Nakdong River Water Research Articles

Potential Self-Attenuation of Arsenic by Indigenous Microorganisms in the Nakdong River.

The toxic element arsenic (As) has become the major focus of global research owing to its harmful effects on human health, resulting in the establishment of several guidelines to prevent As contamination. The widespread industrial use of As has led to its accumulation in the environment, increasing the necessity to develop effective remediation technologies. Among various treatments, such as chemical, physical, and biological treatments, used to remediate As-contaminated environments, biological methods are the most economical and eco-friendly. Microbial oxidation of arsenite (As(III)) to arsenate (As(V)) is a primary detoxification strategy for As remediation as it reduces As toxicity and alters its mobility in the environment. Here, we evaluated the self-detoxification potential of microcosms isolated from Nakdong River water by investigating the autotrophic and heterotrophic oxidation of As(III) to As(V). Experimental data revealed that As(III) was oxidized to As(V) during the autotrophic and heterotrophic growth of river water microcosms. However, the rate of oxidation was significantly higher under heterotrophic conditions because of the higher cell growth and density in an organic-matter-rich environment compared to that under autotrophic conditions without the addition of external organic matter. At an As(III) concentration > 5 mM, autotrophic As(III) oxidation remained incomplete, even after an extended incubation time. This inhibition can be attributed to the toxic effect of the high contaminant concentration on bacterial growth and the acidification of the growth medium with the oxidation of As(III) to As(V). Furthermore, we isolated representative pure cultures from both heterotrophic- and autotrophic-enriched cultures. The new isolates revealed new members of As(III)-oxidizing bacteria in the diversified bacterial community. This study highlights the natural process of As attenuation within river systems, showing that microcosms in river water can detoxify As under both organic-matter-rich and -deficient conditions. Additionally, we isolated the bacterial strains HTAs10 and ATAs5 from the microcosm which can be further investigated for potential use in As remediation systems. Our findings provide insights into the microbial ecology of As(III) oxidation in river ecosystems and provide a foundation for further investigations into the application of these bacteria for bioremediation.

The geochemistry and isotopic compositions of the Nakdong River, Korea: weathering and anthropogenic effects.

The Nakdong River is the longest river in South Korea, and flows through various geological terrains with different land use characteristics; therefore, the geochemistry of its water is expected to be influenced by many factors. In this work, the geochemical characteristics of the Nakdong River were examined, and its chemical compositions, δD, δ18O, and δ13CDIC values, and 87Sr/86Sr ratios were determined to investigate the geological and anthropogenic effects on the geochemistry of the Nakdong River water. The obtained concentrations of major ions were strongly affected by both the anthropogenic activity and weathering of the rocks. With increasing the flow distance, the ion concentrations slightly increased; and after the inflow of the Kumho River, which was the largest tributary running through Daegu (the fourth largest city in South Korea), the concentrations of Na and SO4 ions abruptly increased and decreased again, suggesting the existence of strong anthropogenic effects caused by sewage treatment plants and dyeing industrial complex. Other activities such as agricultural ones also increased the NO3 concentration. In July, the high precipitation level from tropical cyclones and downpours decreased the ion concentrations as well as the δD and δ18O values. The δ13CDIC magnitudes showed that the dissolved inorganic carbon mainly originated from mineral weathering upstream, while the oxidation of soil organic materials influenced by agricultural activity became more important downstream. The 87Sr/86Sr ratios revealed that in the upstream regions, the weathering of granite and gneiss complex was dominant, while in the downstream regions, the weathering of sedimentary rocks became more important. The weathering and anthropogenic effects on the river water chemistry were also demonstrated using statistical analysis, which revealed that the water geochemistry was mostly influenced by the anthropogenic sources, including industrial complex, represented by Na, Cl, and SO4. The obtained results show that, as compared to the geochemistry of the Han River (which is also a major river in Korea), the geochemistry of the Nakdong River is more influenced by anthropogenic activities (including agriculture and the industrial complex) due to the different land use.

