• 상하수도학회지
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• 제33권6호
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• pp.413-420
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• 2019

Pretreatment system of desalination process using seawater reverse osmosis(SWRO) membrane is the most critical step in order to prevent membrane fouling. One of the methods is coagulation-UF membrane process. Coagulation-UF membrane systems have been shown to be very efficient in removing turbidity and non-soluble and colloidal organics contained in the source water for SWRO pretreatment. Ferric salt coagulants are commonly applied in coagulation-UF process for pretreatment of SWRO process. But aluminum salts have not been applied in coagulation-UF pretreatment of SWRO process due to the SWRO membrane fouling by residual aluminum. This study was carried out to see the effect of residual matal salt on SWRO membrane followed by coagulation-UF pretreatment process. Experimental results showed that increased residual aluminum salts by coagulation-UF pretreatment process by using alum lead to the decreased SWRO membrane salt rejection and flux. As the salt rejection and flux of SWRO membrane decreased, the concentration of silica and residual aluminum decreased. However, when adjusting coagulation pH for coagulation-UF pretreatment process, the residual aluminum salt concentration was decreased and SWRO membrane flux was increased.

• 한국막학회:학술대회논문집
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• 한국막학회 2003년도 추계 총회 및 학술발표회
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• pp.223-225
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• 2003

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1999년도 춘계학술발표회요약집
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• pp.319-319
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• 1999

• 상하수도학회지
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• 제25권3호
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• pp.285-291
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• 2011

Membrane fouling is an unavoidable phenomenon and major obstacle in the economic and efficient operation under sea water reverse osmosis (SWRO). When fouling occurs on the membrane surface, the permeate quantity and quality decrease, the trans-membrane pressure (TMP) and operation costs increase, and the membrane may be damaged. Therefore, chemical cleaning process is important to prevent permeate flow from decreasing in RO membrane filtration process. This study focused on proper chemical cleaning condition for Shuaibah RO plant in Saudi Arabia. Several chemical agents were used for chemical cleaning at different contact time and concentrations of chemicals. Also autopsy analysis was performed using LOI, FT-IR, FEEM, SEM and EDX for assessment of fouling. Specially, FEEM analysis method was thought as analyzing and evaluating tool available for selection of the first applied chemical cleaning dose to predict potential organic fouling. Also, cleaning time should be considered by the condition of RO membrane process since the cleaning time depends on the membrane fouling rate. If the fouling exceeds chemical cleaning guideline, to perfectly remove the fouling, certainly, the chemical cleaning is increased with membrane fouling rate influenced by raw water properties, pre-treatment condition and the point of the chemical cleaning operation time. Also choice of cleaning chemicals applied firstly is important.

• 상하수도학회지
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• 제24권1호
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• pp.93-101
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• 2010

Reverse osmosis (RO) membranes have been widely used for desalination as well as water and wastewater treatment facilities. Cleaning process is important to maintain stable operation as well as prevention of membrane fouling. Purpose of this research is to analyze electrostatistic and chemical characteristics after cleaning of RO membrane against $SiO_2$ scale. Four RO membranes of polyamide are used and examined about effect of chemical cleaning. EDTA (ethylene diamine tetraacetic acid) and SDS (sodium dodecil sulfate) and NaOH are applied for cleaning process after operation in synthetic water. Then, cleaning was performed with chemicals such concentration as 6hr, 12hr and 24hr, respectively. As a result, transmittances of FT-IR of four membranes are compared at each cleaning concentration. Ta/Tv shows difference of chemical composition between new membrane and cleaning membrane after cleaning. Type B of RO membrane is turned out to be most vulnerable to cleaning among four membranes. In terms of zeta potential, new membrane has -16 mV to +6 mV on pH while scaled membrane has -18 mV to 2 mV. However, it changed -23mV to 0.9 mV after cleaning. In comparison with existing salt rejection of RO membranes after cleaning, the rejection of the membranes goes down 0.7% maximum. Though cleaning changes the characteristics of membrane surface, it does not greatly affect salt rejection. pH is a critical factor to flux change in PA (polyamide) membrane.

