title: Aerobic biodegradation of a sulfonated phenylazonaphthol dye by a bacterial community immobilized in a multistage packed-bed BAC reactor.
abstract: A microbial community able to aerobically degrade the azo dye Acid Orange 7 was selected from riparian or lacustrine sediments collected at sites receiving textile wastewaters. Three bacterial strains, pertaining to the genera Pseudomonas, Arthrobacter, and Rhizobium, constitute the selected community. The biodegradation of AO7 was carried out in batch-suspended cell culture and in a continuously operated multistage packed-bed BAC reactor. The rapid decolorization observed in batch culture, joined to a delay of about 24 h in COD removal and cell growth, suggests that enzymes involved in biodegradation of the aromatic amines generated after AO7 azo-bond cleavage (1-amino-2-naphthol [1-A2N] and 4-aminobenzenesulfonic acid [4-ABS]), are inducible in this microbial consortium. After this presumptive induction period, the accumulated byproducts, measured through COD, were partially metabolized and transformed in cell mass. At all azo dye loading rates used, complete removal of AO7 and 1-A2N was obtained in the multistage packed-bed BAC reactor (PBR).; however, the overall COD (eta ( COD )) and 4-ABS (eta ( ABS )) removal efficiencies obtained in steady state continuous culture were about 90%. Considering the toxicity of 1-A2N, its complete removal has particular relevance. In the first stages of the packed-bed BAC reactor (Fig. 4a-c), major removal was observed. In the last stage, only a slight removal of COD and 4-ABS was obtained. Comparing to several reported studies, the continuously operated multistage packed-bed BAC reactor showed similar or superior results. In addition, the operation of large-packed-bed BAC reactors could be improved by using several shallow BAC bed stages, because the pressure drop caused by bed compaction of a support material constituted by small and fragile particles can be reduced.
authors.affiliation: Departamento de Ingeniería Bioquímica, Escuela Nacional de Ciencias Biológicas, IPN, Carpio y Plan de Ayala, Col. Santo Tomás, México, D.F., Mexico.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Ruiz-Arias
authors.forename: Cleotilde
authors.initials: C
authors.lastname: Juárez-Ramírez
authors.forename: Daniel
authors.initials: D
authors.lastname: de los Cobos-Vasconcelos
authors.forename: Nora
authors.initials: N
authors.lastname: Ruiz-Ordaz
authors.forename: Angélica
authors.initials: A
authors.lastname: Salmerón-Alcocer
authors.forename: Deifilia
authors.initials: D
authors.lastname: Ahuatzi-Chacón
authors.forename: Juvencio
authors.initials: J
authors.lastname: Galíndez-Mayer
mesh_terms: D000327:Adsorption; D000332:Aerobiosis; D001391:Azo Compounds / Q000378:metabolism*; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001557:Benzenesulfonates / Q000378:metabolism*; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology*; D002244:Carbon / Q000737:chemistry; D018914:Cells, Immobilized / Q000378:metabolism; D004396:Coloring Agents / Q000378:metabolism*; D007218:Industrial Microbiology / Q000295:instrumentation / Q000379:methods*; D011205:Povidone / Q000737:chemistry
chemical_list: D001391:Azo Compounds; D001557:Benzenesulfonates; D004396:Coloring Agents; C078073:carbon colloid; D002244:Carbon; D011205:Povidone; C014722:2-naphthol orange