• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.201-201
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• 2019

세계적인 기상이변으로 가뭄발생 빈도 및 영향이 증가하고 있으며, 급속한 산업화로 사용 가능한 수자원이 점차 고갈되어 있어, 국내에서도 해수담수화(Seawater Desalination)는 새로운 대체수자원으로 많은 관심을 받고 있다. 해수담수에 필요한 에너지 약 50~70%는 역삼투(Reverse Osmosis) 공정에서 발생되며, 해수온도 및 염분도에 따라 많이 변동될 수 있으므로 국립해양조사원(KHOA)의 과거 20년 자료를 이용하여 해수담수화 시설물 위치에 따른 영향을 분석하였다. 해수담수화에 필요한 에너지는 막 제조사에서 제공하는 RO Projection Software를 적용하여 에너지 소모량을 평가하고, 이를 고려한 시설물 위치에 대한 평가 모델을 구축하였다. 기존 해수담수화 시설은 대규모 물 공급이 필요한 지역을 우선적으로 고려했기 때문에 시설물 위치에 대한 객관적인 평가기준 마련이 어려웠다. 그러나 해수담수화 플랜트는 한번 설치되면 장기적인 시설물 유지 및 관리가 필요함으로 경제성을 고려한 최적 입지의 선정은 매우 중요하다. 본 연구는 국립해양조사원의 수집된 자료를 바탕으로 해수담수화 시설물 입지선정을 정량적으로 평가함으로서, 시설물 위치에 대한 의사결정시 참고할 수 있는 기초자료로 활용될 것으로 기대한다.

• Membrane and Water Treatment
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• v.6 no.4
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• pp.309-321
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• 2015

We report in this study the synthesis of mixed matrix reverse osmosis membranes by interfacial polymerization (IP) of thin film nanocomposite (TFNC) on porous polysulfone supports (PS). This paper investigates the synthesis of ZnO nanoparticles (NPs) using the sol-gel processing technique and evaluates the performance of mixed matrix membranes reached by these aerogel NPs. Aqueous m-phenyl diamine (MPD) and organic trimesoyl chloride (TMC)-NPs mixture solutions were used in the IP process. The reaction of MPD and TMC at the interface of PS substrates resulted in the formation of the thin film composite (TFC). NPs of ZnO with a size of about 25 nm were used for the fabrication of the TFNC membranes. These membranes were characterized and evaluated in comparison with neat TFC ones. Their performances were evaluated based on the water permeability and salt rejection. Experimental results indicated that the NPs improved membrane performance under optimal concentration of NPs. By changing the content of the filler, better hydrophilicity was obtained; the contact angle was decreased from $74^{\circ}$ to $32^{\circ}$. Also, the permeate water flux was increased from 26 to 49 L/m2.h when the content of NPs is 0.1 (wt.%) with the maintaining of lower salt passage of 1%.

• Journal of Korean Society on Water Environment
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• v.37 no.5
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• pp.355-362
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• 2021

This study investigated the fate of dissolved organic matter (DOM) in a water reclamation facility (WRF) in Korea. The WRF consists of coagulation, sedimentation, microfiltration, and reverse osmosis (RO) components. The production capacity of WRF is 90,000 m³/day. The reclaimed water is reused as industrial water. We also characterized DOM in raw, processed, and finished waters based on analysis of dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm (UVA₂₅₄), fluorescence excitation emission matrix (FEEM), and DOC fractions via liquid chromatography-organic carbon detection (LC-OCD). Based on the results of DOC, UVA₂₅₄, and FEEM analyses, neither the coagulation/sedimentation nor the microfiltration at the WRF effectively removed DOM. The RO process removed more than 94% of DOM. The raw water (i.e., secondary treated effluent obtained from a wastewater treatment plant) exhibited tryptophan-like peaks, which are a promising marker of wastewater, in the FEEM analysis. Coagulation and microfiltration failed to eliminate the wastewater marker, whereas RO completely removed it. The raw water also carried high levels (89.4%) of hydrophilic and low-molecular weight substances, which are difficult to remove via coagulation-sedimentation or microfiltration. Humic substance was a major component of the hydrophilic fractions. Based on the LC-OCD analysis, RO effectively removed the humic and polymeric materials from DOM.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.423-433
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• 2020

