Cavitation air flotation system (CAF) is the kind of dissolved air flotation machine (TDAF) for waste water treatment applications. The air flotation purifying process is a method of generating a large amount of fine bubbles in the water to adhere to the impurity flocs, causing the overall specific gravity to be smaller than the water, and relying on buoyancy to float to the surface of the water, thereby obtaining solid-liquid separation. RUNNENG brand cavitation air flotation system has the advantages of low investment, stable and efficient operation, simple operation and maintenance, etc. Our cavitation air flotation system is widely used in meat processing, vegetable cleaning and processing, workpiece pickling and phosphating, breeding, wine making, oil refining, aquatic product processing, meat processing and other industries wastewater treatment process.

RUNNENG Cavitation Air Flotation System Working Principle

RUNNENG cavitation air flotation system uses a rotary cutting impeller to rotate at high speed under the action of the motor. The centrifugal force pulls out the air in the impeller at high speed to generate atomized bubbles. Negative pressure is formed in the impeller,and air is inhaled from the intake pipe. Under the agitation of the impeller, air is crushed into tiny bubbles. After fully mixing with water, these bubbles are thrown out to the blade and stabilized by the rectifier plate. After continues flow, they rise steadily and vertically in the flotation tank. Fine bubbles adhere the oil and suspended substances in the water to form a floating sludge with a specific gravity less than water to separate them from the water surface, thus purifying the wastewater.

The traditional pressurized dissolved air flotation method works by relying on a pump to recirculate a part of the purified water after the air floatation into the dissolved gas tank, and simultaneously pressurizing the air through the pressure of the air compressor or the ejector. In a dissolved gas tank, the air is dissolved in water under a certain pressure condition, and then the pressure of the dissolved gas water is restored to a normal pressure by a release device, and a large amount of fine bubbles are released to adhere the floc in the raw water, so that the floc is removed.

However, the air flotation system has the phenomenon that the dissolved water is unstable and the removal effect is unstable. The main reason is that the reflux water and the air sometimes do not form dissolved gas in the dissolved gas tank, even if the pressure of the dissolved gas tank is as high as 0.4 MPa. The released dissolved water is either a large bubble or a small water droplet. Even if it appears to be milky white dissolved water, the release effect is poor, and the removal rate of the pollutant is low, so that the purification purpose is not achieved. 

Refining Wastewater Treatment Process Transformation

At a Oil refinery in Weifang, the original sewage treatment process adopts pressurized dissolved air flotation system, which consists of 4 backflow pumps, 4 gas storage tanks, 56 floatation vacuum release units, 2 air compressors, etc. Among them, the service life of 4 backflow pumps has been up to 10 years, and the maintenance cost is high. The floatation release device has not been replaced since it was put into use, and has reached the replacement period, because it is easy to cause blockage after one year of operation. The flotation tank must be emptied every time, which is not conducive to the long-term operation of the unit. At the same time, because the air volume is not easy to adjust, the treatment effect is seriously affected. According to the actual investigation, RUNNENG engineers adopt 4 sets of power 4kw TDAF, replaced one of 25kw air compressors and 3 sets of 37kw return pumps, which improved the treatment effect, and saved the operating cost by 360,000 yuan.

Application of cavitation air flotation system in refinery wastewater treatment
Application of cavitation air flotation unit in refinery wastewater treatment

RUNNENG Cavitation Air Flotation System Specifications

Model: JHZ62.5

Treatment capacity: 62.5m3 / h

Performance parameters: grid gap: 3mm

Number: 1 set

Material: stainless steel

RUNNENG Cavitation Air Flotation System Features 

1.Savings on investment

After revamping, one 25kw air compressor, three 37kw backflow pumps are out of operation, four new power 4kw air floatation machines are added , and the annual power saving is: (725+3×37-4×4) ×24×365=1051200kwh. Each kilowatt-hour, calculated at $0.40, 1051200kwh×0.4=420480 $ can be saved per year.

2.Stable and efficient operation

The original DAF operation is unstable, the adjustment is difficult, and the flotation export oil content is very unstable. The modified RUNNENG cavitation air flotation system can ensure the removal effect of the pollutants, make the flotation outlet oil content stable, and operate stably and efficiently.

3.Easy to maintain

Since the mechanical structure or parts of RUNNENG cavitation air flotation system is not complicated, only one TDAF has a low failure rate. Once a fault occurs, it is only necessary to set up the TDAF for maintenance without processing the flotation cell. Therefore, it has the characteristics of simple maintenance, short maintenance time and low cost, and is suitable for long-term operation of the device.

In March 2018, with the cooperation of RUNNENG engineers and construction personnel, the original DAF for Weifang customers was replaced and four cavity air flotations were installed. Since the equipment was put into production, it has performed well and achieved the expected effect. After the transformation, the flotation outlet oil content is 17mg/L, and the removal rate is 87.24%. This kind of cavitation air flotation system can fully meet the process requirement of oil content less than 25mg/L. Cavitation air flotation system has significant energy-saving effect, and the investment recovery period is short, so it has greater economic and environmental benefits.


Shandong RUNNENG Environmental Technology Co., Ltd (RUNNENG) had been dedicated to supplying one stop wastewater equipment and Water Resource Recovery Facility (WRRF) solutions to worldwide customers for over 20 years. RUNNENG has over 30 professional experts and more than 150 staffs. Our high quality innovative wastewater equipment includes sludge scraper system, dissolved air flotation machine and integrated sewage treatment equipment, etc. All our wastewater equipment has been passed the certificates of ISO9001, ISO14001 and OHSAS18001, we also have the Grade B engineering design certificate issued by the Ministry of Environmental Protection. Hope to be your partner.

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