• 한국물환경학회지
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• 제36권3호
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• pp.185-193
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• 2020

Bimodal flocculation describes the aggregation and breakage processes of the flocculi (or primary particles) and the flocs in the water environment. Bimodal flocculation causes bimodal size distribution with the two separate peaks of the flocculi and the flocs. Extracellular polymeric substances and ionic species common in the water environment increase the occurrence of bimodal flocculation and flocculi-floc size distribution, under the flocculation mechanisms of electrostatic attraction and polymeric bridging. This study investigated bimodal flocculation and flocculi-floc size distribution, with respect to the extracellular polymeric substance concentration and ionic strength in the kaolinite-containing suspension. The batch flocculation tests comprising 0.12 g/L of kaolinite showed that the highest flocculation potential occurred at the lowest xanthan gum (as extracellular polymeric substances) concentration, under all the ionic strengths of 0.001, 0.01, and 0.1 M NaCl. Also, it was important to note that the higher ionic strength resulted in the higher flocculation potential, at all the xanthan gum concentrations. The bimodal flocculation and flocculi-floc size distribution became apparent in the experimental conditions, which had low and intermediate flocculation potential. Besides the polymeric bridging flocculation, steric stabilization increased the flocculi mass fraction against the floc mass fraction, thereby developing the bimodal size distribution.

• KSBB Journal
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• 제14권1호
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• pp.66-70
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• 1999

A pullulans와 S Cerevisiae의 납 제거 특성을 비교하고, 미생물이 분비하는 세포외고분자물질의 영향에 대해 고찰하였다. A pullulans의 경우에 미생물의 보관시간이 증가할수록 미생물이 분비하는 세포외고분자물질의 양도 증가하였으며, 납 제거능도 우수해졌다. 그러나 세포외고분자물질을 제거한 A pullulans세포에서는 납 흡착량이 약 10%로 매우 적었다. S Cerevisiae의 경우에는 세포외고분자물질은 거의 분비되지 않았으며, 보관시간에 따른 납 흡착량의 변화는 거의 없었다. 또한 보관시간이 경과할수록 흡착 평형에 도달하는 시간은 점점 짧아졌다. 따라서 A pullulans와 S Cerevisiae의 납제거 기작은 세포외고분자물질의 유무에 따라 매우 달라짐을 알 수 있었다.

• Membrane and Water Treatment
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• 제9권3호
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• pp.147-153
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• 2018

This study investigates the role of microbial extracellular polymeric substances (EPSs) as bioflocculants to harvest microalgae (water-microalgae separation). The EPS extracted from waste activated sludge (WAS) by heat extraction were fractionated into soluble EPS (S-EPS), loosely-bound EPS (LB-EPS) and tightly-bound EPS (TB-EPS) forms. All the EPSs facilitated the flocculation of microalgal cells from stable growth medium. Of those EPSs, the TB-EPS showed the highest flocculating activity (FA) resulting in the substantial decrease in the amount of EPS added in terms of total organic carbon (TOC) during flocculation. The FA of microalgae was improved with the increase in TB-EPS dose, however, excessive dose of TB-EPS adversely affected it due to destabilization. Both LB- and TB-EPS could be utilized for flocculating microalgae as a sustainable option to the existing chemical-based flocculants. In addition to the conventional assessments, the effectiveness of the two bioflocculants for floc forming was also confirmed using a novel assessment of lens-free shadow imaging technique (LSIT), which was firstly applied for the rapid and quantitative assessment of microalgal flocculation.

• 식물병연구
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• 제24권3호
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• pp.242-247
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• 2018

Pseudomonas chlororaphis O6 induces systemic tolerance in plants against drought stress. A volatile, 2R, 3R-butanediol, produced by the bacterium causes partial stomatal closure, thus, limiting water loss from the plant. In this study, we report that applications of extracellular polymeric substances (EPS) from P. chlororaphis O6 to epidermal peels of leaves of Arabidopsis thaliana also reduce the size of stomatal openings. Growth of A. thaliana seedlings with applications of the EPS from P. chlororaphis O6 reduced the extent of wilting when water was withheld from the plants. Fluorescence measurements showed photosystem II was protected in the A. thaliana leaves in the water stressed EPS-exposed plants. These findings indicate that P. chlororaphis O6 has redundancy in traits associated with induction of mechanisms to limit water stress in plants.

