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The utilization of amendments in soil remediation
2010 (English)Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

Soil originating from old wood preservation industries is often contaminated by a mixture of polycyclic aromatic hydrocarbons (PAH) and heavy metals, from the simultaneous utilization of creosote and CCA salts (copper, chromium, arsenic), respectively. Multi-element contaminated sites are usual and pose large difficulties for remedy selection, most techniques were not developed for these situations and stepwise or combined techniques are often required. Choice of a remediation technique depends primarily on target contaminant/s and soil properties but site specific conditions and economics are always to be considered. Thermal treatment is effective for organic contaminants but tend to increase leaching of chromium (Cr) and arsenic (As), while the leaching of copper (Cu) decreases. Soil washing is primarily most effective for solely inorganics or organic contaminants. Soil washing applications efficient for the simultaneous removal of inorganic and organic contaminants are rare. In these applications the soil washing extractant solutions could be recalcitrant and toxic in nature. Whenever treatment goals are not fulfilled after these treatments chemical stabilisation could be an option for contaminant immobilization. Choice of an appropriate amendment for chemical stabilisation could be based on the affinity of As, Cr and Cu for different soil fractions such as metal oxides and sulphides. Aim for this study was to develop an extractant in a soil washing application efficient for simultaneous removal of inorganic and organic contaminants with environmental concern taken. For the stabilisation of remaining contaminants this study also aimed to evaluate how the addition of certain products (iron compounds, fly ash, gypsum and zeolite) prior to thermal treatment could effect leaching of As, Cu and Cr. Leaching was evaluated in oxidizing or anoxic conditions. The addition of these products was also evaluated with no prior thermal treatment. Results were compared with EU landfill regulations and guideline values for contaminated soil. Leaching of As, Cu and Cr was reduced by all amendments after thermal treatment, most prominent exception is a raised leaching of Cr due to an addition of fly ash which raised pH in soil. The most significant leaching element in anoxic conditions was As. Gypsum and metallic iron were chosen based on their inherent content of Ca, S and Fe which could bind As in certain conditions. A mixture of gypsum and iron reduced leaching most extensively in anoxic conditions. Gypsum decreased leaching of As at a higher extent in anoxic than oxidized conditions. Leaching of As was most extensively reduced by an addition of iron compounds and increased in a fly ash mixture in soil with no prior thermal treatment. All amendments decreased leaching of Cu and Cr except for fly ash which increased leaching of Cr. Leaching of soil with no prior thermal treatment was evaluated solely in oxidized conditions. A two-step soil washing test was performed for the evaluation of a humic acid (HA) extract in remediating soil contaminated with high levels of trace metals and polycyclic aromatic hydrocarbons (PAH). pH was initially set to 11 in the first step and 7 in the second step. Heated soil washing solutions of a humic acid extract, pH-adjusted water and solely water were compared. Humic acid extract significantly enhanced the extraction of PAH and Cu, Cr and As in comparison with other solutions tested but solely to a minor extent. The enhancement was most prominent concerning high molecular weight PAH. PAH was removed at a higher extent than trace metals using extractants containing HA.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Soil remediation amendments
Keyword [sv]
URN: urn:nbn:se:ltu:diva-48593ISRN: LTU-DUPP--10/099--SELocal ID: 608c7469-d267-4577-a208-5d77260b3f0eOAI: diva2:1021936
Subject / course
Student thesis, at least 15 credits
Educational program
Environmental Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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