Statistical analysis of optimum Fenton oxidation conditions for landfill leachate treatment

Optimal operating conditions observed by peer reviewed publications for Fenton oxidation of raw and biological and coagulation treated leachates were reviewed and statistically analyzed. For the first-stage Fenton oxidation, the optimal pH range of 2.5-4.5 was observed for raw and coagulation treated leachates with a median pH of 3.0, whereas, for biologically treated leachate the optimum pH range was 2.5-6.0 with a median pH of 4.2. Theoretically, the optimal ratio of H2O2/Fe2+ should be the ratio of rate constants of the reactions between OH center dot radical with Fe2+ and H2O2, which is approximately 11; however, for leachate treatment, a median optimum relative dose of 1.8 (w/w) (3.0 M/M) was observed. Biologically treated leachate showed relatively lower optimum ratio of H2O2/Fe2+ doses (median: 0.9 w/w) as compared to raw (median: 2.4 w/w) and coagulation treated (median: 2.8 w/w) leachate. Median absolute doses of H2O2 and Fe2+ were 1.2 mg H2O2/mg of initial COD (COD0) and 0.9 mg Fe2+/mg COD0, respectively and raw leachate required higher reagent doses compared to pretreated leachates. A universal Fenton oxidation relationship between COD removal efficiency (eta) and COD loading factor (L-COD) for landfill leachate treatment was developed. As L-COD increases from 0.03 to 72.0, eta varies linearly as eta = 0.733L(COD) - 0.182. This robust linear relationship between L-COD and eta holds for Fenton oxidation of raw as well as biological and coagulation treated leachates. The relationship was validated using Leave-one-out cross validation technique and errors in predicting eta using L-COD were evaluated by applying Monte Carlo Simulation. As a result, the relationship can be used as a universal equation to predict Fenton treatment efficiency for a given COD0 loading in the range of 0.03-72.0 for landfill leachate treatment. (c) 2012 Elsevier Ltd. All rights reserved.