Research On Anaerobic Biodegradation Effect And Wechanism Of Azo Dye Wastewater

With the development of social economy,the acceleration of urbanization and industrialization,people's constant pursuit of a better life,a variety of dyes appear in people's daily life.China is a large dye production country.At present,China's dye production occupies the first place in the world.In the process of dye production,a large amount of water resources will be used,and a lot of wastewater with the characteristics of poor biochemical COD,high toxicity,high salinity,high chromaticity,high composition and so on will be produced.Therefore,a method of wastewater treatment with low cost and good treatment effect is urgently needed to treat the dye production wastewater.In previous studies,various physical and chemical methods have been reported to degrade dye wastewater,such as polymerization,adsorption,oxidation,electrochemistry and ultrafiltration.These methods can effectively remove some substances in dye wastewater,but due to the high cost and the by-products need to remove in the treatment process,these methods cannot be used in actual production.Biological treatment method is an economic method to treat the dye wastewater.At present,many studies have proved that biochemical method can effectively degrade dye wastewater,but aerobic biological method will produce a large number of excess sludges that needs to be treated.Due to little excess sludge,simple operation and renewable bio fuel biogas,the anaerobic digestion technology is more suitable for practical production.At present,UASB is the most widely used anaerobic reactor,and the anaerobic granular sludge is also the one with better activity and rich microbial community,which can effectively degrade complex organic matters.In this study,anaerobic granular sludge and UASB were used to treat azo dye production wastewater,and starch was used as co-digestion substrate.This paper introduces the whole process from the domestication of raw sludge to the co-digestion of starch-wastewater and the single digestion of wastewater.Evaluates the operation of UASB reactor by various analysis methods,analyzes the water quality of inlet and outflow water from multiple perspectives and levels.evaluates the treatment effect of UASB on wastewater and takes out sludge from UASB in different stages for activity and microbial community analysis.The structure of microbial community in different time periods was described in detail,and the effect of wastewater on anaerobic dominant microorganisms was further evaluated.It is concluded that in this study,when the starch concentration in the influent water sample is around 3-7g/L and the wastewater concentration is 10%,the optimal operation condition of UASB is achieved,the removal rate of COD is stable at more than 90%,and 88%of COD in the influent water is converted into biogas production of about 8 L day-1.At this time,the sludge reached the highest activity of this experiment,which could effectively degrade 10%concentration wastewater to produce biogas,and the microbial communities such as Bacteroidetes vadinHA17,Methanolinea,Methanosaeta,Methanobacterium and toluene-' methanogenic consortium bacterium increased significantly which could degrade complex organic matter.In this study,the degradation path in the anaerobic reaction system was determined by LCMS,and the azo breaks in azo dyes were determined to generate n,n-diethyl p-phenylenediamine(C10H16N2).Moreover,through the peak changes of molecular ion fragments in MS,p-nitroaniline(C6H6N2O2)and n,n-diethyl m-phenylenediamine(C10H16N2),which may exist in wastewater,was determined to be degraded by anaerobic digestion and further degraded after forming aniline or nitrobenzene.However,when only a single wastewater is used as substrate in UASB,the stable operation of UASB reactor is broken,the biogas production of UASB reactor drops sharply,the COD removal rate is reduced to 40%.The community abundance of methanogenic microorganisms was reduced,the methanogenic stage in anaerobic digestion was inhibited due to the wastewater has a negative impact on sludge activity and microbial community.Single wastewater will inhibit anaerobic digestion.Through this study,the single wastewater inhibits the anaerobic digestion,but the anaerobic co-digestion system composed of starch and wastewater is able to maintain the stability of the system,and promote the growth of some microorganisms,enrich the diversity of microbial community.This study provides a low-cost and sustainable treatment method for azo dye wastewater.