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Colour removal of dyes from synthetic and real textile wastewaters in one- and two-stage anaerobic systems

Firmino, Paulo Igor M., da Silva, Marcos Erick R., Cervantes, Francisco J., dos Santos, André B.
Bioresource technology 2010 v.101 no.20 pp. 7773-7779
azo dyes, color, decolorization, electron transfer, fabrics, wastewater
Decolourisation of the azo dye model compound, Congo Red (CR), and real textile wastewater, was assessed in one- and two-stage anaerobic treatment systems (R₁ and R₂, respectively). High colour removals were achieved in both treatment systems even when a very high CR concentration (1.2mM) was applied. However, R₂ presented a slightly better stability, in which the acidogenic reactor (R₂,A) played a major role on dye reduction, as compared to the methanogenic reactor (R₂,M), evidencing the role of fermentative microorganisms. The minimum electron donor concentration required to sustain dye reduction was much higher than the stoichiometric amount. Additionally, a decrease on the hydraulic retention time (from 24 to 12h) did not significantly affect decolourisation, indicating that electron transfer was not a concern. Finally, experiments with real textile wastewater showed low decolourisation efficiencies in both systems, most likely due to the presence of dyes not susceptible to reductive decolourisation under these experimental conditions.