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Laboratory and pilot scale soil washing of PAH and arsenic from a wood preservation site: Changes in concentration and toxicity
Örebro University, School of Science and Technology. (MTM research center)
Sakab AB. (MTM Research Center)
Show others and affiliations
2009 (English)In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 172, no 2-3, 1033-1040 p.Article in journal (Refereed) Published
Abstract [en]

Soil washing of a soil with a mixture of both polycyclic aromatic hydrocarbons (PAH) and As was evaluated in laboratory and pilot scale, utilizing both single and mixtures of different additives. The highest level of decontamination was achieved with a combination of 0.213 M of the chelating agent MGDA and 3.2xCMC* of a nonionic, alkyl glucoside surfactant at pH 12 (Ca(OH)2). This combination managed to reach Swedish threshold values within 10 min of treat­ment when performed at elevated temperature (50°C), with initial conta­minant concentrations of As = 105±4 mg/kg and US-EPA PAH16 = 46.0±2.3 mg/kg. The main mechanisms behind the removal were the pH-effect for As and a combina­tion of SOM-ionization as a result of high pH and micellar solu­bilization for PAHs. Implementation of the laboratory results utilizing a pilot scale equipment did not improve the performance, which may be due to the shorter contact time between the washing solution and the particles, or changes in physical characte­ristics of the leaching solution due to the elevated pressure utilized. The ecotox­icological evaluation, Microtox®, demonstrated that all soil washing treatments increased the toxicity of soil leachates, possibly due to in­creased availability of contaminants and toxicity of soil washing solutions to the test organism.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2009. Vol. 172, no 2-3, 1033-1040 p.
Keyword [en]
Arsenic, Microtox®, PAH, Soil washing, Surfactant
National Category
Environmental Sciences
Research subject
Enviromental Science
Identifiers
URN: urn:nbn:se:oru:diva-7988DOI: 10.1016/j.jhazmat.2009.07.092ISI: 000271980800068PubMedID: 19699582Scopus ID: 2-s2.0-71049155866OAI: oai:DiVA.org:oru-7988DiVA: diva2:236453
Available from: 2009-09-23 Created: 2009-09-23 Last updated: 2017-02-17Bibliographically approved
In thesis
1. Remediation of materials with mixed contaminants: treatability, technology and final disposal
Open this publication in new window or tab >>Remediation of materials with mixed contaminants: treatability, technology and final disposal
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Contaminated soils are a large issue worldwide and much effort has been made to find efficient remediation methods. At many contaminated sites, mixtures of dif­ferent contaminants with different properties are present, which may lead to addi­tional problems, and thus additional costs, during the remediation process. This thesis presents the results from soil remedia­tion of two mixed contaminated soils, containing explosives and heavy metals and polycyclic aromatic hydrocarbons (PAH) and arsenic, respectively. The re­sults demonstrate that bioremediation may be an efficient method for moderate explosives concentration, but that too high contaminant concentrations may prevent the biodegradation, measured by both chemical and ecotoxicological analyses. If the contaminant concentration is very high, soil washing with alkaline pH (~12, NaOH) may be a good alterna­tive, which was observed to remove both explosives and heavy metals.

For a PAH and arsenic contaminated soil, little degradation of organics was ob­served during the bioremediation. However, the arsenic present was re-distributed in the soil, which could poten­tially lead to increased availability and thus in­creased risk for contaminant spreading. Soil washing at alkaline pH (~12-13; Ca(OH)2) with a combination of a biodegradable non-ionic sur­factant and a biodegradable chelating agent, executed at high temperature (50°C), reached treatment goals for both arsenic and PAH after 10 min treatment. Measurement of ecotoxicity using Microtox® demonstrated that remaining surfactant in the soil may lead to increased toxicity despite lower con­taminant concentrations.

Soil is a basically non-renewable resource and thus re-cycling of remediated soil ought to be commonly occurring. Yet, the re-cycling of remediated masses has so far been limited in Sweden, mainly because of the risk of spreading of pollu­tant remains. However, a recent proposition from the Swedish EPA opens for re-cycl­ing, even though the thresholds are very con­servative. Risk assessment of the re­mediated soil includes the utilization of leach­ing tests to estimate the risk of spreading of remaining pollutants. A comparison of the leaching from four reme­diated soils using three different leaching solutions reveals that leaching of both heavy metals and PAH occurs. In addition, differ­ences between different legisla­tions were observed, which could imply that the same soil could be re-cycled in one country (the Netherlands) but not another (Sweden).

Place, publisher, year, edition, pages
Örebro: Örebro universitet, 2009. 54 p.
Series
Örebro Studies in Environmental Science, ISSN 1650-6278 ; 13
Keyword
Bioremediation, Microtox®, mixed contaminants, re-cycling, soil remediation, soil washing.
National Category
Environmental Sciences
Research subject
Enviromental Science
Identifiers
urn:nbn:se:oru:diva-7993 (URN)978-91-7668-683-6 (ISBN)
Public defence
2009-10-23, HSP2, Fakultetsgatan 1, Örebro, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2009-09-29 Created: 2009-09-23 Last updated: 2011-04-29Bibliographically approved
2. Organic complexing agents for remediation of heavy metal contaminated soil
Open this publication in new window or tab >>Organic complexing agents for remediation of heavy metal contaminated soil
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Soil washing of heavy metal contaminated soil may be enhanced by the addition of synthetic chelators. Since many of these chelators may imply stress to soil organisms and are poorly biodegraded, identification and evaluation of effective biodegradable or recyclable chelators (synthetic and/or naturally produced) is of great interest. The efficiency of biodegradable synthetic chelators was evaluated both in bench- (0.3 kg) and meso- (10 kg) scale. Results demonstrated that the solubilization of copper, lead, and zinc was similar in bench- and meso-scale systems, which indicated that these systems could be used in a technical scale. However, the arsenic extraction in meso-scale system, were non-conclusive. Due to the high cost involved in the purchase of synthetic chelating agents, recycling of the solutions is of great interest, and this was achieved in five consecutive washing cycles. Considering the economy of a full-scale process, recycling of complexing solutions with sulfide addition at each cycle, both at the 100 mM-level, appears feasible. Naturally derived chelators were produced by saprotrophic fungi and through alkaline degradation of humic substances and cellulose. The results demonstrated that these types of complexing agents are not as effective as the synthetic chelators. In the fungal systems, desorption of metals was related to production of organic complexing acids, but mainly to the pH-decrease. Nonetheless, in some systems, formation of soluble complexes was indicated (copper). Enhancement of copper, lead, and zinc release with the use of alkaline leachates from wood and peat appeared possible. Since these agents have a natural origin and are derived from rather cheap raw material, recycling is not an issue.

 

Place, publisher, year, edition, pages
Örebro: Örebro universitet, 2009. 59 p.
Series
Örebro Studies in Environmental Science, ISSN 1650-6278 ; 12
Keyword
soil washing, heavy metals, chelators, recycling
National Category
Natural Sciences Environmental Sciences
Research subject
Enviromental Science
Identifiers
urn:nbn:se:oru:diva-7913 (URN)978-91-7668-680-5 (ISBN)
Public defence
2009-10-02, HSP1, Fakultetsgatan 1, Örebro, 10:15 (English)
Opponent
Supervisors
Available from: 2009-09-11 Created: 2009-09-11 Last updated: 2011-04-29Bibliographically approved

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