Laboratory Study on Sludge Treatment by Electro-Osmosis Combined with Pile-Loading

Abstract

In practical engineering, electro-osmotic treatment of large-scale silt projects will cause a lot of electricity waste. Some scholars have made an electro-osmotic method to treat silt and combine pile-loading to reduce the energy consumption of electric energy. In this paper, the effects of electro-osmotic treatment combined with pile-loading experiment on the consolidation of municipal sludge and the content of heavy metals in the sludge before and after electro-osmosis are analyzed and the conclusions are drawn.(1)The combination of electro-osmotic method and pile-loading experiment has strong capacity of drainage consolidation.(2)The contents of copper and zinc decreased obviously, and the electro-osmotic method combined with pile-loading method had a certain effect on the treatment of heavy metals in silt. Keyword: Electro-osmotic method, combined pile-loading, heavy metal, silt 1 Research Status of Electro-osmosis Zang Junchao and others did the experiment of electro-osmosis reinforcement of contaminated soil in February 2017. They studied the characteristics of electro-osmotic reinforcement of contaminated soil from domestic sources, and analyzed the four parameters of water content reduction percentage, energy consumption per unit displacement, shear strength and soil settlement. The sequence of primary and secondary factors influencing the effect of electro-osmotic drainage reinforcement of contaminated soil is obtained: Power supply voltage > electrification time > initial water content > CaCl2 addition > electrode material[1]. In the study of treatment of heavy metals in sludge of municipal sewage treatment plant by electrodialysis, Chen Wenting[2] used electrodialysis device to carry out electrodialysis experiment on sludge of sewage treatment plant. Samples were taken every 2 hours and then treated with Tessier five-step method. It is found that electro-osmotic method is feasible for heavy metal treatment. Wang Jun and others made use of the independently developed experimental device in 2014 to conduct indoor model tests on the combination of electro-osmotic method and closed vacuum preloading method to strengthen soft clay foundation. It was found that vacuum preloading and electro-osmotic method can promote each other under the combined action. The results show that the compatibility is better than that of vacuum preloading alone in the treatment of soft clay foundation[3]. In 2014, Jiao Dan carried out the electro-osmotic test of soft clay under different initial and electrified conditions in axisymmetric working conditions on a self-made electro-osmotic consolidation device. It was found that under the same water content and voltage, the electric energy utilization ratio of soil was higher when intermittent electricity was switched on. And the overall difference of soil after electro-osmosis is small[4]. In the experimental study of low energy dynamic compaction combined with electro-osmotic method for strengthening soft clay foundation, Fu Hongtao found that the electric energy consumption increases during the process of electro-osmosis, and the problem of electro-osmosis can be effectively remedied after combined dynamic compaction[5]. Ren Jubo has found in the experimental study of the new surcharge electro-osmosis method to reinforce the foundation of dredged silt that the combined action of electro-osmosis and surcharge can effectively reduce the soil moisture content, improve the shear strength of the soil, and make the soil settle and consolidate[6]. A large number of experiments on sludge treatment by electro-osmosis have only been focused on reinforcement effect and electro-osmosis research on the basic physical properties of sludge. Nowadays, if the heavy metal content in the silt can be treated well, the stress of the urban soil can be greatly alleviated. In this paper, the changes of heavy metals in the sludge of urban sludge treated by electro-osmotic method 18 Modern Civil and Structural Engineering, Vol. 2, No. 2, April 2018 https://dx.doi.org/10.22606/mcse.2018.22002 MCSE Copyright © 2018 Isaac Scientific Publishing combined with loading experiments are described. 2 Research Content Methods and Basic Parameters 2.1 Research