• 유기물자원화
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• 제27권4호
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• pp.43-49
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• 2019

본 연구는 알칼리·초음파 전처리를 통한 하수슬러지의 가용화 정도를 확인하기 위해 슬러지 가용화율과 VSS 감량화율을 측정하였다. 또한 슬러지 가용화와 EPS간의 관계를 확인하기 위해 LB-EPS(Loosely-Bound EPS), TB-EPS(Tightly-Bound EPS)를 측정하였다. 실험 결과, TS 1.0%, pH 12 조건에서 슬러지 가용화율은 27.7% 증가하였고, LB-EPS as Carbohydrate와 Protein은 각각 14.6, 13.3 mg/L/g TS가 증가하여 가용화에 따른 유기물의 변화와 유사한 경향을 나타내었다. 또한 VSS는 26.7% 감량되었고, TB-EPS as Carbohydrate와 Protein은 각각 15.7, 21.9 mg/L/g TS 용출되어 가용화에 따른 고형물의 변화 역시 유사한 경향을 나타내었다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 추계학술발표대회 및 bio-venture fair
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• pp.135-136
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• 2000

A bacterial strain producing a large amount of EPS was isolated from marine sediment sample collected from the Cheju Island, Republic of Korea. In the present study, the isolation and identification of this isolate, which is named Hahella chejuensis gen. nov., sp. nov., the effects of nutrients on the production of EPS, and some properties of this EPS are reported.

• 상하수도학회지
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• 제18권5호
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• pp.619-627
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• 2004

Purposes of this study were to examine closely the extracellular polymeric substances (EPS) which was a membrane fouling contaminant, to control detected EPS by powdered activated carbon (PAC) dosage etc. and to evaluate the possibility of practical reuse facility. With high removal efficiency of general pollutants, when the PAC is added to MBR, improvement of removal efficiency of $COD_{cr}$, and color was expected and treated wastewater can be reused. It was judged that the correlation between EPS and membrane fouling was very high. Carbohydrate and DNA in the EPS were judged to be cause of membrane fouling. If EPS could be controled, not only membrane fouling would be decreased but also operation time would be extended. In experiment of powdered activated carbon (PAC), characteristics of the best PAC for membrane fouling control were the particle size of $7{\mu}m$, lodine Number of 1,050, surface area of peat of $1,150m^2/g$. In lab test, operation time of MBR by PAC dosage of 200mg/gVSS was longer than one of MBR by without PAC dosage. Because EPS, especially carbohydrate and DNA, was controled successfully by PAC, membrane fouling in MBR could be decreased.

• Membrane and Water Treatment
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• 제5권1호
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• pp.1-14
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• 2014

A pilot-scale hybrid membrane bioreactor (HMBR) for real municipal wastewater treatment was developed by adding biofilm carriers into a conventional membrane bioreactor, distribution and dynamic changes of the extracellular polymeric substances (EPS) and their roles in membrane fouling were investigated. The results showed that the concentrations of loosely bond EPS (LB-EPS) and tightly bond EPS (TB-EPS) in activated sludge, carrier biofilm and sludge cake layer have been increased significantly with the running time of HMBR, during operation of the HMBR, EPS demonstrated positive correlations with membrane fouling. Compared to TB-EPS, LB-EPS showed more significant correlations with sludge physical properties and specific resistance to filtration (SRF) in HMBR, and thus demonstrated that LP-EPS have a stronger potential of fouling than TB-EPS. It was also found that a lower organic loading in HMBR could result a significant increase in EPS concentration, which would in turn influence membrane fouling in HMBR. This critical investigation would contribute towards a better understanding of the behavior, composition and fouling potential of EPS in HMBR operation.

• Membrane and Water Treatment
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• 제8권6호
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• pp.543-551
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• 2017

Membrane fouling in membrane bioreactor (MBR) remains a primary challenge for its wider application. The focus of this study to investigate the influence of iron distribution in activated sludge on gel layer fouling in MBR. Significant reduction in the transmembrane pressure (TMP) rise rates was observed in the presence of iron as result of retarding the gel layer formation time. The spatial distribution of iron had a significant impact on the stratification structure of extracellular polymeric substances (EPS) fractions, such as proteins (PN) and polysaccharides (PS). A mitigation of PN or PS from the supernatant to the EPS inner layers was observed in the presence of iron. Compared with the control reactor, the reduction in PN and PS of the supernatant and lower PN/PS rates of the LB-EPS were beneficial to decrease the membrane fouling potential during the gel layer formation. Consequently, the iron addition managed to control gel layer fouling could be a useful strategy in MBR.

• Journal of Microbiology and Biotechnology
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• 제15권3호
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• pp.455-460
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• 2005

A pilot-scale sulfur particle autotrophic denitrification (SPAD) process for the treatment of municipal wastewater was operated for 10 months at Shihwa, Korea, and higher than $90\%\;NO^{-}_{3}-N$ removal efficiency was observed. Plate counting showed that the lower part of the denitrifying column reactor had the most autotrophic denitrifiers. The biofilm thickness formed on sulfur particles from the SPAD reactor was approximately $25-30\;{\mu}m$, measured by DAPI (4,6-diamidino-2-phenylindole) staining. The presence of bacteria inside the highly porous sulfur particle was also monitored by SEM observation of the internal surfaces of broken sulfur particles. Biofilm extracellular polymeric substances (EPS) analysis showed that the ratio of carbohydrate to protein decreased with the reactor heights at which biofilm-formed sulfur particles were obtained.