Experimental Study about Activation of Heavy Metals (Cu, Zn) in Residual Sludge Using Eisenia foetida

The aim of this work was to investigate the potential of Eisenia foetida to survival and grow in the sludge and increase the bioavailability of heavy metals in it which came from a wastewater treatment plant of China University of Mining and Technology under laboratory conditions. The results indicated that Eisenia foetida could not only grow normally in the sludge mixed with a certain concentration of Cu and Zn, but also have a certain tolerance of them, which was related to the type and the content of heavy metal and the physical-chemical properties of sludge. Eisenia foetida could activate Cu and Zn in the sludge to some extent. The maximum increase of activation rate of heavy metals was recorded in the sludge mixed with 150 mg/kg Cu as CuSO4·5H2O or 200 mg/kg Zn as ZnSO4·7H2O, which were 13.89% and 20.34% respectively.