|Title||Improving bioremediation of PAH contaminated soils by thermal pretreatment|
|Source||Wageningen University. Promotor(en): W.H. Rulkens; J.T.C. Grotenhuis. - S.l. : S.n. - ISBN 9789058083630 - 139|
|Publication type||Dissertation, internally prepared|
|Keyword(s)||bioremediëring - verwarming - polycyclische koolwaterstoffen - besmetting - biodegradatie - desorptie - volksgezondheidsbevordering - verontreinigingsbeheersing - bodemverontreiniging - bioremediation - heating - polycyclic hydrocarbons - contamination - biodegradation - desorption - sanitation - pollution control - soil pollution|
|Categories||Bioremediation / Soil Pollution|
Numerous sites and large volumes of sediments in the Netherlands are contaminated with polycyclic aromatic hydrocarbons (PAH), which are of great concern because of their toxic and carcinogenic effects. Since PAH tend to sorb very strongly to the soil matrix, bioremediation is a slow process with often high residual concentrations after remediation. In this study it was tried to develop methods to improve bioremediation, this means to decrease residual concentrations after bioremediation. In a literature survey, several methods were evaluated and two methods were selected for further study: soaking of soil with an organic solvent and short-term heating of soil. In biodegradation experiments with PAH contaminated soils short-term heating resulted in the largest increase of the PAH fractions that could be degraded (Figure 1).
Desorption experiments revealed that desorption of PAH took place in two stages: a fast-desorption stage and a slow-desorption stage. The increase of the biodegradable fractions after heating in the biodegradation experiments could be related to an increase of the fraction of PAH that exhibited fast desorption. A comparison between biodegradation kinetics and desorption kinetics showed that desorption experiments could predict biodegradation results, except for high molecular weight PAH (5 or more aromatic rings). Biodegradation rates of high molecular weight PAH were always lower than desorption rates, possibly caused by slow growth of microorganisms that had to degrade these compounds.
A mathematical model, describing desorption and biodegradation of PAH contaminants, showed that this slow growth could be caused by the low aqueous phase concentrations of the soil sorbed high molecular weight PAH. A technical and economical evaluation of a thermal pretreatment of PAH contaminated soils showed that a thermal pretreatment can be succesfully incorporated in current remediation practices and that it can be a competive alternative to current remediation techniques.