| چکیده انگلیسی مقاله |
The present study investigates the effects of recirculation on the leachate pollutions and biogas production in a waste processing in the west of Tehran province, Iran. Recirculation is considered as an effective way in leachate pollutants reduction and biogas production rate increase. For this purpose, a trench with a size of 3*3*2.5 m was dug, and one pipe was applied for sampling. Parameters were examined, including the chemical oxygen demand, biochemical oxygen demand, turbidity, total suspended solids, ammonium, phosphate, copper, iron, cadmium, lead, and zinc. To evaluate the production of gases, the periodical measurements of CH4, H2S, and SO2 were performed. Moreover, biogas production in the trench was measured in seven repetitions. Then, leachate recirculation in the landfill was performed at the leachate volume ratio of 20:1, 10:1, 5:1, and 40:1. Comparison of the results indicated that the recirculation volume ratio of 1:20 maximized the reduction of pollutants. At this volume ratio, the maximum productions of CH4, H2S, and SO2 were obtained to be 50127 ppm, 21.12 ppm, and 0.23 ppm, respectively. The recirculation at the ratio of 20:1 reduced COD, BOD, ammonium, phosphate, TSS, and turbidity by 1650 mg/L (26%), 889 mg/L (20%), 1650 mg/L (26%), 10 mg/L (23%), 63 mg/L (11%), and 11.2 NTU (23%), respectively. Although the effects of recirculation on the reduction of pollutants, particularly organic ones, were found to be satisfactory, complementary treatment is required for the secondary utilization of wastewater. |