Fractionation and Reduction in Bioavailability of Toxic Heavy Metals During Rotary Drum Composting of Paper Mill Sludge

摘要

Composting is the most suitable recycling option for paper mill sludge (PMS) due to high organic content. However, final compost produced from PMS contain high concentration of heavy metals, resulting in restricted land application of compost. The aim of the study was to reduce bioavailable form of heavy metals during the composting of PMS using rotary drum composter. Therefore, this study was carried out to identify the variation in distribution of different fractions (exchangeable, carbonate, reducible, oxidizable and residual fraction) of Cd, Pb and Cr during rotary drum composting of PMS. Tessier sequential extraction method was applied for speciation of heavy metals. Residual fraction of most of heavy metals was found to be dominant fraction in all treatments. The concentration of Cd was not very high; however, its bioavailable fractions were found to be high. This study shows that addition of cattle manure in appropriate quantity can influence the physico-chemical parameters, resulting in decrease in the bioavailable fraction (exchangeable and carbonate) of heavy metals during composting process. An addition of cattle manure decreased the exchangeable and carbonate fractions of metals during the composting process. A reduction in bioavailability factor was also observed in all treatments during the composting process.