Characteristics of Dissolved Organic Carbon in the Leachate from Moonam Sanitary Landfill

Abstract

Abstract This study determinated of the characteristics of dissolved organic carbons (DOCs) in the leachates and the effluents from a treatment unit of a medium scale sanitary landfill, which is supposed to be in the early stage of methane fermentation. In particular, interest is focused on the distribution of molecular weight of DOCs determined from ultrafiltration fractionation, the separate recovery of humic acids with resins XAD-8 and XAD-4, and the determination of their spectrophotometric characteristics. The bulk properties of leachates were as follows; pH: 7.1–7.8, BOD5: 400–1 100 mg l−1, COD: 2100–8200 mg l−1. The ratio of BOD5/COD falls in the range of 0.14–0.24 and total organic acids comprise 55% of the DOC contents. Spectroscopically determined dominant wavelength of the leachates is 575 nm. DOCs with a molecular size above 1.5 nm appear to cause 60 % of the absorbance at 575 nm and those adsorbed by the resin XAD-8 are found to cause 70–80 % of the absorbance. Size distribution of DOCs is found to shift to relative abundance in smaller molecules after treatment of the raw leachates by flocculation-sedimentation process. Fractionation with XAD-8 resin shows that 20–30 % of the DOCs are hydrophobic in nature and that about 8 mg of humic acid can be recovered from 1 l of the leachates. The FT-IR spectrum of leachate humic acid proved to be similar to the Aldrich humic acid except the lack of absorption peak near 1 050 cm−1. The values of E4/E6 and E2/E4 of the leachate humic acid are 5.85 and 4.57 respectively. Keywords: Dissolved organic carbonleachatesanitary landfillhumic acidfractionation