Realization And Salt Resistance Acclimation Of Shortcut Nitrification And Variation Of Microbial Community Structure

High salinity wastewater will have inhibition and toxic effects on microorganisms, when dealing with high salinity wastewater using biological methods, in order to solve the inhibition of salinity on microorganisms, researchers usually use existing halophilic bacteria or domesticate microorganisms to salt. In order to ascertain the relationship between ammonia removal rate, nitrite accumulation rate and salinity in autotrophic and heterotrophic reactor, analyze the character of microorganism number of shortcut nitrification, dynamic changes of population diversity, variation of amoA gene expression in autotrophic and heterotrophic reactor, clarify salt stress on ecological control mechanisms shortcut nitrification microorganisms preliminary, this study uses a fixed-bed biofilm reactor, based on shortcut nitrification, gradually increase the salinity of the water, thus achieving microbial acclimation to salt. The main conclusions are as follows:(1)Adopting strategies to limit oxygen, we achieved and strengthened shortcut nitrification in the two reactors. The ammonia removal rate and nitrite accumulation rate reached more than80%in both reactors. Analysis of bacterial16SrRNA clone library and diversity index showed that the bacterial diversity in the heterotrophic reactor was significantly higher than autotrophic reactor, and the community structure is more complex. Autotrophic reactor clone library sequences can be divided into six groups:Bacteroidetes, Proteobacteria, Planctomycetes, Chloroflexi, Verrucomicrobia and Chlorobi; heterotrophic reactor clone library sequences can be divided into eight groups:Proteobacteria, Bacteroidetes, Chloroflexi, Planctomycetes, Fusobacteria, Acidobacteria, Spirochaetes and Firmicutes.(2) While the salt concentration is increasing, ammonia removal rate and nitrite accumulation rate remained at over80%in autotrophic reactor, ammonia removal rate and nitrite accumulation rate remained70%and90%in heterotrophic reactor, achieving the acclimation of salt tolerance of short-nitrification microorganisms. Real-time PCR results showed that the amount of total bacteria and AOB in the two reactors are declining; the proportion of the AOB to the total bacteria in the autotrophic reactor declined first and increased late, the proportion of the AOB to the total bacteria in heterotrophic reactor showed a gradual decline in the process. PCR-DGGE results showed that there are obvious differences between the microbial community structures of the two reactors. Shannon-Wiener diversity indexes(H) and Simpson’s indexes (D) in both reactors increaseed as salt concentration and decreased. DGGE band sequencing analysis showed that AOB in autotrophic reactor belong to Nitrosomonas, AOB in heterotrophic reactor belong to Nitrosospira and Nitrosomonas.