Effect of Removal of Household Hazardous Wastes on Leachate Toxicity Based on Toxicity Characteristic Leaching Procedure

Abstract

The aim of the study was to investigate the effect of separation of household hazardous wastes on leachate toxicity using the toxicity characteristic leaching procedure (TCLP). In the study, 1,000 kg of conventional municipal waste, 1,000 kg of municipal waste after separation of hazardous components, and 8 kg of household hazardous waste were buried in three separate trenches. After 6, 12, and 24 months, a sample of 500 mL was taken from each trench’s leachate and the TCLP conducted. The results showed that the numbers of heavy metals, volatile organic compounds, and pesticides with concentrations above permissible levels after 24 months in the leachate of conventional municipal waste were 3, 11, and 3, respectively, whereas those in the leachate of waste without household hazardous components were 1, 2, and 1, respectively. The ratios of biochemical oxygen demand (BOD) to chemical oxygen demand (COD) in the leachate of conventional municipal waste and waste without hazardous components were 0.51 and 0.61, respectively, indicating a 20% increase in biodegradability. The highest and lowest concentrations of heavy metals were those of barium (161 mg/L) and mercury (1.7 mg/L), respectively. The levels of heavy metals, volatile organic compounds, and pesticides in the leachate after 12 months exceeded the permissible levels. The results showed that the separation of hazardous components decreased the amount of heavy metals, volatile organic compounds, and pesticides in the leachate and hence reduced toxicity. The separation of hazardous components also caused less decrease in the biological degradability of the leachate over time.