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RISS 인기검색어
- 검색키워드
- 저자 : Seockheon Lee (검색결과 42 건)
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The Rejection of Turbidity, Dissolved Matter and Bacteria by MF Process
Lee,Seockheon 이화여자대학교 환경문제연구소 1998 이화환경연구 Vol.2 No.-
The rejection of raw turbidity, dissolved matter and bacteria by MF(microfiltration) process, was investigated. Pilot-scale MF system was constructed and a river water pumped into the system as a raw water without any pre-treatment. A hydrophilic hollow-fiber membrance made of polyethylene was used. The surface area of membrane module was 10㎡ and the flux of filtrate was 0.5㎥/㎡day. The Trans-Membrane Pressure(TMP) had increased to 1.5kg/㎠ after 100 days operation. The turbidity of raw water was rejected effectively (>94%, rejection). Absorbance at 260 and 390 nm was measured to investigate the rejection of dissolved color-inducing matter. The rejection was at most 50% and 60%, respectively. The concentration of HPC (heterotrophic plate count) and coliform group in raw water, filtrate and ()rain were analysed to determine the rejection of bacteria. At the beginning of experiment, the HPC of filtrate was much lower than that of raw water. However, during some periods of experiment the HPC of filtrate was much higher than that of raw water, even though coliform group was not detected in the filtrate through the experiment. This results suggested that there was an apparent bacterial growth on the membrance module and consequent come-offs of the bacterial growth into the filtrate. So, the disinfection step should follow the MF process to assure the safety of filtered water.
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Molecular layer-by-layer assembled forward osmosis membranes
Kwon, Soon-Bum,Lee, Jong Suk,Kwon, Soon Jin,Yun, Seong-Taek,Lee, Seockheon,Lee, Jung-Hyun Elsevier 2015 Journal of membrane science Vol.488 No.-
<P><B>Abstract</B></P> <P>A recently devised, molecular layer-by-layer (mLbL) approach based on the alternative cross-linking of monomers was employed to fabricate high-performance thin film composite (TFC) forward osmosis (FO) membranes with excellent rejection toward monovalent NaCl salt. An ultrathin and highly dense polyamide (PA) selective layer with a precisely controlled structure was created on a tailored porous support via mLbL. The intrinsic separation properties of the mLbL-assembled TFC membranes were tuned by adjusting the mLbL cycle number to optimize the FO performance. The best FO performance was achieved at 10 mLbL cycles (mLbL-10), where the permeability and selectivity were properly balanced. Importantly, the mLbL-10 membrane exhibited superior FO performance compared to the commercial HTI FO membranes as well as hand-cast TFC membranes prepared by the conventional interfacial polymerization: the mLbL-10 membrane showed ~3.5 times higher water flux, ~60% lower reverse salt flux and ~85% lower specific salt flux compared to the cellulose triacetate HTI membrane, with 0.5M NaCl draw solution and DI water feed solution in FO mode. The stability and the associated membrane performance of the mLbL-assembled membrane depending on the ionic strength of the environment were explained by the swelling behavior of the polyelectrolyte-assembled interlayer adhered underneath the PA selective layer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PA TFC FO membrane is fabricated via a molecular layer-by-layer (mLbL). </LI> <LI> Separation properties are tuned by adjusting the mLbL cycle number. </LI> <LI> The mLbL achieves higher membrane permselectivity than interfacial polymerization. </LI> <LI> The mLbL-assembled membrane shows FO performance exceeding the commercial one. </LI> <LI> The mLbL-assembled membrane׳ stability at high ionic strengths should be improved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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오정익,이석헌,이보영 대한상하수도학회 2004 상하수도학회지 Vol.18 No.2
Behavior of hazardous organic compounds including bisphenol A, phtalic acid, and phosphoric acid in low pressure nanofltration process were investigated. In the case of NTR729HF, rejection of all target organic compounds except 2-H-Benzothiazol and 2-isopropyl phenol was more than 90%. The lowest rejection for 2-H-Benzothiazol was observed in another membranes. The UTC60 and UTC20 showed similar rejection characteristics of hazardous organic compounds. Although the rejection of Bisphenol A, n-buthyl benzenesulfoneamide, N-ethyl-p-toluensulfonamide, 2-H-benzothiazol, p-t-butylphenol and 2-isopropyl phenol was less than 30%, the rejection of tribuiyl phosphate, triethyl phosphate, camphor, 2,2,4 trimethyl 1,3 pentandiol and diphenyl amine was more than 90% in the case of UTC60 and UTC20. The rejection characteristics of various hazardous organic compounds were converted into one parameter Ks, which was proposed in the diffusion-convection model. The Ks of hazardous organic compounds were discussed by comparing with their solute size represented by Stokes radius. The diffusion convection model considering Ks was successful to interpret rejection characteristics of hazardous organic compounds by low-pressure nanofiltration membranes.
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INACTIVATION OF PHAGE QβBY 254 nm UV LIGHT AND TITANIUM DIOXIDE PHOTOCATALYST
Nakamura,Miyako,Lee,Seockheon,Ohgaki,Shinichiro 이화여자대학교 환경문제연구소 1998 이화환경연구 Vol.2 No.-
The disinfection efficacy of UV light irradiation at wavelength of 254 nm over a titanium dioxide(TiO₂) suspension was compared to that of UV alone. Bacteriophage QB was used as a model virus for the study. QB in sterilized pure water and TiO₂ suspension was irradiated by a 0.4m/㎠ intensity of 254nm UV light. The UV light over TiO₂was more effective than 254nm UV alone in inactivating QB. 3.5-log()QB inactivation was achieved by UV irradiation over TiO₂ suspension (10³mg/L) after 2 minutes of irradiation, While UV alone inactivated 2-log(). Using a MPN-PCR method, a ca 1-log()-unit decrease in QB RNA concentration was detected after 3 minutes of photocatalytic irradiation. The decrease was explained by damage to nucleic acid of phage QB due to radical oxidation, which is generated by photocatalysis.
