• Journal of Korean Society on Water Environment
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• v.16 no.4
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• pp.513-521
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• 2000

Intermittently aerated activated sludge process was applied as a water reuse process of $70m^3/day$ for the upgrade of organic, nitrogen and phosphorus removal efficiency and clarifier performance. After application of the intermittently aeration, removal efficiency of BOD, SS, T-N and T-P were achieved 95%, 90%, 80% and 60%, respectively. Removal efficiencies in intermittently aerated process were considerably increased. comparing to those of continuously aerated activated sludge process. Also sludge rising problem in clarifier was improved. Average concentration of supplied reusing water were BOD 5 mg/L, turbidity 4 NTU and after chlorination, residual chlorine 0.4 mg/L, coliform 0 MPN/100mL. Intermittently aerated activated sludge process could be one of the best alternative process for the retrofit of conventional activated sludge process for the removal of nutrient in water reuse system.

• Korean Journal of Environmental Biology
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• v.22 no.4
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• pp.524-531
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• 2004

Photosynthetic activities and primary production of phytoplankton were investigated in Lake Gocheonam from October 1999 to August 2000. As an estuary lake with a barrage in the Southwestern coast of the Korean peninsula, the lake has received more attention after it became known as the habitat of large population of rare and endangered bird- Baikal Teal. As the lake had high algal biomass ranging from $20\mu{g}\;chl-aL^{-1}\;to\;125\mu{g}\;chl-aL^{-1}$ in average values and rich eutrophication indicator species, the freshwaters were in a very productive or hypertrophic state. In the results obtained from the phytoplankton incubation in the laboratory, the maximum photosynthetic rate $(P_{max})$ varied according to seasons and sampling stations. Photo- synthetic activities were higher during the warm season than the cold seasons and the serial order of $P_{max}$ was August dominated with Microcystis, April with Chlamydomonas and Nitzschia, October with Chlamydomonas and January with Stephanodiscus. The water of the lake was persistently turbid throughout the year due to strong winds from the adjacent sea. Despite the water turbidity, the phytoplankton productions estimated from a mathematical model had very broad range from 18mg C $m^{-2}day^{-1}\;to\;10,300mg\;C\;m^{-2}day^{-1}$.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.2
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• pp.169-175
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• 2017

This study applied microbubbles to reduce membrane fouling in wastewater reuse membrane processes, evaluated and compared the transmembrane pressure with or without the application of microbubbles and the cleaning efficiency with the application of aeration and microbubbles. In addition, this study analyzed foulants removed from the membrane surface. Changes in the transmembrane pressure of membranes with the presence or absence of microbubbles were observed. As a result, transmembrane pressure (TMP) increasing rate decreased twofold when applying microbubbles to realize stable operations. This study compared and evaluated cleaning efficiency applying aeration and microbubbles. As a result, the cleaning efficiency was 5% higher on average when applying microbubbles. In turbidity and total organic carbon (TOC), foulants were discharged when applying microbubbles twice as much as applying aeration. It is thought that particulate foulants precipitated on the membrane surface were more likely to desorb because the adhesion between the membrane surface and particle was weakened by microbubbles. Therefore, it is considered possible to effectively control membrane fouling because of the increase in cleaning efficiency when applying microbubbles to wastewater reuse membrane processes.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.538-541
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• 2008

The carbon laden suspensions in water with no surfactants have poor stability caused by the hydrophobic layer of particles. In this study, the water-based carbon nano colloide(CNC) was successfully produced using electro-chemical one-step method without agent. The properties of CNC were characterized by using various techniques such as particle size analyzer, TEM, FT-IR, turbidity meter, viscometer, and transient hot-wire method. The average size of the suspended in the CNC was 15 nm in diameter. The thermal conductivity of CNC compared with water was increased up to 14% with 4.2wt% concentration. The CNC was stable over 600hr. The enhanced colloidal stability of CNC may be caused by the chemical structures, such as, hydroxide and carboxyl groups formed in outer atomic layer of carbon, which (i) made the carbon nanofparticles hydrophilic and (ii) prevented the aggregation among nanoparticles.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.6
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• pp.492-497
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• 2004

Waste concentration and waste generation rate in seawater aquaria by common conger (Astrocongey myriaster) and olive flounder (Paralichyhus olivaceus) were investigated. The initial fish density of common conger and olive flounder were $3{\%}\;and \;2.8{\%}$ of total weight of aquarium water, respectively Wastes in the seawater aquaria, such as protein, total suspended solid (TSS), ammonia, turbidity and chemical oxygen demand (COD) increased with days after stocking. Protein generation rate of common conger increased until 1 day after stocking while that of olive flounder increased until 3 days. The average protein generation rates of common conger and olive flounder were $0.28g/kg{\cdot}day\;and\;0.21g/kg{\cdot}day$, respectively. The trends of other waste generation rate were similar to protein generation rate.

