HEAVY METAL UPTAKE BY SLUDGE PARTICULATES IN THE PRESENCE OF DISSOLVED ORGANIC MATTER

摘要

The presence of dissolved organic matter (DOM) significantly affects the uptake ofrnheavy metals by sludge particulates. The uptake of seven metals including Cu(II),rnNi(II), Co(II), Pb(II), Zn(II), Cd(II), and Cr(III) by sludge in the presence of DOM wasrninvestigated. Results showed that the uptake of heavy metals increases with pH atrnneutral and low pH conditions. At alkaline pH region, the organic mater dissolutionrnincreases significantly. As a result, the uptake of the metal-DOM complexes,rnspecifically, Cu(II), Ni(II), and Co(II), decreases. The uptake of other metals such asrnPb(II), Cd(II), Zn(II), and Cr(III), however, is not significantly affected by the presencernof DOM. Results also showed that Pb(II), Cr(III), Cu(II) are the most uptakable metalsrnamong the seven metals studied and Ni(II) and Co(II) are the least uptakable.rnA mathematical model was developed to describe the uptake of heavy metals inrnsystems containing DOM using pH as the master variable. In relatively low metalrnconcentrations, a much simplified version of the model can be used. The stabilityrnconstants of metal-sludge complexes and metal-DOM complexes can be determinedrnusing both models. Results showed that stability constants of Cu(II)-sludge complexrn(logK_S) and Cu(II)-DOM complex (logK_L) are respectively 4.9 and 4.4. They are 3.0rnand 2.4 for Ni(II)-sludge complex and Ni(II)-DOM complex, respectively. The modelsrncan well describe the metal uptake by sludge at various DOM and pH conditions.