Bioleaching of metals from anaerobic sewage sludge: Effects of total solids, leaching microorganisms, and energy source

The effects of municipal sewage sludge solids concentration, leaching micro organisms (Thiobacillus thiooxidans or Thiobacillus ferrooxidans) and the a ddition of energy source (SO or Fe(II)) on the bioleaching of metals from s ewage sludge has been investigated under laboratory conditions using shake flasks. The results show that metal solubilization was better accomplished if additional energy source is supplemented to the microorganisms and that T. thiooxidans furnishes, in general, more adequate conditions for the biol eaching than T. ferrooxidans. At a total solids concentration of 70 g L-1 ( originally present in the sludge) pH drop and ORP increase are attenuated, so metal solubilization is negatively affected. Tt was also demonstrated th at if lead (Pb) solubilization is to be achieved, than a special combinatio n of microorganism/energy source must be applied.