A case study of dissolved air flotation for seasonal high turbidity water in Korea

2004 ◽  
Vol 50 (12) ◽  
pp. 245-253 ◽  
Author(s):  
S.B. Kwon ◽  
H.W. Ahn ◽  
C.J. Ahn ◽  
C.K. Wang
Keyword(s):  
Operation Mode ◽  
Raw Water ◽  
Freshwater Algae ◽  
Water Turbidity ◽  
Dissolved Air Flotation ◽  
Flotation Process ◽  
Direct Filtration ◽  
Air Flotation ◽  
Full Scale Tests ◽  
Dissolved Air

A DAF (Dissolved-Air-Flotation) process has been designed considering raw water quality characteristics in Korea. Although direct filtration is usually operated, DAF is operated when freshwater algae blooms occur or raw water turbidity becomes high. Pre-sedimentation is operated in case when the raw water turbidity is very high due to rainstorms. A main feature of this plant is that the operation mode can be changed (controlled) based on the characteristics of the 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 the conventional sedimentation process. Moreover, low-density particles (algae and alum flocs) are easily separated while the removal of them by sedimentation is more difficult. One of the main concerns for DAF operation is a high raw water turbidity. DAF is not adequate for raw water, which is more turbid than 100 NTU. In order to avoid this problem, pre-sedimentation basins are installed in the DAF plant to decrease the turbidity of the DAF inflow. For simulation of the actual operation, bench and full-scale tests were performed for highly turbid water conditions. Consequently, it is suggested that pre-sedimentation with optimum coagulation prior to DAF is the appropriate treatment scheme.

Dissolved air flotation in potable water treatment: the Dutch experience

1995 ◽  
Vol 31 (3-4) ◽  
pp. 149-157 ◽  
Author(s):  
Jan van Puffelen ◽  
Paul J. Buijs ◽  
Peter N. A. M. Nuhn ◽  
Wim A. M. Hijnen
Keyword(s):  
Dissolved Air Flotation ◽  
Flotation Process ◽  
Direct Filtration ◽  
Advantages And Disadvantages ◽  
Air Flotation ◽  
Water Companies ◽  
Micro Organisms ◽  
Chlorophyll A Content ◽  
Dutch Experience ◽  
Dissolved Air

This paper reviews the experience the drinking water companies in The Netherlands have gained in the last twenty years in the field of dissolved air flotation. An overview of the Dutch flotation plants with their individual objectives is presented. The efficiency of flotation towards the removal of different parameters, such as turbidity, organic matter and micro-organisms is good, which is illustrated by data from the water companies. Both in the past and at present water companies compare flotation to other floc separation techniques, such as sedimentation or direct filtration. Specially for waters with (relative) low turbidity and high chlorophyll-a content, flotation proved (in combination with rapid sand filtration) to be very effective. The efficiency of the flotation process has been improved by the development of different nozzle-types. Some of these types are described here, each with their advantages and disadvantages. In general dissolved air flotation has proved to be as sturdy and reliable as sedimentation techniques, such as lamellae settling.

Characterization of Nova Scotia surface waters and treatment options for removal of colour and trihalomethane precursors

1996 ◽  
Vol 23 (6) ◽  
pp. 1316-1325 ◽  
Author(s):  
D. H. Waller ◽  
M. J. MacPhee ◽  
P. W. Prendiville ◽  
R. F. McCurdy ◽  
A. W. Gates ◽  
...  
Keyword(s):  
Nova Scotia ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Surface Waters ◽  
Carbon Surface ◽  
Raw Water ◽  
Dissolved Air Flotation ◽  
Direct Filtration ◽  
Air Flotation ◽  
Dissolved Air

This paper provides an overview of the results of a study undertaken to provide a basis for predesign evaluation of the effectiveness of options for treatment of municipal surface waters in the province of Nova Scotia. Seasonal samples of raw water were obtained from the fall of 1992 through the fall of 1993 from five sites. Results were compared with a Nova Scotia Department of Health data base of randomly collected samples. For project samples, strong relationships were evident between raw water total organic carbon (TOC) and both colour and trihalomethane formation potential. Laboratory batch tests, supported by plant results, indicated that percentage removals of TOC increase with raw water TOC, and that settling-filtration was more effective than direct filtration for waters with higher raw TOC concentrations. Results of solids settling tests were consistent with TOC results. A treatment optimized for TOC removal also ensured removal of colour. TOC removals by dissolved air flotation followed by filtration exceeded removals by direct filtration or settling-filtration, based on laboratory bench tests, particularly at sites with higher values of raw TOC. Colour removal by dissolved air flotation was consistently higher at all sites. Key words: enhanced coagulation, trihalomethane precursors, total organic carbon, surface water treatment, dissolved air flotation.

Cryptosporidium removal during water treatment using dissolved air flotation

1995 ◽  
Vol 31 (3-4) ◽  
pp. 125-135 ◽  
Author(s):  
T. Hall ◽  
J. Pressdee ◽  
R. Gregory ◽  
K. Murray
Keyword(s):  
Water Treatment ◽  
Metal Ion ◽  
Ion Concentration ◽  
Sudden Increase ◽  
Water Turbidity ◽  
Dissolved Air Flotation ◽  
Treatment Processes ◽  
Air Flotation ◽  
The Uk ◽  
Dissolved Air

The occurrence of the protozoan parasite Cryptosporidium parvum in water supplies, and the resultant outbreaks of cryptosporidiosis in the UK and USA, have led to concern over the ability of conventional water treatment processes to remove Cryptosporidia from water sources. Large scale pilot plant trials of water treatment have been carried out in the UK to establish the degree of removal that can be achieved by a range of treatment processes, including dissolved air flotation, and to compare the performance of different treatment options. Results from part of these trials are presented in this paper. These results suggest that well operated chemical coagulation based treatment, using either dissolved air flotation or floc blanket clarification, should be capable of achieving removal of Cryptosporidium oocysts of over 99%. There was no evidence of differences in performance between the different types of filter media investigated. The risk of increased Cryptosporidium concentration in the filtered water will increase as filtrate turbidity increases. However, other factors such as high coagulant metal-ion concentration in the filtered water, or a sudden increase in clarified water turbidity, without any increase in filtered water turbidity, may also indicate treatment problems and associated risk from Cryptosporidia. Recycling of backwash waters may also increase the risk.

