The Study About Of Heavy Metals’ Migration Behavior In The Leachate Concentrates Recharge System

Currently, For the sake of economy and operability, Re-injection to the landfill body is commonly used for the membrane filtration concentrates processing. But so far,there is few research of the heavy metals in the concentrate re-injection system. Reasonable removal of heavy metals is not only to guarantee the safety of the surrounding soil and the groundwater, but also has obvious influence for the normal operation of the leachate treatment facilities. By means of laboratory simulation experiments and using concentrated liquid re-injection way, this paper will study the behavior of heavy metals(Cu、Zn、Ni、Cr) migration and the influencing factors. The re-injection experiments were made for the waste in different landfill years, in different re-injection conditions (like recharge load, recharge frequency, recharge speed and the way of water distribution). Based on the above studies, to establish an optimal re-injection system, which can show the optimal combination of heavy metal removal. At last, migration and transformation mechanism of heavy metals in the concentrate re-injection system were exploration.The results show that:In the 1-year landfill system, heavy metals of concentrate like Cu, Zn, Ni, Cr showed some removal within the recharge cycle, the average removal rates were:19.58%,39.30%, 20.39% and 26.12%. The waste with 5-year landfill and 15-year landfill is in stabilization stage, biological response becomes weak, with the changes in the internal environment of the landfill, heavy metals Cu, Zn continuous dissolution, Ni appears to be removed early, late dissolution of the phenomenon, Cr has effectively removal, the average removal rates about Cr of the 5-year and 15-year were 34.58% and 16.35%.The effluent concentrations of heavy metals of 3.0L/d was significantly lower than 4.5L/d and 6.0 L/d,effluent concentrations of heavy metals in 0.2L/min was less than 0.3L/min and 0.4L/min.Which shows that the lower the recharge load and recharge rate, the greater the amount of heavy metals change. And different recharge frequency (1 time/d,3 times/d,6 times/d) and the way of water distribution (distribution in the full points, water distribution in the middle, surrounded by water distribution) had no influence on the effluent concentrations of heavy metals.By orthogonal test to determine the optimal injection parameters which combination can conducive to the removal of heavy metal the concentrates.The parameters were:the recharge load of 2.0 L/d, landfill medium diameter of 5mm, with adjusting pH (8.5) of the landfill, compaction of landfill, and the recharge rate of 0.2L/min. Among all the study factors, the recharge load and the pH of landfill is mostly import for the content of heavy metals in the concentrates. It also shows that the lower the recharge load (0.2L/min) and the higher the pH(8.5) were, the higher of removal rate of heavy metals were.Changes in the content of heavy metals in different forms by comparing before and after the recharge, obtained that Cu, Zn, Ni, Cr mobility rates was decreasing while the ages of landfill was increasing. That is to say, the more stable the garbage is, the lower the heavy metals mobility; four metals mobility in descending order:Zn-Cu-Ni-Cr. In 15-year landfill, for example, four heavy metals migration rates were 1.81%,1.75%,0.9%and 0.68%. Cr exists in the form of the most stable, which can be quickly fixed in the concentrated liquid re-injection system.The research not only can provide the reference for the reasonable design of injection system, but also has reference significance of pollution prevention of heavy metals in the leachate.