• Journal of Korean Society on Water Environment
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• v.20 no.6
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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.

• Journal of Korean Society on Water Environment
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• v.22 no.1
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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.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.4
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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.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.3
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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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• v.2 no.4
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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.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.2
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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.

• Journal of Environmental Science International
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• v.25 no.7
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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.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.221-226
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• 2006

This study is about backwash condition and membrane fouling at continuous filtration process in ballast water treatment. Displayed result that handle particle contaminant and hydrospace organism included a number of ballast that is happened in ship using automatic back washing filter. Reason that removes first contaminant that is included in number of ballast is that heighten processing effect of after processing process of the filter. Another advantage is to drop off the solids with controlling revolution of drum screen in pretreatment filtration process. The capacity of pilot plant was $10m^3/h$. The result of the test, Backwash cycle time and duration time and a signification effect on the efficiency of system and backwash Backwash duration time was determined to be fixed in 6 seconds of the system with more than 95% removal rate, It needed 1hour backwash frequency. Filtration system removal aquatic organism over $70{\mu}m$ in ballast water. This study shows that the filtration treatment system has a potential for the treatment of ballast water.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.4
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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.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.9
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• pp.656-661
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• 2011

The performance of a domestic ceramic membrane with pore size of $0.1{\mu}m$ was evaluated to produce drinking water. A pilot-scale ceramic membrane filtration plant with a capacity of $1m^3/d$ was operated at the filtration flux of $3.0m^3/m^2{\cdot}d$ to investigate the effect of both backwash interval and pre-ozonation on TMP (trans-membrane pressure) increasing rate. The TMP increased with increasing the backwash interval. However, the application of pre-ozonation reduced the TMP increasing rate remarkably. When 1 mg/L of ozone was dosed with contact time of 5 min, TMP increasing rate at the backwash interval of 1 hr was reduced by 30%. This result indicated that pre-ozonation was very effective in reducing membrane fouling. There was almost no change in TMP increasing rate when the ozone contact time was maintained in the range of 5 to 15 min. Increasing ozone concentration up to 3 mg/L showed beneficial effect on TMP increasing rate.