• 상하수도학회지
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• 제25권4호
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• pp.489-495
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• 2011

Silt Density Index (SDI) has been used as a fouling index for reverse osmosis (RO) processes for decades. In order to decrease RO fouling, feed water should meet SDI standard, which was used to select a proper pretreatment system for RO processes. However, SDI is supposed to be sensitive only to particles larger than 0.45 ${\mu}m$ in terms of diameters while nanoparticles and dissolved organic matter can be potent foulants for RO processes. Our study started from the suspected performance of SDI as a RO fouling index. SDI data from pilot plants located world wide including South Korea were collected and analyzed. Suspended partcle concentration (i.e., turbidity and particle counts), and dissolved organic matter concentration (i.e., dissolved orgnaic carbon (DOC) concentration) data were also collected and compared to SDI values of same water samples. We found that SDI values were not only affected by suspended particle concentration but also by dissolved organic matter concentration. Therefore SDI can be used as a reasonable fouling index for RO feed water because the main foulants for RO processes are suspended particle and dissolved organic matter.

• 상하수도학회지
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• 제28권6호
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• pp.713-723
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• 2014

Biofouling in brackish water reverse osmosis (RO) membranes still needs extensive research to understand cause and mechanism and to obtain methods for reduction of its impact on RO applications. Natural compounds with biofilm formation inhibitory properties are being investigated. Two compounds, vanillin and Epigallocatechin gallate (EGCG), were selected due to their great potential on biofilm formation inhibition. Vanillin shows inhibition on quorum sensing mechanisms of biofilm formation. EGCG has potential to inactivate microbial activity. The two compounds were incorporated in typical polyamide reverse osmosis membranes and evaluated on flux behaviours and biofilm formation potential. The surface properties of membrane coated with vanillin were changed tremendously compared to those with EGCG. As a result, the flux was reduced substantially. The biofilm formation seems hindered with EGCG coated membranes compared to the virgin membranes. More research is needed to optimize coating methods applicable to RO membranes and to enhance biofouling reduction.

• 한국물환경학회지
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• 제28권5호
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• pp.657-662
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• 2012

This study was carried out to evaluate the removal rate of organic and inorganic matters from landfill leachate using pre-treatment process as coagulation and limonite adsorption, and membrane process as RO (reverse osmosis) and NF(nanofiltration). By adding limonite adsorption as pre-treatment process, about 40% of organic matters in leachate was removed through pre-treatment process and 74.7% of boron was removed after RO process without pH adjustment. The rejection rate of boron in RO process mainly depends on the pH and increased at pH value of 10. RO process was performed as two stage system adjusting pH condtion to 7 and 10 in second RO stage for boron removal. Most (>90%) of TOC, Cl- and inorganic matters as Ca was rejected in first RO stage, the residue was rejected in second RO and the rejection rate was above 97%. Considering economic efficiency of operation cost, NF substituted for the first RO and total removal rate of TOC was above 90%. Through RO system toxicity to Daphnia in leachate was removed completely.

• 한국물환경학회지
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• 제18권2호
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• pp.159-168
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• 2002

A lab-scale Reverse Osmosis(RO) membrane reactor was installed to investigate the membrane permeability, characteristics of membrane fouling at each conditions, and performance of elimination at different trans-membrane pressure(TMP) in the liquid fertilizer accumulated system. Experimental setup was divided to three different TMP conditions. As a result of experiment, permeability of RO membrane was proportional to the increase of TMP and temperature. After experiment was completed, two types chemical cleaning(remove the organic foulant and inorganic foulant) was done, and recover rate of permeability was each 99.8, 99.7 and 99.7%, respectively. From this experimental data, membrane fouling could be determined that the most of it was recoverable in this system, and major reason of fouling was concentration polarization. Elimination rate of solute substance in the liquid fertilizer indicated very stable(above 99%), except ammonia nitrogen, and the most stable elimination rate was investigated at the highest TMP condition (Run 3).

• Nuclear Engineering and Technology
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• 제47권7호
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• pp.859-866
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• 2015

The aim of this work is to investigate the transport mechanism of radioactive nuclides through the reverse osmosis (RO) membrane and to estimate its effectiveness for nuclide separation from radioactive liquid waste. An analytical model is developed to simulate the RO separation, and a series of experiments are set up to confirm its estimated separation behavior. The model is based on the extended Nernst-Plank equation, which handles the convective flux, diffusive flux, and electromigration flux under electroneutrality and zero electric current conditions. The distribution coefficient which arises due to ion interactions with the membrane material and the electric potential jump at the membrane interface are included as boundary conditions in solving the equation. A high Peclet approximation is adopted to simplify the calculation, but the effect of concentration polarization is included for a more accurate prediction of separation. Cobalt and cesium are specifically selected for the experiments in order to check the separation mechanism from liquid waste composed of various radioactive nuclides and nonradioactive substances, and the results are compared with the estimated cobalt and cesium rejections of the RO membrane using the model. Experimental and calculated results are shown to be in excellent agreement. The proposed model will be very useful for the prediction of separation behavior of various radioactive nuclides by the RO membrane.

