb and Zn above the critical regulatory threshold limit by 91 and 42%, respectively. Validated by pilot-scale remediation trials, soil extractions exhibit little scale-dependency of extraction efficiency. EDTA extraction also significantly reduced the bio-accessibility of toxic metals that remained in the soil after remediation using the unified bio-accessibility method. Pb and Zn concentrations accessible from the simulated intestinal phase were reduced by up to 99 and 96%, respectively. © 2013 Elsevier B.V.

Voglar D.,University of Ljubljana | Lestan D.,University of Ljubljana | Lestan D.,Envit Ltd
Environmental Technology (United Kingdom) | Year: 2014

We demonstrate here, in a pilot-scale experiment, the feasibility of ethylenediaminetetraacetate (EDTA)based washing technology for soils contaminated with potentially toxic metals. Acid precipitation coupled to initial alkaline toxic metal removal and an electrochemical advanced oxidation process were used for average recovery of 76±2% of EDTA per batch and total recycle of water in a closed process loop. No waste water was generated; solid wastes were efficiently bitumen-stabilized before disposal. The technology embodiment, using conventional process equipment, such as a mixer for soil extraction, screen for soil/gravel separation, filter chamber presses for soil/liquid and recycled EDTA separation and soil rinsing, continuous centrifuge separator for removal of precipitated metals and electrolytic cells for process water cleansing, removed up to 72%, 25% and 66% of Pb, Zn and Cd from garden soil contaminated with up to 6960, 3797 and 32.6 mg kg-1 of Pb, Zn and Cd, respectively, in nine 60 kg soil batches. Concentrations of Pb and Zn remaining in the remediated soil and bioaccessible from the simulated human intestinal phase soil were reduced by 97% and 96% and were brought under the level of determination for Cd. In the most cost-effective operation mode, the material and energy costs of remediation amounted to 50.5≠uro ton -1 soil and the total cost to 299≠uro ton-1. © 2013 © 2013 Taylor & Francis.

Voglar D.,University of Ljubljana | Lestan D.,University of Ljubljana | Lestan D.,Envit Ltd
Chemosphere | Year: 2013

Pb, Zn and Cd contaminated garden soil (5249, 3348 and 20.6mgkg-1, respectively) rich with fines and organic matter was washed with a solution of 120mmol EDTA kg-1 of soil in a pilot-scale remediation plant operating in a batch (60kg of soil) mode. After soil washing, the solid phase and used washing solution were separated in a chamber filter press. A base/acid pair Ca(OH)2/H2SO4 was used to impose a pH gradient for EDTA recycling from used washing solution and, coupled with an electrochemical advanced oxidation process using a graphite anode, for cleansing and recycling the process water, which was used for rinsing the soil solid phase in the press. On average (5 batches), 75%, 26% and 66% of Pb, Zn and Cd, respectively, was removed from the soil, 71% of EDTA was recycled and no waste water was generated. The variable costs of the novel remediation process (materials, energy but not labour) amounted to 66€t-1 of remediated soil. The results of the pilot-scale testing indicate that scaling-up the process to a commercial level is technically and economically feasible. © 2012 Elsevier Ltd.

Jez E.,University of Ljubljana | Lestan D.,University of Ljubljana | Lestan D.,Envit Ltd
Journal of Hazardous Materials | Year: 2015

The Meza Valley, Slovenia, has been contaminated by Pb smelting, resulting in an epidemic of lead poisoning in childhood. The potential of remediation with EDTA soil washing to mitigate the risk from Pb poisoning was investigated by applying the Integrated Exposure Uptake Bio-kinetic (IEUBK) model. Soils from 79 locations were collected and the total and bio-accessible Pb concentrations were determined before and after extraction with 60mmolkg-1 EDTA. Extraction reduced the soil Pb concentration in towns of Mezica, Zerjav and Crna by 53, 67 and 62%, respectively, and the concentration of in vitro bio-accessible Pb in the simulated human gastric phase by 2.6-, 3.2- and 2.9-times, respectively. The predictions of the IEUBK model based on Pb contamination data were verified with data on blood Pb levels in children. The IEUBK model predicted that, after soil remediation, the number of locations at which the expected blood Pb level in children was higher than the stipulated 10μgdL-1 would decrease by 90, 38 and 91% in the towns of Mezica, Zerjav and Crna, respectively. The results confirmed the feasibility of soil washing with EDTA as an efficient remediation measure in Mezica and Crna and advice for soil capping/removal for the most polluted town of Zerjav. © 2015.

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