Study On Nitrogen Removal Characteristics Of Heterotrophic Nitrification-Aerobic Denitrification In A Membrane Biological Reactor

There are many studies about heterotrophic nitrification-aerobic denitrification since the first bacterium which was capable of heterotrophic nitrification and aerobic denitrification was isolated in the1980s. This kind of bacteria grows fast with organic matter as carbon source and can aerobically convert ammonium to N2without NO2--N/NO3--N accumulation. Compared with conventional biological denitrification, heterotrophic nitrification-aerobic denitrification has some advantages:(1) The utilization of organic matter and tolerance for oxygen make it possible to achieve simultaneous removal of COD and ammonia. And nitrification and denitrification could carry out in a single-stage reactor, which could save the covering area and operation costs;(2) Heterotrophs have high growth rate and so it is easily kept in the treatment system;(3) It makes mixed culture feasible with a variety of bacterial strain that the possible substrates and products of heterotrophic nitrification-aerobic denitrifiers are diversity. This expands the scope of the possible applications.So, many researchers paid more attention to the influence factors on and potential application value of heterotrophic nitrification-aerobic denitrification on biological denitrification.Recent researches about heterotrophic nitrification-aerobic denitrification mainly focused on the study of pure bacteria. However, there are few studies about whether the pure culture could be applied to practice. For preliminary understanding the nitrogen removal characteristics of the bacteria community, the key influence factors on denitrification characteristics, the denitrification pathway and nitrogen balance were investigated in sequencing batch experiments after enrichment culture of the isolated bacterium in laboratory. Then, one membrane bio-reactor (MBR) was started up. The main purpose was to study the long-term effect of key influence factors on total nitrogen removal. At the same time, PCR-DGGE and16S rRNA sequencing were conducted for indicating the dominant bacteria in the MBR. The results showed that the optimal running conditions of the MBR were as following:Glucose as carbon source, COD/N ratio10, DO<2mg/L, HRT=24h. Under the conditions, the ammonia and total nitrogen removal efficiencies reached83%and74%, respectively. PCR-DGGE and clone library analysis both indicated some changes in the bacterial diversity under different conditions. Sequencing analysis showed that Rhodocyclaceae, Arcobacter butzleri and Klebsiella sp. were dominant in the community. It was probably that Rhodocyclaceae played a major role in heterotrophic nitrification-aerobic denitrification.Simultaneous removal of COD and total nitrogen was investigated during the study. The results indicated that the COD removal efficiency of the MBR remained high (nearly100%) and stable after stability running period. And the sludge concentration was also stable. The MLVSS/MLSS was about0.63. At last, a primary research with actual wastewater was conducted. The total nitrogen removal efficiency was about36.83%(30%-40%) after running stability. The main reason for the low total nitrogen removal efficiency was due to the high nitrate accumulation in the effluent. The results showed that this system had a potential value in the actual wastewater treatment.