• Journal of Korean Society on Water Environment
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• v.21 no.2
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• pp.125-131
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• 2005

Natural organic matter(NOM) is defined as the complex matrix of organic material and abundant in natural waters. It affects the performance of unit operations for water purification. Several kinds of analytical indicators such as DOC, specific ultraviolet absorbance(SUVA), apparent molecular weight (AMW), fractionation and high performance size exclusive chromatography(HPSEC) have been used to understand characteristics and variations of NOM. This study aims to evaluate the characteristics of NOM in the Geum River system comprising with stream flows and reservoirs. It was identified that SUVA denoting the portion of humic substance in water ranged within 1.60~3.36. Using resin adsorbents, dissolved organic carbon(DOC) was fractionated into three classes: hydrophobic bases(HOB), hydrophobic acids(HOA) and hydrophilic substances(HI). HI dominates in all samples, collectively accounting for more than 62% of the DOC. HOA was the second dominated fraction and it varied considerably but accounted for about 30% of the DOC. The distribution of high molecular weight(HMW) measured by HPSEC being used to determine the molecular weight distribution of aquatic humic substances was 40.1% and 38.7% in reservoir and stream flow, respectively. The distribution of low molecular weight(LMW) in stream flow was 13.2% higher than that in reservoir. And apparent molecular weight less than 1KDa, which include the molecular weight of hydrophilic organic matter, occupied with 69.2% and 68.2% in stream flow and reservoir, respectively. While the molecular weight of 1 to 100 KDa including humic substances ranged with 18.6% and 21.6% in stream flow and reservoir, respectively. Seasonal variation of refractory dissolved organic carbon was similar to that of SUVA.

• Journal of Environmental Health Sciences
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• v.27 no.2
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• pp.92-99
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• 2001

This present study was aimed to investigate the characteristics of dissoloved organic matter (DOC) in sewage. The results are summarized as follows ; The plateaux reached in 3~4 days by the biodegradability test on sewage samples based on DOC. 쏭 rations of BDOC to DOC were 48, 21, 13 and 11% for raw sewage, primary treatment effluent, secondary treatment effluent and final treatment effluent, respectively. As the SUVA values ranged less 3L/m.mg for the effluent of sewage treatment plant, the DOC is composed largely of non-humic materials, hydrophilic, less aromatic as compared to waters with higher SUVA values. Through the biodegradability test, Dissolved organics showed that the quantity of LMW(Low Molecular Weight) less than 1,000 daltons was decreased, HMW(High Molecular Weight) more than 30,000 daltons had a tendency to increase. Large portion of UV$^{254}$ in final treatment effluent was increased of MMW(Medium Molecular Weight). Also, average removal efficiency of DOC was 32% during sewage treatment.

• Journal of the Korean Wood Science and Technology
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• v.45 no.4
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• pp.471-481
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• 2017

As the molecular weight (MW) of urea-formaldehyde (UF) resins had a great impact on their properties, this work was conducted to study effect of analytical parameters of gel permeation chromatography (GPC) on the MW measurement of UF resins. GPC parameters such as flow rate, column, detector temperature, and sample injection temperature were selected to compare number-average molecular weight (Mn), weight-average molecular weight (Mw), molecular weight distribution (MWD) and polydispersity index (PDI) of two UF resins with different viscosities. As expected, UF resin with higher viscosity resulted in greater Mn and Mw than those of low viscosity UF resin. When the flow rate increased, both Mn and Mw of UF resins decreased and MWD became narrower. By contrast, both Mn and Mw increased and MWD became wide when the column, detector, and sample injection temperature increased. The column, detector, and sample injection temperature of $50^{\circ}C$ at a flow rate of $0.5m{\ell}/min$ resulted in the highest MW and broadest MWD for the GPC analysis. These results suggest that the apparent molecular size or a hydrodynamic radius of UF resin molecules dissolved in the mobile phase affect to Mn, Mw and MWD.

• Journal of Environmental Health Sciences
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• v.27 no.2
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• pp.60-66
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• 2001

Natural organic matters(NOMs) are found everywhere such as soil, surface and ground waters and consist of both humic and nonhumic components, and their heterogeneith makes each source unique. This study was carried to evaluate the removal characteristics of NOMs by mixing coagulants and the variation of apparent molecular weight distribution(AMWD) in coagulation process. Ratio of optimum coagulants dosage for removal of DOC and turbidity by mixing coagulants was 1.83 mM F $e^{3+}$/mM $Al^{3+}$. DOC removal increased at lower pH. The pH6 control focused on the removal of organic matters could reduce the amount of coagulant consumption by 2 to 3 times based on the pH8.5 of natural water. The dissolved organic matters in the natural water from the mid-stream of Han River were composed of the low molecular weight(LMW,<1 K) of 59.7%, and the medium and high molecular weight(M.HMW, 1~30 K) of 40.3%, respectively. At pH6, the DOC removal efficiencies of LMW(<1 K) and M.HMW(1~30 K) in coagulation process were 27~35%, 62~72%, respectively. The fraction smaller than 1 K was not eliminated to a noticeable degree, while the fraction of 1~30 K was relatively well removed. In conclustion, mixing coagulants were fairly effective in the removal of natural organic matter.r.

