• 상하수도학회지
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• 제34권6호
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• pp.411-423
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• 2020

To remove phosphorus from the effluent of public wastewater treatment facilities, hundreds of enhanced phosphorus treatment processes have been introduced nationwide. However, these processes have a few problems including excessive maintenance cost and sludge production caused by inappropriate coagulant injection. Therefore, the optimal decision of coagulant dosage and automatic control of coagulant injection are essential. To overcome the drawbacks of conventional phosphorus removal processes, the integrated sedimentation and dissolved air flotation(SeDAF) process has been developed and a demonstration plant(capacity: 100 ㎥/d) has also been installed. In this study, various jar-tests(sedimentation and / or sedimentation·flotation) and multiple regression analyses have been performed. Particularly, we have highlighted the decision-making algorithms of optimal coagulant dosage to improve the applicability of the SeDAF process. As a result, the sedimentation jar-test could be a simple and reliable method for the decision of appropriate coagulant dosage in field condition of the SeDAF process. And, we have found that the SeDAF process can save 30 - 40% of coagulant dosage compared with conventional sedimentation processes to achieve total phosphorus (T-P) concentration below 0.2 mg/L of treated water, and it can also reduce same portion of sludge production.

• 상하수도학회지
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• 제20권2호
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• pp.303-309
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• 2006

Yongdam reservoir located in Jeoliabuk-do has had a lot of concerns for its algal blooming since it has started to fill water. Many water utilities near Yongdam area use reservoirs even though they have some problems with certain algae that cause tastes and odors and clog filters. In this research, dissolved air flotation (DAF) technology was examined for feasibility for removal of algae. OAF can save the capital cost for its compactness, because its hydraulic loadings (overflow rates) are 10 times higher than sedimentation, and hydraulic detention times are much shorter, typically 5 to 15 minutes. As a result of this research, PAC is effective rather than Alum to DAF for pretreatment. Higher DOC plays an important role to change zetapotential negatively to inhibit destabilization of particle to coagulation. The length of pipeline to carry pressurized water into reactor does not affect reaction.

• 상하수도학회지
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• 제35권1호
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• pp.1-14
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• 2021

Eutrophication and algal blooms can lead to increase of taste and odor compounds and health problems by cyanobacterial toxins. To cope with these eco-social issues, Ministry of Environment in Korea has been reinforcing the effluent standards of wastewater treatment facilities. As a result, various advanced phosphorus removal processes have been adopted in each wastewater treatment plant nation-widely. However, a lot of existing advanced wastewater treatment processes have been facing the problems of expensive cost in operation and excessive sludge production caused by high dosage of coagulant. In this study, the sedimentation and dissolved air flotation (SeDAF) process integrated with sedimentation and flotation has been developed for enhanced phosphorus removal in wastewater treatment facilities. Design and operating parameters of the SeDAF process with the capacity of 100 ㎥/d were determined, and a demonstration plant has been installed and operated at I wastewater treatment facility (located in Gyeonggi-do) for the verification of field applicability. Several empirical evaluations for the SeDAF process were performed at demonstration-plant scale, and the results showed clearly that T-P and turbidity values of treated water were to satisfy the highest effluent standards below 0.2 mg/L and 2.0 NTU stably for all of operation cases.

• 상하수도학회지
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• 제27권2호
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• pp.261-272
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• 2013

Algae boom (Red tide) in south coastal area of Korea has been appeared several times during a decade. If algae boom appears in the desalination plant, media filter and UF filter are clogged quickly, and the plant should be shutdown. In general, Algae can be removed from water by flotation better than by sedimentation, because of the low density of algal cell. The purpose of this study conducts the CFD simulation of DAF flotation basin to apply the design of the dissolved air flotation with ball filter in the Test Bed for SWRO desalination plant. In this study, Eulerian-Eulerian multiphase model was applied to simulate the behavior of air bubbles and seawater. Density difference model and gravity were used. But de-sludge process and mass transfer between air bubbles and seawater were ignored. Main parameter is hydraulic loading rate which is varied from 20 m/hr to 27.5 m/hr. Geometry of flotation basin were changed to improve the DAF performance. According to the result of this study, the increase of hydraulic loading rate causes that the flow in the separation basin is widely affected and the concentration of air is increased. The flow pattern in the contact zone of flotation basin is greatly affected by the location of nozzle header. When the nozzle header was installed not the bottom of the contact zone but the above, the opportunity of contact between influent and recycle flow was increased.

