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In situ bioremediation of an oil-polluted subsoil: Results of the experiments in undisturbed columns

In situ biorestauratie van een met olie verontreinigde bodem: Resultaten van het onderzoek in ongestoorde grondkolommen

Synopsis

Column experiments were carried out for the project "in situ bioremediation of an oil-polluted subsoil". The experiments were aimed at examining the possibility of remediating soil in situ with the help of microorganisms. The six undisturbed columns were filled at a location contaminated with petrol in Asten (the province of North Brabant). Different nutrients were applied to the columns to examine the effect on the activity of the microorganisms. From the results the petrol components can be shown to be eliminated from the soil by leaching and degradation carried out by microorganisms, the relative importance of the process depending on the additions. The columns were cleaned, first where the percolation water enters the column. Almost all the oxygen supplied was used in the columns. Aerobic conversions are concluded to have taken place. In column 5 a large amount of nitrogen was used in the column. Probably conversions under anaerobic conditions took place in this column due to the nitrate supply. It is not clear if this took place in the other columns. The lowest residues of petrol components were found in columns 3 and 4, in which hydrogen peroxide was supplied. Nevertheless, the largest amount of petrol was dissipated in column 5. Whether this is caused by anaerobic conversions during the first phase of the experiments or by recirculation during the second phase is not known. Good results were achieved in column 6, in which only the effluent was recirculated. The residues of petrol components in the lower part of the columns were below the detection limit in all columns, except column 1. Only in column 4 was this also found in the upper part. The best results were achieved in the columns in which hydrogen peroxide was supplied and in the columns where the effluent water was recirculated. Since the operation time in columns 4 and 5 was the longest, the results in these columns were better by comparison than columns 3 and 6, respectively. It is not certain, however, that the Dutch target values will be met in all columns. The research shows in situ bioremediation to be a promising technique for the remediation of soil with oil compounds. Further development of this technique through large-scale bioremediation is recommended.
 

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