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Wuxi Wanchuan Environmental Equ-Ipment Technology Co.,Ltd

Procedures of dissolved air flotation and respective characteristics

According to the type, nature, treatment water purification degree and pressurized way of the suspended substance in the waste water, there are three basic procedures of dissolved air flotation.

1.Whole process dissolved air flotation

Whole process dissolved air flotation is to pressurize all the waste water and inject air before or after the pump. In the dissolved gas tank, the air is dissolved in the waste water, and then the waste water is sent to the air flotation tank through the pressure reduction valve. Many small bubbles in the waste water form the emulsified oil or suspended solids to escape from the water, forming a scum on the surface of the water. The scum should be discharged into the scum trough by the scraper, and the treated waste water is discharged through the downflow weir and the outlet pipe through the dross pipe discharge pool.

Its advantages are:

①The dissolved gas is large, and the contact chance of oil particles or suspended particles and bubbles is increased.

②Under the same treatment condition, the size of the air flotation tank is smaller than that of part circumfluence dissolved air flotation, thus reducing the investment in infrastructure. However, because all the waste water is through the pressure pump, the emulsified degree of the oily waste water is increased, and the pressure pump and the dissolved gas tank are larger than the other two procedures, the investment and operation power consumption are greater.

2.Part dissolved air flotation

Part dissolved air flotation is to take part waste water to pressurize and dissolve. The remaining waste water directly enters into the air flotation tank and mixes with dissolved gas in the air flotation tank.

Its characteristics are:

①The pressure pump is smaller than the whole process dissolved air flotation, so the power consumption is low.

②The amount of emulsified oil produced by the pressure pump is lower than that of the whole process dissolved air flotation.
③The size of the air flotation tank is the same as that of the whole process dissolved air flotation, but is smaller than the part circumfluence dissolved air flotation.

3.Part circumfluence dissolved air flotation

Part circumfluence dissolved air flotation is to take a part of effluent recycle after unoiling to pressurize and dissolve air, and then directly enters the air flotation tank after decompression, mixing and air floating with oily waste water from the flocculation basin. The quantity of reflux

is generally 25 % ~ 50 % of the oily waste water.

 Its characteristics are:

①Pressurized water is less and the power consumption is low.

②The emulsification is not promoted in the process of air floatation.

③The alumen ustum is formed well, and the post flocculation is less.

④The volume of the air floating pool is larger than the previous two procedures. In order to improve the treatment effect of air flotation, coagulant or aerofloat agent is often added to the waste water. The dosage varies with the water quality, and is generally determined by the test.

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