Hydrogeological Characteristics of a Riverine Wetland in the Nakdong River Delta, Korea

Investigating the physical and chemical properties of riverine wetlands is necessary to understand their distribution characteristics and depositional environment. This study investigated the physical (particle size, color, and type) and chemical properties (organic, inorganic, and moisture contents) of sediments in Samrak wetland, located in the Nakdong River estuary area in Busan, South Korea. The particle size analysis indicated that the hydraulic conductivity values for the coarse grain and the mixture of coarse and fine grains ranged from 2.03 to 3.49×10−1 cm s−1 and 7.18×10−3 to 1.24×10−7 cm s−1 , respectively. In-situ water quality and laboratory-based chemical analyses and radon-222 measurement were performed on groundwater and surface water in the wetland and water from the nearby Nakdong River. The physical and chemical properties of Samrak wetland was characterized by the sediments in the vertical and lateral direction. The concentrations of chemical components in the wetland groundwater were distinctly higher than those in the Nakdong River water though the wetland groundwater and Nakdong River water equally belonged to the Ca-HCO3 type.

Influence of Abiotic Factors on the Growth of Cyanobacteria Isolated from Nakdong River, South Korea1.

Changes in physico-chemical factors due to natural climate variability and eutrophication could affect the cyanobacterial growth patterns in aquatic systems that may cause environmental health problems. Based on morphological and 16S rRNA gene analysis, three cyanobacterial species isolated for the first time from the Nakdong River water sample in South Korea were identified as Amazoninema brasiliense, Microcystis elabens, and Nododsilinea nodulosa. The variations in temperature, pH, nitrogen, or phosphorus levels significantly impacted the cyanobacterial growth patterns. The optimal temperature range for the growth of isolates was from 25-30°C. A neutral or weak alkaline environment favored growth; however, A. brasiliense resulted in 44.2-87.5% higher biomass (0.75g·L-1 as dry solids, DS) and growth rate (0.24·d-1 ) at pH 7 than the other isolates (0.4-0.52gDS·L-1 , 0.16-0.19·d-1 ). The increased nitrate-nitrogen (NO3 -N) concentrations significantly (P<0.05) favored biomass production and growth rate for A. brasiliense and M. elabens, respectively, andthe maximum growth rate was observed for A.brasiliense at 3.5mgNO3 -N·L-1 . The orthophosphate concentration (PO4 -P) from 0.1 to 0.5mgPO4 -P·L-1 increased the growth of the isolates. These observations suggest that isolate growth rates in water bodies can vary depending on different physico-chemical parameters. This study contributes to the further understanding of the growth of microalgae in natural freshwater bodies under fluctuating environmental conditions and aquatic ecosystem stability.

Characterization of Algal Organic Matter of Microcystis sp.: Disinfection By-Product (DBP) Formation Potential and Treatability

