• Journal of Korean Society of Water and Wastewater
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• v.22 no.3
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• pp.359-366
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• 2008

The series of experiments under the various conditions were carried out to evaluate the feasibility of dissolved air flotation (DAF) as an alternative of conventional gravity sedimentation (CGS) and to investigate the decrease of the loadings following to biological wastewater treatment processes in livestock wastewater system. On the basis of the experiment result between CGS and DAF processes, for the other water quality criteria as well as suspended solid the removal efficiency of DAF process was about 20~25 % better than CGS process on average. In addition, the particle removal efficiency of DAF process became higher in proportion as the increase of air to solid (A/S) ratio and the general wastewater treatment efficiency of DAF process was enough to meet the requirement of loading decrease to following biological process even at low A/S ratio range. Though DAF process is widely known as an solid separation unit, there was not the notable relationship between particle separation efficiency and several pollutant removal efficiencies like $COD_{Cr}$ and nutrients (T-N, T-P). Assume that the $COD_{Cr}$ was removed as the fraction of particle separation in this experiment, the removal efficiency of T-N and T-P were sensitive to removal efficiency of $COD_{Cr}$, especially.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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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.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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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.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.516-520
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• 2008

There are many water treatment plants built over couple of decade ago in Korea. For most of those plants, they are required a countermeasure to cope with the deterioration caused from the superannuated facilities and the objective materials change of water treatment from inorganic particles like clay to algae particles due to eutrophication of lake and reservoir. A series of field and laboratory experiments was performed to investigate the feasibility of DAF hybrid process and the variation of particle characteristics by applying the additional DAF unit in conventional water treatment processes. On the basis of this experiments, the DAF was effective as an additive process in filtration basin (DAF-CSF combination processes). Using DAF-CSF combination process, the efficiency of stable particle removal can be achieved to produce the safe drinking water.

• 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).

• Journal of Korean Society of Water and Wastewater
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• v.22 no.5
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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.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.208-214
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• 2004

Dissolved air flotation (DAF) is an effective solid/liquid separation process for low density floc particles such as algal, color-alum and clay-alum flocs produced from low turbidity water. The removal of taste and odor-causing organics (2-mthylisoboneol and geosmin) originating from algae in drinking water is a local and worldwide concern. Although DAF has been effectively applied for the removal of suspended solid, its application for the treatment of dissolved organic carbon is very limited. In this study, a new hybrid system consisting of adsorption and DAF processes was introduced for the simultaneous removal of algae and taste and odor-causing organics. Powdered activated carbon (PAC) was used as an adsorbent. In this proposed system, the major concern of eliminating the spent PAC from the system was also addressed. It was found that zeta potential of algae and PAC was increased with coagulant dosage, and the removal efficiency in DAF was also enhanced up to 90~95% under the given experimental conditions. Based on this study, the hybrid process was found to be a promising technology for the simultaneous removal of algae and dissolved organic pollutants.

• Journal of Environmental Health Sciences
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• v.33 no.1 s.94
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• pp.68-74
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• 2007

The objective of this study is to examine the effect of the coagulation and homogenization in bulking sludge thickening of paper manufacturing plant using DAF(Dissolved Air Flotation) and gravitational sedimentation. The effects of parameters such as dosage of coagulant and homogenization time were examined. The results showed that DAF and sedimentation was affected aluminum sulfate and anion polymer coagulant differently. At the optimum dosage of aluminum sulfate, thickening efficiency of DAF and sedimentation process were increase 1.25 time and 2.02 time, respectively. At the optimum dosage of anion polymer coagulant, thickening efficiency of DAF process was increase 1.35 time, but thickening efficiency at sedimentation was 1.06 time. When anion polymer coagulant of 0.5 mg/l was added in DAF process, water content of sludge was decreased from 96.6% to 90.7% in dewatering process using Buchner funnel test device. After homogenization(20500 rpm, 10 min), Sauter mean diameter of sludge floc was decreased from 631 ${\mu}m$ to 427 ${\mu}m$, however increase of flotation efficiency by DAF was only 1.09 time.

• Proceedings of the KIEE Conference
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• 2007.04b
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• pp.61-63
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• 2007

In these days there are many troubles - system data error, control malfunctions, cable overheating - in water treatment plant. Specially DAF(Dissolved Air Floation Process) plant has high frequency than previous water treatment process. DAF plant has diverse equipment, nonlinear loads for the precise control. But there is no sufficient overall study about harmonics condition of water treatment plant just taking a following partial action without a fundamental solution. On designing of power system, designer should have regard to harmonics condition, but there is no guide reflected harmonics condition on DAF plant This study says what is the result of guideless design about harmonics. With the result of diagnosis and analysis in DAF plant, economical efficiency and safety of plant will be upgraded in the next design.

• Journal of Korean Society of Water and Wastewater
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• v.11 no.4
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• pp.118-125
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• 1997

Conventional sedimentation method has some limitations for turbidity removal in water treatment because drinking water sources are getting polluted. Removal rates of turbidity using DAF and sedimentation process were compared for various water conditions to know whether DAF is effective to improve sedimentation process. Water samples were clay(gravity 2.65) water 100mg/l, H raw water, mixed water of H raw water and clay 100mg/l, and mixed water of HA(Humic Acid) 5mg/l and clay 100mg/l. Other parameters were temperature, coagulants(Alum, $FeCl_3$), and treatment time. Water temperature greatly affected in removal rates of turbidity for sedimentation and DAF. Generally DAF was more effective in removal rates of turbidity than sedimentation at the same experimental condition. Removal rates of $UV_{254}$ were high to over 90%, and independent of temperature and coagulant.