• Journal of Korean Society of Water and Wastewater
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• v.31 no.5
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• pp.409-414
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• 2017

In this study, we divided the process operation scenarios into three categories based on raw water temperature and turbidity. We will select and operate the process operation scenario according to the characteristics of the raw water. The number of algae in the DAF treated water has been analyzed to be less than 100 cells/mL. These results indicated that the DAF process is effective in removing the algae. In addition, the scenario of the integrated management decision algorithm of the DAF process was developed. DAF pilot plants ($500m^3/day$) process has shown a constantly sound performance for the treatment of raw water, yielding a significantly low level of turbidity (DAF treated water, 0.21~1.56 NTU).

• 기계와재료
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• v.13 no.4 s.50
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• pp.16-22
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• 2001

• Journal of Korean Society of Water and Wastewater
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• v.26 no.1
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• pp.107-113
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• 2012

Pollutants in aquaculture system effluent mostly originated from solid wastes including uneaten feed and excreta of cultured species. In this research, DAF(Dissolved Air Flotation) unit is suggested as an integrated solid control unit especially as a form of IIBG(Inline Injection Bubble Generation) process in aquaculture system. Solid removal performance of DAF unit was examined under various operation and salinity conditions with turbidity and suspended solid. Solid waste removal efficiencies were found to be affected by operation conditions including saturator pressure, recycle ratio, coagulant concentration. Solid removal efficiency was higher under higher saturator pressure and recycle ratio under which condition larger number of bubbles is generated. Coagulant is thought to have important role in creating bubble-particle aggregate by showing better removal efficiency with higher concentration. However higher saline water showed less effectiveness in removing solids by DAF(IIBG). Application of DAF(IIBG) process also showed additional effect in phosphate removal and DO(Dissolved Oxygen) supply. Phosphate existed in polluted water was removed up to 46% after treatment, which is thought to attribute to aluminium phosphate precipitation. And DO concentration was found to increase over 50% of initial saturation concentration after the injection of micro-bubbles. Through experiments on solid removal from aquaculture effluent, DAF(IIBG) process is estimated to be effective solid control method. This property can help aquaculture system being installed and operated simply and effectively.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.7
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• pp.743-750
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• 2008

In water treatment plant the Dissolved Ozone Flotation(DOF) System may be employed because this system has various abilities, such that it can remove SS using microbubbles, and it can exert strong oxidation power in removing taste and odor, color, and microbial agents. In order to investigate effectiveness of the DOF system in water treatment, removal characteristics of various water quality parameters were observed depending on the different levels of ozone concentrations. Removal efficiencies of water quality parameters in DOF system were compared with those in DAF(Dissolved Air Flotation) system and in CGS(Conventional Gravity Settling) system. Optimum ozone dose obtained in the pilot experiments was 2.7 mg/L. With increasing ozone dose higher than 2.7 mg/L, removal rates of turbidity, KMnO$_4$ consumption, UV$_{254}$ absorbance, and TOC were reversely lowered. High concentration of ozone dissociate organic matter in water, so that increasing dissolved organic level in effluent. Removal rates of water quality parameters at optimum ozone dose were obtained, such that removal rates of turbidity, KMnO$_4$ consumption, TOC, and UV$_{254}$ asorbance were 88.9%, 62.9%, 47%, and 77.3% respectively. Removal rate of THMFP was 51.6%. For all the parameters listed above, the DOF system was more effective than the DAF system or the CGS system. It is found that the DOF system may be used in advanced water treatment not only because the DOF system is more efficient in removing water quality parameters than the existing systems, but because the DOF system is also required smaller area than the CGS system for the treatment plant.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.6
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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 $40^{\circ}C$.

