Volume 1 (2003) Issue 2 Pages 217-224
Biodegradability improvement of refractory pollutants by hydrothermal reaction was investigated based on their structural conversion. Di- and Trichloroacetic acid were used as test sample, representing linear hydrocarbon structured refractory pollutants. At 250 °C and 4 MPa, attached recalcitrant chlorine atoms were eliminated by hydrolysis at the beginning of hydrothermal reaction. Biodegradable organic acids were yielded from hydrolyzed intermediates by dehydration and thermal decomposition. The decomposition rates of chloroacetic acids increased with increasing the number of attached chlorine atoms. During the initial structural conversion by hydrothermal reaction, the reduction of carbon contents of dichloroacetic acid did not exceed 6 % under the tested conditions. The similar results, however, were not observed in case of trichloroacetic acid. Biodegradable products were reduced by thermal decomposition as reaction time increased. The biodegradability of reaction products was not fatally retarded despite the presence of chlorine ions under the tested conditions. Hydrothermal reaction was proved as suitable pretreatment method to obtain biodegradable products from the structural conversion of refractory pollutants such as chloroacetic acids for the following biological treatment methods.