• 상하수도학회지
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• 제25권5호
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• pp.659-666
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• 2011

Although DAF(Dissolved Air Flotation) has been successfully accepted for water and wastewater treatment, the fundamental characteristics of the process have not been fully investigated. Water is saturated with compressed air to dissolve the air into the water at high pressure in saturation tank. Then the water containing dissolved air is released into a floatation tank at a lower pressure, generating micro-bubbles that rise gently through the water and carry the suspended matter to the surface. This study investigated the removal of sewage using automatic mixture type DAF pump and non-powered flotation tank. Characteristics of two devices were compared and analyzed with samples. The results showed that the PAC exhibited higher performance than other coagulants. When air dosage was 2.5ml/l/min, treatment was stable in operation. In the DAF pump with a pressure of 4 atm., the average size of bubbles was 36.2${\mu}m$. Removal efficiency of SS was 80%. At this time removal efficiency of COD was about 80%, of T-N was 30% and T-P was 70% in stable operation. It was concluded that DAF pump system with micro bubble performed higher efficiencies compared to general DAF system for treating wastewater.

• 상하수도학회지
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• 제18권2호
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• pp.242-246
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• 2004

Dissolved air flotation (DAF) is an effective solid/liquid separation process for low density particles, such as algal flocs, humus materials and clay particles produced from low turbidity water. The fraction of humic substances for natural organic matters (NOMs) are considered problematic in water because it can readily react with chlorine to form harmful by-products (trihalomethanes) and can be exposed to undesirable color, tastes and odors in drinking water. A broad class of NOMs includes fulvic acid, humic acid and humin. This paper will discuss the results from a study that performed with a DAF pump process using synthetic wastewater contained humic substance. Batch jar tests were performed to evaluate coagulant dose and recycle ratio on flotation efficiency.

• 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.

• 한국환경과학회지
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• 제20권5호
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• pp.639-645
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• 2011

This study found that flotation efficiencies for removing algae and micro particles in raw water were optimized on mixing intensity and time of the mixing and flocculation conditions with a continuous DAF system. It is more efficient for mixing intensity at 23.1 $s^{-1}$ and time at 660 s(Gt value : 15246) to float flocculated floc with the raw water in M water treatment plant. Flotation efficiency was more than about 0.9 when operated pressure and A/S ratio were sustained at 5 $kg_f{\cdot}cm^{-2}$ and up to 0.056 $mL{\cdot}mg^{-1}$. The continuous DAF system made by the study could be continuously operated for 20 days and sustained not exceeding 4 NTU with raw water with low turbidity(13.4~9.8 NTU).

• 한국환경과학회지
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• 제23권1호
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• pp.97-104
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• 2014

The sludge flotation/thickening apparatus equipped a micro-bubble generating pump was used to investigate micro-bubble generating properties on operational parameters. We evaluated micro-bubble generating properties as results to be operated the apparatus by operational parameters which are pump discharge pressure, air/water ratio(A/W ratio), air flow rate, and water flow rate. Micro-bubble generating efficiencies in pumps without recycling flow and with 50% of recycling flow was found to be very efficient on optimum A/W ratio from 1.06 to 3.62% and optimum A/W ratio from 1.05 to 4.06%, respectively. In condition of 3.6% of A/W ratio, we showed that the apparatus could be generated 36,000 ppm of micro-bubble concentration to be optimum treatment efficiency in sludge thickening process.

• 한국환경과학회지
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• 제25권6호
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• pp.829-837
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• 2016

The mechanism of micro-bubble generation with a pump is not clarified yet, so the design of water treatment systems with a micro-bubble generating pump is based on trial and error methods. This study tried to explain clearly quantitative relationships of experimental micro-bubble concentration ($C_{air}$) of continuous operation tests with a micro-bubble generating pump and theoretical air solubility. Operation parameters for the tests were discharge pressure ($P_g$), water ($Q_{w0}$) and air ($q_0$) flow rates, orifice diameter ($D_o$), and retention time (t). The experimental micro-bubble concentrations ($C_{air}$) at 4.8 atm of discharge pressure ($P_g$) were in the range of 21.04 to 25.29 mL/L. When the retention time (t) by changing the pipe line length ($L_p$) increased from 1.22 to 6.77s, the experimental micro-bubble concentrations ($C_{air}$) increased from 25.86 to 30.78 mL air/L water linearly. The dissolved and dispersed micro-bubble concentrations ($C_{air}$) are approximately 4 times more than the theoretical air solubility.

• 한국환경과학회지
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• 제23권11호
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• pp.1835-1842
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• 2014

The goal of this study was to evaluate micro-bubble concentration ($C_{air}$) in water by air/water ratio (A/W ratio) with a micro-bubble generating pump. The estimation of micro-bubble concentration is based on the balance of inlet/outlet air and water flow rate. On net A/W ratio to be generated micro-bubble, we found that the obtained the $C_{air}$ are shown as a function of discharge pressure ($P_g$) of the micro-bubble generating pump. The correlation of the $C_{air}$ and the $P_g$ ($C_{air}=3.261P_g-1.754$) was adequately described by the least square methods with a high correlation coefficient (r = 0.9459) and calculated values fit the experimental data quite well. The $C_{air}$ was lower than theoretical dissolved air concentration ($C_{aq}$) calculated by Henry's law. The $C_{air}$ for being operated the micro-bubble generating pump was 6.75 - 39.53 mL/L, however, we found that the optimum of the $C_{air}$ to generate micro-bubble was the range from 10 to 12 mL/L.

• 한국물환경학회지
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• 제21권5호
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• pp.528-534
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• 2005

Ozone, a powerful oxidant, is widely used to remove microorganisms, pesticides, taste and odor compounds effectively. Dissolved air flotation (OAF) has been known as an economical process for treating algae and low turbid water quality. An ozoflotation system, combining ozone and OAF processes, has a merit which can operate the ozonation and flotation process simultaneously in a single compartment. This study investigated the application of the ozoflotation process for advanced water treatment by carrying out the pilot-plant experiment. During the test, ozone microbubbles were generated through a OAF pump and many kinds of parameters were evaluated under several conditions, such as raw water flow rate and ozone dose. As a result of the test, the optimum operating conditions of ozoflotation were decided to be 1.2 mg/L ozone dose and about 34 minute Hydraulic retention time (HRT). Finally, it could be demonstrated that the ozoflotation system can effectively improve the drinking water quality.