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Treatment of sanitary landfill leachate with peat Lidkea, Thomas Roy

Abstract

Leachate is generated by the action of water on the solid wastes deposited in sanitary landfills or dumps. In this research, peat was investigated as a means of removing metal ions from leachate. The leachate used in the investigation was obtained from a project at the University of British Columbia in which leachate is generated under controlled conditions. Two different types of locally available peat were used in initial batch tests. These were a fibrous peat derived mainly from sphagnum moss and in a middle stage of humification, and a well humified sample of woody peat from the surface. These samples were used to treat distilled water solutions of Fe, Cr, Zn, AI, Cd, and Pb, The fibrous peat was found to be superior and was used in subsequent tests. In the batch tests performed on distilled water solutions of the above metals, it was found that the fibrous peat adsorbed between 12 and 38 mg of metal per gm of peat. In the batch treatment of leachate, the fibrous peat was found to have a capacity of 55 mg/gm. A test conducted to investigate the dependence of adsorption on pH showed that adsorbance was best in the range between pH 3.0 and 4.0. Column tests were performed on distilled water solutions of Cr in order to optimize the column's design. Based on these tests, 60 gm of wet fibrous peat were packed in a column 12 inches high and 0.75 inches in diameter. A flow rate of 0.100 gpm/ft² was used in treating two different samples of leachate. In treating the first leachate, which had a high strength (total metal concentration was 5,360 mg/1) and a pH of 4.84, it was found that the treatment capacity of the peat was about 48 mg/gm. At treatment efficiencies of 90 per cent and 75 per cent, peat capacities were 31.4 and 43.3 mg/gm, respectively. The test of a low strength leachate (total metal concentration was 1,830 mg/1) of pH 5.35 was not valid for assessing the performance of the column since many of the metals were present as solids which were simply filtered out in the column. The usefulness of peat in treating leachate depends on the type and concentration of the leachate. In order to be effective, large amounts of peat may have to be used. For example, to remove 90 per cent of metal ions from 1,000 gal. of the high strength leachate would require roughly 0.77 tons (dry) of peat.

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