STUDY ON VARIATION OF HEAVY METALS SPECIATION IN SLUDGE STABILIZATION PROCESS

Heavy metals( including Cd，Pb，Cu，Zn and Ni) solution was added into the dewatered sludge for composting． The influence of sludge composting on stabilization of these heavy metals was evaluated． The total contents and speciation of each heavy metal were tested during the whole conposting process． After heavy metals were added into sludge，the total metal content of exchangeable and carbonate bound was in sequence as Cd ( 72. 31%) ＞ Ni ( 65. 83%) ＞ Zn ( 33. 67%) ＞ Cu ( 19. 49%) ＞ Pb( 7. 40%) ． The reaction of Pb，Cu，Zn with sludge went on faster，but that of Cd and Ni were relatively slower． In the whole composting process，Pb reached the stable state first，Cu and Ni ranked the second，followed by Zn and Cd． This conclusion could provide theoretical references for application of sewage compost on soil heavy metals pollution．