Immobilization Of Reactive Black 5-Decoloring Bacteria And Study On Application Of Dye Wastewater Treatmenti

The efficient decolorizing bacteria for Reactive Black 5 were isolated and identified as Enterobactor sp.S8 in the early experiments. The Enterobactor sp.S8 was respectively immobilized in calcium alginate gel, polyvinyl alcohol (PVA) and Luffa cylindrica sponge and optimal conditions for their immobilization were obtained. On the basis, the treatment effects of simulated dye wastewater by three kinds of immobilized cells were compared. Their microstructure was observed by scanning electron microscope (SEM). It was found that Luffa cylindrica sponge was the optimal immobilization carrier. Finally Reactive Black 5-degrading bacteria was immobilized by Luffa cylindrica sponge and supplemented to AnSBR systems and its effects on the removal of Reactive Black 5 in the systems were studied. In addition, the contributions of the supplemented culture and indigenous culture in the bio-augmented system at different operation stages were compared.Firstly, Enterobactor sp.S8 was embedded with sodium alginate, and was used to decolor reactive black 5. The optimal condition of immobilization and the decolorization performance at this condition were studied. The reusability and kinetics of the immobilized bacteria were also studied. The results showed that the optimum conditions for preparation were that the concentration ratios of sodium alginate and CaCl2 were 3% and 3%, respectively, the ratio of the embedding dose and bacteria amount was 1:1, the time of calcification was 16 h, and the appropriate activated carbon could improve decolorization rate. The optimum pH and temperature for decolorization were for the 7.0 and 30℃. Immobilized bacteria could be reused, the decolorization rate of the immobilized bacteria could still reach 75.96% after 7 times reused. The decolorization of immobilized bacteria on Reactive Black 5 at various initial concentrations conformed to the second-order reaction mode.Secondly, Enterobactor sp.S8 was embedded with PVA, and was used to decolor Reactive black 5. The condition of immobilization operation of Enterobactor sp.S8 and the condition of application of immobilized cell were inspected. The reusability of the immobilized bacteria was also studied. The results showed that the optimum conditions for preparation were that the concentration ratios of PVA and SA were 10% and 1%, respectively, the ratio of solution to cells was 20:1, the temperature of cross-linking agent was saturated boric acid contained 1% CaCl2 at 4℃and the cross linking time was 24 h. The optimal conditions for decolorization was that the reaction temperature was 30℃, pH was 7 and reaction time was 30 h. Immobilized bacteria can be reused for three times, the decolorization rate of the immobilized bacteria could reach above 70% after every time.Afterwards, the decolorization of Reactive Black 5 by Enterobactor sp.S8 immobilized on Luffa cylindrica sponge was studied. The effects of bacteria age, bacteria amount, pH and temperature on decolorization were discussed. The reusability and kinetics of the immobilized bacteria were also studied. The results showed that the optimum conditions for decolorization by immobilized bacteria were 3-day culture, inoculation of 2%, temperature at 30℃, and pH 6.0. The decolorizaton of immobilized bacteria on Reactive Black 5 at various initial concentrations conformed to the second-order reaction mode. After nine times reused, the decolorization rate of the immobilized bacteria could still reach 76.8%. According to the UV-Vis spectrum before and after 3 d degradation under the optimum conditions, Reactive Black 5 was not completely mineralized to CO2 and H2O. Instead, some organic intermediates were produced.On the basis of respective optimal immobilization conditions obtained in the previous experiments, The Enterobactor sp.S8 was respectively immobilized in calcium alginate gel, polyvinyl alcohol (PVA) and Luffa cylindrica sponge and their microstructure were observed by scanning electron microscope (SEM). It was found that calcium alginate gel might dissolve in the wastewater, and the activity was restricted as cells wrapped in PVA, so the COD removal ratio was low. The method of immobilized cells using Luffa cylindrica sponge was simple and COD removal efficiency could be achieved. In addition, the immobilized bacterium could not be separated easily from the Luffa cylindrica sponge in the wastewater.Finally, Reactive Black 5-degrading bacteria was immobilized by Luffa cylindrica sponge and supplemented to AnSBR systems and its effects on the removal of Reactive Black 5 in the systems were studied. In addition, the contributions of the supplemented culture and indigenous culture in the bio-augmented system at different operation stages were compared. Results showed that the start-up time for the AnSBR system to treat Reactive Black 5 was shortened by augmentation with high effect bacteria and its ability to endure Reactive Black 5 shock loading was strengthened. Control AnSBR system without augmenting immobilized bacteria could endure 67 mg·L-1 shock loading, while the AnSBR systems supplemented with 0.5%,1%,1.5%,2% high effect bacteria could endure the shock loading of 180,280,280,280 mg·L-1 respectively. Immobilized special culture added in the system played the main role in removing Reactive Black 5 at initial stage, while both the indigenous and the augmented bacteria had very strong ability to degrade Reactive Black 5 after the operation of one month.