• 한국지반환경공학회 논문집
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• 제11권8호
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• pp.25-32
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• 2010

석유계 탄화수소 화합물로 인한 토양과 지하수 오염은 환경과 건강에 영향을 미치는 주된 원인으로 제기되어 왔다. 이러한 오염물질들은 흡착포, 활성탄 또는 중력 방식의 유수분리 장치 등을 이용하여 처리하고 있다. 하지만 이러한 경우 자유상 유류(free product)로 존재하는 경우에는 효과적이나 에멀젼 상태의 유류는 제거할 수 없는 것으로 알려져 있다. 따라서 본 연구에서는 굴착시 예상되는 지하수의 고농도 현탁성 고형물로 인한 지하수 처리시 문제점과 TPH(Total Petroleum Hydrocarbon)를 어떻게 효율적으로 제거할 수 있는지 방안을 제시하고자 한다. 고분자 폴리머를 사용하여 혼화 응집 실험을 수행한 결과 5분 이내에 SS(Suspended Solids)와 COD(Chemical Oxygen Demand) 농도가 지하수 수질 기준을 만족하는 것을 나타났으나, TPH 농도는 방류수 수질 기준을 만족하지 못하는 것으로 나타났다. DAF(Dissolved Air Flotation) 실험 결과 단일 DAF 공정으로는 방류수 수질 기준을 만족하지는 못하였다. 단일 DAF 반응조를 이용하여 DAF와 혼화 응집 반응을 동시에 수행하는 경우 20분에 모든 기준을 만족하는 것으로 나타났다.

• 상하수도학회지
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• 제22권5호
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• pp.531-540
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• 2008

The main advantage of dissolved air flotation (DAF) in water treatment process is the small dimension compared with conventional gravity sedimentation and it can be basically reduced by the separation zone performed with the short solid-liquid separation time. Fine bubbles make such a short time possible to carry out solid from liquid separation as a collector on the course of water treatment. Therefore, the dimension of separation zone in DAF process is practically determined by the rise velocity of the bubble-floc agglomerates, which is a floc attached with several bubbles. To improve flotation velocity and particle removal efficiency in DAF process, many researchers have tried to attach bubbles as much as possible to flocs. Therefore, the maximum number of attached bubble on a floc and the rise velocity of bubble-floc agglomerates considered as the most important factor to design the separation zone of flotation tank in DAF process was simulated based on the population balance theory. According to the simulation results of this study, the size and volume concentration of bubble influenced on the possible number of attached bubble on a floc. The agglomerates attached with smaller bubble was more sensitive to hydraulic loading rate in the separation zone of DAF process. For the design of a high rate DAF process applied over surface loading 40 m/hr. it is required a precise further study on the variation of bubble property and behavior including in terms of bubble size distribution.

• 상하수도학회지
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• 제18권2호
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• pp.191-200
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• 2004