Objectives This study was evaluated the disinfection by-product formation potential (DBPFP) in the algal organic matter of Microcystis sp. (M-AOM), which lives in the downstream Maeri area of Nakdong River, and the removal efficiency by each drinking water treatment process. Methods M-AOM were prepared by ultrasound/extraction/filtration using Microcystis sp. from Maeri area in the downstream of Nakdong River. M-AOM and Nakdong river water sample (N-NOM) were compared to removal efficiency of dissolved organic matter (DOM) and DBPFP in the coagulation/settlement (Coag./Sedi.), biological activated carbon (BAC) and granular activated carbon (GAC) processes. The treatment efficiency characteristics of DOM were evaluated by LC-OCD and fluorescence spectrophotometer. DBPFP was analyzed for trihalomethane formation potential (THMFP), haloacetic acids FP (HAAFP), haloacetonitrile FP (HANFP) and chloral hydrate FP (CHFP), respectively. Jar-tester was used for the Coag./Sedi., the BAC and GAC process were conducted using a laboratory scale acrylic column with an empty bed contact time (EBCT) of 20 min. Results and Discussion The contents of humic substances (HS) was high at 50.9% in N-NOM, whereas it was content 26.0% of biopolymers (BP) and LMW-acid (LMW-A) was high at 30.6% in M-NOM. In case of DBPFP, THMFP accounted for 59.5% of the total in N-NOM but CHFP and HANFP accounted for 49.6% and 23.3%, respectively in M-AOM. Thus, There were many differences in the composition of DOM and DBPFP of N-NOM and M-AOM. Both N-NOM and M-AOM showed a high removal efficiency of high molecular weight (HMW) organic matters (BP and HS) during the Coag./Sedi. process, whereas low molecular weight (LMW) organic matters (BB and LMW-org) was high during the GAC and the BAC processes, and the removal efficiency was somewhat different. Residual BP after Coag./Sedi. process was more easily removed by the biodegradation in BAC process rather than GAC process. THMFP and HAAFP which originated from AOM, were able to eliminated about 90% by the Coag./Sedi. process, which was very similar to the removal rate of BP and HS among DOM constituents and they were judged to be involved in THM formation. However, the removal rate of HANFP and CHFP was low, and it could be suspected that HANFP and CHFP formation were occurred in LMW organic matters showing low removal rate by the Coag./Sedi. process. The removal rates of CHFP and HANFP relatively high in the BAC process and total DBPFP showed high removal efficiency in the GAC process. Conclusions N-NOM had high contents of HS (50.9%), but M-AOM had high contents of BP (26.0%) and LMW-A (30.6%). THMFP accounted for 59.5% in total DBPFP of the N-NOM and CHFP (49.6%) and HANFP (23.3%) occupied high rate in the DBPFP of M-AOM. N-NOM and M-AOM were high removal from HMW organic matters (BP, HS) showed high removal efficiency by the Coag./Sedi. process, LMW organic matters showed high removal efficiency in the GAC and BAC processes. Also, residual BP after Coag./Sedi. was easily removed by biodegradation in the BAC rather than adsorption in the GAC process. THM and HAA formed in M-AOM could be removed about 90% by Coag./Sedi. process, whereas it was difficult to remove HANFP and CHFP by Coag./Sedi. process. CHFP and HANFP had relatively high removal efficiency in the BAC process and DBPFP removal was excellent overall in the GAC process. Key words: Microcystis sp., Algal Organic Matter (AOM), Disinfection By-Product, Drinking Water Treatment Process, Treatability

Flavobacterium magnum sp. nov., Flavobacterium pallidum sp. nov., Flavobacterium crocinum sp. nov. and Flavobacterium album sp. nov.

Four new limnic bacterial strains, namely HYN0048T, HYN0049T, HYN0056T and HYN0059T, were isolated from two lakes in the Nakdong River water system in Korea. 16S rRNA gene sequence analyses indicated that strains HYN0048T, HYN0049T, HYN0056T and HYN0059T belonged to the genus Flavobacterium by showing the highest sequence similarities with the type strains of F. soli (94.9 %), F. keumense (95.1 %), F. dispersum (97.7 %) and F. hauense (97.6 %), respectively. The low sequence similarities and tree topologies implied the novelty of the four isolates, as novel genomic species of the genus Flavobacterium. Numerous physiological and biochemical features also supported the distinctiveness of the isolates from previously known bacterial species. On the basis of the phylogenetic and phenotypic data presented in this study, four novel species are suggested with the following names: Flavobacterium magnum sp. nov. (type strain HYN0048T=KACC 19180T=NBRC 112740T), Flavobacterium pallidum sp. nov. (HYN0049T=KACC 19181T=NBRC 112741T), Flavobacterium crocinum sp. nov. (HYN0056T=KACC 19182T=NBRC 112743T) and Flavobacterium album sp. nov. (HYN0059T=KACC 19183T=NBRC 112744T).

