Analysis Of MBR Or IAMBR On Nitrogen Removal And Microbial Community Constructure In The Oligotrophic Condition

At the mention of nitrogen removal of membrane bioreactor, nitrification reactscompletely while denitrification incompletely in traditional aeration mode. Comparedto traditional mode the efficiency of denitrification in modified intermittent aerationmembrane bioreactor is better. The organic loading will decrease with the increasingof sludge concentration both in traditional and modified membrane bioreactor.Microorganisms tend to live in a poor nutritional state. The purpose of the study liesin exploring removal effect of nitrogenous pollutants on the two types of membranebioreactor and change of microbial community structure in the oligotrophic condition.Influent with no carbon source is defined as the oligotrophic condition in thestudy. It compares continuous aeration process with intermittent aeration process inparallel running. The ammonia nitrogen removal rate of MBR and IAMBR are76%and81%respectively. Both of their total nitrogen removal rate drop sharply. Due tothe accumulation of the nitrate nitrogen and the release of nitrogen cased byendogenous respiration collapse effluent of total nitrogen of MBR is13.46mg/L morethan influent while IAMBR is3.84%at the end of the experiment. The sludge ofMBR is affected more significantly and more likely to occur sludge bulking. Researchshows that intermittent aeration obtains relatively higher removal rate and the sludgeof IAMBR shows stronger ability to resist harsh environment.PCR-DGGE and the associated molecular biological technic are used to studymicrobial community on actived sludge. So can we deeply understand the influence ofoligotrophic condition on stable operation for IAMBR. The results show thatcharacteristics of total bacteria on diversity, similarity and ethnic affiliation have ahigh degree of cooperativity. Numerous ammonia-oxidizing bacteria are dominantamong total bacteria. Their structure shows slightly single while similarity keeps well.Denitrifying bacteria show lower diversity index and weaker stripe through the mapof DGGE. Their similarity changes greatly in amplitude and frequency, indicating thatdenitrifying bacteria are particularly sensitive to the sudden shortage of carbon source.The cluster analysis shows that as time goes by the population of total bacteria andammonia-oxidizing bacteria experience a drastic succession at the end of theoligotrophic period. Denitrifying bacteria are in continuous fluctuant adjustment from the outset. By means of DNA sequencing we find that the total bacteria of IAMBRmostly belong to uncultured bacteria and Nitrosospira hold the dominant position. Inadditon, other microoganism have been found including Pseudomonas, Acidobacteria.Research shows that oligotrophic condition badly influence on microbial communityof IAMBR especially denitrifying bacteria. The function-oriented is obvious that thenitrifying bacteria hold the dominant position.