DAF process has been designed considering raw water quality characteristics in Korea. Although direct filtration is usually operated, DAF is operated when the freshwater blooms occut or raw water turbidity become high. Pre-sedimentation iS prepared in case when raw water turbidity is very high by rainstorms. A main feature of this plant is that the operation mode can be changed (controlled) based on the characteristics of raw water to optimize the effluent quality and the operation costs. Treatment capacity (surface loading rate) and efficiency of DAF was found to be better than conventional sedimentation process. Moreover, low-density particles (algae and alum flocs) are easily separated while it is difficult to remove in sedimentation. One of the main concerns in adoption of DAF (Dissolved Air-Flotation) process is a high raw water turbidity problem. That is, DAF is not adequate for raw water, which is more turbid than 100NTU. In order to avoid this problem, pre-sedimentation basins are prepared in DAF plant to decrease the turbidity of DAF influent. For simulation of the actual operation, bench and full-scale tests were performed for highly turbid water conditions. Consequently, DAF process coupled with sedimentation is suggested that pre-sedimentation with optimum coagulation prior to DAF would be appropriate.

• 대한환경공학회지
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• 제35권12호
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• pp.929-936
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• 2013

DAF (Dissolved air flotation) 공정에서 공기포화장치(Saturator)와 미세기포 발생노즐은 미세기포 형성에 중요한 영향을 미치는 장치이다. 미세기포 발생 효율을 증가시키기 위해서는 공기포화장치 용기 안에서 기-액 접촉 효율을 증가시키고, 미세기포 발생노즐까지 이송 배관 내 압력을 일정하게 유지해 주어야 한다. 본 연구에서는 공기포화장치 내 순환수 유입 분사노즐과 포화수 이송 배관, 미세기포 발생노즐에 의한 미세기포 발생에 미치는 영향을 공기체적법과 기포 크기, 기포의 잔류시간 측정을 통해 비교해 보았다. 순환수 유입 분사노즐을 설치하고, 포화수의 이송 배관 내 압력손실이 발생하지 않는 구조, 미세기포 발생노즐의 통과유속을 증가시킬 경우 미세기포 발생 성능이 증가하였다.

• 대한환경공학회지
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• 제31권1호
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• pp.58-63
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• 2009

용존공기부상(Dissolved Air Flotation)은 조류, 휴믹물질, 및 저밀도 입자가 포함된 원수의 처리에서 침전지보다 우수한 성능을 가지는 공정이다. 본 연구는 실험실과 실규모의 DAF 펌프형 시스템을 이용하여 정수처리공정의 전처리(응집/응결) 조건에 따른 처리효율을 비교하여 나타하였다. 실규모 DAF 펌프형 시스템(Full scale DAF pump system ; F-DAF)은 처리용량과 수력학적 부하량을 각각 5,000 톤/일과 10 m/hr이며, F-DAF는 D 정수장의 원수에서 전처리(혼화/응집) 및 운전성능을 최적화하기 위해 운전하였다. 실험실 규모의 실험결과는 원수 탁도 13.8~56.3 NTU에서 최적 PSO-M 주입량은 2.7~4.5 mL/$m^3$/NTU이었다. 이와같이 최적 응집제 주입 조건에서 유출수의 탁도를 1.0 NTU 이하로 1개월 동안 유지하며 F-DAF의 운전이 가능하였다.

• 상하수도학회지
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• 제20권4호
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• pp.617-626
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• 2006

Compared with the sludge from gravity sedimentation, it is difficult for operations to settle the sludge occurred from dissolved-air-flotation (DAF). Even though there are some problems in treating DAF sludge with conventional gravity thickeners, those has been used until now. In this study, Solid Flux theory for gravity thickening was applied to the Solid Flux of DAF sludge through flotation in order to develop new methodology for treatment of DAF sludge. Also, characteristics of DAF sludge were investigated. From the experiment results, it was revealed that the higher the polymer dosage, at fixed the solid concentration, the greater the rising velocity becomes. When we applied solid flux theory, the relationship, which is similar to that of gravity thickening, has been achieved. Also, we could find the proper polymer dosage from the rising velocity is about 50 mg/L. Consequently, the limiting solid flux can be derived from the relationship between the total solid flux and the withdrawal velocity of DAF sludge. Furthermore, the factors, such as solid concentrations, bubble volume, pH, zeta potential, and temperature, have effects on the flotation and sedimentation for DAF sludge treatment.