Decolorization Of Reactive Red Azo Dyes By Immobilized Citrobacter Sp. CK3

The decoloring characteristics of Citrobacter sp.CK3 stain was studied in this paper.The aims of this study were to establish a bio-augmentation technics,optimize the decoloring process,and explore the degradation mechanism of the dyestuff.The Citrobacter sp.CK3 stain was immobilized then used to degrade synthetic dye wastewater(SDW) containing Reactive Red azo dyes.These Reactive Red azo dyes were commen used in the dyeing industry.The immobilization methods were immobilized bio-film(IBF) and immobilized microbial cells(IMC).The results were as follows:(1) An Anaerobic-aerobic Bio-filter(A/O Bio-filter) was based as the technics of immobilized bio-film.The anaerobic bio-filter(AF) was inoculated with Citrobacter sp.CK3.The Aerobic Bio-filter(ABF) was incubated with activated sludge taken from a domestic wastewater treatment plant.The effect of defferent influent conditions for color and COD removal of synthetic dye wastewater was detected, results show that:the optimum pH for the decolorization of Reactive Red azo dyes and degradation of organics is weak acidic;external carbon source is needed for the strain to decolorize Reactive Red azo dyes;furthermore,decolorization efficiency is improved when the carbon source concentration is increasing;decolorization efficiency is still more than 93%when influent NaCl concentration reaches to 30 g·L^-1;decolorization efficiency could still be 95%when the initial dye concentration reaches to 500 mg·L^-1.The results based on UV-Vis Spectrophotometer analysis to synthetic dye wastewater before and after decolorizing reaction suggest that Reactive Red azo dyes may be removed mainly due to the biodegradation.The results of High Performence Liquid Chromatography(HPLC) analysis show the azo group was broken after anaerobic treatment,the intermediate products were further transformed after aerobic treatment,and the fine structure was degraded,but some Benzene groups still remain.(2) The cell entrapment method was based as the technics of immobilized microbial cells.Synthetic dye wastewater containing Reactive Red azo dyes was treated by the cell-entraped gel beads under anaebic batch process.The effect of influent conditions on the decolorization was investigated.And the relationship between influent conditions,physical characteristic of the gel beads and decolorization effeciency was discussed refers to the experimental phenomena. Results show that weak alkaline is better for the decolorization of Reactive Red azo dyes due to the decrease of the gel beads' hardness;but also cause a mass of organic compounds released in to the wastewater.By contrast,the hardness of gel beads maintained well in acid condition,but the decolorization efficiency was low.The decolorization efficiency is higher when glucose is used as external carbon source;the influent without glucose could cause the decrease of decolorization efficiency and also do great harm to the hardness of gel beads.The decolorization efficiency is good when the influent NaCl concentration reachs to 15 g·L^-1.The morphological observation use Scanning Electron Microscopy(SEM) shows there are fiber and pore structures inside the gel beads,and Citrobacter sp.CK3 can grow well in the entrapment gel beads.