• Membrane and Water Treatment
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• v.11 no.1
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• pp.11-23
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• 2020

The effectiveness of in situ sediment capping as a technique for heavy metal risk mitigation in Hyeongsan River estuary, South Korea was studied. Sites in the estuary were found previously to show moderate to high levels of contamination of mercury, methylmercury and other heavy metals. A 400 m × 50 m section of the river was selected for a thin layer capping demonstration, where the total area was divided into 4 sections capped with different combinations of capping materials (zeolite, AC/zeolite, AC/sand, zeolite/sand). Pore water concentrations in the different sites were studied using diffusive gradient in thin film (DGT) probes. All capping amendments showed reduction in the pore water concentration of the different heavy metals with top 5 cm showing %reduction greater than 90% for some heavy metals. The relative maxima for the different metals were found to be translated to lower depths with addition of the caps. For two-layered cap with AC, order of placement should be considered since AC can easily be displaced due to its relatively low density. Investigation of methylmercury (MeHg) in the site showed that MeHg and %MeHg in pore water corresponds well with maxima for sulfide, Fe and Mn suggesting mercury methylation as probably coupled with sulfate, Fe and Mn reduction in sediments. Our results showed that thin-layer capping of active sorbents AC and zeolite, in combination with passive sand caps, are potential remediation strategy for sediments contaminated with heavy metals.

• Membrane and Water Treatment
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• v.9 no.3
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• pp.163-172
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• 2018

This study investigated the effect of organic matter on the precipitation of struvite and calcium phosphate for phosphorus recovery from synthetic dairy wastewater. Batch precipitation experiments were performed to precipitate phosphorus from solutions containing $PO_4{^{3-}}$ and $NH_4{^+}$ by the addition of $Mg^{2+}$ and $Ca^{2+}$, separately, at varying pH, Mg/P and Ca/P molar ratios, and organic matter concentrations. Soluble total organic solids exhibited more inhibition to precipitation due to potential interaction with other dissolved ionic species involved in phosphorus precipitation. Xylan with low total acidity only exhibited significant inhibition at very high concentrations in synthetic wastewater (at up to 100 g/L). No significant inhibition was observed for Mg and Ca precipitation at relatively lower concentrations (at up to 1.2 g/L). MINTEQ simulations show that dissolved organic matter (DOM) as humic substances (HS) can cause significant inhibition even at relatively low concentrations of 0.165 g/L fulvic acid. However, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis suggested that xylan altered the crystal structure of both precipitates and had caused the formation of smaller sized struvite crystals with slightly rougher surfaces This could be due to xylan molecules adhering on the surface of the crystal potentially blocking active sites and limit further crystal growth. Smaller particle sizes will have negative practical impact because of poorer settleability.

• Membrane and Water Treatment
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• v.9 no.3
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• pp.137-146
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• 2018

Soil washing is one of the most frequently used remediation technologies for heavy metal-contaminated soils. Inorganic and organic acids and chelating agents that can enhance the removal of heavy metals from contaminated soils have been employed as soil washing agents. However, the toxicity, low removal efficiency and high cost of these chemicals limit their use. Given that humic substance (HS) can effectively chelate heavy metals, the development of an eco-friendly, performance-efficient and cost-effective soil washing agent using a nano-scale chelator composed of HS was examined in this study. Copper (Cu) and lead (Pb) were selected as target heavy metals. In soil washing experiments, HS concentration, pH, soil:washing solution ratio and extraction time were evaluated with regard to washing efficiency and the chelation effect. The highest removal rates by soil washing (69% for Cu and 56% for Pb) were achieved at an HS concentration of 1,000 mg/L and soil:washing solution ratio of 1:25. Washing with HS was found to be effective when the pH value was higher than 8, which can be attributed to the increased chelation effect between HS and heavy metals at the high pH range. In contrast, the washing efficiency decreased markedly in the low pH range due to HS precipitation. The chelation capacities for Cu and Pb in the aqueous phase were determined to be 0.547mmol-Cu/g-HS and 0.192mmol-Pb/g-HS, respectively.

