Characteristics of landfill leachates in central Taiwan.

Due to the complex nature of landfill leachates, the leachate treatment plants have difficulty to meet the current Taiwan EPA's effluent standards. Three typical types of landfills, closed landfill A, mixed landfill B (disposal of MSW with bottom ashes from MSW incinerators) and direct MSW landfill C, (disposal of MSW only), are investigated in this research in order to have a better understanding of characteristics of leachates. Factors investigated in this research include landfill age, pH, BOD, COD, TS, DS, VS, seasons, metals (Pb, Ca, Cd, Hg, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, and Zn), humic substances (humic acid, fulvic acid, and non-humic substance), aromaticity and toxicity. Results show that the active landfills B and C had the significant higher concentration of COD, VSS, TS, PtCo, TOC and conductivity. The mixed landfill B had the higher DS, TS, Na, Ca, Mg and conductivity than that of direct MSW landfill C. Direct MSW landfill C had the highest contents of Fe, Cr, Ni and acute toxicity among these landfills. A significant degree of variation was encountered and factors which may influence leachate quality were identified and discussed.