The present work evaluates some new developments concerning research into the removal of heavy metals from sewage sludge and discusses the significance for practical application. As such, the complete process of sludge treatment as an integral part of a sludge management process is considered. Two conceptual designs of a treatment process that may be applied in practice for heavy metals removal from sewage sludge are discussed. One refers to a physical-chemical treatment and the other to a biological-physical-chemical treatment. In the physical-chemical treatment, the solubilization of heavy metals is achieved by acidification with HCl (pH around 1) with a previous oxidative pre-treatment (in the same reactor) either by aeration or by hydrogen peroxide. In the biological-physical-chemical treatment, the approach is to use a heavy metal mobilization technique, which is mediated by acidophilic bacteria (Thiobacillus) able to produce sulfuric acid. This system consists of an anaerobic bioreactor fed with elemental sulfur as a reduced sulfur source component, which is oxidized by Thiobacillus and converted into sulfuric acid. In this system, a biological sulfate-reducing step, where sulfate is converted into sulfur, is included and, thus, a closed sulfur cycle can be achieved. Based on a brief qualitative evaluation, the feasibility of both treatment systems is accessed. The biological-physical-chemical process seems to be more attractive than the physical-chemical process.
|Journal||Journal of Residuals Science & Technology|
|Publication status||Published - 2004|