| With the increase in the amount of urban sewage and the increasingly complex composition of pollutants,the traditional sewage treatment process is difficult to meet the requirements of sewage denitrification and phosphorus removal,and the difficulty of sewage treatment increases.The sewage area of a sewage treatment plant in Xuzhou was connected to industrial wastewater containing high ammonia nitrogen.The quality and quantity of the influent water changed,the concentration of organic matter was low,and the content of ammonia nitrogen was high,resulting in poor denitrification and phosphorus removal.The pressure poses a threat to the surrounding water environment.Aiming at the existing problems of the original process of sewage treatment plant"hydrolysis and acidification+A2/O",put forward the transformation process of"anoxia+UCT",and study the transformation process;Through single-factor experiments,the influence of mixed liquor recycle ratio,sludge recycle ratio,sludge retention time,DO and other factors on the treatment effect of the transformation process was studied,the optimal process parameter combination was determined,and the optimal working condition parameters were used to study the removal of pollutants along the process;High-throughput sequencing was used to compare the microbial diversity and population structure of the biological treatment unit;the multi-point water inflow method was used to further optimize the process to achieve a reasonable distribution of carbon sources,while taking into account the effects of nitrogen and phosphorus removal and reducing operating costs,and concluded as following:（1）The effluent quality indicators of the"anoxic+UCT"process were all raised to the first-level A emission standard,and the removal rates of ammonia nitrogen,TN,and TP were increased from 88%,73%,and 89%to 96%,80%,and 96%,respectively.It can improve the denitrification and phosphorus removal effect of the system.The best process operating parameter combination is obtained through single-factor experiments:the mixed liquid recycle ratio is 150%,the sludge recycle ratio is 100%,the sludge retention time is 15d,and the DO concentration is 1.0-2.0 mg/L.（2）The effect of mixed liquor recycle ratio and sludge recycle ratio on the removal effect of COD and NH4+-N is not obvious.When the mixed liquor recycle ratio is 150%,the removal rates of TN and TP are 82.8%and 96.9%respectively.When the sludge recycle ratio is 100%,the removal rates of TN and TP are 80.0%and 96.4%,and the system has the best denitrification and phosphorus removal effect;when the SRT is shortened to 5d,the average phosphorus released concentration of phosphorus accumulating bacteria in the anaerobic stage decreased from 17.7 mg/L to 12.2 mg/L.When the SRT is 15d,the removal effects of TN and TP are 80.7%and 97.1%,respectively.MLSS showed stabilized at 3500-4000 mg/L,SVI is maintained at 70-90m L/g;when the DO decreased to 1.0-2.0 mg/L,the removal rate of TN increased from79.2%to 85.1%,and the TP removal rate increased from 84.4%to 95.6%%,the SVI is between 140-180 m L/g,which belongs to the micro-expansion range of filamentous bacteria.（3）The removal rate of COD in anoxic tank 1 reached 71.4%;96%of the influent TN was ammonia nitrogen,the contribution rate of the anoxic tank to the TN removal accounted for 89%of the TN removal rate,and the concentration of nitrate nitrogen in the aerobic stage increased from 2.97 mg/L increased to 9.59 mg/L;The concentration of TP increased by 242%in the anaerobic stage,and then decreased by 92%in the aerobic stage.The Alpha diversity index showed that the bacterial population diversity in anoxic tank 2 was relatively high,and the dominant phylum levels in the sludge were Proteobacteria,Bacteroidetes,the relative abundance reaches 63.4%-69.7%,the dominant genus levels are Methylotenera,Nitrospira,unclassified＿Chitinophagaceae,the relative abundance reaches 16.7%-18.8%.There are certain differences in microbial structure and abundance in anaerobic,anoxic,and aerobic tanks,but similar in type.（4）On the basis of the"anoxia+UCT"process,the influent water is distributed to the anoxic tank 1,the anaerobic tank and the anoxic tank 2,and the optimized process operation is studied.The results show that the removal rate of COD and NH4+-N by the water inflow method is stable above 90%,and the removal rate of TN and TP in the three-point water inflow is 4.6%and 5.4%higher than that of the single-point water inflow,respectively.After passing through the anoxic tank 1,the COD concentration was reduced to below 50 mg/L,and the carbon source was fully utilized,and the pollutant removal effect of working condition III was the best.The daily pharmaceutical cost of the optimized process was reduced from 2982 yuan to 2632 yuan,a decrease of11.7%.In terms of energy consumption,the average daily electricity consumption before the multi-point water intake was 4281 k W·h,an increase of 16.9%,and the daily electricity cost increased by 195 yuan.Compared with the process operation cost before optimization,it shows that the optimization process has certain feasibility.The thesis contains 49 figures,11 tables,and 134 references. |
