| Eutrophication is becoming more and more serious due to excessive nitrogen and phosphorus in water.The conventional biological nitrogen and phosphorus removal processes can not meet discharging standard which is becoming more and more stringent.In recent years,the denitrifying phosphorus removal technology were widely attractive for its less carbon source demand,less aeration and less sludge discharge,which has solved the problem of the competition of carbon source and contradiction of sludge retention time.However,there are many problems such as large area,complicated control and high cost of construction in the existing denitrifying phosphorus removal process.So it is significant to develop a new economical and efficient process of nitrogen and phosphorus removal which have low carbon source for city sewage treatment.In this paper,denitrifying phosphorus removal biofilm was successfully built up.DPB(Denitrifying Phosphorous Bacteria)were induced and enriched by adding nitrate in the biofilters for stable operation.And the environment of anaerobic / anoxic / aerobic was constructed by alternating aeration which was suitable for DPB.The efficiencies and characteristics of denitrifying phosphorus removal was investigated to reveal the mechanism of nitrogen and phosphorus removal.Also,the influent parameters were optimized to further improve the efficiency of phosphorus removal in the system.At the same time,the microbial community structure of each stage in the system was studied by high-throughput sequencing,and the biodiversity and similarity were analyzed to discuss the evolutionary changes of microbiologic population in the system,to provide a new reference for the technology and theory of denitrifying phosphorus removal.The results showed that the finish time of enriching DPB in denitrifying phosphorus removal biofilm was 60 d.After that the average removal rates of ammonia nitrogen,phosphorus and nitrate were 100%,65.99% and 93.85%,respectively.The phosphorus uptake amount in the anoxic accounted for 90.89% of the total phosphorus uptake amount,and DPB accounted for 84% of the total phosphorus accumulating organisms in the system.The changes of PHB(Poly-β-Hydroxybutyrate)and polyphosphate particles in biofilm cells suggested that the denitrifying phosphorus removal play a major role phosphorus removal in the system.The optimal influent ammonia nitrogen,phosphorus and carbon source of denitrifying phosphorus removal biofilm were 10mg/L,12mg/L and 350mg/L,respectively.During the stable operation of the system,the average removal rate of ammonia nitrogen and phosphorus were 100% and 85.19%,respectively.At the same time,the removal rate of nitrate in the anoxic was about 100% and there was no nitrite nitrogen accumulation.After the optimization of the influent parameters,the system had excellent ability of ammonia oxidation,and its phosphorus removal capacity increased significantly.The microscope analysis showed that,the system presented a complete biological phase in each stage,prokaryotic microorganisms of system such as cocci,bacillus,protozoan and metazoan coexist in the system,which played an important role in water treatment.Based on the analysis of the diversity of biofilm samples in each stage,it was found that the distribution of the biofilter was more even and the diversity was the highest.In the early stage of the system,the diversity of microorganism was low.As time goes by,the system has a higher biodiversity after enrichment completion of DPB,but still lower than the biofilter.The difference of microbial community in each stage of the system showed that there were some differences in the microbial community structure during the construction of denitrifying phosphorus removal biofilm.At the same time,cluster analysis showed that the microbe in the prime of enrichment of DPB and the microbe after enrichment completion of DPB belong to different clustering branches,which reflected the microbial community structure expressed significant differences during the construction of denitrifying phosphorus removal biofilm.The analysis of the dominant bacterial community in denitrifying phosphorus removal biofilm after enrichment completion of DPB showed that Proteobacteria was the predominant flora at phylum level,which accounted for 34.19% in seed sludge and 58.64% after demonstration,especially,the percentage of Betaproteobacteria increased from 4.74% to 19.93%.And the dominant population of denitrifying phosphorus removal biofilm in the "order" classification were Burkholderiales,Aeromonadales,Rhodocyclales and Xanthomonas.The proportion of Aeromonas was 0.41% in the seed sludge,and it increased to 3.66% after enrichment completion of DPB in denitrifying phosphorus removal biofilm.As one of the dominant bacterial community,Aeromonas absorbed phosphorus by using nitrate as the electron acceptor in coordination with Pseudomonas,Sphingomonas,Propionivibrio,Dechloromonas,Hyphomicrobium,Moraxella,Enterobacter,Aminobacter,Thauera and Bacillus,playing an important role in the removal of nitrogen and phosphorus.Long-term operation results showed that the system had stable effluent quality and the ability of simultaneous removal of nitrogen and phosphorus,which provide a technical reference for the new nitrogen and phosphorus removal process. |
