Reduction of hexavalent chromium by Sphaerotilus natans a filamentous micro-organism present in activated sludges

• Published in: Journal of hazardous materials Vol. 156; no. 1; pp. 214 - 222
• Main Authors: Caravelli, Alejandro H., Giannuzzi, Leda, Zaritzky, Noemí E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-08-2008; Elsevier
• Subjects: Applied sciences; Biological and medical sciences; Biological reduction; Biomass; Biotechnology; Chromium - metabolism; Cr(VI); Exact sciences and technology; Filamentous micro-organisms; Fundamental and applied biological sciences. Psychology; General purification processes; Methods. Procedures. Technologies; Others; Oxidation-Reduction; Pollution; Respirometry; Sewage - microbiology; Sphaerotilus - metabolism; Sphaerotilus natans; Various methods and equipments; Wastewaters; Water Pollutants, Chemical - metabolism; Water treatment and pollution; Cr(VI); Filamentous micro-organisms; Biological reduction; Respirometry; Sphaerotilus natans; Activated sludge; Aerobe; Biomass; Modeling; Waste water; Biological purification; Heavy metal; Biosorption; Health and environment; Ecosystem; Aqueous solution; Waste water purification; Public health
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2007.12.014

Wastewaters produced by various industries may contain undesirable amounts of hexavalent chromium (Cr(VI)), as chromate and dichromate, a hazardous metal affecting flora and animals of aquatic ecosystems as well as human health. One removal strategy comprises the microbial reduction of Cr(VI) to Cr(III), a less soluble chemical species that is less toxic than Cr(VI). In this work, the ability to reduce Cr(VI) of
Sphaerotilus natans, a filamentous bacterium usually found in activated sludge systems, was evaluated. In aerobic conditions,
S. natans was able to efficiently reduce Cr(VI) to Cr(III) from dichromate solutions ranging between 4.5 and 80
mg Cr(VI)
l
−1 in the presence of a carbonaceous source. A simultaneous evaluation of the microbial respiratory activity inhibition was also carried out to analyze the toxic effect of Cr(VI). Cr(VI) reduction by
S. natans was mathematically modeled; chromium(VI) reduction rate depended on both Cr(VI) concentration and active biomass concentration. Although it is known that
S. natans removes heavy metal cations such as Cr(III) by biosorption, the ability of this micro-organism to reduce Cr(VI), which behaves as an oxyanion in aqueous solutions, is a novel finding. The distinctive capacity to reduce Cr(VI) to Cr(III) than remain soluble or precipitated becomes
S. natans a potential micro-organism to decontaminate wastewaters.