Statistical analysis of optimum Fenton oxidation conditions for landfill leachate treatment
► Optimal conditions for Fenton oxidation of leachate were statistically analyzed. ► Median values of optimum pH and H 2 O 2 /Fe 2+ were 3.0 and 1.8, respectively. ► Median H 2 O 2 /COD 0 and Fe 2+ / COD 0 doses were 1.2 and 0.9, respectively. ► Treatment efficiency linearly varied with COD loading factor as η = 0.733 L COD -0.182. 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 H 2 O 2 /Fe 2+ should be the ratio of rate constants of the reactions between OH radical with Fe 2+ and H 2 O 2 , 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 H 2 O 2 /Fe 2+ 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 H 2 O 2 and Fe 2+ were 1.2 mg H 2 O 2 /mg of initial COD (COD 0 ) and 0.9 mg Fe 2+ /mg COD 0 , respectively and raw leachate required higher reagent doses compared to pretreated leachates. A universal Fenton oxidation relationship between COD removal efficiency ( η ) and COD loading factor ( L COD ) for landfill leachate treatment was developed. As L COD increases from 0.03 to 72.0, η varies linearly as η = 0.733 L COD - 0.182 . This robust linear relationship between L COD and η 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 η 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 COD 0 loading in the range of 0.03–72.0 for landfill leachate treatment.