Treatment Efficiency Of Automobile Coating Wastewater Using Aerobic Granular Sludge And Analysis Of Its Microbial Community Structure

The composition of automobile coating wastewater is complex,and there are many types of it.The water quality and quantity of water vary greatly.In actual engineering,the method is mainly based on the conventional floc activated sludge method.However,its emission control problem is an important issue in the field of water treatment.The aerobic granular sludge,as a special bioaggregates,has better treatment performance for the waste water due to its unique structure and characteristics.Studies have shown that,under normal circumstances,its treatment of sewage is better than ordinary flocculent sludge.In view of this situation,aerobic granular sludge was cultivated in the SBR reactor in this study,using automobile coating wastewater as the the research object and sucrose as a co-substrate matrix.The sludge microbial community during the granulation process was examined while examining its treatment effect,exploring the relationship between the degradation effect of pollutants in automobile coating wastewater and the structure of microbial community.And the removal effects of aerobic granular sludge and flocculent sludge on the automobile coating wastewater treatment were compared.The aim was to provide reference for the treatment of automobile coating wastewater using aerobic granular sludge and the selection of the treatment process of automobile coating wastewater in practical engineering.The main contents,methods and research results of this article are as follows:?1?Aerobic granular sludge was cultivated in the SBR reactor,using flocculent sludge as the seeding sludge,automobile coating wastewater as the research object and sucrose as a co-substrate matrix.The growth status of aerobic granular sludge was investigated from the changes in sludge morphology,microstructure,and physical characteristics of sludge as well as the effect of wastewater treatment.Fine particles appeared around 45 days,and they were basically granulated on the 90 th day.The sludge SVI was stable at about 36 m L/g,indicating its sedimentation performance was good.The mature granular sludge was brownish-yellow,regular in shape,spherical,with an average particle size of 1.12 mm,and the surface was covered with bacilli of varying lengths.The outer layer of mature granules was mainly live bacteria,and the interior was dominated by dead bacteria.In the EPS,?-polysaccharides,?-polysaccharides and proteins mainly distributed on the surface of the particles,also a small number of them distributed inside while none in the core.The content of ?-polysaccharide is the highest,which is the maincomponent of EPS.At the time when granular sludge was stable,the removal rates of COD?NH₄⁺-N and PO₄^3--P in the automobile coating wastewater reached 85%?95% and 65%,respectively.The removal effect was good.?2?The analysis of microbial community during sludge granulation.High-throughput sequencing technology was used to inspect the sludge in different stages of granulation.The results showed that the species and quantity of microbial flora were also constantly changing with the increase of automobile coating wastewater in the influent and the granulation of sludge.After the maturation and stabilization of aerobic granular sludge,microbial community successioned to the top level,which gradually tended to stable community structure,and these changes were basically consistent with the removal of pollutants.To a certain extent,it can be shown that the changes in the microbial community correspond to the effect of the degradation of pollutants.During the whole process of operation,the microbial composition of the aerobic granular sludge was not as rich as that of the inoculated sludge.What's more,the bacterial community composition of the granular sludge in the growth stage was smaller than that of its formation process.While the influent water quality and sludge sedimentation time were constantly changing,the overall bacteria in the system still maintained similar functions,indicating that the microbial community could maintain its function by adapting to the changing environment.?3?Comparison and analysis of degradation performance of automobile coating wastewater by aerobic granular sludge and flocculated sludge.Compared with aerobic granular sludge and flocculent sludge,the former has better treatment effect on automobile coating wastewater.The removal of COD and NH₄⁺-N was 8% or 2.5% higher than that of the latter,respectively,while there was no difference in the removal of PO₄^3--P.During the acclimation process,the removal rate of pollutants from both sludges were generally on the rise,and the contents of protein and polysaccharide in the sludge were continuously increasing.The protein content in the aerobic granular sludge was significantly higher than that in the flocculation sludge.These results can explain to a certain extent that the automobile coating wastewater has no obvious inhibitory effect on aerobic granular sludge or flocculent sludge,and the ability of aerobic granular sludge to resist external impact is better than that of flocculent sludge.Also,the treatment effect of the former is better than that of the latter.