Abstract
The aim of this study was to check the effectiveness of the Fenton’s reagent (Fe 2+ + H 2O 2 + H +) for the pre-treatment of a municipal landfill leachate with the objective of improving its overall biodegradability, evaluated in terms of BOD 5/COD ratio, up to a value compatible with biological treatment. The leachate came from a municipal sanitary landfill located in southern Italy and the average values of its main parameters were: pH=8.2; COD=10 540 mg l −1; BOD 5=2300 mg l −1; TOC=3900 mg l −1; NH 4-N=5210 mg l −1; conductivity=45350 μS cm −1; alkalinity=21 470 mg l −1 CaCO 3. The effect of initial pH value on the pre-treatment effectiveness was evaluated by titrating the amount of acidic by-products formed. The extent of leachate oxidation was monitored and controlled by both pH and redox potential measurements. The best operational conditions for achieving the desired goal (i.e., BOD 5/COD ⩾ 0.5) resulted: Fe 2+=275 mg l −1; H 2O 2=3300 mg l −1; initial pH=3; reaction time=2 h. At the end of the Fenton’s pre-treatment, in order to permit a subsequent biological treatment, residual ferric ions were removed increasing the pH up to 8.5 by adding 3 g l −1 of Ca(OH) 2 and 3 mg l −1 of a cationic polyelectrolyte, the latter as an aid to coagulation. This final step also resulted in a further modest removal of residual COD due to co-precipitation phenomena.
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