Removal of microcystin-LR using UV-assisted advanced oxidation processes and optimization of photo-Fenton-like process for treating Nak-Dong River water, South Korea

UV-assisted advanced oxidation processes (AOPs) are promising for the removal of microcystin-LR (MC-LR), one of cyanotoxins released during harmful algal blooms. Nevertheless, the efficiency and potential of the photo-Fenton-like process (UV-C/Fe(III)/H2O2) in treating MC-LR have not been explored in much detail. In this study, MC-LR degradation efficiencies of various UV-assisted AOPs were compared that they were higher in the order: UV-C/Fe(III)/H2O2 > UV-C/Fe(II)/H2O2 > UV-A/TiO2 > UV-C/H2O2 > UV-C > UV-A/Fe(II)/H2O2 > UV-A/H2O2 > UV-A. The concentrations of Fe(III) and H2O2 used in the photo-Fenton-like process were varied to evaluate their influences on MC-LR degradation in both deionized water and a water sample from Nak-Dong River, Daegu (South Korea). The highest removal efficiency (>80%) for MC-LR was achieved after 15 min by the photo-Fenton process at a low optimum Fenton reagent concentration (Fe = 0.5 mg L−1 and H2O2 = 1 mg L−1) in the river water. Twelve transformation products of MC-LR were identified with 1029.5, 1012.5, 1015.5, 1011.5, 965.6, 835.5, 815.4 and 783.4 m/z (two products) with the presence of four reaction sites: the conjugated diene bond of Adda, the methoxy group of Adda, the CC bond of Mdha, and the acid group of MeAsP. Theses alleviated the hepatotoxicity of MC-LR, as indicated by a protein phosphatase (PP) 2A assay. Considering the impacts of the chemistry for the treatment of river water, natural organic matter has a slightly higher impact on MC-LR degradation than the initial pH and alkalinity. The kMC-LR were maintained at 0.167–0.187 min−1 and t1/2 (min), obtained from the different river water samples, were all within 5 min in spite of the relatively high dissolved organic carbon concentrations.

Analysis of the Coordinated Operation of Reservoirs and Weirs during the Management of Nakdong River Water Resources

AbstractThis study discerns optimal rules for coordinated operation of existing dams and eight newly constructed weirs in the Nakdong River through use of a system network while considering the wat...

Effect of pH Control, Ozonation and Coagulation on THMs Formation in Dringking Water Treatment Process of the Downstream of Nakdong River

This study was conducted to evaluate the effects of pH control and ozonation, coagulation on trihalomethanes (THMs) formation during prechlorination of the Nakdong river water. The results showed that lower pH was reduced THMs formation during prechlorination. THMs formation of water lowered pH 9.5 to 9.0, was reduced 18.3% and lowered pH 9.0 to 8.0 was reduced 14%, lowered pH 8.0 to 7.0 was reduced 7%, lowered pH 9.5 to 8.0 was reduced 29%. A low ozone dose (0.11~0.48 mgï½¥O3/DOC) before chlorination reduced the yields of THMs (reduced 6~24% in chlorination) compared with no preozonation. Thus the low ozone dose pretreatment is relatively effective plan to reduce THMs formation during chlorination. When ozone 1.0 mg/L, Alum 40 mg/L and sulfuric acid 6 mg/L dosed, The yields of THMs formation was reduced 42% compared with only chlorination. Input of chlorine after preozonation (followed coagulation, pH control) is more effective than only decline pH at a intake station to control THMs formation in a water treatment process. When chlorine 2.5 mg/L was added before coagulation (alum 40 mg/L), THMs formation was reduced 19% by lower pH and decreased 18% by a natural organic matter (NOM) removal compared with only chlorine 2.5 mg/L addition. Because coagulation could induce simultaneously lower pH and NOM removal, THM formation concentration is more effectively lowed than decreasing pH in the Nakdong river water. Key words: THM Formation, pH Control, Coagulation, Ozonation, Drinking Water Treatment, Nakdong River

Oxidation of geosmin and 2-methylisoborneol by the photo-Fenton process: Kinetics, degradation intermediates, and the removal of microcystin-LR and trihalomethane from Nak-Dong River water, South Korea

