Abstract: Stabilizing heavy metals for sludge harmlessness is of great significance. The results of ICP and Tessier analysis of heavy metals in biochemical residual sludge of a certain refinery showed that the contents of Ni, Cu, Pb, Zn, Ba, Cr, Cd, Ag, As, and Hg are high, and these metals exist in five different forms; Na2S has a good stabilizing effect on these heavy metals from the unstable state into the steady state, so that the leaching concentration of heavy metals from the sludge reaches the requiremene of the national standard on solid waste.

Key words: biochemical sludge, heavy metal, form, stabilization