| With the acceleration of China's urbanization, the quantity of sewage increases, and many sewage treatment plants have been constructed, which increases the output of sludge, and how to dispose sludge has become a problem. Sludge reduction and resource has become a topic of wide concern, and heavy metal is a major obstacle in resource utilization.Electrokinetic technology has been used in food processing industry and remediation of contaminated soil by heavy metals. For its high removal efficiency, and can remove a variety of heavy metals. Recently it has been begun to be used in the research of the removal of heavy metals in sewage sludge. Based in Shanghai Bailonggang sewage treatment plant dewatered sludge, and under the condition of constant voltage, we analyse the Voltage distribution of sludge bed, electroosmotic flow direction and changes in the physical and chemical properties of the experimental research.From the experiment, we found that during the treatment of original sludge, the electroosmotic flow flows to the cathode and the system's voltage drop occurred mainly in the anode sludge bed, which results the dehydration driving force reduces. The sludge moisture is very uneven after treatment, and it gradually increase from the anode to the cathode. By opening small holes on the anode plate and gradually moving the anode plate to the cathode direction to alleviate this phenomenon in this paper.Opening small holes on the anode plate can reduce polarization, which can slower the increase speed of sludge bed resistance, and the electroosmotic flow increase faster. After treatment of 12h, the resistance of system with holes is about three-fifths of the sytem without hole. After 72h, there is not much difference between the two systems sludge bed of resistance. However the electroosmotic flow accumulation of the sytem with holes is 20% more than the sytem without holes. After treatment with AA method, the moisture of sludge bed is more evenly. After treatment 96h with FA method, the water moisture of anode sludge bed can be reduced from 74.61% to 49.5%, while the water moisture of cathode sludge bed only can be reduced to 61.9%, and the average moisture content is 55.5%. Under the same conditions, using AA method, the moisture of the whole sludge bed can be reduced to 53％～57.2%, and the average is 55.3%. What's more, AA method cost less energy than FA method. While, the removal efficiency of heavy metal is not high.During the process of electrokinetic treatment, the direction of electroosmotic flow is related to the pH value of the sludge, and affectes the movement heavy metal ions. When the pH value is higher than its isoelectfic point, the direction of electroosmotic flow is to the cathode, and the concentration of heavy metals in sludge is increased from the anode to the cathode. When the pH value of the sludge is equal to its isoelectric point, the electroosmotic flow flows to both directions—the anode and cathode, and the concentration of heavy metals in the middle region is lower than the anode and cathode regions. When the pH value is lower than its isoelectric point, the direction of electroosmotic flow is to the anode, and the concentration of heavy metals in the anode region is higher than other regions.After the origin sludge was treated by electrokinetic technology, the content of heavy metals in it has been reduced, but the removal efficiency is not high. Preacidification of the sludge can enhance the removal of heavy metals. But, the pH value of the sludge must be higher than its isoelectric point, so as to the direction of electroosmotic flow is consistent with the direction of heavy metal ions moving. When the sludge is acidified to pH 6.35, and deionized water was used as processing fluid in anode chamber, and nitric acid solution with pH 2 was used as processing fluid in cathode chamber, and also maintain the cathode processing fluid pH 2. After treatment of 120h, the average removal efficiency of Zn, Cu, Ni is 46.9%, 36.9%, 53.1% respectively.
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