Chemical Partitioning of Metals in Thermally Treated Sewage Sludge

Abstract

Anaerobically treated sludge from two wastewater treatment plants was found to contain significant amounts of heavy metals (Cr, Cu, Fe, Ni, Pb and Zn). The metal form distribution in the sludge samples found by the application of a sequential extraction procedure indicated that an important part of the metal content is carried by the organic and the reducible fractions. The sludge was thermally treated at two different temperatures, 105°C and 900°C. By applying sequential analysis, it was found that most of the metal content was removed from the initial mobile phases to more stable ones and also significant amounts were transformed to the gaseous phase. Finally, in order to estimate the metal leachability of the sludge samples, before and after thermal treatment, the Generalized Acid Neutralization Capacity procedure was used.

Keywords:

• Anaerobically treated sludge
• heavy metals
• thermal treatment
• sequential chemical extraction (SCE)
• Generalized Acid Neutralization Capacity (GANC) test