PH16 Metals in the Environment: Chemistry and Fate Issues
Exhibit Hall
8:00 AM - Thursday, 13 November 2003
(PH155) Heavy metal binding capacity (HMBC) of Municipal Solid Waste (MSW) landfill leachates.
Ward, M1, Bitton, G1, Townsend, T1, 1 University of Florida, Gainesville, FL, USA
ABSTRACT- Landfilling remains the predominant management method for municipal solid waste (MSW) in the United States. Modern sanitary landfills are lined and contain systems for the collection of leachates, a waste byproduct created as water entering the landfill exceeds the wastes field capacity. A specific heavy metal toxicity assay, MetPLATE was used for the identification of metal toxicity, bioavailability and heavy metal binding capacity (HMBC) of municipal solid waste (MSW) landfill leachates. The MSW leachates collected from 14 landfills in Florida displayed a wide range of chemical and physical characteristics. The toxicity of the leachates was low, which was attributed to site-specific parameters, including, high concentrations of both organic and inorganic ligands. The HMBC was determined by the ratio of metal toxicity in the sample to the metal toxicity in the control water and incorporated the influence of site-specific parameters on metal toxicity. The potential for MSW leachate to bind and, thus, detoxify heavy metals was investigated with copper, zinc, and mercury. The HMBC values obtained ranged from 3 to 115, 5 to 93 and 4 to 101 for HMBC-Cu+2, HMBC-Zn+2, and HMBC-Hg+2, respectively. Additionally, the high strength leachates displayed the highest binding capacities, although the landfills sampled represented a wide range of characteristics. For comparison, the HMBC values reported with local lake water, Lake Alice and Lake Beverly, and a wastewater treatment plant effluent were all below 3. A partial fractionation of MSW leachate samples from sites 1, 5, and 8 was conducted to further investigate the influence of selected site-specific physico-chemical parameters on metal binding. The fractionation revealed that the HMBC of the leachate samples was heavily influenced by the concentration of solids, organics and hardness. The results presented represent the first quantitative determination of metal toxicity, bioavailability and metal binding capacity in landfill leachates using toxicity assays.
Key words: heavy metal binding capacity, MSW landfill leachates, metals