Heavy metals removal from anaerobically digested sludge by chemical and microbiological methods

Bioleaching of cadmium and nickel from synthetic sediments by Acidithiobacillus ferrooxidans

“…The mechanisms of bioleaching are usually described in terms of either a direct bacterial attack on metal sulfides or an indirect attack via ferric iron (Tyagi et al 1988;Fowler & Crundwell 1998).…”

“…In spite of good metal extraction achieved by some chemical treatment methods, factors such as cost, operational difficulties, and large chemical requirements have limited the practical application of these methods (Tyagi et al 1988). An alternative to chemical methods is the use of microorganisms to remove metals from these contaminated materials; a process commonly referred to as ''microbial leaching'' (Blais et al 1992a).…”

Bioleaching of heavy metals from sewage sludge: A review

“…Bioleaching process uses the catalytic effect produced by the metabolic activities of iron-oxidizing and sulfur-oxidizing microorganisms resulting in an acceleration of the chemical degradation of the sulfides (Morin et al, 2005). It is a low cost environment friendly technique which is 80% cheaper in terms of chemical consumption compared to the traditional chemical methods employed for metals leaching from the sludge and recovery of metals from the leachate (Tyagi et al, 1988).…”

Effect of Solids Concentration on Bacterial Leaching of Heavy Metals from Sewage Sludge

“…5,6,[12][13][14] The mixed cultures of T. ferrooxidans and T. thiooxidans have also been examined with or without an addition of alternative energy sources such as Fe (II) and elemental sulfur. 7 Previous studies have indicated that the microbial leaching method has several advantages over the chemical method in terms of its simplicity, high yield of metal extraction, lower acid and alkali consumption, and minimum reduction in sludge nutrients such as N and P. 8 The preservation of sludge nutrients is important for further application to agricultural land. Using both airlift and continuous stirred tank reactors, heavy metals in anaerobically digested sludge have been readily solubilized to the recommended level at a residence time of 0.75 day.…”

“…1 Several methods have been studied for leaching heavy metals from sewage sludge, [2][3][4][5][6][7] and they can be broken down into two categories: chemical leaching [8][9][10] and microbial leaching. [2][3][4][5][6][7][11][12][13][14][15] The chemical leaching method generally involves the use of mineral acids, such as H 2 SO 4 and HCl, at pH 1.5-2.0.…”