Effects of lime on bioavailability and leachability of heavy metals during agitated pile composting of water hyacinth.

In the present study composting of water hyacinth was done with cattle manure and saw dust (6:3:1) ratio and effects of addition of lime (1%, 2% and 3%) on heavy metal bioavailability and leachability was evaluated during 30 days of composting period. The changes in temperature, pH, electrical conductivity (EC), organic matter and extractable heavy metal contents were measured. Results showed that the total concentration of heavy metals was increased during the composting process. Due to addition of lime initial pH of the compost was raised effectively, caused a decrease in water soluble, diethylene triamine pentracetic acid (DTPA) and toxicity characteristics leaching procedure (TCLP) extractable metal contents in the final compost. Water soluble metals (Ni, Pb and Cd) and DTPA extractable metals (Pb and Cd) were not detected during water soluble fraction. Addition of lime significantly reduced the bioavailability and leachability of heavy metals during water hyacinth composting process.