Due to the increased intensity and frequency of cyanobacterial blooms, taste and odor (T&O) causing compounds, geosmin (GSM) and 2-methylisoborneol (MIB), have become a cause for great concern in drinking water treatment plants (DWTPs). Advanced oxidation processes (AOPs) have been studied for the removal of GSM and MIB. However, in this work, a photo-Fenton treatment was investigated for the first time for the degradation of GSM and MIB in both synthetic and Nak-Dong River water from DWTPs. Synthetic water-based experiments were performed to investigate the optimal operation conditions for the removal of GSM and MIB, and the effects of water quality parameters of the photo-Fenton process, including the Fe(II)/H2O2 concentration, reaction time, pH, organic matter, and initial concentration of GSM and MIB. Degradation intermediates of dehydration and ring-opening were observed during the photo-Fenton process. The optimal conditions were determined to be 2mg/L Fe(II) and 20mg/L H2O2 at pH 5 considering both efficiency and cost. The degradation efficiency was lower than that of DI water, mainly because of the pH (7.2–7.6). Nevertheless, the photo-Fenton process meets the guideline levels (20ng/L) in South Korea when the initial concentration in the river water is below 50ng/L. In addition, trihalomethanes (THMs) and microcystin-LR (MC-LR), derived from cyanobacterial blooms and another cause for concern, were degraded effectively using the photo-Fenton process on the river water.

Oxidation of microcystin-LR by the Fenton process: Kinetics, degradation intermediates, water quality and toxicity assessment

The Fenton process was assessed as a cost-effective technology for the removal of Microcystin-LR (MC-LR) among UV, UV/H2O2, and Fenton process according to efficiency and electrical energy per order (EE/O). The determined practical concentrations of the Fenton reagents were 5mg/L Fe(II) and 5mg/L H2O2, respectively. The Fenton process is a fast reaction, completed within 5–30min (Fe(II), H2O2=0.2–10mg/L; MC-LR0=200μg/L). The degradation intermediates of MC-LR by the Fenton process were firstly reported as m/z 1029.5, 1011.5, 835.5, 795.4, and 783.4, associated with the diene bond in the Adda chain, then alleviate their toxicity. The effects of organic matter were examined in the range of Nak-Dong River water, as a drinking water source, monitored for six months in 2015. Fulvic acid was affected more than humic acid and natural organic matter (NOM). The degradation efficiency in the raw water was lower than that of distilled water because of the competing effect of NOM, geosmin, and 2-methylisoborneol, and the higher pH (7.64), furthermore, dissolved organic matter, geosmin, and 2-methylisoborneol was removed 7.39%, 4.28% and 12.30% after the Fenton process in the river water. The final concentration of MC-LR after treatment was under the drinking water guideline level with initial MC-LR concentration of 2μg/L. No acute toxicity was observed to Daphnia magna (TU=0) after the Fenton process.

정수처리 응집효율 개선을 위한 Al(III)염과 Fe(III)염 응집제의 비교

The experimental results of the characteristics of aluminum based and ferric based coagulants for the Nakdong River water showed that the main hydrolysis species contained in alum and FeCl3 are monomeric species of 98% and 93.3%, respectively. The PACl of r=1.2 produced by the addition of base contained 31.2% of polymeric Al species and the PACl of r=2.2 contained 85.0% of polymeric Al species, as showing more polymeric Al species with increasing r value. Coagulation tests using Al(III) and Fe(III) salts coagulants for the Nakdong River water showed that the coagulation effectiveness of turbidity and organic matter was high in the order of FeCl3 > PACl (r=2.2) > PACl (r=1.2) > alum. FeCl3 has showed better flocculation efficiency than Al(III) salts coagulants. In addition, in case of Al(III) coagulants, the Al(III) coagulants of higher basicity, which contained more polymeric Al species, resulted in better coagulation efficiency for both turbidity and organic matter removed. The optimum pH range for all of the coagulants investigated was around pH 7.0 under the experimental pH range of 4.0~9.5. Especially, the highest basicity PACl (r=2.2) and FeCl3 were considered as more appropriate coagulants for the removal of turbidity in the case of raw water exhibiting higher pH.

An assessment of selected hydrochemical parameter trend of the Nakdong River water in South Korea, using time series analyses and PCA.

