Heavy metal contamination in leachate from spent batteries in municipal solid wastes

Abstract

To determining the risk of heavy metals from spent batteries disposed of directly into the municipal solid waste. Two types of experimental tests were performed on the spent batteries, i.e. batch leaching tests and simulated landfill lysimeter tests. These two types of tests were conducted in order to address the concerns associated with the leaching of chemicals from batteries into the landfill leachate. A series of batch leaching tests, TCLP tests, utilizing four types of batteries with thirty-six samples of spent batteries of various types and sizes, were performed. Five lysimeters, made from PVC pipes, each with a height and diameter of 2 m and 20.32 cm, respectively were prepared for the leaching column tests. Two lysimeters were filled solely with batteries, one with broken batteries and the other without. The other three lysimeter were filled with municipal waste mixed with batteries at zero, 1 and 5 percent by weight of the waste, respectively. It was found that in the batch leaching tests, only the Cd concentration, which leached from Ni-Cd batteries, exceeded the US TCLP Toxicity Characteristic Regulatory limit. Mainly, Zn was found as a major element in the leaching solution due to the composition of the zinc plate in the anode. The leachate characteristics generated from the lysimeter filled with and without broken batteries could not be compared due to a clogging problem. Among the three landfill lysimeters, Fe was found to be the major metal that leached out. The landfill lysimeter with five percent batteries generated significantly higher concentrations of Cd, Mn, Zn, Ni, Pb and Fe than the lysimeter filled solely with municipal wastes and the lysimeter containing municipal waste mixed with one percent of batteries. The results also indicated that Fe, Ni and Zn concentrations in the leachate generated from the lysimeter containing municipal waste mixed with one percent of batteries were significantly higher than the lysimeter filled solely with municipal wastes. Moreover, when the leachate characteristics were compared against the Groundwater Standards for drinking purposes, the concentrations of Cd, Fe, Mn and Zn were found to be much higher than the allowance standards as ruled under the Groundwater Act B.E.2520 (1977). It could be concluded that the disposal of spent batteries into the municipal waste stream creates a high potential risk of heavy metal contamination in landfill leachate.