Removal Of Heavy Metals From Sludge By Electrokinetic Technology

With the rapid development of modern cities, in order to alleviate the problem ofpollution of urban sewage effectively, urban sewage treatment plant is in theconstruction, but it also brings the problem that a lot of sludge are generated in thewastewater treatment process. The sludge is rich in nitrogen, phosphorus, potassiumand other nutrients, and the application in agricultural has become a hot research areatoday, but heavy metals in the sludge are the limiting factor in agricultural. How toeffectively remove heavy metals form sewage sludge is currently a hot research topicof municipal and environmental engineering.As an emerging green remediation technology of treating environmental pollution,electrokinetic remediation possess many advantages, such as, less investment, highremoval efficiency and short processing time, especially for the poor waterpermeability sludge. Electrokinetic remediation technology has good applicationprospects.According to electrodynamics basic principle, the study conducted by removingharmlessly heavy metals from sewage sludge through electrolytic treatment usingthree groove electrolyzer, and we used ion-exchange membrane instead of thetraditional permeable membrane to investigate the impacts on heavy metals removalrate.1. Using the sludge from sewage treatment plant of Jianxi District sludge objectas the research object, the electrolysis time and pH value of sludge were studied,which have a great influence on heavy metals removal rate in the electrokineticprocess. The results show that electrolysis time has an important influence on heavymetals removal, and removal efficiency of Pb, Cu, Zn, Cr and Cd were improved invarying degrees with the electrolysis time lengthened, Zn is the most obvious, whoseremoval rate increased from3.8%to35.9%. As pH of the sludge decreased, theremoval effect of heavy metals becomes more obvious. When the sludge pH value is1, the removal rate of Pb reached85.7%.2. Using dewatered sludge in secondary sedimentation tank in sewage treatmentplant of Henan Yuguang Gold&Lead Co as research project, the sludge pH,electrolyte pH and the electrolysis time’s impacts on Pb, Cu, Zn, Cr and other heavymetal removal rate in the conditions of were researched. Experimental results are asfollows: the longer is the electrolysis time, and the removal rate of heavy metals is thehigher in a certain range. As the electrolysis time reached20h, the removal rate wouldremain stable. the reduction of sludge pH is good to the removal of heavy metals, andthe reduction of the electrolyte pH is also beneficial to the heavy metal removal tosome extent.3. the consolidated results of the above tests are summarized. The sludgeacidification is conducive to remove heavy metals, and the each heavy metals removalrates are increasing with electrolysis time, but not the same degree of influence on theeach heavy metal. That ion exchange membrane replaces filter paper and othertraditional permeable membrane can not only improve the removal of heavy metals inthe sludge and avoid over-acidification, but also facilitate follow-up treatment. Themixing sludge agricultural is not conducive to heavy metal sludge removed. The heavymetal removal rate is a positive correlation with the voltage, Updating the pH of thecatholyte, which can reach dual effect of controlling the catholyte and exporting theprecipitate and to improve the removal of heavy metals to some extent. so circulatinganolyte and the use of ion-exchange membrane integrated can greatly improve theefficiency of the heavy metals removal, but the actual processing parameters should beoptimized according to the nature of the sludge.