Study On The Treatment Of Azo Dye Wastewater By Marine Bacteria Aliiglaciecola Lipolytica

With the rapid development of the textile industry,the use of dyes is dramatically increasing,as an important raw material in the dye family,azo dyes have attracted widespread attention due to their toxicity,mutagenicity and mutagenicity.A large amount of dyeing wastewater entered into the water body,which lead to servere human health problems and environmental ecology hazard,so it is essiental to search an ervironmentally friendly and efficient treatment technology.Microbes which have low energy consumption and no secondary pollution characteristics were widely used in the treatment of azo dye wastewater,however,anaerobic-aerobic combination are main method to degrade azo dyes,and the mud-water separation effect is relatively poor after treatment.The aerobic bacteria with good sedimentation properties have rarely been reported.In this study,a novel marine self-flocculating strain,Aliiglaciecola lipolytica,was selected to decolorizate Congo red(CR)of azo dye under aerobic conditions,and the effect of mud-water separation was investigated,the role of extracellular polymer(EPS)in the self-flocculation process was studied.This study developed a new strain for the biological decolorization of CR and provided an efficient,economical,environmentally friendly,easy-to-use method for the treatment of azo dye wastewater.The main research content and results are as following:(1)A single-factor batch experiments were conducted to investigate the effects about different environmental factors on the decolorization of Aliiglaciecola lipolytica(A.lipolytica),such as initial dye concentration,temperature,electron donor/acceptor,pH,DO.The optimum environmental conditions were as following:temperature 35?,salinity 20 g/L,pH=6,initial inoculums 1.5 g/L,aerobic conditions,glucose as a co-metabolism substrate,the decolorization rate of CR with an initial concentration of 100 mg/L was about 95%at 24 h,indicating that the bacteria had high decolorization ability for CR.(2)The mechanism of this strain on the CR decolorization was investigated.The SEM and AFM showed that the strain's morphology changed from long rod to short rod,and the yield of EPS decreased significantly.Besides,the pseudo second-order kinetics and Langmuir adsorption isotherm showed the best fitting effect with the decolorization results.FTIR analysis explained the functional groups of-OH,N-H,-SO3 and C-OH involved in the bioadsorption of CR.The UV/VIS spectroscopy and HPLC-MS analysis revealed that the N=N?-SO3 were cleavaged,which decomposed into smaller organic molecules molecular weight.Laccase and azoreductase were involved in biodegradation process.In the whole process of decolorization,the adsorption ratio accounted for 54.67%,while the degradation ratio was 40.33%.(3)The sedimentation performance of this strain was studied,suggesting an excellent ability.And the effect on environmental factors on EPS yield?the role of EPS in the self-flocculation process were investigated.Correlation analysis showed that salinity was one of the key factors affecting the self-flocculation efficiency;LB-EPS and TB-EPS played indispensable roles in self-flocculation process;UV-VIS analysis,three-dimensional fluorescence spectroscopy,XPS analysis and extracellular gel protein electrophoresis analysis indicated that the interaction between the hydrophobic functional group as well as the macromolecular protein to bind the cells to the cells of the LB-EPS and TB-EPS,aggregating into a mass to settle under the gravity.