Study On Treatment Of Automotive Coating Wastewater By Aerobic Granules From Different Inoculated Sources

The types of pollutants in automobile coating wastewater are complex,and the wastewater of each coating process is irregularly discharged.The traditional materialized and biochemical methods for treating automotive coating wastewater have high cost and complicated process,so how to treat automobile coating wastewater with low cost and high efficiency is a difficult problem for researchers.The physical structure of aerobic particles is that microbes aggregate into dense granules,and there are aerobic,anoxic and anaerobic regions inside the particles,so they exhibit excellent degradation ability in treating many kinds of toxic waste water.In this study,floc sludge inoculated with different inoculation sources was first cultivated into granular sludge.Then,the effects of two kinds of granular sludge treatment on automobile coating wastewater were compared.Finally,the dominant flora and its resistant bacteria in the granular sludge were found through the change of microbial community structure.(1)The experiment of culturing aerobic granular sludge was carried out in two SBR reactors,R1 and R2.The floc sludges of two different inoculation sources,R1 and R2,were cultured with synthetic wastewater containing sodium acetate as carbon source.and finally granulation was successful.Fine particles appeared on the 30 th day of R1,granulation was completed in 45 days,particles appeared on R2 for 35 days,and granulation was completed in 51 days.The R1 and R2 reactors have good COD removal effects in synthetic wastewater.The R1 effluent COD is always 100mg/L,and the R2 is about 100mg/L.The TN removal rate of R1 is about 55%,the average TN removal rate of R2 is 53% and the fluctuation is large,and the TP removal rate of R1 and R2 at the initial stage is more than 90%.The removal rate of the reactor decreases slowly with the operation.The final effluent TP is around 2mg/L.(2)Granular sludge(R1,R2)cultured in different inoculation sources were analyzed by high-throughput sequencing in the treatment of automotive coating wastewater,and the microbial community structure was analyzed in the pre-accident and medium-term At the level of microbial community structure at the door level,after 20 days from the start of domestication to the end of the whole automotive coating wastewater,Proteus and Bacteroides are always the dominant flora in R1 and R2.At the level of microbial community structure,?-proteobacteria,?-proteobacteria,?-proteobacteria are always the dominant genus of R1 and R2,while Flavobacteriia and Bacteroidetes_VC2.1_Bac22 are dominant bacteria in R1.In the R2,the automotive coating wastewater is continuously enriched,and the above five bacterial groups are important degradation bacteria in the automotive coating wastewater.In the genus of microbial community structure,the dominant flora of R1 contains Thauera,Zoogloea,Azoarcus,Stenotrophomonas,Sediminibacterium,Flavobacterium,Methyloversatilis,Acidovorax,while Acidovorax and Flavobacterium are absent in R2.Both R1 and R2 Venn analysis and Beta diversity analysis showed that the microbial structure changed minimally during the operation of all automotive coating wastewater and has stabilized.The diversity analysis of R1 and R2 Alpha showed that R1 was more abundant in microbial community structure than R2 after adding wastewater.It can be seen from the second-level distribution of KEGG predicted by PICRUSt of R1 and R2 that the main metabolic pathways of microorganisms in R1 and R2 are amino acid metabolism and carbohydrate metabolism,and the abundances of metabolic pathways in each period of R1 and R2 are not much different.At the same time,the external water environment changes during the experiment,and the relative abundance changes are not obvious.(3)The aerobic particles were well adsorbed and degraded in the treatment of automotive coating wastewater.The average COD removal rate of R1 and R2 reached 88% and 90%.The domestication time is short,and the impact is less under the impact of toxic automobile coating wastewater.The comparison of R1 and R2 shows that the granular sludge prepared from the floc sludge of different inoculation sources has good adaptability,and has no obvious relationship with the floc sludge from the inoculation source.Automotive coating wastewater contains two kinds of fluorescent substances,protein-like and humic-like.The protein-like substances are easily adsorbed and degraded by the aerobic particles of R1 and R2 reactors,while humic acids are difficult to be completely degraded.It shows that granular sludge and flocs have certain limitations in the treatment of humic substances.