Decolorization and partial degradation of selected azo dyes by methanogenic sludge |
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Authors: | Natalia Yemashova Anna Telegina Irina Kotova Alexander Netrusov Sergey Kalyuzhnyi |
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Institution: | (1) Department of Chemical Enzymology, Moscow State University, 119992 Moscow, Russia;(2) Department of Microbiology, Moscow State University, 119992 Moscow, Russia |
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Abstract: | The toxicity potential and decolorization of three acid azo dyes (Acid Orange 6, Acid Orange 7, and Acid Orange 52) by methanogenic
granular sludge from an anaerobic expanded granular sludge bed reactor was assayed. Complete bioreduction was found for all
three azo dyes. Sulfanilic acid and 4-aminoresorcinol were detected from the decolorization of Acid Orange 6, sulfanilic acid
and 1-amino-2-naphtol were detected from the reduction of Acid Orange 7, and sulfanilic acid and N,N-dimethyl-1,4-phenylenediamine (DMP) were found to be intermediates of Acid Orange 52 degradation. Sulfanilic acid and 1-amino-2-naphtol
were persistent in the anaerobic conditions, whereas 4-aminoresorcinol was completely mineralized by anaerobic sludge and
DMP was transformed into 1,4-phenylenediamine. Enrichment cultures obtained via consecutive passages on basal medium with
only azo dye as a carbon and an energy source seemed to be morphologically heterogeneous. Baculiform and coccus cells were
found when viewed under a light microscope. Cocci were joined in chains. Because anaerobic sludge contains sulfate-reducing
bacteria and therefore may generate sulfide, azo dyes were tested for chemical decolorization by sulfide to compare rates
of chemical and biologic reduction. |
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Keywords: | Azo dyes methanogetic sludge toxicity bioreduction chemical reduction |
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