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Intermittent chlorination shifts the marine biofilm population on reverse osmosis membranes
Jeong, Dawoon,Lee, Chang-Ha,Lee, Seockheon,Bae, Hyokwan Techno-Press 2019 Membrane Water Treatment Vol.10 No.6
The influence of chlorine on marine bacterial communities was examined in this study. A non-chlorine-adapted marine bacterial community (NCAM) and a chlorine-adapted bacterial community (CAM, bacterial community treated with <TEX>$0.2mg-Cl_2/L$</TEX> chlorine) were cultivated for 1 month. A distinct difference was observed between the NCAM and CAM, which shared only eight operational taxonomic units (OTUs), corresponding to 13.1% of the total number of identified OTUs. This result suggested that chlorine was responsible for the changes in the marine bacterial communities. Kordiimonas aquimaris was found to be a chlorine-resistant marine bacterium. The effect of intermittent chlorination on the two marine biofilm communities formed on the reverse osmosis (RO) membrane surface was investigated using various chlorine concentrations (0, 0.2, 0.4, 0.6 and 0.8 mg <TEX>$Cl_2/L$</TEX>). Although the average number of adherent marine bacteria on the RO membrane over a period of 7 weeks decreased with increasing chlorine concentration, disinfection efficiencies showed substantial fluctuations throughout the experiment. This is due to chlorine depletion that occurs during intermittent chlorination. These results suggest that intermittent chlorination is not an effective disinfection strategy to control biofilm formation.
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Jeong, Dawoon,Cho, Kyungjin,Lee, Chang-Ha,Lee, Seockheon,Bae, Hyokwan Elsevier 2018 PROCESS BIOCHEMISTRY Vol.73 No.-
<P><B>Abstract</B></P> <P>The objective of this study was to evaluate the effects of salt accumulation on nitrifying bacterial communities in a nitrifying bioreactor combined with forward osmosis. The conversion of nitrite to nitrate was inhibited at a total dissolved solids (TDS) concentration of 17.3 g/L, whereas conversion of ammonia to nitrite was inhibited at a higher concentration (52.8 g-TDS/L). The gene copies of ammonia-oxidizing bacteria (AOB) were more abundant than those of nitrite-oxidizing bacteria (NOB) throughout the entire operating period of 225 days. Among NOB, the number of copies of <I>Nitrobacter</I> spp. were 100–1000 times higher than those of <I>Nitrospira</I> spp. A total of 140 operational taxonomic units were identified using 454 pyrosequencing. The relative abundances of autotrophic AOB and NOB accounted for 34.1–57.8% during 225 days. Dominance of <I>Nitrosomonas eutropha</I> was stable as a salt-tolerant AOB, but the representative NOB, <I>Nitrobacter winogradskyi</I>, showed salt-sensitive variations in their relative abundance. Nonmetric multidimensional scaling and hierarchical clustering analysis clearly illustrated the shift in bacterial community due to external conditions, i.e., ammonia loading rate, alkalinity availability, and salinity. Heterotrophic bacteria contributed to changes in overall bacterial community structure in the nitrifying osmotic membrane bioreactor despite the absence of carbon sources in the influent.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bacterial population dynamics were studied in an osmotic membrane bioreactor. </LI> <LI> Ammonia, alkalinity, and salinity caused changes in the bacterial community. </LI> <LI> Increased salinity led to NOB activity inhibition at 17.3 g-TDS/L. </LI> <LI> AOB were more tolerant than NOB to the high ammonia-loading rate and salinity. </LI> <LI> <I>Nitrosomonas eutropha</I> was dominant at high ammonia and salt concentrations. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Cho, Kyungjin,Choi, Minkyu,Lee, Seockheon,Bae, Hyokwan Elsevier 2018 CHEMOSPHERE - Vol.208 No.-
<P><B>Abstract</B></P> <P>This study investigated the effect of seeding source on the mature anaerobic ammonia oxidation (ANAMMOX) bacterial community niche in continuous poly(vinyl alcohol) (PVA) gel systems operated under high nitrogen loading rate (NLR) condition. Four identical column reactors packed with PVA gels were operated for 182 d using different seeding sources which had distinct community structures. The ANAMMOX reaction was achieved in all the bioreactors with comparable total and ANAMMOX bacterial 16S rRNA gene quantities. The bacterial community structure of the bioreactors became similar during operation; some major bacteria were commonly found. Interestingly, one ANAMMOX species, “<I>Candidatus</I> Brocadia sinica”, was conclusively predominant in all the bioreactors, even though different seeding sludges were used as inoculum source, possibly due to the unique physiological characteristics of “<I>Ca</I>. Brocadia sinica” and the operating conditions (i.e., PVA gel-based continuous system and 1.0 kg-N/(m<SUP>3</SUP> <B>·</B>d) of NLR). The results clearly suggest that high NLR condition is a more significant factor determining the final ANAMMOX community niche than is the type of seeding source.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Four up-flow bioreactors inoculated with different seeding sludges were compared. </LI> <LI> High NRR was established in the bioreactors with comparable ANAMMOX gene quantity. </LI> <LI> The bacterial community structures of the reactors became similar during operation. </LI> <LI> “<I>Candidatus</I> Brocadia sinica” became absolutely predominant in the bioreactors. </LI> <LI> Seeding source effect on final ANAMMOX community was negligible. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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