Effect of Fly Ash on Solidification and Heavy Metals Chemical Speciation of Sludge

In order to explore new municipal sewage sludge treatment method and reduce its harm for environment, fly ash discarded from power plant was used as conditioner in sludge treatment in the paper. The properties of sewage sludge were changed after adding fly ash. The optimum fly ash amount 0.03 kg/kg was obtained through the compressive strength test. After adding optimum amount fly ash, the percentages of Cu, Zn and Ni of the residual fraction in sludge increased, while the other fractions changed accordingly. But the percentages of Cd in the five forms changed slightly. By adding proper fly ash, the compressive strength of sludge increased significantly, and the availability of Cu, Ni and Zn was reduced. All the results provide a new way for sludge treatment and a new thinking for resource utilization of fly ash.