RESUMO
Landfill leachates contain a wide variety of pollutants such as organic matter, refractory compounds, ammonia, particulate and dissolved solids and hazardous metals requiring application of advanced and well designed treatment processes before release to the environment. The main purpose of this research was to evaluate the efficiency of combined air stripping, Fenton oxidation and biological treatment in treating landfill leachate, especially the elimination of ammonia and refractory organics. The laboratory scale set-up consisted of three sequential but separate steps. The optimum conditions for air stripping and the Fenton oxidation were determined for landfill leachate from Karaj city, Iran. The final step was a moving bed bioreactor with HRTs of 18, 12 and 6 h. The highest NH(3)-N removal was 79% in the air stripping process at pH 10.5. At the optimum conditions for the Fenton reaction at a reaction time of 90 min, pH 3 and a H(2)O(2)/Fe(2+) mass ratio of 20, the COD removal was 61% and improved the BOD/COD ratio from 0.42 to 0.78. The overall COD removal including the final biological reactor with a HRT of 6 h resulted in an effluent COD concentration of less than 100 mg L(-1).