Time series analyses (autocorrelation, spectral density, and cross-correlation) and principal component analysis (PCA) were used to understand the characteristics of the selected hydrochemical parameters pH, turbidity, alkalinity, Cl, hardness, total dissolved solids (TDS), and metals Fe and Mn in the Nakdong River, South Korea. Autocorrelation and spectral density for pH, alkalinity, hardness, and Cl were very similar to TDS, whereas Fe, Mn, and turbidity showed different trends from TDS. Cross-correlograms of pH, alkalinity, hardness, and Cl versus TDS were very similar to each other. Those of Fe and turbidity represented the opposite relations with other components. Cross-correlation coefficients had the highest values at zero lag, indicating that pH, alkalinity, hardness, and Cl are controlling factors for TDS. On the other hand, Fe and turbidity showed the highest values at 6-month lag and Mn at a month lag. PCA indicated that TDS had very close relation with hardness, pH, and Cl and very small relation with Mn. Turbidity and Fe had relatively opposite relations with TDS. It was concluded that the geostatistical methods were very useful for evaluating the hydrochemical characteristics of the Nakdong River water in South Korea.

On-line 모니터링 기법을 이용한 Al염계와 Fe염계 응집제의 응집특성 평가

Effects of coagulation types on flocculation were investigated by using a photometric dispersion analyzer (PDA) as an on-line monitoring technique in this study. Nakdong River water were used and alum and ferric chloride were used as coagulants. The aim of this study is to compare the coagulation characteristics of alum and ferric chloride by a photometric dispersion analyzer (PDA). Floc growing rates (<TEX>$R_v$</TEX>) in three different water temperatures (<TEX>$4^{\circ}C$</TEX>, <TEX>$16^{\circ}C$</TEX> and <TEX>$30^{\circ}C$</TEX>) and coagulants doses (0.15 mM, 0.20 mM and 0.25 mM as Al, Fe) were measured. The floc growing rate (<TEX>$R_v$</TEX>) by alum was 1.8~2.8 times higher than that of ferric chloride during rapid mixing period, however, for 0.15 mM~0.25 mM coagulant doses the floc growing rate (<TEX>$R_v$</TEX>) by ferric chloride was 1.1~2.3 times higher than that of alum in the slow mixing period at <TEX>$16^{\circ}C$</TEX> water temperature. Reasonable coagulant doses of alum and ferric chloride for turbidity removal were 0.1 mM (as Al) and 0.2 mM (as Fe), respectively, and the removal efficiency of those coagulant doses showed 94% for alum and 97% for ferric chloride. The appropriate coagulant dose of alum and ferric chloride for removing dissolved organic carbon (DOC) showed about 0.3 mM (as Al, Fe) and at this dosage, DOC removal efficiencies were 36% and 44%, and ferric chloride was superior to the alum for removal of the DOC in water.

자성체 이온교환수지(MIEX®)를 이용한 수중의 과불화화합물(PFCs) 제거 특성

Abstract Perfluorooctanoic acid (PFOA) and perfluorooctyl sulfonate (PFOS) is a new persistent organic pollutants of substantial environmental concern. This study investigated the potential of magnetic ion exchange resin (MIEX) as the adsorbent for the removal of PFOA and PFOS from Nakdong River water. In our batch experiments, we studied the effect of some parameters (pH, temperature, sulfate concentration) on the removal of PFOA and PFOS. The results of sorption kinetics on MIEX show that it takes 90 min to reach equilibrium but the economical contact time and dosage were 30 min and 10 mL/L. An increase in pH (pH 610) leads to a decrease in PFOA (2.0%) and PFOS (3.6%) sorption on MIEX. The sorption of both PFOA and PFOS decreases with an increase in ionic strength for sulfate ion (SO 42- ), due to the competition phenomenon. An increase in water temperature (828) in water leads to a increase in PFOA (2.8%) and PFOS (4.3%) sorption on MIEX. Based on the sorption behaviors and characteristics of the adsorbents and adsorbates, ion exchange and hydrophobic interaction were deduced to be involved in the sorption, and hemi-micelles possibly formed in the intraparticle pores.Key words: Perfluorinated compounds (PFCs), Magnetic ion exchange resin (MIEX), pH, Water temperature, Sulfate ion

