• 한국물환경학회지
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• 제20권6호
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• pp.652-656
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• 2004

Both surface wash and backwash are considered as one of the most important methods that can improve the filtration efficiency in the existing water treatment plant. This study has mainly focused on the improvement of filtering efficiency by controlling surface wash and backwash time, and water level before backwash (when drained up to the trough, when drained up to 10 cm above filter bed, and when drained below 10 cm filter bed). Filtration efficiency was shown a little bit of differences depending on the operating conditions like surface wash injection pressure, the distance control between filter bed and the facility, and the types of surface wash. When the water level before backwash was reached up to 10 cm below filter bed after draining, however, the filtration velocity and the turbidity removal efficiency in the filter bed was improved. When the surface wash followed by backwash is longer, it showed a similar result. Because the proper adjustment of surface washing time makes filtration efficiency higher, therefore, it is necessary to set up the backwash time moderately.

• 한국물환경학회지
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• 제22권1호
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• pp.17-22
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• 2006

This study is about backwash condition and membrane fouling at continuous coagulation/ultrafiltration process in water treatment. The capacity of pilot plant was $0.06m^3/d$. The result of the test, Backwash cycle time and duration time had a significant effect on the efficiency of system and backwash. Backwash duration time was determined to be fixed in 30 seconds for the system with more than 95% recovery rate, It needed 30 minute backwash frequency. During the continuous operation, membrane fouling was analyzed by determining the filtration resistance ($R_i$) and cake layer resistance ($R_c$). At the initial stage, filtration resistance highly influenced the fouling behavior. But after 1.5 hours, cake layer resistance became more important than filtration resistant.

• 상하수도학회지
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• 제22권4호
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• pp.437-444
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• 2008

Many other countries have investigated the new backwash water treatment process to save the existing water resource. There are various methods for reusing backwash water, but the membrane system has received the most interest for its efficiency. The objective of this study was to certify the application of membrane filtration system for the backwash water treatment. The experiment equipment was composed of Lab scale tubular membrane filtration system. Generally, cross-flow operation mode is used in the tubular membrane system but cross-flow operation mode demands high electric cost mainly for the pump energy. So to cut off electric cost, dead-end operation mode was used in this experiment. Filtration and bleed operation cycle was used in this membrane system. Backwash water was concentrated during the filtration process and when backwash water reached our target suspended solid concentration, it was discharged from this system. For efficient operation of filtration and bleed, mathematical matrix was drawn up and with this matrix we could simulate various sets of filtration and bleed time.

• 상하수도학회지
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• 제13권3호
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• pp.61-72
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• 1999

To obtain the experimental data for design and operation of actual filtration processes, a sand filter and three kinds of dual media filters in pilot-plant scale were operated in this study. We analyzed the effect of filter medium composition on the filter performance and the effects of backwash water flow rates, length of stream line and air flow rate on the filter backwash efficiency. We also compared the efficiencies of the combined air-water backwashing and the water backwashing in dual media filters. As the backwash water flow rates or the length of stream line increased, the final turbidity of backwash water was decreased and the filtration duration time after backwash was increased. In the case of the combined air-water backwashing, the backwash water quantity needed for backwashing the dual media filters could be decreased. The total volume of filtered water for the dual media filters during filter run was over three times larger than that for the sand filter. The dual media filters could be operated at a high filtration rate of 360 m/day.

• Membrane and Water Treatment
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• 제2권4호
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• pp.225-237
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• 2011

In this study, response of reversibility of membrane flux during chemically enhanced backwash (CEB) to changes in filtration time, filtration flux and coagulant concentration dosing during ultrafiltration (UF) process was investigated using a regression model. The model was developed via empirical modelling approach using response surface methodology. In developing the model, statistically designed UF experiments were conducted and the results compared with the model output. The results showed that the performance of CEB, evaluated in terms of the reversibility of the membrane flux, depends strongly on the changes in coagulant concentration dosage and the filtration flux. Also the response of the reversibility of membrane flux during CEB is independent of the filtration time. The variance ratio, VR << $F_{value}$ and $R^2$ = 0.98 obtained from the cross-validation experiments indicate perfect agreement of the model output with experimental results and also testify to the validity and suitability of the model to predict reversibility of the membrane flux during CEB in UF operation.

• 상하수도학회지
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• 제23권2호
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• pp.207-214
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• 2009

This study examines the optimum filtration conditions in pretreatment of seawater desalination by reverse osmosis. For this purpose, Masan bay seawater is treated through a gravity filter column while $FeCl_3$ is added as coagulant. The conditions of coagulantd osage, media depth, filtration rate, and backwash time are evaluated. The study results show that the filtrate quality improved with increasing coagulant dosage, but head loss rapidly increased. After 4mg/L, the unit filter run volume reduced to less than $200m^3/m^2$. Considering the head loss development, 4mg/L is determined as the optimum dosage. The better filtrate qualities are obtained with depth of 100cm than that of 80cm. The two stage filtration, which outperformed the single stage filtration, is suggested for treatment of Masan bay. The filtration rate of 5m/h is decided as the optimum condition considering the head loss development. At 10m/h, the filtrate quality deteriorated even though the extent was minimal, and head loss increased rapidly. The backwash time of 10 min is decided appropriate.

