• 대한환경공학회지
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• 제38권9호
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• pp.513-520
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• 2016

수중에 용존된 가스뿐 아니라 소독부산물과 같은 휘발성 화합물은 탈기에 의해 효과적으로 제거할 수 있는 것으로 알려져 있다. 탈기공정에 사용되는 미세 기포는 수백~수천 ${\mu}m$이지만 부상 공정의 기포는 수 ${\mu}m$ 정도로 작다. 이에 따라 부상공정에서의 마이크로 기포는 수중의 휘발성 화합물이 대기로 방출될 수 있는 매우 넓은 기-액 비표면적을 제공한다. 또는 마이크로 기포는 상승 속도가 느려서 휘발성 화합물이 방출될 수 있는 긴 체류시간을 갖게 된다. 본 연구에서 일련의 탈기와 부상 실험을 실시한 결과, THMs의 제거율에서 상당히 큰 차이가 있었다. THMs의 물질전달계수 $K_La$ 역시 큰 차이를 보였다. 따라서 부상공정에서 THMs과 같은 휘발성 화합물을 제거하기 위해서는 일반적으로 입자제거를 위하여 적용되는 통상적인 운전범위보다 더 높은 기포체적농도가 필요함을 알 수 있다.

• 대한환경공학회지
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• 제30권7호
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• pp.743-750
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• 2008

본 연구에서는 용존오존부상법(Dissolved Ozone Flotation; DOF)을 이용한 정수처리 효과를 파악하기 위하여 적정 오존 주입 농도와 오존 주입 농도별 처리 특성에 대해서 연구하였으며, 또한 용존공기부상법(Dissolved Air Flotation; DAF) 및 중력식 침전법(Conventional Gravity Sedimentation; CGS)과 DOF의 처리 성능을 비교하였다. 최적 오존 주입 농도를 산정하기 위한 실험에서 최적 오존 주입농도는 2.7 mg/L로 나타났으며, 오존 주입 농도가 증가할수록 탁도 및 KMnO$_4$ 소모량, UV$_{254}$ 흡수도, TOC 등과 같은 제거효율이 낮아지는 것으로 나타났다. DOF와 DAF, CGS의 처리성능을 비교한 결과 오존 주입 농도 2.7 mg/L로 운전한 DOF시스템의 탁도 제거효율은 88.9%, 유기물질 항목의 경우 KMnO$_4$ 소모량은 62.9%, TOC 47%, 그리고 UV$_{254}$ 흡수도 77.3% 그리고 THMFP 제거율의 경우 51.6%로 다른 두 공정보다 높거나 비슷하게 나타났다. 따라서 응집 부상 공정과 오존 산화 공정이 하나의 반응기에서 일어나는 DOF 시스템은 정수처리시설의 소유부지 감소와 기존 CGS 시스템에서 처리가 어려운 조류 및 용존성 유기물질의 제거를 통해 소독부산물의 생성을 감소시킴으로 향후 고도정수처리시스템으로 적용 가능성이 충분한 것으로 판단된다.

• 대한기계학회논문집B
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• 제39권7호
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• pp.617-624
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• 2015

용존공기부상법이란 오염물에 미세기포를 부착하여 수표면으로 부상시킴으로써 이를 제거하는 수처리 방법이다. 본 연구에서는 난류모델에 따른 용존공기부상조 내부 유동해석의 변화를 고찰하기 위해 물과 기포의 혼합물에 대한 2상 유동을 모사하였다. 이때, 주어진 용존공기부상조 형상 및 조건에 대하여 다양한 난류모델에 따른 용존공기부상법 내부의 미세기포 분포량, 계산시간 및 수렴성 등을 비교하였으며, 그 결과 기존에 주로 사용되었던 표준 ${\kappa}-{\varepsilon}$ 모델이 타 난류모델과는 다른 거동을 예측하는 것으로 확인되었다.

• 상하수도학회지
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• 제10권2호
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• pp.80-87
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• 1996

Treatment efficiencies of water quality parameters such as $KMnO_4$ Demand, $UV_{254}$, Turbidity, and LAS(Linear Alkyl Sulfonate) were compared between DAF(Dissolved Air Flotation) and CGS(Conventional Gravitational Sedimentation). The experimental results showed that DAF is much more efficient in treatment of water quality parameters than CGS. The optimum pH was about 7, and optimum alum($Al_2(SO_4)_3$) dose was about 30 ppm for DAF treatment. Economic aspects were also analyzed for bath systems. Even though production cost per ton of drinking water is slightly higher in DAF than in CGS, it turned out that construction cost and land value of CGS far surpass the production cost. DAF system is superior in removal efficiency of impurities and in production cost as a whole to CGS system.

• 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 $40^{\circ}C$.

• 자원환경지질
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• 제35권6호
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• pp.581-588
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• 2002

• 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.

• 한국물환경학회지
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• 제23권6호
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• pp.837-842
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• 2007

This study was conducted to test the effect of residual Al on plankton community after dissolved air flotation (DAF) application. Growth rate of phytoplankton after DAF application ($0.37day^{-1}$) was about 2 times lower than that before DAF application ($0.70day^{-1}$). Under the condition of addition of nitrogen and phosphorus without light, growth rate phytoplankton in treatment without residual Al increased in difference with showing the negative growth rate in treatment with residual Al. Under the condition of light without addition of nutrient, growth rate of phytoplankton was no noticeable difference between the before and after DAF application. The relatively high settling rate (0.47 m/day) was observed in treatment after DAF application. Although the abundance of rotifer decreased, the abundance of copepod and cladoceran such as Daphnia galeata, Diaphanosoma sp. and Bosmina longirostris with relative higher grazing was no noticeable difference between the before and after DAF application. In the treatments before and after DAF application with zooplankton, growth rate of phytoplankton was $0.41{\pm}0.08day^{-1}$, $0.20{\pm}0.03day^{-1}$, respectively. This difference was in treatment after DAF application similar with those in treatments before and after DAF application without zooplankton. Those indicate that the filter-feeding effect of zooplankton on phytoplankton community may be not changed by residual Al after the DAF application. These results suggest that residual Al after DAF application be to improve water quality by inhibition of growth rate as well as increasing settling rate of phytoplankton.

• 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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• 제19권2호
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• pp.155-160
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• 2005

Gravity thickening process has been widely used in WTP sludge thickening at domestic water treatment plant. The operation method of the process is very simple, however, the process requires long detention time about 24~48 hours for sludge thickening, uses polymer, and low total solids of thickened sludge to increase sludge thickening efficiency. To solve there problems, we studied about flotation process, especially, electro-flotation (EF) process in WTP sludge thickening. Electro-flotation process is simpler than dissolved-air-flotation(DAF) process because EF needs only electrode and current to generate micro-bubbles and the operation is easy. This study was performed at two batch columns to compare interface height, total solids, effluent turbidity between an electro-flotation thickening and a gravity thickening. According to the result, an electro-flotation thickening was that interface height was decreasing, total solids had high concentration, and effluent turbidity was low in comparison with a gravity thickening. Also, it will make the high efficiency of following process, such as a dehydrating process and digestive process. because of high total solids and low moisture content in the sludge.