Treatment of landfill leachate by integrated sequence of air stripping, coagulation–flocculation and adsorption

This research work has been performed to institute a proper landfill leachate treatment program by the integrated sequence of air stripping, coagulation–flocculation (CF), and adsorption. In this study, air stripping removes up to 96.3% of NH3–N, 49.3% of COD, and 74.1% of BOD5 within an optimum retention period of 36 h. Optimization of CF and adsorption were accomplished by employing central composite design of response surface methodology. The application of CF resulted in the removal of COD by 55.3%, BOD5 by 83.9%, color by 91.8%, and Hg by 42.2% at the optimized state of pH 5.2 and FeCl3 dose of 3.1 g/L. In case of adsorption, about 56.1% of COD and 89.2% of Hg removal were observed at the optimum conditions of pH 7, adsorbent dose of 0.6 g/L of chitosan beads, and 66.4 min of contact time. Langmuir isotherm model satisfactorily described adsorption isotherm and fitted with pseudo-second-order kinetic model. Adsorbent was characteristically specified by FTIR and SEM with EDAX analysis. Desorption study showed that 77.2% of adsorbed Hg could be recovered effectively by EDTA. The overall treatment schedule demonstrates a net removal of 96.3% of NH3–N, 91.8% of color, 95.8% of BOD5, 90.0% of COD, and 95.8% of Hg.