Analysis The Microbiology Community Structure And Function Of Aerobic Nitrifying Granules Based On DGGE

Aerobic granular sludge has become a research hotspot in water treatment field, since it hasbeen successfully cultured. Aerobic granular sludge technique has obvious advantages, forexample, it is of good settling properties, high biomass retention, and higer anti-shock loadingstability. Besides, the aerobic granular sludge is three-dimensional, so that an anoxic zone couldexist in the inner pellet, which makes it possible to realize Simultaneous Nitrification andDenitrification (SND) in it. In order to further explain the formation mechanism of aerobicgranulation, and to raise its efficiency and treatment stability, this paper focused on analysis themicrobiology community structure and function of aerobic nitrifying granules cultured insequencing batch reactors (SBRs) using denaturing gradient gel electrophoresis (DGGE)technology. And the main conclusions are as follows.1. Sequencing batch reactors (SBRs) were employed to cultivated aerobic granules withglucose as the organic carbon source. After 14 days, amounts of dense, mature, regular and goodsetting properties aerobic granule was formed, with particle size between 2-3mm, like sphere orellipse. In the starting process, the influent of COD concentration increased gradually from 900mg/L to 3000 mg/L, and its effluent was always below 100mg/L. In a running cycle the reactordissolved oxygen(DO) fluctuated between 5.5-6.5mg/L, when the NH₄⁺-N concentration was300mg/L, its loading was 0.6kg/(m³d), NH₄⁺-N and TN removal rate may achieved 94.4% and66.4% respectively, which indicated that the aerobic granules had realized the SND. And themicrobiology community structure and function in the process of aerobic granulation wasanalysised by the DGGE technology. It indicated that some bacteria which promted granulationand had nitrogen removal function were enriched, such as filamentous bacteria, the bacteria ableto synthesize poly-β-hydroxybutyrate (PHB) and the bacteria could producing excellularpolymeric substances (EPS), which might be a convincing evidence to explain the aerobicgranulation and SND achievement.2. Free filamentous aggregates existed in the SBR had ineviTab, relations with the process ofaerobic granulation. The process of aerobic granulation was both a natural selection under manualcontrols, and an environmental adaption. The latter was a process that a cell itself speeds up thebacterial gathering through changing its cell surface hydrophobicity, superficial electric chargenature and excellular polymeric substances (EPS) secretion, when Ca²⁺ (or other inertmaterial)and fungi provided carriers for the bacteria cell gathering. After the granulation, fungi vanished gradually in the system as carriers. Meanwhile, the filamentous bacteria played double roles asthe carrier and the bridge to enhance the attachment between cells.3. In SBR, the biomass increased rapidly along with the NH₄⁺-N loading increase. After theNH₄⁺-N loading increased to 0.8kg/(d·m³), the volume of aerobic granules augmented, its edgeroughness enhanced, and its shape became irregular, so that the mass transfer distance of thesubstrate was able to be shortened, which could be seen as a response to environment changes.The NH₄⁺-N removal rate continuously maintained at a relatively high level, and could reach max.97%, even when the load was 2.0 kg/(d·m³), when heterotrophic bacteria were critical to NH₄⁺-Nremoval. TN removal rate changed obviously due to the NH₄⁺-N loading increase; the maximumrate was 84.8%, but it had no removal in the minimum, which had relations with the fact thatdenitrifying bacteria change obviously, and that relatively high NH₄⁺-N concentration may beharmful to the activeness of denitrifer bacteria.4. After NH₄⁺-N loading increased to 1.2 kg/(d·m³), there was a significant accumulation ofNO₂^--N with the average rate above 70%. Such nitrite accumulation occurred under the conditionof normal temperature (25℃) and high DO level (＞3mg/L), which was considerably lower thanthat in Sharon or Oland process, so it could possibly be a low-energy-consumption shortcutnitrogen removal technology. In the process increasing of NH₄⁺-N loading, autotrophicnitrification bacteria had not been enrichment definitely in Our aerobic granular sludge. Thecultivated granular sludge of this pilot was still aerobic granular sludge, whose major bacteriawere heterotrophic bacteria, and heterotrophic nitrification bacteria played a major role innitrification process. In addition, it is to be further studied as how to achieve nitrification processin which autotrophic bacteria plays a major role through the aerobic granules which are cultivatedunder the conditions of using organic carbon as the main carbon source.