Direct current (DC) electric fields have been used for electro-osmotic dewatering. Under DC conditions, however, the electrical contact resistance between the electrode and the dewatering material increases considerably during the process of dewatering. Such a circumstance hinders the continuation of effective electro-osmotic dewatering. To reduce this hindrance, an applied pulse electric field with periodic reversals of the electrode polarity should improve electro-osmotic dewatering. In this study, electro-osmotic dewatering under pulse conditions was experimentally investigated for electrode polarity reversals. During the dewatering process, the pulse electric field was able to reduce the hindrance caused by the DC, resulting in an increased final dewatered amount relative to that under a DC electric field. For a constant applied voltage, the reversed polarity condition, under which the electric current passing through the material was almost unchanged with time, yielded the maximum final dewatered amount. This technique can be used to enhance drainage from a water storage facility during a period of extreme drought and the seawater desalination plants using reverse osmosis in drought stricken coastal regions.

• Membrane and Water Treatment
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• v.12 no.1
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• pp.1-9
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• 2021

This study optimized the chemical cleaning process of discarded RO membranes for reuse in less demanding separation processes. The effect of physicochemical parameters, including the temperature, cleaning time, pH of the cleaning solution, and addition of additives, on the cleaning process was investigated. The membrane performance was evaluated by testing the flux recovery rate and salt rejection before and after the cleaning process. High temperatures (45-50 ℃) resulted in a better flux recovery rate of 71% with more than 80% salt rejection. Equal time for acid and base cleaning 3-3 h presented a 72.43% flux recovery rate with salt rejection above 85%. During acid and base cleaning, the best results were achieved at pH values of 3.0 and 12.0, respectively. Moreover, 0.05% concentration of ethylenediaminetetraacetic acid presented 72.3% flux recovery, while 69.2% flux was achieved using sodium dodecyl sulfate with a concentration of 0.5%; both showed >80% salt rejection, indicating no damage to the active layer of the membrane. Conversely, 0.5% concentration of sodium percarbonate showed 83.1% flux recovery and 0.005% concentration of sodium hypochlorite presented 85.2% flux recovery, while a high concentration of these chemicals resulted in oxidation of the membrane that caused a reduction in salt rejection.

• Membrane Journal
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• v.4 no.1
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• pp.38-45
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• 1994

The experiment was conducted to evaluate the effects of variables in preparing TFC membrane by interfacial polymerization. Obtained results are as follow: As the concentration of MPD increses, the rejection rate incresed, the total volume flux was decresed. As the dipping time in MPD solution increases, the rejection rate increased, the total volume flux was increased until reach optimum point. As the dipping time in TMC solution increses, the total volume flux increased, the rejection rate was increased until reach optimum point. As the curing temperature increases, the total volume flux increased was an optimum point in the rejection rate. Since the quantity of generating hydrochloric acid was small, the required quantity of NaOH for neutriliztion was small. The post-treatment with ethanol, isopropanol and water in the temprerature ranging of $5~7^{\circ}C$ brought an increment of the rejection and the total volume flux, For water temperature ranging of $5~7^{\circ}C$was the optimum temperature in the post treatment.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.4 s.107
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• pp.16-24
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• 2004

The reduction of paper machine water usage is precursor to the water system closure of any mills. This reduction in water consumption reduces the loss of solids; especially fine particulates and their surface adsorbed chemical additives, from mills, which causes an inevitable increase of fine materials in papermaking systems. Also the reduction of paper machine water usage causes substantial increase of organic and inorganic substances in process water. The deterioration of the papermaking process water quality accompanying the reduction of papermaking system closure can be a prime source of the aggravation of paper quality and process efficiency. It is of great importance for paper mills to investigate the influence of the level of papermaking system closure on the paper properties and process runnabililty before implementing process closure. To predict the changes in paper properties at different levels of system closure, highly cotaminated white water was prepared using reverse osmosis technology and used to prepare handsheets from fine paper and newsprint stocks. Results showed that the quality of process water affects the strength. Preparation of highly contaminated process water and handsheet forming with headbox stocks provided important criteria to determine the relationship between the qualities of process water and paper products.