• 한국환경과학회지
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• 제25권7호
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• pp.999-1005
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• 2016

The H water treatment plant has been operating since 1982 and has had no renovation. It is assumed that the filters have been operated for more than 30 years and therefore are deteriorated. Many of the filters show an unequal state of air scouring during backwashing. For this study one filter, which was presumed most deteriorated among eighteen filters, was selected as a model filter for renovation. Some of the effects seen after renovation of the underdrain system were a lower average filtrated turbidity by approximately 0.02 NTU and an equal backwash state throughout the filter bed. Sand wash efficiencies by backwash before renovation of the underdrain system were 28%, 8%, and 5% at the surface, 50 cm depth, and 100 cm depth, respectively, and after renovation of the underdrain system were 94%, 26%, and 15%, respectively. The standard deviation of the effective sand size was 0.025-0.033 mm before renovation of the underdrain system and 0.002-0.011 mm after renovation of the underdrain system, meanings there was equal backwash pressure throughout the filter. Filtration time after renovation was approximately 2 times longer than before renovation.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 춘계학술대회 및 창립 30주년 심포지엄(논문집)
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• pp.221-226
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• 2006

본 연구는 밸러스트수를 처리하기 연속여과 공정에서 역세척 조건에 따른 막오염 특성을 관찰하였다. 선박에서 발생되는 밸러스트수를 전처리하기 위하여 수중에 포함되어 있는 입자상 오염물질과 수중생물체를 자동역세척 여과장치를 이용하여 처리한 결과 클 나타내었다. 밸러스트수를 처리하기 위한 전처리의 장점은 입자상의 오염물질을 제거하여 후처리공정의 처리효과를 높이는데 있다. 처리장치의 용량은 $10m^3/h$ 이다. 테스트 결과 역세척 주기와 역세척 지속시간은 전체 시스템의 효율과 역세척 효율을 고려하여 역세척 지속시간은 6초가 적당한 것을 나타났으며, 도출된 지속시간을 기준으로 하여 95%의 제거효율은 얻었다. 1시간동안의 역세척 주기가 필요하였다. 여과처리를 통하여 $70{\mu}m$ 이상의 식물성 플랑크톤과 동물성 플랑크톤을 포함하는 수중생물체를 제거할 수 있었다. 실험결과를 통하여 밸러스트수 처리에 적용 가능한 기술임을 알 수 있었다. 이 연구에서 밸러스트수 처리를 위한 우수한 여과처리시스템임을 보여 주었다.

• 상하수도학회지
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• 제21권4호
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• pp.503-508
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• 2007

Small scale D-water treatment plant(WTP) where has slow sand filtration was using raw water containing high concentration of manganese (> 2mg/l). The raw water was pre-chlorinated for oxidation of manganese and resulted in difficulty for filtration. Thus, sometimes manganese concentration and turbidity were over the water quality standard. Two stage rapid manganese sand filtration pilot plant which can treat $200m^3/d$ was operated to solve manganese problem in D-WTP. The removal rate of manganese and turbidity were about 38% and 84%, respectively without pH control of raw water. However, when pH of raw water was controlled to average 7.9 with NaOH solution, the removal rate of manganese and turbidity increased to 95.0% and 95.5%, respectively and the water quality of filtrate satisfied the water quality standard. Manganese content in sand was over 0.3mg/g which is Japan Water Association Guideline. The content in upper filter was 5~10 times more than that of middle and lower during an early operation but the content in middle and lower filter was increased more and more with increase of operation time. This result means that the oxidized manganese was adsorbed well in sand. Rapid manganese sand filter was backwashed periodically. The water quality of backwash wastewater was improved by sedimentation. Thus, turbidity and manganese concentration decreased from 29.4NTU to 3.09NTU and from 1.7mg/L to 0.26mg/L, respectively for one day. In Jar test of backwash wastewater with PAC(Poly-aluminum chloride), optimum dosage was 30mg/L. Because the turbidity of filtrate was high as 0.76NTU for early 5 minute after backwash, filter-to-waste should be used after backwash to prevent poor quality water.

• 대한환경공학회지
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• 제33권9호
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• pp.656-661
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• 2011

본 연구에서는 공경 $0.1{\mu}m$, 막여과 유속$3.0m^3/m^2{\cdot}d$의 국산 세라믹 막을 이용하여 음용수를 생산하는 기술에 대해 조사하였다. 세라믹 막의 성능 평가를 위해 $1m^3/d$ 규모의 pilot-scale 실험장치를 제작하였으며, 역세주기에 따른 차압변화와 전오존이 차압변화에 미치는 영향을 조사하였다. 차압상승률은 역세주기에 비례하여 증가하였으나, 전오존 주입을 통해 차압상승률을 낮출 수 있었다. 이 결과는 전오존이 파울링 감소에 효과가 있음을 의미한다. 1 mg/L의 전오존을 주입하고 5 min간 접촉하였을 때, 역세주기 1시간에서 차압상승률은 약 30% 감소하였다. 전오존 접촉시간을 5~15 min으로 변경하면서 운전한 결과, 접촉시간에 따른 차압상승률에는 차이가 없었다. 그러나, 차압상승률은 오존 주입농도가 증가하면 감소하는 경향을 보였다.