title: Decolorization and partial degradation of monoazo dyes in sequential fixed-film anaerobic batch reactor (SFABR).
abstract: Decolorization of two monoazo dyes, acid orange 6 (AO6) and acid orange 7 (AO7), were studied in sequential fixed-film anaerobic batch reactor (SFABR) with varying dye concentrations and 500 mg/L glucose as the co-substrate. More than 90% dye decolorization could be achieved, even at 300 mg/L, with both AO6 and AO7 and dye decolorization rates were 168 mg/L/d and 176 mg/L/d, respectively. COD removals with these two monoazo dyes were significantly different, as 75% and 35% decrease were observed with AO6 and AO7, respectively. UV-visible spectral as well as HPLC analysis of SFABR treated effluent showed the accumulation of 4-aminobenzenesulfonate (4-ABS) from AO6 and AO7. Aminoresorcinol (AR) formed from AO6 decolorization could not be detected at the end of SFABR cycle. This along with high COD removal indicated its further degradation. Formation of pink coloration on exposure to air indicated the presence of 1-amino-2-naphthol (AN) in AO7 fed reactor effluent. Thus both 4-ABS and AN were resistant to further degradation under anaerobic conditions. Presence of nitrate did not decrease the observed decolorization at the end of 24h SFABR cycle, although initial rate was decreased. This indicates the suitability of SFABR configuration for the treatment of azo-dye containing wastewaters in the presence of nitrate.
authors.affiliation: Biotechnology laboratory, Department of Chemistry, IIT, Kanpur 208 016, India.
authors.forename: Poonam
authors.initials: P
authors.lastname: Singh
authors.forename: Rashmi
authors.initials: R
authors.lastname: Sanghi
authors.forename: Anjali
authors.initials: A
authors.lastname: Pandey
authors.forename: Leela
authors.initials: L
authors.lastname: Iyengar
mesh_terms: D001391:Azo Compounds / Q000737:chemistry / Q000378:metabolism*; D001421:Bacteria, Anaerobic / Q000378:metabolism*; D001557:Benzenesulfonates / Q000737:chemistry / Q000378:metabolism*; D001673:Biodegradation, Environmental; D019149:Bioreactors; D002851:Chromatography, High Pressure Liquid; D004396:Coloring Agents / Q000737:chemistry / Q000378:metabolism*; D005947:Glucose / Q000737:chemistry / Q000378:metabolism; D018508:Water Purification / Q000379:methods
chemical_list: D001391:Azo Compounds; D001557:Benzenesulfonates; D004396:Coloring Agents; D005947:Glucose; C520100:Acid Orange 6; C014722:2-naphthol orange