Azo Dye Specific Degradation Microbial Community And Its Application Research

Due to the structure and the various color, azo dyes had become the most extensive dye for application, which were widely used in printing and dyeing, leather, food and other industries. Annual output accounted for 80% of all dyes. Waste water containing azo dyes discharged into the water environment would make light transmittance decrease, affect photosynthesis and destruct the ecological system balance, and the degradation of azo dyes would consume the dissolved oxygen threatening the survival of aquatic organisms. Synthetic azo dyes often had toxicity, carcinogenicity and mutagenicity. And many studies showed that azo dyes had negative impact on the germination rate and growth rate of a variety of plant seeds. Although the traditional physicochemical method had a better effect in treatment of azo dyes, the higher cost and serious secondary pollution limited its application in practice. Biological method was widely used because of its cheap efficient and environment-friendly advantages. With the good mechanical properties and chemical stability, polyurethane foam as carrier can effectively fixed microorganisms. And polyurethane foam immobilized microorganism can also improve decolorization rate effectively.To screen effective bacterial strains capable of decolorizing azo dyes in dewatered sludge. 9 bacterial stains(named T-1―T-9) were isolated from the dewatered sludge in municipal wastewater treatment system after proper acclimation. Physiological and biochemical tests and 16 S r RNA gene based bio-molecular identification were adopted to identify the isolates. Decolorization performances of pure cultures and mixed cultures of the isolates were determined and compared. 9 isolates belonged to Bacillus sp., Exiguobacterium sp., Stenotrophomonas sp. and Paracoccus sp. according to preliminarily identification. The structure and concentration of azo dyes had a certain impact on the decolorization efficiency during domestication. This study suggests that, as a new source for the functional flora of decolorizing azo dyes, the dewatered sludge and its isolates are of great value in zao dye containing wastewater.The relationship between azo dyes structure and microbial community structure was explored and the microbial community structure in acclimated sludge of different azo dyes was analyzed using the T-RFLP technology. The analysis showed that the microbial community after domestication had a drastic shift, and different azo dyes corresponded to different microbial community structures. Therefore, the formation of the microbial community was depended on the structures of azo dyes. And a complex microbial community structure including the dominant population with a large abundance and other population with small abundance would form after acclimating by each of azo dyes. Also canonial correspondence analysis was used to analyze the relationship between the environment similarity after acclimating and variables. It had found that the decolorization rate had the most contribution rate for the environment distribution and the Shannon diversity index least, which indicated that the formation of the microbial community structure was determined by azo dyes, and the effect of the microbial community diversity may not be notable.The characteristic of electricity generation accompanying by decolorization of azo dye was investigated using a simple membrane-less single-chamber microbial fuel cell(MFC) with non-carbon-source-depended azo dye degrading strain. Batch experiments results showed that accelerated decolorization of 1-phenylazo-2-naphthol-6,8-disulfonic acid disodium(orange G) was achieved in the MFC as compared to merely bacterial treatment. The present study suggests that our MFC mediated azo dye wastewater treatment process is of valuable when considering its low cost.Soluble microbial product(SMP), being an important metabolite of the microbes in activated sludge system of wastewater treatment, plays an essential role in the formation of sludge flocs and the stable operation of treatment system. The characteristics of SMP and extracellular polymeric substances(EPS) from the sludge of cyclic activated sludge system(CASS) and anaeroxic-anoxic-oxic(A2O) treatment processes, cultured anaerobically and aerobically, were investigated after long-term(60 days) cultivation and used for the enhancement of the electricity generation and decoloring rate of the microbial fuel cell(MFC) to treat azo dye-containing wastewater. The results showed that the SMP and EPS from different processes and cultivating methods were of high similarity in composition while the EPS had higher content of macromolecular substances than that in SMP according to the data of PACl sedimentation test. The present study suggests that EPS and SMP are of valuable as auxiliary in the electricity reclamation from azo dye-containing wastewater treatment.