title: Cooperation between two Thiobacillus strains for heavy-metal removal from municipal sludge.
abstract: A mixed culture of two fast-growing bacterial strains for heavy-metal solubilization of municipal sewage sludge has been developed. Strain VA-7 decreases the initial sludge pH (7-8.5) to a value between 4.0 and 4.5. Then, strain VA-4 begins growing and further reduces the pH to values below 2.0. The rapid decrease of sludge pH by a mixed culture through sulfur oxidation into sulfuric acid solubilizes the toxic metals (Cd 83-96%, Cr 16-54%, Cu 85-87%, Mn 91-94%, Ni 78-79%, Pb 28-46%, Zn 82-96%) to levels recommended for intensive use of residual sludge in agriculture. A study of the physiological and metabolic characteristics of these strains revealed that isolate VA-7 is a strain of Thiobacillus thioparus (ATCC 55127), while isolate VA-4 corresponds to a Thiobacillus thiooxidans (ATCC 55128). These bacterial strains possess distinctive physiological characteristics that allow them to easily grow and solubilize heavy metals in municipal sludge.
authors.affiliation: Institut national de la recherche scientifique (INRS-EAU), Université du Québec, Sainte-Foy, Canada.
authors.forename: J F
authors.initials: JF
authors.lastname: Blais
authors.forename: J C
authors.initials: JC
authors.lastname: Auclair
authors.forename: R D
authors.initials: RD
authors.lastname: Tyagi
mesh_terms: D006863:Hydrogen-Ion Concentration; D008670:Metals / Q000302:isolation & purification / Q000378:metabolism*; D012722:Sewage; D012995:Solubility; D013431:Sulfates / Q000378:metabolism; D013855:Thiobacillus / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D008670:Metals; D012722:Sewage; D013431:Sulfates