Treatment of sanitary landfill leachate by the combination of photo-Fenton and biological processes

In this work, the pollutant reduction performance in landfill leachate by combining both photo-Fenton and biological processes was investigated. First, conventional biological treatment was performed, consisting of a decantation process, with centrifugation at 5000 rpm for 15 min, followed by the biological process conducted at 236 +/- 0.1 mg mg(-1) (BOD5/MLSS) and 0.571 +/- 0.04 vvm (L L-1 min(-1)) for 40 h. At the same time, in the application of the photo-Fenton process, a central composite rotatable design (CCRD) was applied to evaluate the effect of main process variables. The quadratic models of chemical oxygen demand (COD) and 5 days biological oxygen demand (BOD5) removal were proposed and validated, being separately used as objective functions during the search for optimal operating conditions. After the application of the conventional biological process, removals of 87 +/- 2% and 84 +/- 2% were obtained for COD and BOD5, respectively. For the photo-Fenton process under optimum conditions (3400 mg H2O2 L-1, 80 mg Fe2+ L-1, pH = 2.40 and 120 min), removals of 89 +/- 3% COD and 75 +/- 1% BOD5 were obtained. However, both processes did not meet effluent discharge standards. So, the optimized photo-Fenton process was then combined with the biological process, performed for 150 h with 1.571 +/- 0.06 vvm and 4.41 +/- 0.3 mg mg(-1) (BOD5/MLSS). With the combined process, it was possible to treat an effluent with high organic load, achieving a removal of 98% COD and BOD5 and meeting the restrictive standards of release in recipient water bodies. (C) 2018 Elsevier Ltd. All rights reserved.