• Journal of Energy Engineering
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• v.21 no.3
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• pp.292-300
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• 2012

KHNP CRI has been developing APR+ nuclear power plant since 2007, which is GEN III+ model with 4,361 MWth capacity. To develop safer and more economical nuclear power plant than APR1400, we studied domestic and foreign nuclear power plants under construction. We also reviewed nuclear power plants which are appropriate for domestic construction in Korea and also for export. Economic assessments were made twice during the second phase of standard detailed design of the plant. The result of the second phase of economic analysis for APR+ standard detailed design showed that APR+ N-th plant was 24.6% more economical than coal-fired 1,000MW power plant, and was evaluated to be competitive enough in global market for construction of the nuclear power plant.

• Journal of Korean Medicine Rehabilitation
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• v.21 no.2
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• pp.227-238
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• 2011

Objectives : This study was to investigate the effects on using Virtual reality exercise program($Wii-Fit^{TM}$) for dynamic balance and walking ability in patients with stroke. Methods : The 22 subjects were randomly selected from the patients of the S hospital who met the study conditions. They were divided into a $Wii-Fit^{TM}$ balance game group of 12 patients and a conventional physical therapy group of 10 patients. The $Wii-Fit^{TM}$ balance game group received $Wii-Fit^{TM}$ balance game group general physiotherapy for 5 days a weeks, 30 minutes a day, for a 4 weeks and the conventional physical therapy group received general physiotherapy for the same period. The subjects were measured and compared for Brunel balance assessment, functional gait assessment, 6 minute walk test, GAITRite system before and after the program. Results : The experimental group tend to improve more than control group in shifting the weight to the affected side(p=0.040) and tap test(p<0.001). The experimental group tend to improve more than control group in FGA(p=0.016). The experimental group improved significantly more than control group in 6MWT(p=0.008). The experimental group improved significantly more than control group in gait speed, cadence, stride length. Conclusions : Virtual Reality program($Wii-Fit^{TM}$) with conventional physical therapy shows the benefits on dynamic balance and gait parameters in patients with stroke.

• Current Photovoltaic Research
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• v.1 no.1
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• pp.17-26
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• 2013

In contrast to conventional crystalline cells, back-contact solar cells feature high efficiencies, simpler module assembly, and better aesthetics. The highest commercialized cell and module efficiency was recorded by n-type back-contact solar cells. However, the mainstream PV industry uses a p-type substrate instead of n-type due to the high costs and complexity of the manufacturing processes in the case of the latter. P-type back-contact solar cells such as metal wrap-through and emitter wrap-through, which are inexpensive and compatible with the current PV industry, have consequently been developed. In this paper the characteristics of EWT (emitter wrap-through) solar cells and their status and prospects for development are discussed.

• Membrane and Water Treatment
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• v.6 no.3
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• pp.237-249
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• 2015

In this study we investigate a laboratory scale vacuum membrane distillation system to produce pure water from model oil in water emulsion. Experimental determination of liquid entry pressure (LEP) of a commercial Durapore$^{TM}$ GVPH flat sheet membrane using model emulsions in various oil concentrations has been carried out. Two different methods of liquid entry pressure determination - a frequently used, so-called static and a novel dynamic method - have been investigated. In case of static method, LEP value was found to be 2.3 bar. No significant effect of oil content on LEP was detected up to 3200 ppm. In contrast, LEP values determined with dynamic method showed strong dependence on the oil concentration of the feed and decreased from 2.0 bar to a spontaneous wetting at 0.2 bar in the range 0-250 ppm, respectively. Vacuum membrane distillation tests were also performed. The separation performance is evaluated in terms of flux behavior, total organic carbon removal and droplet size distribution of the feed and final retentate. No significant effect of oil content on the flux was found ($5.05{\pm}0.31kgm^{-2}h^{-1}$) up to 250 ppm, where a spontaneous wetting occurred. High separation performance was achieved along with the increasing oil concentration between 93.4-97.0%.

