1. DAF System Air Supply Pressurizing Pump Retention Tank
Flotation Chamber

2. SKEMATIK PROSES DAF

4. DAF Configuration Full Flow Pressurization Partial Flow Pressurization
Recycle Flow Pressurization

5. Full Flow Pressurization
The entire influent feed stream is pressurized by a pressurizing pump and held in the retention tank
The system is usually applicable to the feed stream with suspended solids exceeding 800 mg/L in concentration
It is not susceptible to the shearing effects caused by the pressurizing pump and the high pressure drop at the pressure release valve
Suspended solids will flocculate rapidly with the addition of chemical coagulants in the inlet compartment in the presence of the released air

6. Partial Flow Pressurization
Only about 30–50% of the influent feed stream is pressurized by a high- pressure pump and held in the retention tank.
Materials with low specific gravity can be removed with the partial flow pressurization system.
The increased hydraulic flow on the flotation chamber due to the flow recirculation must be taken into account in the flotation chamber design.

7. Recycle Flow Pressurization
A portion (15–50%) of the clarified effluent from the flotation chamber is recycled, pressurized, and semisaturated with air in the retention tank.
The system is usually employed in applications where preliminary chemical addition and flocculation are necessary ahead of flotation.
This system is not recommended for use when the suspended solids are susceptible to the shearing effects of the pressurizing pump and the high- pressure drop at the pressure release valve.
The suspended solids concentrations are low.

8. Faktor-Faktor Yang Mempengaruhi Kinerja DAF
Sifat Partikel
Ukuran Partikel
Dispersing Agents
Komposisi dan sifat Influent
Arus Cairan
Rasio A/S
Float Removal

9. Sifat Partikel
The specific gravity is a characteristic of the particle or liquid to be abated or separated.
It can easily be accepted that sand, for example, cannot be floated while voluminous material, such as activated sludge, or a water immiscible liquid such as oil, can be floated.

10. Ukuran Partikel
Generally, floatability increases with the size of the particle.
In many cases,the size of particles can be increased by flocculation with various chemical coagulants.

11. Dispersing Agents
Certain wastewaters and liquids contain unusual concentrations of various chemicals, resulting in specific flotation problems or advantages.
Surfactants, such as detergents, tend to alter the physical properties of the sludge particle surface to be floated.

12. Komposisi dan sifat Influent
The composition and nature of the influent is most important.
Equalization of composition and flow improves the performance of the flotation unit.

13. Arus Cairan
The liquid currents are governed by the physical design and hydraulics of the flotation unit.
This becomes a consideration in the design of the tank and hydraulic loadings of the flotation unit.

14. Rasio A/S
The amount of air and the method of mixing the air with the material to be floated are functions of the design of a particular flotation unit.
For a specific application, a definite amount of air is necessary for flotation.
In thickening applications it has been shown that increased performance is obtained at higher A/S ratios.

15. Air to Solids Ratio

16. Float Removal
A float-removal mechanism must be designed to have adequate capacity to remove water carryover.
Various items to be considered in this design are the depth of submergence of the scooping mechanism and the speed of scoop operation.

17. Gas to Solids Ratio : Full Flow Pressurized System
Gin
Gout Q Cf X Q Cr Q Ce G
Correction factor, F or f, because complete gas saturation of liquid is often not achieved in a pressurized retention tank
P ≥ 2 atm
F = 0,5 – 1,0
P < 2 atm
f = 0,167 – 1,0
Henry’s law

18. Gas to Solids Ratio : Partial Flow Pressurized SystemQ Cf X G Qn Cf
Gin
Gout Q Ce Qp Cr G
P ≥ 2 atm
F = 0,5 – 1,0
P < 2 atm
f = 0,167 – 1,0
The Qp/Q ratio ranges between 0.3 and 0.5

19. Gas to Solids Ratio : Recycle Flow Pressurized SystemQr Cr Q Ce G Cf X
Gin
Gout
P ≥ 2 atm
F = 0,5 – 1,0
R = Qr/Q
P < 2 atm
f = 0,167 – 1,0

20. Air Solubility in Water at 1 Atm (a)
Temp. oC
Air Sol. (mL/L)
28,8 10
23,5 20
20,1 30
17,9

21. Air Characteristics and Solubilities

22. Pressure Calculations

23. Design Parameters Hydraulic loading rate Solids loading rate
Air to Solids ratio
Retention Tank Pressure

24. Basic Design Concept The ratio of Q/As
is also defined as the hydraulic loading rate
VH = horizontal velocity (m/s),
Q = influent flow rate (m3/s),
Ac = cross-sectional area of a flotation chamber (m2)
VT = vertical rise rate of suspended solids (m/s),
D = effective depth of the flotation chamber (m),
T = detention time (s),
Q = influent flow rate (m3/s),
AS = surface area of flotation chamber (m2)

25. Basic Design Concept The D/W ratio is usually between 0.3 and 0.5
D = effective depth (m)
W = effective width (m)
L = effective length (m)
The D/W ratio is usually between 0.3 and 0.5
F′= factor for short circuiting and turbulence, assumed as 1.4.

26. The influence of Loading Rate

27. DAF Operation and Performance

28. Terima Kasih