Concentrated Leachate Treatment by Electro-Fenton and Electro-Persulfate Processes Using Central Composite Design

Current work deals with the treatment of leachate nanofiltration concentrate which was exposed to ultrafiltration membrane treatment following anaerobic biological process and nitrification–dentrification process before. Advanced electrocoagulation processes [electro-Fenton (EF) and electro-persulfate (EF)] were applied to the wastewater characterized by high inert COD content arising from resistant organic matter. Response surface methodology and central composite design were employed for modeling and optimizing the processes. Adequacy of the model was examined by application of variance analysis that verified the conformity of experimental and predicted data. Under statistically obtained optimized conditions for COD removal (H 2 O 2 /COD ratio 1.42, current 2.27 A, pH 2.9, and reaction time 30.3 min for EF; and S 2 O 8 −2 /COD ratio 1.72, current 1.26 A, pH 5.0 and reaction time 34.8 min for EP processes), predicted COD removal efficiencies were determined to be 67.1% and 72.6% for EF and EP treatments, respectively. By performing experimental sets for validation, 60.8% and 71.4% COD removals through EF and EP processes were obtained under these conditions. NF concentrate COD fractions were also determined before and after treatment processes. Soluble COD fraction increased from 71.4 to 83.2% and 87.7% whereas biodegradable COD fraction increased from 12.2 to 19.2% and 32.5% after EF and EP processes, respectively. Results of the study showed that both EF and EP processes were efficient alternatives for leachate NF concentrate treatment but EP process can be preferred due to lower energy consumption. Article Highlights Electro-Fenton and Electro-Persulfate processes were applied for inert COD removal from leachate nanofiltration concentrate. Response surface methodology approach using Central Composite Design was employed for modelling. Under statistically optimized conditions 60.8% and 71.4% COD removals through EF and EP processes were obtained. Biodegradable COD fraction increased and insoluble COD fraction was significantly converted to soluble fraction. Total cost of EF process (5.0 €/ m 3 ) was found to be higher than that of and EP process (2.8 €/ m 3 ).