Aged Chlorophenol Contaminated Soil's Integrated Treatment by Ozonation, Soil Washing and Biological Methods

Abstract

Traditionally soils contaminated by organic compounds have been treated by biological methods, but aged contaminated soils usually contain refractory and toxic compounds not any more responsive to biological treatment. By oxidation and soil washing the biodegradability and bioavailability of these otherwise recalcitrant compounds can be enhanced. The aim of the study was to optimize and integrate soil washing, ozonation (+ hydrogen peroxide) and biological treatment for the remediation of old saw mill soil contaminated by chlorophenols (CPs). The integration of different treatment train variables and the alternation of pHs (3, 7 and 10) and different ozone doses were studied in a laboratory scale. The soil was heavily contaminated aged soil (> 4000 mgCP kg(-1)), so more than 99% of removal should be attained in order to reach the Finnish guideline values. All the individual methods studied were able to degrade/transfer 25 - 95% of the CPs from the soil matrix. By biological treatment only 25% of the CPs were degraded. After soil washing, 40- 80% of the contaminants were transferred from the soil phase and by ozonation 35 - 95% decrease of CPs were achieved. All the methods studied successfully enhanced the biodegradability of the target compound. After biological treatment of ozonated and washed samples even 93 - 100% degradation of CPs was obtained. The most effective treatment was the combination of soil washing + ozonation (in pH 10) followed by biological treatment.

Remediation of soils contaminated by hydrophobic organic compounds: How to recover extracting agents from soil washing solutions?

“…For example, degradation kinetic rates observed for the removal of PAH from SW solutions by electro-oxidation using graphite electrodes were in the range 0.02-0.2 h -1 [21,164]. As regards to ozone, it was observed significant removal of PAH and chlorophenols from SW solutions (45-65% removal) only when using high doses (> 500 mg O3 L -1 ) [165,166]. Besides, it was reported that high concentration of surfactant decreases gas-liquid mass transfer for both (semi)-volatile pollutants and ozone, thus reducing the effectiveness of the ozone process [167].…”