Analysis On The Performance And Microbial Community Succession Of Liquor Wastewater Treatment By Multi-stage AO Process

At present,the application and research of multi-stage influent and multi-stage AO process for wastewater treatment are mostly focused on the treatment of municipal domestic sewage by multi-stage AO process,as well as the design parameter control and operation technology of the process,etc.The research on the multi-stage AO process for brewing wastewater treatment and the microbial functional flora in the process is worth further exploration.This experiment adopted the multistage AO process simulated brewery wastewater.On the condition that COD in water was 650 mg/L,TP was 35 mg/L,ammonia nitrogen was 60mg/L,total nitrogen was 100 mg/L,dissolved oxygen pool（A pool）was 0.1～0.3 mg/L,aerobic pool（O pool）was 2.5～4.5 mg/L,the influence of hydraulic retention time（8,11 and14 h）,the ratio of water（40:40:30,55:35:10 and 65:25:10）and different raw water proportions（0%,30%,70%and 100%）on the treatment effect of multi-stage AO process was inspected;At the same time,high-throughput sequencing technology and 16S r RNA gene sequencing technology were used to analyze the differences of microbial community structure under different raw water proportions.Finally,metagenomic sequencing technology was used to analyze the functional genes of the reactor when 100%brewing wastewater raw water was taken into the water,and the nitrogen metabolism pathway under the influent mode was analyzed.Through taking single factor experiment investigation multistage AO process operation features,various process parameters on the multistage AO pollutants removal effect were explored.The test result shows that the water quality index of different hydraulic retention times had different effects on brewery wastewater.With the reduction of HRT,a gradual rise in the average effluent COD concentration was witnessed,and the average concentration water were 35.71,39.08,and 202.49 mg/L.When HRT was 8 h,the effect of hydraulic retention time on COD was most significant,and at this moment,the COD removal rate was 68.91%and the effluent concentration was 202.49 mg/L.The effluent could not meet the standard of COD discharge less than 100 mg/L in"GB27631--2011 Discharge Standard for Water Pollutants in Fermented Alcohol and Liquor Industry".The concentrations of TP,NH₄⁺-N and TN all showed a trend of decreasing first and then increasing with the decrease of HRT.Under this influent mode,HRT=11h was the optimal hydraulic retention time.Different water distribution ratio（40:40:30、55:35:10 and 65:25:10）had little influence on the removal of COD and TP in brewing wastewater by multi-stage AO system,but had great influence on the removal efficiency of ammonia nitrogen and TN and the optimal influent water distribution ratio is 55:35:10.At the same time,its removal rate could reach about 94.02%,90.38%,81.93%and 81.10%.With the increase of raw water influent proportion,the effluent indexes of the reactor would increase to different degrees.However,with the further increase of raw water,the removal effect would be weakened,the impact resistance of the reactor would be strong,and the effluent was stable.According to 16S r RNA gene sequencing,the coverage rate of 24 samples in the experiment was above 99%,which indicated that the sequencing data was highly reliable.With the addition of raw water,the number of total bacteria in the reactor did not change much under the four different influent modes,and the total species richness was roughly the same,but there were differences in species species.Proteobacteria,Patescibacteria and Actinobacteriota were the most abundant microorganisms in the four influent patterns at the phylum level,and played a dominant role in the water treatment process.Acidobacteriota was a unique phylum when the proportion of raw water was 0%,which was conducive to the degradation of single carbon compounds.After the addition of raw water,the ecological environment changed,and it was no longer a dominant phylum.Gamma-Proteobacteria and alpha-Proteobacteria were the dominant bacteria at class level.When the proportion of raw water was increased to 30%,a new microorganism population Gracilibacteria appeared,which played an important role in host symbiosis and parasitism.When the proportion of water intake was increased to 70%,the abundance of Parcubacteria decreased to less than 1%and was no longer shown separately.When 100%raw water was filled with water,a new class of bacteria,Kapabacteria,appeared,which participated in the process of sulfate reduction and cytochrome metabolism and oxidation,and could adapt to oxygen concentration and potential fluctuation within a certain range.At the genus level,Candidatus-Competibacter,Propionicicella,Terrimonas,and Hyphomicrobium were the main bacterial genera under four influent water modes,with similar microbial flora species and large differences in abundance in different raw water proportions,indicating that the structure of microbial flora was greatly affected by water quality impact.Metagenomic sequencing was carried out on the reactor samples of 100%raw water influent,and the functional genes were statistically analyzed by KEGG.The results showed that the functional genes could be divided into 8 categories among which the abundance of genes related to metabolic mechanism was the most significant,accounting for 59.58%～60.28%.According to the KEGG sublevel statistics,the number of functional genes related to the metabolic mechanism was the largest,which proved that there were a large number of functional genes closely related to the growth and metabolism of microorganisms and the degradation of pollutants in the multi-stage AO reactor samples.In the nitrogen metabolism pathway,it was found that nitrification and denitrification played a dominant role in the nitrogen metabolism pathway in the multi-stage AO process.Among them,the abundance level of the functional gene enzyme（EC1.7.99.4）for the conversion of NO₃-N to NO₂-N was high,which was conducive to the denitrification.The content of Amo CAB,Hao and Nxr AB genes responsible for encoding EC:1.14.18.3 and 1.14.99.39 nitrosases and EC:1.7.2.6 nitrosases was relatively low,which might be one of the reasons for the low ammonia nitrogen removal rate in this study.This study investigated the influence of different process parameters on the effluent water quality,analyzed the structure characteristics of the microbial community in the process of brewing wastewater treatment and its response mechanism on related environmental factors,revealed the brewery wastewater multistage AO process of microbial community structure and the relationship between effluent water quality change,and provided theory basis and data support for the application of multilevel AO craft brewing wastewater treatment parameter optimization.