High-rate dissolved air flotation for water treatment

2001 ◽  
Vol 43 (8) ◽  
pp. 43-49 ◽  
Author(s):  
M. A. P. Raeli ◽  
M. Marchetto
Keyword(s):  
Reynolds Numbers ◽  
Pilot Scale ◽  
Water Velocity ◽  
High Rate ◽  
Raw Water ◽  
Parallel Plates ◽  
Dissolved Air Flotation ◽  
Removal Efficiencies ◽  
Air Flotation ◽  
Dissolved Air

This paper presents the results of an experimental investigation about the performance of a horizontal flow high-rate pilot scale Dissolved Air Flotation (HRDAF) unit containing inclined parallel plates for treating a coloured and low turbidity raw water. Experiments were performed with the DAF unit in order to verify the influence on flotation of : (i) the water velocity (Vh) between the plates, in the range 18 to 96.5 cm.min−1 with corresponding Reynolds numbers between 240 and 1060; (ii) the supplied air (S*) value ranging from 2.2 to 8.5 g of air/m3 of water ; (iii) the angle of the plates (60° or 70°). The best pilot plant operational condition was obtained applying only 4.0 g/m3 (S*) with Vh around 18 cm.min−1 for treatment of water coagulated with a Al2(SO4)3 dosage of 40 mg.l−1. In these conditions, the unit presented very good removal efficiencies of colour (90%, residual of 10 uC), turbidity (88%, residual of 0.8 NTU ) and TSS (94%, residual of 1.8 mg.l−1). Furthermore, the unit could operate at higher Vh values up to 76 cm.min−1 and still present good results. The DAF unit thus behaved as a high rate unit presenting good performance with low air requirement.

Treatment Spent Filter Backwash Water using Dissolved Air Flotation (DAF) in Isfahan WTP

2008 ◽  
Vol 3 (3) ◽  
Author(s):  
Mohammad Hassan Mahmoodian ◽  
Mohammad Mehdi Amin ◽  
Mohammad Reza Shahmansouri ◽  
Mohammad Ghasemian
Keyword(s):  
Low Dose ◽  
Saturation Pressure ◽  
Raw Water ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Recycle Rate ◽  
Polyaluminium Chloride ◽  
Significant Concentration ◽  
Dissolved Air ◽  
Filter Backwash Water

Recovering spent filter backwash water is currently receiving a great deal of attention. EPA published the Filter Backwash-Recycling Rule (FBRR) in 2001. Recycle stream may contain significant concentration of pathogens, such as, cryptosporidium and Giardia. Dissolved Air Flotation (DAF) was investigated as a possible technology alternative to simple or advanced sedimentation technology. In this study with using a pilot of DAF effluent turbidities of >20NTU could be easily obtained, when raw water turbidities were in excess of 800 NTU. Chemical requirements were low with only a single low dose of polyaluminium chloride (PACl) required binding the floc particles to form a solids matrix suitable for flotation. The results showed that the efficiency of continuous flow DAF with using PACl as coagulant for removal of Turbidity, COD, HPC, SS and MPN were 97, 72, 75, 95 and 100 percent, respectively. The statistical analyses indicated that the optimum saturation pressure is 4-5 atm, during recycle rate of 20-25 percent. The removal efficiencies of turbidity and bacteria in coagulation with sedimentation were reported up to 70 and 65 percent, while in this study using DAF with coagulant PACl could remove turbidity, COD, SS and bacterial up to 97,72, 95 and, 72 percent respectively.

scholarly journals Application of dissolved air flotation process for industrial sludge thickening: A laboratory-scale study

2017 ◽  
Vol 4 (1) ◽  
pp. 22 ◽  
Author(s):  
MohammadBagher Miranzadeh ◽  
Ali Atamaleki ◽  
Gholamreza Mostafaii ◽  
Hossein Akbari ◽  
Leila Iranshahi ◽  
...  
Keyword(s):  
Laboratory Scale ◽  
Industrial Sludge ◽  
Dissolved Air Flotation ◽  
Flotation Process ◽  
Air Flotation ◽  
Sludge Thickening ◽  
Dissolved Air

scholarly journals The evaluation of polymeric organic coagulants for potable water treatment by dissolved air flotation

2001 ◽  
Author(s):  
◽  
Rachigan Rajagopaul
Keyword(s):  
Water Treatment ◽  
Ferric Chloride ◽  
Potable Water ◽  
Raw Water ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Potable Water Treatment ◽  
Dissolved Air

Historically inorganic coagulants were the coagulants of choice for OAF treatment of potable water. Water treatment practitioners using OAF technology preferred ferric chloride, an inorganic coagulant. Ferric chloride formed light, floatable floes at relatively low flocculation intensities and detention times. The inorganic coagulant was also more forgiving during incidents of overdosing and raw water and pH variability

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