Effect of electro-kinetics on the elimination of major heavy metals in sludge

Effects of electro-kinetics at the optimal voltage drop on the elimination of major heavy metals in urban sludge were studied with various chelating agents.The results showed that the elimination of Cr in sludge was the greatest using citrate among all treatments under 1.0 V·cm-1 voltage drop.A 67.52% elimination rate was obtained,which was 6.31% and 6.79% higher than those using EDTA and lactate,respectively.The rates of Pb and Cd elimination using citrate,EDTA,and lactate under 1.0 V·cm-1 voltage drop were similar,ranging from 60% to 80%.The Cr,Pb,and Cr eliminations using citrate under 1.0 V·cm-1 voltage drop increased with treatment time.The elimination rates for Cr,Pb,and Cr in sludge after 144 h of treatment were more than 98%.The contents of Cr,Pb,and Cd in the resultant treated sludge were 599.84 mg·kg-1,128.88 mg·kg-1 and 3.38 mg·kg-1,respectively.They were all below the national standards for heavy metals in sludge for agricultural applications.