| The concept of Reducing Barrier is introduced by Professor Huyuan Zhang firstly. That is an artificial layer for water-proving, in which the microbial anaerobic respirations are intensified. It is used to obstruct and envelop heavy metal contaminants in the facilities-about waste processing. The theory of Reducing Barrier is a learned innovation. The purpose of this research is to study the osmotic characteristic and biochemical changes of sewage sludge as material of Reducing Barrier, because of its high contents of organic compounds and microorganisms, and to examine its effects for immobilizing heavy metals such as Fe, Zn and Cd, in order to realize the aid of controlling wastes with wastes and develop a new method for utilization of sewage sludge as resource. The sewage sludge from sewage processing plant of Lanzhou University is main material in this research. The flexible wall penetrometer is used in the solidification and seepage tests under 100kPa, 200kPa and 300kPa solidification pressure. It gains hydraulic conductivity results, those are 1.1912×10-8cm.s-1, 0.8825×10-8cm.s-1 and 0.6335×10-8cm.s-1 responding to 100kPa, 200kPa and 300kPa solidification pressure. Through analyzing and studying the data about Eh, pH and EC from the tests, the following conclusions can be drawn: The sewage sludge has very low hydraulic conductivity under 100kPa, 200kPa and 300kP solidification pressure, and it may substitute clay (k＜10-7cm.s-1) as barrier material in point of osmosis; The increasing dry density and decreasing hydraulic conductivity are occured with the increasing press, and microbial activities in the samples are inhibited on some extent; That is found concentration of Fe in the leachate of all samples are reduced the level of under low limit(0.02ppm) of the apparatus after 50 days, and concentration of Zn and Cd are under low limit(0.02ppm) of the apparatus from beginning to end; These can validate that Reducing Barrier made of sewage sludge has very satisfying immobilization effects for these three heavy metals, especially Zn and Cd. |
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