Fenton Process for Landfill Leachate Treatment: Evaluation of Biodegradability and Toxicity

The single Fenton or the Fenton process implemented in combined scheme as a posttreatment after the ferric chloride coagulation was applied for leachate collected from a real waste disposal site. Depending on the ratios of H(2)O(2)/chemical oxygen demand, H(2)O(2)/Fe(2+), and pH, the Fenton oxidation or both the Fenton oxidation and the Fenton coagulation were involved in chemical oxygen demand reduction. The implementation of ferric chloride coagulation as a pretreatment stage or acidification of raw leachate did not result in the improvement of chemical oxygen demand reduction efficacy of the following Fenton process comparing with that obtained by the direct Fenton treatment of raw leachate. The direct Fenton treatment with a higher (3/1) H(2)O(2)/chemical oxygen demand ratio applied to raw leachate without pH preadjustment (H(2)O(2)/Fe(2+)=10/1), produced more oxidized organic compounds (measured as dissolved organic carbon/chemical oxygen demand ratio), more biodegradable by-products (measured as a 7-day biological oxygen demand/chemical oxygen demand ratio), and required a considerably lower dosage of NaOH for neutralization, making it preferable for the leachate treatment. Although up to a twofold reduction in the toxicity was observed after the overall Fenton process application, the treated leachate remained extremely toxic to Daphnia magna.