• Membrane and Water Treatment
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• 제13권1호
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• pp.39-49
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• 2022

Seawater desalination is doubtlessly a viable option to supply fresh drinking water. Nevertheless, RO (reverse osmosis) desalination plants in specific areas may be intermittently operated to match the imbalance between water demand and supply. Although a handful of works have been done on other membrane systems, few studies have attempted to mitigate fouling in intermittent RO systems. Accordingly, the objectives of this paper were to examine the effect of the intermittent operation on RO fouling; and to compare four intermittent operation modes including feed solution recirculation, membrane storage in the feed solution, deionized water (DI) recirculation, and membrane storage in DI water. Results showed that intermittent operation reduced RO fouling under several conditions. However, the extents of fouling mitigation were different depending on the feed conditions, foulant types, and membrane lay-up methods. When the feed solution was recirculated during the lay-up, the restoration of the flux was less significant than that by the feed solution feed-up. The use of deionized water during the lay-up was effective to restore flux, especially when the feed solution contains scale-forming salts (CaSO₄) and/or colloidal silica.

• 상하수도학회지
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• 제28권5호
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• pp.549-554
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• 2014

This study was evaluated the applicability of the membrane filtration process (Micro Filtration (MF), nanofiltration membranes (NF), reverse osmosis (RO)) on the major radioactive substances, iodine ($I^-$) and cesium ($Cs^+$) using membranes produced in Korea and domestic raw water. Iodine ($I^-$) or cesium ($Cs^+$) in the microfiltration membrane (MF) process could not be expected removal efficiency by eliminating marginally at the combined state with colloidal and turbidity material. At the domestic raw water (lake water, turbidity 1.2 NTU, DOC 1.3 mg/L) conditions, nanofiltration membrane (NF) and reverse osmosis (RO) showed a high removal rate of about 88 ~ 99% for iodine ($I^-$) and cesium ($Cs^+$) and likely to be an alternative process for the removal of radioactive material.

• 대한환경공학회지
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• 제22권12호
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• pp.2125-2134
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• 2000

본 연구는 매립지에서 발생되는 침출수를 배출허용기준 이내로 처리함은 물론 경제적인 처리 공정을 개발하기 위한 것이다. 이를 위해 현장 pilot test 이전에 최적 공정 선정과 장치 설계인자를 도출하기 위해 실험실에서 기초실험을 수행하였다. 본 연구에서 개발하고자하는 처리공정은 역삼투시스템을 이용하는 공정인데 전처리로서 침지형분리막 생물반응기를 이용하였으며, 역삼투시스템에서 발생되는 농축수는 매립가스를 열원으로 하는 직화식 증발기를 이용하여 처리하는 공정이다. 실험결과 침지형분리막 생물반응기에서 SS, $BOD_5$, $COD_{cr}$, $NH_4{^+}-N$은 각각 99.0%, 43.0%, 12.9%, 48.5%, 18.7%의 제거효율을 보였다. 역삼투시스템온 $BOD_5$, $COD_{cr}$, $NH_4{^+}-N$, T-N을 각각 97.5%, 97.6%, 79.7%, 85.4% 제거할 수 있었다. 증발기는 $COD_{cr}$, $NH_4{^+}-N$, T-N을 각각 90.5%, 50.6%, 63.3% 제거할 수 있었으나 배출허용기준 이내로 처리하기는 어려운 것으로 나타나 응축수는 역삼투시스템 전단으로 보내서 전처리수와 함께 처리되어야할 것으로 나타났다.

• 멤브레인
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• 제23권5호
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• pp.343-351
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• 2013

혼합 비료를 유도용액으로 하는 정삼투식 해수담수화에서 담수화 성능에 대한 유도용액 농도의 영향을 조사하였다. 혼합비료용액(DS)의 농도가 증가함에 따라 수투과선속은 거의 선형적으로 증가하였으나, PR (performance ratio)은 감소하였다. 또한 혼합비료용액의 농도가 600 g/L일 때, 해수 및 탈이온수를 각각 공급용액으로 하였을 경우 각각의 PR은 5.39 및 6.50이었다. 혼합비료용액의 농도가 증가함에 따라 N, P 및 K의 역용질선속은 거의 선형적으로 증가하였으나, 비역용질선속은 감소하였다. 역용질선속과 비역용질선속은 모두 질소(N) > 칼륨(K) > 인(P) 순으로 높게 나타났다.

• 한국식품과학회지
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• 제29권2호
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• pp.279-283
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• 1997

국내에서 과잉 생산되고 있는 감을 이용하며 제품화할 뿐만아니라 고품질화 기술 개발을 위하며 막분리 시스템을 적용하였다. 즉 역삼투법을 이용하여 감과즙을 농축시에 시간, 압력, 공급액의 온도 및 농도가감 과즙의 투과플럭스에 미치는 영향을 조사하고 제품의 성분을 분석하여 다음과 같은 결과를 얻었다. 감 과즙을 역삼투막을 이용하여 농축시에 공정온도가 높고 공정압력이 높을수록 투과유속이 증가하였으며, 온도의 영향보다는 공정압력의 영향이 더 큰것으로 나타났다. 또한 감 과즙의 농도변화에 따른 투과유속의 변화는 공정압력이 낮을수록 더 급격히 저하되었으며, 본 실험에 사용한 역삼투막의 농축한계 농도는 $30^{\circ}Brix$ 전후를 나타내었다. 본 시스템을 이용하여 감 과즙을 농축시에 당의 잔존율은 90% 이상이었으며 공정조건에 큰 영향을 받지 않았다. 또한 휘발성 성분의 잔존율은 60% 이상이었으며, 공급액의 온도가 낮고 공정압력이 높을 때 잔존율이 높게 나타났다.