• Journal of Korean Society on Water Environment
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• v.28 no.3
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• pp.367-374
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• 2012

A flotation process has a shorter processing time and needs less space than a sedimentation process. Dissolved air flotation process (DAF) is an efficient flotation method and used in a conventional wastewater treatment process. However, DAF requires the circulation of water containing compressed air and requires expensive installation and operation cost. Plasma Air Flotation (PAF) process is able to float flocs by micro bubbles generated from underwater plasma without the circulation of bubbly water and additional saturators. Therefore, PAF can be an alternative solution overcoming economic barriers. In this study, Humic acid removal efficiency by PAF process was compared with that of sedimentation process. 44.67% and 87.3% reduction rate based on UV 254 absorbance has been measured in sedimentation and PAF respectively. In particular, PAF in the flocculation zone can dramatically remove humic acid from water. In flocculation zone, PAF can separate organic matters but sedimentation cannot.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.7
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• pp.617-624
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• 2015

The dissolved air flotation (DAF) system is a water treatment process that removes contaminants by attaching micro bubbles to them, causing them to float to the water surface. In the present study, two-phase flow of air-water mixture is simulated to investigate changes in the internal flow analysis of DAF systems caused by using different turbulence models. Internal micro bubble distribution, velocity, and computation time are compared between several turbulence models for a given DAF geometry and condition. As a result, it is observed that the standard ${\kappa}-{\varepsilon}$ model, which has been frequently used in previous research, predicts somewhat different behavior than other turbulence models.

• Economic and Environmental Geology
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• v.35 no.6
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• pp.581-588
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• 2002

• Journal of Korean Society of Water and Wastewater
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• v.19 no.4
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• pp.421-428
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• 2005

Dissolved air flotation (OAF) is a solid-liquid separation system that uses fine bubbles rising from bottom to remove particles in water. In this study, we investigated the effect of L/W (L; Length, W; Width) on the hydro-dynamic behavior in DAF system using CFD (Computational Fluid Dynamics) and ADV (Acoustic Doppler Velocimetry) technique. The factual full-scale DAF system, L/W ratio of 1:1, was selected and various L/W ratio (2:1, 3:1, 4:1 and 5:1) conditions were simulated with CFD. For modelling, 2-phase (gas-liquid) flow equations for the conservation of mass, momentum and turbulence quantities were solved using an Eulerian-Eulerian approach based on the assumption that very small particle is applied in the DAF system. Also, for verification of CFD simulation results, we measured the factual velocity at some points in the full-scale DAF system with ADV technique. Both the simulation and the measurement results were in good accordance with each other. As the results of this study, we concluded that L/W ratio and outlet geometry play important role for flow pattern and fine bubble distribution in the flotation zone. In the ratio of 1:1, the dead zone is less than those in other cases. On the other hands, in the ration of 3:1, the fine bubbles were more evenly distributed.

• Journal of Korean Society on Water Environment
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• v.35 no.1
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• pp.64-71
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• 2019

In recent years, carbon dioxide ($CO_2$) bubbles emerged as the most widely applied material with the recycling of sequestrated storage to decrease global warming. Flotation using $CO_2$ as an alternative to air could be effective in overcoming the high power consumption in the dissolved air flotation (DAF) process. The comparison of DAF and DCF system indicated that, the carbon dioxide flotation (DCF) system with pressurized $CO_2$ only requires 1.5 ~ 2.0 atm, while the DAF system requires 3.0 ~ 6.0 atm. In a bid to understand the characteristics of particle separation, the single collector collision (SCC) model was used and a series of simulations were conducted to compare the differences of collision and flotation between $CO_2$ bubbles and air bubbles. In addition, laboratory experiments were sequentially done to verify the simulation results of the SCC model. Based on the simulation results, surfactant injection, which is known to decrease bubble size, cloud improved the collision efficiency of $CO_2$ bubbles similar to that of air bubbles. Furthermore, the results of the flotation experiments showed similar results with the simulation of the SCC model under anionic surfactant injection. The findings led us to conclude that $CO_2$ bubbles can be an alternative to air bubbles and a promising material as a collector to separate particles in the water and wastewater.