เนื้อหา
ความรูทั่วไป
รูปแบบของการลอยตัว
การเติมสารเคมี
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การเติมสารเคมีสมรรถนะการละลายน้าํของอากาศการออกแบบระบบ flotation
ความรูท่ัวไป
Flotation is a separation process basedon the use of very fine gas bubbles thatattach themselves to the solid particles insuspension to make them buoyant and
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suspension to make them buoyant anddrive them toward the free surface of theliquid
Air is the only flotation agent used inwastewater treatment
ความรูท่ัวไป
เปาหมายหลกั
แยกตะกอนที่เบากวาน้ําหรือหนักพอ ๆ กัน
แยก FOG ออกจากน้ํา
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แยก FOG ออกจากน้ํา
รูปแบบของการลอยตัว
Dispersed-air flotation
Vacuum flotation
Dissolved-air flotation
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Dissolved-air flotation
Dispersed-air flotation
Air bubbles are formed by mechanicallydispersing air injected under rotatingimpellers or sparged by diffusers
The bubbles formed under these
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The bubbles formed under theseconditions are typically too coarse forfine solid removal
Some scum forming waste can beremoved by air dispersion flotation
Vacuum flotation
Air is first dispersed into the wastewaterto achieve saturation conditions
Partial vacuum is then applied to thewastewater
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wastewater
This results in the generation of small airbubbles that attach themselves to thesolid particles and make them rise
Dissolved-air flotation
โดยทั่วไปใชกับ activated sludge (ถ.พ. ~1.0)
ใชในระบบ “sludge thickening”
Air is dissolved in pressurized wastewater
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Air is dissolved in pressurized wastewaterby adding air to the pump suction point(P>Patmosphere)
Dissolved-air flotation
The air-wastewater mixture is admitted toa retention tank having a residence timeor a few minutes to allow the air todissolve
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dissolve
The wastewater passes through a pressurereducing valve and then enters a flotationunit where small bubbles (30 - 120 mm)are generated within the bulk of thewastewater
Dissolved-air flotation
In the flotation unit the solid particles arecarried by the bubbles toward thesurface of the water where they areskimmed off by a skimming mechanism
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skimmed off by a skimming mechanism
Flotation units can be provided with arecycle to prevent the incoming solids tobe subjected to the shearing action of thepressurizing pump
การเตมิสารเคมี
Chemical additives that promote theattachment or entrapment of airbubbles to solid particles or flocs canbe effectively used to enhance flotation
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be effectively used to enhance flotationFlotation additives include:aluminum and ferric saltsactivated silicaorganic polymers
การออกแบบระบบ Flotation
Design of floating thickeners is based onthe knowledge of:
Wastewater flow rate and solid loading
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Air-to-solid ratio (typically expressed asvolume of air/mass of solids or mass ofair/mass of solids)
Overflow rate (or rise velocity of solids)
Final solid loading in sludge
การออกแบบระบบ Flotation
Design of floating thickeners is based on theknowledge of:
Wastewater flow rate and solid loading Air-to-solid ratio (typically expressed as
volume of air/mass of solids or mass of
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Air-to-solid ratio (typically expressed asvolume of air/mass of solids or mass ofair/mass of solids)
Overflow rate (or rise velocity of solids) Final solid loading in sludge