• Environmental Engineering Research
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• 제15권1호
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• pp.3-7
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• 2010

To better understand the ecology of tetrade forming organisms (TFOs) floating in a large amount of dairy wastewater treatment plant (WWTP) effluent (sequencing batch reactor [SBR]) during the inefficient phosphorus (P) removal process of an enhanced biological P removal system, the TFOs from the effluent of a full scale WWTP were separated and attempts made to culture the TFOs in presence/absence of oxygen. The intact TFOs only grew aerobically in the form of unicellular short-rods. Furthermore, to identify the intact TFOs and unicellular short-rods the DNAs of both were extracted, analyzed using their denaturing gradient gel electrophoresis (DGGE)-profiles and then sequenced. The TFOs and unicellular short-rods exhibited the same banding pattern in their DGGE-profiles, and those sequencing data resulted in their identification as Acinetobacter sp. The intact TFOs appeared in clumps and packages of tetrade cells, and were identified as Acinetobacter sp., which are known as strict aerobes and efficient P-removers. The thick layer of extracellular polymeric substance surrounding Acinetobacter sp. may inhibit phosphate uptake, and the cell morphology of TFOs might subsequently be connected with their survival strategy under the anaerobic regime of the SBR system.

• 한국물환경학회지
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• 제29권4호
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• pp.459-465
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• 2013

A sequencing batch reactor was operated under different pH conditions to see the influence of pH to microbial community in enhanced biological phosphorus removal (EBPR) systems. Long term influences of different steady-state pH conditions on the microbial community composition were evaluated by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) and fluorescence in situ hybridization (FISH). The shift in populations from polyphosphate-accumulating organisms (PAOs) to Alphaproteobacteria was observed when pH was changed from 7.5 to 7.0. Alphaproteobacteria with the typical morphological traits of tetrad-forming organisms (TFOs) eventually became dominant members. The alphaproteobacterial TFOs were the phenotype expected for glycogen-accumulating organisms (GAOs), which accumulate large amount of glycogen into the cell. The results strongly suggested that low operational pH condition encourages the appearance of the GAOs in EBPR process, significantly reducing the EBPR capacity.

• 한국물환경학회지
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• 제27권6호
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• pp.754-759
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• 2011

A sequencing batch reactor (SBR) was operated under different pH conditions to better understand the influence of pH to granulation in enhanced biological phosphorus removal systems. Granules from the SBR were also investigated using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Considerable decreases in the amount of phosphorus released per substrate provided under anaerobic conditions and the content of biomass polyphosphate under aerobic conditions were observed when pH was changed from 7.5 to 7.0, followed by 6.5. Aerobic granulation was also observed at pH 7.0. A number of bacteria with the typical morphological traits of tetrad-forming organisms (TFOs) were observed at pH 7.0, including large members of cluster. Filamentous bacteria were also there in large numbers. The occurrence and growth of granules were further enhanced at pH 6.5. A SEM analysis showed that the aerobic granules had a compact microbial structure with shaperical shape and morphologically consisted of aggregates of small coccoid bacteria and filamentous bacteria encapsulated by extracellular polymeric substance. The main material ions identified by EDX moreover revealed that the structural materials for polyphosphate in the granules include phosphorus, potassium and calcium. Therefore, these results strongly suggested that PAOs are a dominant population in the microbial community of the aerobic granules.

• 한국전기전자재료학회논문지
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• 제19권4호
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• pp.334-338
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• 2006

Poly silicon TFT requires high quality dielectric film; conventional method of growing silicon dioxide needs highly hazardous chemicals such as silane. We have grown high quality dielectric film of silicon dioxide using non-hazardous chemical such as TFOS and ozone as reaction gases by APCVD. The films grown were characterized through C-V curves of MOS structures. Conventional APCVD requires high temperature processing where as in the process of current study, we developed a low temperature process. Interface trap density was substantially decreased in the silicon surface coated with the silicon dioxide film after annealing in nitrogen ambient. The interface with such low trap density could be used for poly silicon TFT fabrication with cheaper cost and potentially less hazards.

• 대한환경공학회지
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• 제28권2호
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• pp.165-172
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• 2006

생물학적 인 제거공정에서 인 제거 효율에 따른 인제거관련 미생물을 포함하는 슬러지 미생물상의 변화를 분석하기 위하여 2개의 반응조(SBR)에 각기 다른 탄소원(초산나트륨, 포도당)을 주입하여 작동시켰다. 초산나트륨을 주입한 SBR1에서는 반응 100일 후, 유출수에서 $PO_4-P$가 3.92 mg/L 검출되었고(제거효율 60.8%) 이때의 미생물상은 ${\beta}$-subclass proteobacteria(39.67%)와 인제거미생물인 PAO(45.10%)가 우점하는 양상을 보인 반면, 포도당을 주입한 SBR 2에서는 $PO_4-P$가 8.3 mg/L 검출되었으며(제거효율 17%), ${\gamma}$-subclass proteobacteria(23.89%)가 우점하였고 PAO는 21.42%를 차지할 뿐이었다. DGGE결과에서도 ${\beta}$-subclass proteobacteria가 SBR1에서 우점하였다. 그러나 수온이 증가할수록 ${\beta}$-subclass proteobacteria and PAOs의 비율이 감소하였고 GAOs는 증가하였다. 그러므로 생물학적인 인제거공정에서 수온과 영양원의 상태 등 환경인자들이 인제거 미생물과 인제거를 저해하는 미생물의 우점도에 영향을 미친다고 할 수 있다.