• Proceedings of the Membrane Society of Korea Conference
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• 2002.07a
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• pp.1-12
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• 2002

Desalination by reverse osmosis (RO), which first entered commercial use in the 1970s, was initially mainly used for treating brackish water. Technological progress led to the development of an RO membrane enabling single-pass seawater desalination. Toyobo succeeded in developing a single-pass seawater desalination RO module composed of hollow fiber type membranes made of cellulose triacetate in 1978, and then in 1979 began production of the first commercially available double-element module. This double-element module has many advantages suitable for seawater desalination. It has high chlorine tolerance and high salt rejection, derived from the properties of the membrane material, and it is highly resistant to fouling and scaling matters due to the unique flow pattern and fiber bundle configuration. These advantages help to explain why the Toyobo double-element module has been used so successfully at the many seawater desalination plants around the world. Since the 1980s, large plants capable of desalinating several tens of thousands of cubic meters a day have sprung up around the Mediterranean and In the Middle East. The Jeddah RO Phase I Plant, which has a capacity of 56, 800m$^3$/day, went into operation in 1989. In 1994, the same sized Phase II Plant came on stream, giving the plant a huge total capacity of 113, 600m$^3$/day. The plant constructor Mitsubishi Heavy Industries, Ltd. (MHI), and the RO membrane manufacturer Toyobo Co., Ltd. In 1998, the world's largest RO seawater desalination plant in operation, which has a capacity of 128, 000m$^3$/day and is run by Saudi Arabia's Saline Water Conversion Corporation (SWCC), went into operation at Yanbu. RO seawater desalination technology has thus already reached the stage of full-scale commercial use. In order to encourage its wider use, however, RO desalination needs to be made more economical by lowering construction and water treatment costs. Toyobo has therefore developed a new economical RO desalination system by a recovery ratio of 60% using a high-pressure module with a high product flow rate. In 2000, Toyobo high recovery membrane module was selected for the largest seawater desalination plant in Japan, which has a capacity of 50, 000m$^3$/day.

• Journal of Korean Society on Water Environment
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• v.26 no.2
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• pp.289-296
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• 2010

The purpose of this study is to evaluate various pre-treatment methods and proprieties of water quality for wastewater reuse using reverse osmosis (RO) processes. Secondary effluents were sampled from wastewater treatment plants and lab scale pre-treatments and RO filtration test were conducted systematically. Specifically, different types of pre-treatments, such as coagulation, microfiltration and ultrafiltration, were employed to evaluate the removal efficiency of particle and organic matters which may affect the membrane fouling rate. RO process was later added to eliminate trace amounts of remaining organic matters and salt from the raw water for wastewater reclamation. The permeate through the RO process satisfied water quality regulations for industrial water uses. The experimental results showed that the initial fouling tendency differed not only by the feed water properties but also by the membrane characteristics. Membrane fouling was greater for the membranes with large surface roughness, regardless of the hydrophobicity and zeta potentials. Thus both careful consideration of pre-treatment options and proper selection of RO membrane are of paramount importance for an efficient operation of wastewater treatment.

• Journal of Korea Water Resources Association
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• v.44 no.10
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• pp.809-817
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• 2011

We analyzed various cost components for approximately 40 small-scale island desalination plants operated by K-water. A significant factor affecting desalination cost was found, and we proposed a way to reduce desalination costs. All plants considered were reverse osmosis (RO) facilities. TDS concentrations of feed water varied from less than 1,000 mg/L (practically considered freshwater) to over 30,000 mg/L (nearly seawater). Analysis of desalination costs from 2005 to 2009 indicated that maintenance, labor, and energy were the three biggest components that accounted for 50.6%, 36.9% and 7.8%, respectively. It was well known that TDS of feed water directly affected energy needed for RO process. In this study we found that maintenance cost was also directly related to feed water TDS. This finding indicated that lowering feed water TDS might result in significant desalination cost reduction.