Treatability of leachate from a sanitary landfill by anaerobic digestion

Pollution control authorities are becoming more and more concerned about the effects of highly polluted leachate from solid waste landfills on receiving waters. Control or treatment of such leachate is thus becoming very important. This study was established to investigate the possibility of reducing the amounts of oxygen demanding material in the leachate by anaerobic digestion without any prior removal of heavy metals which were contained in it. It also included a study of the effects of varied detention time and the changing characteristics of the leachate. BOD₅, removals ranging from 80 to 96 percent were achieved for detention times ranging from 5 to 20 days and influent BOD₅'s ranging from 11,000 to 16,000 mg/1. C.O.D. removals ranged from 65 to 79 percent for influent values ranging from 23,000 to 33,000 mg/1. A variety of metals including aluminum, cadmium, chromium, copper, lead, mercury, nickel and zinc were present in the leachate. Their concentrations covered a broad range with zinc being the highest at 65 mg/1. The anaerobic digestion process was not adversely effected by these metals. Some of these metals, notably aluminum, cadmium, mercury, nickel and zinc were essentially completely associated with the sludge, while the others were associated to a lesser extent. Gas production ranged from 11.9 to 15.0 cubic feet per pound of BOD₅ destroyed, and methane production ranged from 5.8 to 6.8 cubic feet per pound of C.O.D. destroyed. From the results obtained the indications are that leachate treatability by anaerobic digestion holds good prospects. Since at 20 days detention time 96 percent removal was achieved it is likely that detention times beyond 20 days would result in a greater percent removal.Applied Science, Faculty ofCivil Engineering, Department ofGraduat