Zn and Ni of Bottom Ash as a Potential Diffuse Pollutant and Their Application as “Fine Aggregate”

Abstract

Municipal waste collection is included to solid waste management, involving recycling, incineration, dump etc. To minimize the hazards, incineration of medical waste is a significant alternative way for disposal of this category of waste. But relatively less attention has been given to bottom ash. Now bottom ash is dumped on the soil which mixes in to the soil as diffuse pollutant. In this study bottom ash samples were collected from a typical Municipal waste incinerator and typical pollutants including heavy metals (Zinc and Nickel) and nutrients (Calcium and Magnesium) concentration were examined by following standard extraction and detection procedure. In our test, the concentration of Zn (578mg/kg to 1108mg/kg), Ni (105 mg/kg to 410 mg/kg) exceeded the tolerable level of Zn (300mg/kg) and Ni (40mg/kg).The concentration of the nutrients Ca(435mg/kg to 754mg/kg) and Mg(372mg/kg to 1103mg/kg) were found. Pollution Load Index , Ecological Risk Index, Enrichment Factor and Geo-accumulation Index were applied to assess the level of heavy metal contamination. Co-relation factors of those heavy metals were also established. Ash samples were subjected to solidification/stabilization studies, by making blocks in different sand-ash ratios, using Ordinary Portland Cement (OPC) as binder. The Compressive strength of blocks is obtained through tests using American Standard Testing Machine (ASTM). The leaching characteristics of solidified ash in to block, were also examined by standard testing procedure. The ash can be recycled as construction material (fine aggregate), and can be used in low mortar strength applications, such as rings of pit latrines, pavement tiles for footpaths, wall tiles etc.