| With the rapid development of modern cities, in order to alleviate the problem of pollution of urban sewage effectively, urban sewage treatment plant is in the construction, but it also brings the problem that a lot of sludge are generated in the wastewater treatment process. The sludge is rich in nitrogen, phosphorus, potassium and other nutrients, and the application in agricultural has become a hot research area today, but heavy metals in the sludge are the limiting factor in agricultural. How to effectively remove heavy metals form sewage sludge is currently a hot research topic of municipal and environmental engineering. As an emerging green remediation technology of treating environmental pollution, electrokinetic remediation possess many advantages, such as, less investment, high removal efficiency and short processing time. Electrokinetic remediation technology has good application prospects.According to electrodynamics basic principle, the study conducted by removing harmlessly heavy metals from sewage sludge through electrolytic treatment. The study discussed the removal efficiency of heavy metals. At the same time, the distribution of heavy metals in maize(Zea mays. L.)plants and soil was studied during the process of anaerobic digestion sl udge for pot experiment.Using the sludge from sewage treatment plant of Xianyang Road sludge object as the research object, the electrolysis time, the electrolysis voltage and pH value of sludge were studied, which have a great influence on heavy metals removal rate in the electrokinetic process.The results show that electrolysis voltage and time have an important influence on heavy metals removal, and removal efficiency of Cu, Zn, Cr, Pb were improved in varying degrees with the electrolysis voltage elevated. With the electrolytic time lengthen, heavy metal content reduced first, after a rise. Removal effect of heavy metals is Pb > Cr > Cu > Zn by electrodynamics. Pb is the most obvious. Under 12 V、24 V、36 V、48 V and 60 min, Pb content was 10.69、10.49、7.16、4.83 mg·kg-1 and removal rate was 15.16%、16.75%、43.17%、61.67%.As pH of the sludge decreased, the removal effect of heavy metals becomes more obvious in the electrodynamics experiment. However, removal effect of heavy metal Cr was best under neutral condition.Carry out the Pot experiment using after treatment of anaerobic digestion sludge. Z heng Dan 958 was selected as the seeds of pot experiment and five kinds of fertilization modes were set.After the maize mature, heavy metal content of randomly in each corn root, stem, leaf, seed and plastic containers of the upper, middle and lower level were researched.The experimental results showed that different heavy metal enrich in the different organs. Cu and Cr content in different organs of corn was root > stem >leaf > grain; Zn content in different organs of maize was leaf >root > stem > grain; Pb content in different organs of corn was root > leaf > stem > grain. Absorption capacity of different heavy metal is different in Maize plants. Concentration of four kinds of heavy metal is Cu > Zn > Cr > Pb in different organs. In five treatments, heavy metal content of T3 treatment group are less in plant organs and the soil. Similar to control group, and T3 group is lower than fertilizer. It was prove that the anaerobic sludge after electrokinetic pretreatment as fertilizer could decrease heavy metal content in maize plants and soil.Distribution regularities of heavy metal content in the soil layer was the upper soil < middle < subsoil. This shows that heavy metals could penetrate down and pollute subsoil. Need the further study to prevent damage. |
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