Enhanced Decolorization Of Azo Dye Wastewaters By The Sludge-lysate Under High Salinity Condition

Hyper-salinity azo dye wastewater is considered as one of the most recalcitrant wastewaters. During the anaerobic treattment, the microbial metabolism is seriously repressed because of the high salinity and toxicity. More complex co-metabolic substrates such as yeast extract and peptone are needed by sah-tolerant bacteria in the anaerobic treatment. These two factors will be the bouleneck for the biological treatment of hyper-salinity azo dye waste water.In this paper, bow to solve these two problems will be studied with azo dye wastewater containing5%salinity as the simulating wastewater. Firstly, the acclimatization of the azo-dye-degrading bacteria shewanella sp. XB was conducted by increasing the concentration of the NaCl gradually, and we got the bacteria that could grow well in the LB culture medium which contained5%NaCl. Next, the decolorization capacity of the salt-tolerant bacteria was tested at5%salt. When the azo dye concentration was100mg/L and the bacteria OD660was controlled at0.53,0.7times LB diluent (without NaCl) was needed and95.1%of the azo dye was decolorized in21h.Secondly, four different sludge treatment technologies were examined and the sludge-lysates were used as the substitutions to enhance the decolorization of the azo dye at5%salt. The results showed that all the sludge-lysate had positive effects on the decolorization of azo dye, while the sludge-lysate from C technology showed better effect than the others. And the mixture of the sludge-lysate and LB was researched. It showed that the COD (3000mg/L) of C sludge-lysate and0.3times of LB diluent (without NaCl) was the optimal ratio, and the decolorization efficiency was90.6%. And this meant that57.1%of the LB was replaced by the sludge-lysate (COD3000mg/L).When the C sludge-lysate was divided into supernate and sediment, the supernate showed better than the sediment in the decolorization of azo dye. Through the analysis of the cyclic voltammetry curves of the C sludge-lysate, the supernate and the sediment, it was found that the C sludge-lysate and the supernate had the oxidation peaks and reductive peaks at the same position while one of the oxidation peaks lost in the cyclic voltammetry curve of the sediment. In addition, the humic acids extracted from the C sludge-lysate accounted for52.1%of the COD and it showed good redox activity at its cyclic voltammetry curve. Thus, it’s concluded that there are abundant redox mediators in the C sludge-lysate and they could accelerate the electrons transfer during the decolorization of azo dye. Finally, the dehydrogenase activity of the salt-tolerant bacteria was assayed when the C sludge-lysate and the supernate were added. And the results showed that the dehydrogenases of the two systems were63%and57.6%, both of which were higher than the control system. At the same time, the C sludge-lysate was demonstrated that it could enhance the decolorization of some kinds of azo dyes.