수공구조물의 건설로 인한 하상변동과 안정성에 관한 연구

하천의 유황 및 하상재료의 인위적인 변화에 의한 장기적인 하상변동 효과를 예측하고 분석하는 것은 하천계획 및 관리 면에서 매우 중요하다. 국내에서 수행된 하상변동 예측에 관한 연구들은 대부분 1차원 모형이므로 하천의 사행의 진행이나 유사의 횡방향 분포 등은 고려할 수 없다. 그리고 지류가 유입하는 합류 지점, 교량, 보 등의 다양한 수공구조물이 존재하는 경우 또는 하도 형상의 변화에 따른 국부적인 흐름의 변화 양상의 해석이 어렵다. 본 논문에서는 실제하천을 대상으로 2차원 흐름 및 하상변동 수치모형인 CCHE2D 모형을 이용하여 하상변동 수치모의를 수행 비교 분석 하였다. 모형의 타당성 검증을 위해 자연 하천인 낙동강 일선교 ~ 왜관 수위관측소 구간을 선정하였으며, 대상구간내의 수공구조물인 칠곡보에 대해 50년, 100년, 200년 빈도별로 모의를 실시하였다. 모의 결과, 보 직하류를 제외한 구간에서 칠곡보 건설전보다 퇴적이 많이 발생하였으며, 보직하류 구간에서 다량의 침식이 있음을 보였다. 침식이 계속 진행된다면 보유실과 같은 심각한 결과를 초래할 수 있기 때문에 침식을 방지 할 수 있는 바닥보호공의 안정성을 소류력을 통하여 검토하였으며 빈도별 홍수량에 안정한 것으로 판단된다. In terms of river planning and management, it is very important to predict and analyze the effect of long-term variation of river bed led by artificial changes in the materials of river regime and river bed. The country's studies on the prediction of river bed variation, mostly using one-dimensional model, can not consider the meandering course of the river or similar transverse distribution, and they suitable for application in case of local change in the river flow. The thesis targeting real rivers implemented simulations and made a comparative analysis using CCHE2D model that is a numerical model for two-dimensional flow and river bed variation. To verify the validity of the model, the area was selected between Ilseongyo in Nakdong River and Waegwan water level observatory as a real natural river in which the simulations were conducted according to the frequency of 50 years, 100 years, 200 years at Chilgokbo. The results of this analysis presented that sedimentation highly increased in the area except for right lower reach and show that a great quantity of erosion happen for right lower reach. Because continuous erosion lead to serious problem like weir being washed, stability of measures against erosion like bed pitching was reviewed according to tractive force and the result show that the measures are stable.

낙동강 원수를 대상으로 Al염계 및 Fe염계 응집제를 이용한 고도응집의 적용

Enhanced coagulation is best available technologies to treat NOM in water to produce clean drinking water. In this research, the comparison experiments between conventional coagulation (CC) and enhanced coagulation (EC) using 4 type coa- gulants i.e., ferric chloride, aluminium sulphate (alum), poly aluminium sulphate organic magnesium (PSOM) and poly aluminium chloride (PACl) were performed in terms of surrogate parameters such as dissolved organic carbon (DOC), trihalomethane formation potential (THMFP), haloacetic acid formation potential (HAAFP) and zeta potential variation in order to find out the most effective coagulant and conditions to fit Nakdong River water. When applied to EC process, the turbidity removal efficiency did not increased gradually compared to the CC process when adding coagulants. Furthermore, the removal efficiency of turbidity became decreased much more as coagulants were added increasingly whereas the removal efficiency of DOC, THMFP and HAAFP became increased by 13~18%, 9~18% and 9~18% respectively compared to the CC process. The characteristics of turbidity removal showed relatively high removal efficiency considering the pH variation in entire pH range when using FeCl3 and PACl. Additionally, in case of alum and PSOM steady removal efficiency was shown between pH 5 and pH 8. In terms of DOC surrogate the coagulants including 4 type coagulants indicated high removal efficiency between pH 5 and pH 7. The removal efficiency of dissolved organic matter (DOM) in EC between less than 1 kDa and more than 10 kDa augmented by 11~21% and 16% respectively compared to the CC process. The removal efficiency of hydrophobic and hydrophilic organic matter proved to be increased by 27~38% and 11~15% respectively. In conclusion, the most effective coagulant relating to EC for Nakdong River water was proved to be FeCl3 followed by PSOM, PAC and alum in order.