• 상하수도학회지
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• 제26권6호
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• pp.807-813
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• 2012

Flocculation and flotation are used as pretreatment steps prior to the reverse osmosis (RO) process. During seawater treatment, high temperature can change the water chemistry of seawater during the process of coagulation. It also affects bubble volume concentration (BVC) and bubble characteristics. Coagulants such as alum and ferric salts at $40^{\circ}C$ can also change flux rates in the seawater reverse osmosis (SWRO) process. In this study, the bubble characteristics in dissolved air flotation (DAF), used as a SWRO pretreatment process, were studied in synthetic seawater at $20^{\circ}C$ and $40^{\circ}C$. The flux of an RO membrane was monitored after dosing the synthetic seawater with coagulants at different temperatures. Results showed that BVC increases as the operating pressure increases and as the salt concentration decreases. The bubble size released at $40^{\circ}C$ is far smaller than that at $20^{\circ}C$The addition of a ferric salt is effective for turbidity removal in synthetic seawater at $20^{\circ}C$; it is more effective than alum. When synthetic seawater was dosed with a ferric salt, the RO membrane flux increased by 27 % at $40^{\circ}C$.

• 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.

• 상하수도학회지
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• 제25권2호
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• pp.177-184
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• 2011

Membrane fouling is an unavoidable phenomenon in operation of seawater reverse osmosis (SWRO) and major obstacle for economic and efficient operation. When fouling occurs on the membrane surface, the permeate flux is decreased, on the contrary, the trans-membrane pressure (TMP) is increased, therefore operation and maintaining costs and potential damage of membranes are able to the pivotal risks of the process. Chemical cleaning process is essential to prevent interruptions for effective RO membrane filtration process. This study focused on proper chemical cleaning condition for polyamide RO membranes of 4 companies. Several chemical agents were applied for chemical cleaning under numbers of operating conditions. Additionally, a monitoring tool of FEEM as autopsy analysis method is adapted for the prediction of organic bio-fouling.

• 상하수도학회지
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• 제33권6호
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• pp.437-446
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• 2019

Reverse osmosis seawater desalination facilities can extend the cleaning cycle and replacement time of the reverse osmosis membrane by pretreatment process. Selection of pretreatment process depends on water quality. It was attempted in this study to select approriate pretreatment process for the Masan bay, which was high in particles and organic content. For this purpose, performances of pretreatment processes such as filter adsorber (FA), pore controllable fiber (PCF), and ultrafiltration (UF) were compared based on the silt density index (SDI). The SDI value of the filtrate should be less than 3. The study results showed that UF can produce the filtrate quality satisfying the requirement. However, the transmembrane pressure (TMP) of UF increased quickly, reaching 0.6 bar within 4 days. In order to secure stable operation, FA and PCF were combined with UF. The study results showed that combination of PCF and UF was able to extend the filtration duration (more than 2 months) until to reach TMP of 0.6 bar.

• 상하수도학회지
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• 제33권4호
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• pp.281-289
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• 2019

Desalination plants are generally studied with higher operating costs compared to water supply facilities. This study was conducted to reduce the cost of water production and to preserve existing water resources. Therefore, the purpose of this study was to utilize the control valves to increase maximum efficiency, thereby reducing the power of the pumps and operating costs. Specific energy consumption was shown to reduce the process operating power by up to 1.7 times from 6.17 to $3.55kWh/m^3$ based on seawater reverse osmosis 60 bar. In addition, the water intake process was divided into pre, inter, and post-according to the use method of blasting, and the water treatment process was divided into pre, inter, and post blending. In order to reduce power consumption, the blending process was combined to operate the facility, which resulted in the reduction of power consumption in the order post > pre-inter> inter blending.