• Proceedings of the Korean Environmental Health Society Conference
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• 2001.04a
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• pp.65-66
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• 2001

• Journal of Applied Biological Chemistry
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• v.43 no.1
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• pp.31-36
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• 2000

Apparent MWDs of DOM in natural waters and swine wastewaters were determined through membrane ultrafiltration. The nominal MWCOs of ultrafiltration membranes by the manufacturer were confirmed to be similar with those obtained from the ultrafiltration procedures employed in this study using six MW standard compounds. Natural waters showed a wide range of MWOs, but 62.4~87.5% were in the range of MW<10K. High MW fractions were preferentially removed through water treatment processes. Swine wastewater showed two major ranges of MWDs, 49.0% in <1K and 36% in >50k while anaerobically treated swine wastewaters showed 17.5~18.0% in <1K and 53.0~58.8% in <50K. The overall DOM was reduced during anaerobic treatment by 76.8~80.0% as COD; however. the percentage of low MW fractions decreased and that of the high MW fractions increased.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.1
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• pp.125-133
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• 1999

The objective of present work is to evaluate the optimum coagulation conditions in order to decrease dissolved organic carbon(DOC) and turbidity at different polyaluminum chloride dosage and pH from Nakdong River water. This studies were carried out to examine distribution on apparent molecular weight(AMW) of DOC in the Nakdong River water and its coagulation-sedimentation water. On the basis of jar tests, at the optimum coagulation pH in order to decrease DOC and turbidity were pH 5.0~6.0 and optimum dosage of polyaluminum chloride were 10~15mg $Al_2O_3/L$. The removal percentage of DOC and UV-254 absorbance were 35~40%, 45~60%, respectively. In pilot plant, at the optimum coagulation pH in order to decrease DOC and turbidity were 5.0-6.5, and the removal percentage of DOC were 30~45%. Distributions of AMW in the Nakdong River, less than 6,800dalton were 60.7% 6,800~11,000dalton were 32.8%, more than 11,000dalton were 6.4%. When the polyaluminum chloride dosage was 12~20mg/L, the removal percentages of each AMW for AMW of Nakdong River water, less than 6,800dalton were 25~28%, 6,800~11,000dalton were 65~68% more than 11,000dalton were 10~60%.

• Journal of Environmental Health Sciences
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• v.33 no.2 s.95
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• pp.158-165
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• 2007

본 연구는 근원에 따른 용존 유기물의 특성을 평가하기 위해 하천수, 호소수, 하수 2차 처리 유출수의 자연수 및 Aldrich, Wako 사에서 공급된 휴믹산을 대상으로 분자량 분포에 따른 물리 화학적인 수질 특성, 생분해도, 소독, 부산물의 생성 등을 고찰하였다. SUVA를 이용해서 자연수의 생분해 가능성을 평가한 결과 호소수, 하수, 하천수 순으로 예측되었으며 이는, 실제 생분해도 실험 결과와 유사하였다 생분해 반응 중 저분자 영역대의 용존 유기물은 점차 감소하였고 반면에 고분자 영역대의 용존 유기물은 증가하였다. SMP는 전체 용존 유기물의 0.7-5.5%정도 관찰되었으며 고분자 물질을 많이 함유한 시료에서 높게 나타났다. THM 생성은 대체로 고분자 물질이 높을수록 증가하였으며 THMFP도 Wako 휴믹산을 제외한 샘플에서 이와 유사한 경향을 나타냈다.

• BMB Reports
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• v.34 no.4
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• pp.310-315
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• 2001

The uneven distribution of acidic and basic chitinases in different parts of rice seed, and also the characterization of hull-specific chitinases, are reported here. After extraction of chitinases from polished rice, bran, and rice hulls, the chitinases were separated into acidic and basic fractions, according to their behavior on an anion exchanger column. Both fractions from different parts of rice seed showed characteristic activity bands on SDS-PAGE that contained 0.01% glycol chitin. The basic chitinases from rice hulls were further purified using chitin affinity chromatography. The chitinase, specific to rice hulls (RHBC), was 88-fold purified with a 1.3% yield. RHBC has an apparent molecular weight of 22.2 kDa on SDS-PAGE. The optimal pH and temperature were 4.0 and $35^{\circ}C$, respectively. With [$^3H$]chitin as a substrate, RHBC has $V_{max}$ of 13.51 mg/mg protein/hr and $K_m$ of 1.36 mg/ml. This enzyme was an endochitinase devoid of ${\beta}$-1,3-glucanase, lysozyme, and chitosanase activities.

• Microbiology and Biotechnology Letters
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• v.20 no.3
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• pp.316-323
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• 1992

Studies on the changes in rheological properties, molecular weight distribution and dextran yield after being reacted in lO%(w/w) sucrose concentration were performed with crude dextransucrase produced from Leuconostoc mesenteroides isolated from Sikhae. The reaction rate of dextran formation was monitored by sugar analysis with HPLC and by the changes in apparent viscosity. According to the periodate oxidation test, the dextran produced in this experiment was estimated to have 89% $\alpha$-(1->6) main linkages and 11% $\alpha$-(1->) side linkages. The rheological properties of the dextran solution formed changed with reaction time, and it was related to the changes in molecular weight distribution of dextran as determined by GPC analysis. As the reaction proceeded, the rheological behavior changed from Newtonian to non-Newtonian, showing Binghampseudoplastic and thixothropic flow behavior. The apparent viscosity of dextran formed solution increased with increasing reaction time, reached a maximum value of 2680 cP ($\gamma$=$33.75s^{-1}$, $25^{\circ}C$) by enzyme reaction for 8 hours, and then decreased. The temperature dependency of dextran formed solutions was well expressed by the Arrhenius equation and the activation energy reached a maximum value of 1.69 kcal/mole by enzyme reaction for 8 hours.