Characteristics of disinfection by-products reduction in the processes of drinking water treatment system using Nakdong river water

In this study, batch and continuous experiments were conducted to investigate the influential factors on the distribution and formation of aldehydes, bromate and bromide in Nakdong river water and to investigate the behaviour of disinfection by-products (DBPs) in the processes of drinking water treatment system. The mean influent concentrations were 3.1 mg/L (2.4–3.9 mg/L) for dissolved organic carbon (DOC), 57.6 ug/L (42.0–85.7 ug/L) for total aldehydes (TA) and 55.7 ug/L (17.4–89.3 ug/L) for bromide. As a result, TA and bromide levels in the Nakdong river water increased with the decreasing water flow rate and decreasing water temperature. In pre- and post-ozonation, the DBPs concentration increased with increasing bromide level, ozone dosage and pH value. In particular, the concentration of DBPs formation in both pre-ozonation and winter was relatively higher than that in both post-ozonation and summer. In coagulation and sedimentation, polyaluminium sulphate organic magnesium coagulation resulted in slightly less DBPs removal than polyaluminium silicate chloride coagulation. TA was significantly reduced at the top of sand and biological activated carbon (BAC) filters, whereas bromate was effectively reduced in a three-month-old BAC filter.

오존처리에 의한 수중의 인공 사향물질 제거특성

In this study, three different synthetic musk compounds (SMCs) in the Nakdong river water (raw water) and rapid sand filtered water were treated by O3 process. The experimental results showed that the removal efficiency of musk ketone (MK) was lower than removal efficiency of AHTN (7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene) and HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta[c]-2-benzopyran) for both the raw water and the rapid sand filtered water. And in general, the removal efficiencies of three SMCs in the raw water were lower than that in the sand filtered water. Under the O3 dose of 0.5~ 10.0 mg/L, the removal rate constants (k) of three SMCs for the raw and sand filtered waters increased rapidly with the increased O3 dose. In the case of drinking water treatment plants (DWTPs) which were selected preand post-O3 processes (located in the downstream of Nakdong River), operation conditions of preand post-O3 process were 0.5~2.0 mg・O3/L (2~4 min) and 0.5~2.5 mg・O3/L (6~8 min). Therefore, O3 doses and contact times of same conditions with above were very difficult to remove SMCs in DWTPs.

밀양강 중권역 오염부하 전망 및 삭감 시나리오별 하류 수질예측

Milyanggang mid-watershed is located in downstream of Nakdong river basin. The pollutants from that watershed have an direct effect on Nakdong river water quality and it's control is important to manage a water quality of Nakdong river. A target year of Milyanggang mid-watershed water environment management plan is 2013. To predict a water quality at downstream of Milyang river, we have investigated and forecasted the pollutant source and it's loading. There are some plan to construction the sewage treatment plants to improve the water quality of Milyang river. Those are considered on predicting water quality. As results, it is shown that the population of Milyanggang mid-watershed is 131,857 and sewerage supply rate is 62.2% and the livestock is 1,775.300 in 2006. It is estimated that the population is 123,921, the sewerage supply rate is 75.5% in 2013. The generated loading of BOD and TP is 40,735 kg/day and 2,872 kg/day in 2006 and discharged loading is 11,818 kg/day and 722 kg/day in 2006 respectively. Discharged loadings were forecasted upward 1.0% of BOD and downward 2.7% of TP by 2013. The results of water quality prediction of Milyanggang 3 site were 1.6 mg/L of BOD and 0.120 mg/L of TP in 2013. It is over the target water quality at that site in 2015 about 6.7% and 20.0% respectively. Consequently, there need another counterplan to reduce the pollutants in that mid-watershed by 2015.