• Membrane and Water Treatment
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• v.6 no.3
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• pp.225-235
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• 2015

During low-pressure membrane treatments of cyanobacterial cells, including microfiltration (MF) and ultrafiltration (UF), there have reportedly been releases of intracellular compounds including cyanotoxins and compounds with an earthy-musty odor into the water, probably owing to cyanobacterial cell breakage retained on the membrane. However, to our knowledge, no information was reported regarding the effect of growth phase of cyanobacterial cells on the release of the intracellular compounds. In the present study, we used a geosmin-producing cyanobacterium, Anabaena smithii, to investigate the effect of the growth phase of the cyanobacterium on the release of intracellular geosmin during laboratory-scale MF experiments with the cells in either the logarithmic growth or stationary phase. Separate detection of damaged and intact cells revealed that the extent of cell breakage on the MF membrane was almost the same for logarithmic growth and stationary phase cells. However, whereas the geosmin concentration in the MF permeate increased after 3 h of filtration with cells in the logarithmic growth phase, it did not increase during filtration with cells in the stationary phase: the trend in the geosmin concentration in the MF permeate with time was much different between the logarithmic growth and stationary phases. Adsorption of geosmin to algogenic organic matter (AOM) retained on the MF membrane and/or pore blocking with the AOM were greater when the cells were in the stationary phase versus the logarithmic growth phase, the result being a decrease in the apparent release of intracellular geosmin from the stationary phase cells. In actual drinking water treatment plants employing membrane processes, more attention should be paid to the cyanobacterial cells in logarithmic growth phase than in stationary phase from a viewpoint of preventing the leakage of intracellular earthy-musty odor compounds to finished water.

• Membrane and Water Treatment
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• v.6 no.3
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• pp.205-224
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• 2015

A novel hydrophilic poly (vinylidene fluoride)/poly (p-phenylene terephthalamide) (PVDF/PPTA) blend membrane was prepared by in situ polycondensation of p-phenylene diamine (PPD) and terephthaloyl chloride (TPC) in PVDF solution with subsequent nonsolvent induced phase separation (NIPS) process. For comparison, conventional solution blend membrane was prepared directly by adding PVDF powder into PPTA polycondensation solution. Blend membranes were characterized by means of viscometry, X-ray photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM). The effects of different blending methods on membrane performance including water contact angle (WCA), mechanical strength, anti-fouling and anti-compression properties were investigated and compared. Stronger interactions between PVDF and PPTA in in situ blend membranes were verified by viscosity and XPS analysis. The incorporation of PPTA accelerated the demixing rate and caused the formation of a more porous structure in blend membranes. In situ blend membranes exhibited better hydrophilicity and higher tensile strength. The optimal values of WCA and tensile strength were $65^{\circ}$ and 34.1 MPa, which were reduced by 26.1% and increased by 26.3% compared with pure PVDF membrane. Additionally, antifouling properties of in situ blend membranes were greatly improved than pure PVDF membrane with an increasing of flux recovery ratio by 25%. Excellent anti-compression properties were obtained in in situ blend membranes with a stable pore morphology. The correlations among membrane formation mechanism, structure and performance were also discussed.

• Membrane and Water Treatment
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• v.3 no.1
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• pp.25-34
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• 2012

Carboxylated polysulfone (CPS), poly (1,4-phenylene ether ethersulfone) (PPEES), membranes were prepared and used for the separation of NaCl and $CaCl_2$, in efficient way with less energy consumption. In this work, nanofiltration and reverse osmosis membranes were employed to the salt rejection behavior of the different salt solutions. The influence of applied pressure (1-12 bar), on the membrane performance was assessed. In CM series of membranes, $CM_1$ showed maximum of 97% water uptake and 36% water swelling, whereas, $CM_4$ showed 75% water uptake and 28% water swelling. In RCM series, $RCM_1$ showed 85% water uptake and 32% water swelling whereas, in $RCM_4$ it was 68% for water uptake and 20% for water swelling. Conclusively reverse osmosis membranes gave better rejection whereas nanofiltration membrane showed enhanced flux. CM1 showed 58% of rejection with 12 L/($m^2$ h) flux and $RCM_1$ showed 55% of rejection with 15 L/($m^2$ h) flux for 0.1 wt.% NaCl solution. Whereas, in 0.1 wt.% $CaCl_2$ solution, membrane $CM_1$ showed 78% of rejection with 12 L/($m^2$ h) flux and $RCM_1$ showed 63% rejection with flux of 9 L/($m^2$ h).