Assessment of bioavailability and leachability of heavy metals during rotary drum composting of green waste (Water hyacinth)

Studies were carried out on bioavailability and leachability of heavy metals (Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr) during rotary drum composting of water hyacinth (Eichhornia crassipes) for 20 days. This study investigates the influence of physic-chemical parameters such as pH, temperature and organic matter content on distribution of heavy metal bioavailability and leachability during water hyacinth composting. The bioavailability was investigated in the form of water soluble and diethylenetriamine penta-acetic acid (DTPA) extractable. Results show that during composting, the total metal concentration was increased. Water soluble Ni, Cd and Pb and DTPA extractable Cd and Pb were not detected but all metal concentration were observed by TCLP test during the composting process. Leachability of Cd was very low among all the eight metals analyzed. The optimum proportion of cattle manure can enhance organic matter degradation and humification process; consequently it reduced the toxicity of metals during rotary drum composting. (C) 2013 Elsevier B.V. All rights reserved.