• Journal of Pharmaceutical Investigation
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• v.31 no.1
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• pp.43-47
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• 2001

Sterically stabilized liposomes (SSL) have been introduced for longer circulation in blood than conventional liposomes (CL). However, there are a couple of problems in SSL preparation due to the instability of phospholipid and the degradation of drug in aqueous conditions. To solve these problems, it is necessary to go through lyophilization process. Therefore, in this study, effects of lyophilization on SSL were evaluated for physical characteristics changes upon rehydration of lyophilized SSL such as the particle size, efficiency of drug entrapment, turbidity and drug release. SSL containing streptozocin, a water-soluble anticancer drug as a model compound, were prepared with DSPC and DSPE-PEG 2000. The size was controlled to 100 nm by extrusion with polycarbonate membrane, and sucrose was used as a cryoprotectant for lyophilization at the 1:3 (lipid:sucrose) ratio. Upon rehydration of lyophilized SSL, the average size was in the range of $50{\sim}200\;nm$ which is adequate for longer circulation in blood, and the encapsulation efficiency was kept as its initial state. Rehydrated SSL were not adsorbed to rat plasma protein and revealed a similar drug release profile to that of fresh SSL before lyophilization. Therefore, lyophilization could be introduced efficiently to overcome aqueous instability problems of SSL.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.2
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• pp.65-74
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• 1996

This study was carried out to investigate the water quality of agricutural reservoirs in Chonbuk Province. The water quality of 189 agricultural reservoirs was surveyed in the environmental standard phase of pH, EC, DO, BOD, COD, T-N, T-P, etc. The results obtained in this study are summarized as follows ; 1. The levels of mean reservoir storage were very low as 26.9% in January and February, 29.4% in June, 16.0% in August, and 25.4% as a whole. 2. The water qualities of agricultural reservoirs were shown to be in the average of 6.8in pH, 0.2l0mmhos/cm in EC, 49.Oppm in turbidity, 28.5mg/$\ell$in SS, 3.79mg/$\ell$ in DO, 9. 9mg/$\ell$ in COD, 5.Smg/$\ell$ in BOD, 0.179mg/ $\ell$ in T-P, 4.O9mg/$\ell$ in T-N, 0.416meq/$\ell$ in Na, 0.154meq/$\ell$ in K, 0.320meq/$\ell$ in Ca, 0.166meq/$\ell$ in Mg, respectively. 3. In the analyzed results, the proper counterplan is desirable to be considered because the levels of water quality in most items except DO were comparatively higher than the limit points of agricultural water quality standard.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.6
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• pp.801-806
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• 2004

The pilot study was conducted to (i) investigate the ability of various membrane integrity monitoring methods to detect changes in membrane integrity during operation, and (ii) determine the impact of membrane damage on microbial removal by microfiltration. Two variations of air pressure hold tests were investigated for direct integrity monitoring: pressure decay (PD) and diffusive air flow (DAF) tests which are most commonly used integrity tests for microfiltration (MF) membranes. Both PD and DAF tests were sensitive enough to detect one damaged fiber out of 66,000 under field operaing conditions. Indirect integrity monitoring such as turbidity and particle counting, however, responded poorly to defects in membrane systems. Microbial challenge study was performed using both new and deliberately damaged membranes, as well as varying the state of fouling of the membrane. This study demonstrated that MF membrane with nominal pore size $0.2{\mu}m$ was capable of removing various pathogens including coliform, spore, and cryptosporidium, at the level required by drinking water regulations, even when high operating pressures were applied. A sharp decrease in average log reduction value (LRV) was observed when one fiber was damaged, emphasizing the importance of membrane integrity in control of microbial contamination.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.4
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• pp.397-406
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• 2009

This study was conducted to monitor the floc sizes forming in the mixing zone in the water treatment plant. The dosing amount of poly aluminium chloride(PAC) was determined by particle dispersion analyzer(iPDA) in the lab and field scale test. During a field test period, PAC coagulant was used and the raw water was taken from Nakdong river. PAC wad diluted to activate the coagulant, leading to bring the more homogeneous dispersion in the shorter time. To monitor the floc sizes, the unit of floc size index(FSI) was used. With increasing of raw water turbidity, FSI value was increased. Also, the increased dosing amount of PAC brought the increased FSI and with overdosing of coagulant was in turn decreased. When the PAC was fed into the raw water after dilution in a field scale test, the width of FSI was narrower compared with the feeding of the mother liquor of PAC, implying that the formed flocs are denser and more uniform sizes. The width of FSI in average was varied on depending on the basicity of coagulant. Also, dF value, fractal dimension was evalued with the different coagulants, showing from 2.01 to 2.03. On-line floc monitor was effective for the optimal dosing in the drinking water plant.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.491-491
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• 2013

A novel plasma system has been developed for 3-dimensional modification of the carbon nano-powders. Improvement of dispersion of these nano materials are studied by plasma discharge, not using chemical modification. The plasma process is considered to great advantages over wet chemical process due to environmental, economic viewpoint, and uniformity over the treated volume. The uniform dispersion is a critical factor for these material's nano composite applications. Using this plasma system, graphene, carbon black, and CNT was treated and functionalized. Several key discharge conditions such as Ar/H2/O2 or Ar/H2/NH3 gas ratio, treatment time, power, feeder's vibration frequency are investigated. Hydrophobic of graphene has turned some more into hydrophilic by reaction test with water, electrophoresis, surface contact angle test, and turbidity analysis. The oxygen content ratio in the plasma treated CNT has increased about 3.7 times than the untreatedone. In the case of graphene and carbon black, the oxygen- and nitrogen- content has been enhanced average 10%. O-H (N-H) peak, C-O (C-N) peak, and C=O (C=N) peak data have been detected by FTIR measurement and intensified compared to before-plasma treatment due to O2 or NH3 content.