OIL SHALE SEMICOKE LEACHATE TREATMENT USING OZONATION AND THE FENTON OXIDATION

摘要

The storage of semicoke in Estonian oil shale industry causes a variety of impacts on the environment, including formation of a very toxic leachate, and requires additional efforts to bring the environmental situation into accord with environmental standards. The present study focused on the chemical treatment of the semicoke leachate and the usage of chemical oxidation (ozonation and the Fenton oxidation) for the improvement of conditions for subsequent biodegradation. Moderate ozone doses removed from 40 to 63 % of organics and enhanced the biodegradability. However, 40-45 % of the residual organics remained not biodegradable and ozonation did not lead to detoxification of the leachate. The Fenton oxidation was found to be effective for the treatment of leachate and led to substantial increase in biodegradability. It was ascertained that the Fenton oxidation of the leachate may be applied without pH adjustment. The toxicity reduction in the Fenton oxidation was of great significance. More than 70 % removal of COD values, increase in biodegradability and the reduction in the toxicity suggest that under some circumstances the Fenton treatment may be even applied as the main treatment process for this leachate.