title: The effect of cyclic anaerobic-aerobic conditions on biodegradation of azo dyes.
abstract: The effect of cyclic anaerobic-aerobic conditions on the biodegradative capability of the mixed microbial culture for the azo dye Remazol Brilliant Violet 5R (RBV-5R) was investigated in the sequencing batch reactor (SBR) fed with a synthetic textile wastewater. The SBR had a 12-h cycle time with anaerobic-aerobic periods of 3/9, 6/6 and 9/3 h. General SBR performance was assessed by measurement of catabolic enzymes (catechol 2,3-dioxygenase, azo reductase), chemical oxygen demand (COD), color and amount of aromatic amines. In this study, under steady-state conditions, the anaerobic period of the cyclic SBR was found to allow the reductive decolorization of azo dye. Longer anaerobic periods resulted in higher color removal efficiencies, approximately 71% for the 3-h, 87% for 6-h and 92% for the 9-h duration. Total COD removal efficiencies were over 84% under each of the cyclic conditions and increased as the length of the anaerobic period was increased; however, the highest color removal rate was attained for the cycle with the shortest anaerobic period of 3 h. During the decolorization of RBV-5R, two sulfonated aromatic amines (benzene based and naphthalene based) were formed. Additionally, anaerobic azo reductase enzyme was found to be positively affected with the increasing duration of the anaerobic period; however; it was vice versa for the aerobic catechol 2,3-dioxygenase (C23DO) enzyme.
authors.affiliation: Department of Environmental Engineering, Kahramanmaras Sütçü mam University, Kahramanmaras, Turkey.
authors.forename: Semra
authors.initials: S
authors.lastname: Yaşar
authors.forename: Kevser
authors.initials: K
authors.lastname: Cirik
authors.forename: Ozer
authors.initials: O
authors.lastname: Cinar
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001391:Azo Compounds / Q000737:chemistry* / Q000378:metabolism; D050557:Catechol 2,3-Dioxygenase / Q000737:chemistry / Q000378:metabolism; D004396:Coloring Agents / Q000737:chemistry* / Q000378:metabolism; D009282:Naphthalenesulfonates / Q000737:chemistry* / Q000378:metabolism; D013783:Textile Industry; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D009282:Naphthalenesulfonates; C111247:C.I. Reactive Violet 5; D050557:Catechol 2,3-Dioxygenase