title: Biological decolorization of xanthene dyes by anaerobic granular biomass.
abstract: Biodegradation of a xanthene dyes was investigated for the first time using anaerobic granular sludge. On a first screening, biomass was able to decolorize, at different extents, six azo dye solutions: acid orange 7, direct black 19, direct blue 71, mordant yellow 10, reactive red 2 and reactive red 120 and two xanthene dyes--Erythrosine B and Eosin Y. Biomass concentration, type of electron donor, induction of biomass with dye and mediation with activated carbon (AC) were variables studied for Erythrosine B (Ery) as model dye. Maximum color removal efficiency was achieved with 4.71 g VSS L⁻¹, while the process rates were independent of the biomass concentration above 1.89 g VSS L⁻¹. No considerable effects were observed when different substrates were used as electron donors (VFA, glucose or lactose). Addition of Ery in the incubation period of biomass led to a fivefold increase of the decolorization rate. The rate of Ery decolorization almost duplicated in the presence of commercial AC (0.1 g L⁻¹ AC₀). Using different modified AC samples (from the treatment of AC₀), a threefold higher rate was obtained with the most basic one, AC(H₂), as compared with non-mediated reaction. Higher rates were obtained at pH 6.0. Chemical reduction using Na₂S confirmed the recalcitrant nature of this dye. The results attest that decolorization of Ery is essentially due to enzymatic and adsorption phenomena.
authors.affiliation: Department of Environmental Engineering and Management, "Gheorghe Asachi" Technical University of Iasi, 73 Prof.dr.docent Dimitrie Mangeron Street, 700050 Iasi, Romania.
authors.forename: Laura Carmen
authors.initials: LC
authors.lastname: Apostol
authors.forename: Luciana
authors.initials: L
authors.lastname: Pereira
authors.forename: Raquel
authors.initials: R
authors.lastname: Pereira
authors.forename: Maria
authors.initials: M
authors.lastname: Gavrilescu
authors.forename: Maria Madalena
authors.initials: MM
authors.lastname: Alves
mesh_terms: D000327:Adsorption; D000693:Anaerobiosis; D001391:Azo Compounds / Q000737:chemistry / Q000378:metabolism; D061249:Batch Cell Culture Techniques; D001673:Biodegradation, Environmental; D018533:Biomass; D002606:Charcoal / Q000737:chemistry; D003116:Color; D004396:Coloring Agents / Q000737:chemistry / Q000378:metabolism*; D004583:Electrons; D004801:Eosine Yellowish-(YS) / Q000302:isolation & purification; D004923:Erythrosine / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D012722:Sewage / Q000382:microbiology*; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D013379:Substrate Specificity; D014966:Xanthenes / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D012722:Sewage; D012996:Solutions; D014966:Xanthenes; D002606:Charcoal; D004923:Erythrosine; D004801:Eosine Yellowish-(YS)