Application of integrated sequence of air stripping, coagulation flocculation, electrocoagulation and adsorption for sustainable treatment of municipal landfill leachate

Abstract

Leachate generated from landfill is required to be treated by simple, fast, economic and environmentally sustainable methods before being discharged to the environment since it is considered as a highly pollutant wastewater. The aim of this research work is to check the potential treatability of integrated sequence of air stripping, coagulation flocculation, electrocoagulation and adsorption method for leachate generated from an uncontrolled municipal solid waste landfill site complying with legal discharge standard. At optimum retention period of 36 hours air stripping method exhibited a maximum removal of 96.87% of NH 4 -N, 74.5% of BOD 5 , 52.78% of COD, 8.7% of Hg and 18.43% of Pb from raw leachate at normal pH and air flow rate of 10 L/min. The application of optimized CF process using FeCl 3 as coagulant of dosage 3.09 mg/L resulted a maximum removal of 84.20% of BOD 5 , 57.67% of COD and 46.2% of Hg at pH 5.22. Following CF process EC process was adopted with Fe electrode and optimized by CCD of response surface methodology. At optimum pH 7.46, current density 3.13 mA/cm 2 and electrolysis time 24.83 min the maximum removal was recorded as 51.1% COD and 91.92% Hg. EDAX analysis confirmed the presence of Hg in the precipitates of ECP. Finally fixed bed column adsorption study using chitosan beads resulted in 98.11% of Hg removal. The integrated treatment sequence resulting an overall removal of 96.87% of NH 4 -N, 95.97% of BOD 5 , 90.23% of COD, and 99.93% of Hg which is sufficient enough to reduce pollutants of raw leachate below discharge standards at overall costs of USD 0.036/L. • Integrated sequence of multiple physicochemical treatment methods were used to reduce pollution load from raw municipal landfill leachate. • Process variables of electrocoagulation method were optimized by center composite design of response surface methodology. • EDAX confirmed the removal of Hg by electrocoagulation process using iron electrodes. • Low cost chitosan beads were used for adsorption. • The leachate discharge standard in inland surface water was achieved at nominal cost.