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How to choose a pump for your D.A.F. system?

How to choose a pump for your D.A.F. system?

Nowadays, there is a field of many DAF manufacturers around the world or even in your country.  So whether you are an agent who recommends and purchases a DAF system for your customer or you are an engineer who focuses on the project development process, at some certain point, you will have to verify the quality and performance of a DAF system. To do so, the first thing you will consider would be the core of any dissolved air flotation system, that is, daf pump which always plays an important role and it is the most crucial part of the system. But there are many different kinds of pumps which can be used in the DAF system, what are their characteristics and differences between each other? This article will help you gain some insight of these pumps and their working principles. So if you only need to buy this pump once, buy it right.


There are generally three kinds of pumps that are widely used by the D.A.F. manufacturers around the world. They are multi-stage impeller pumps, regenerative turbine pumps and ANSI pumps. Let us take a look at the three of them respectively. 


Multi-stage impeller pump

Multi-stage impeller pump is a kind of self-priming pump which can absorb the ambient air (or there is an air compressor but it is not necessary) and mix the air and water by the high rotation speed speller to generate micron-sized bubbles that can be dissolved into the liquid. The micro bubbles will slowly raise to the surface of the water then burst with a releasing of sound and light, which is the reason why you can see the water is white and you hear the bubble diffusing sound.


The big advantage of this multi-stage pump is that its discharge pressure can be adjusted by increasing the number of impellers. But generally, the discharge pressure for the D.A.F application is at 100 psi. For multi-stage pump, any solid particles can be fatal as any particles can be accelerated by the high-speed impeller and cause serious damage to the impeller and pump eventually. So particular filtration must be carefully applied. 


About the maintenance, we have all the spare parts in the stock so if there is any mechanical failure, we will provide the standby parts for free to our customers if the machine is in its warranty.


Multi-stage impeller pump has a wide spectrum of other applications with high-pressure service. Like descaling, pressurize feed water before the reverse osmosis membrane application, pipeline water giving and boiler feed water. 


But if you do not want to apply a multi-stage pump and need the whitewater, then a regenerative turbine pump (micro bubble generator) would be your choice. 


Regenerative Turbine Pumps

Regenerative turbine pump is a kind of centrifugal pump but with a different impeller than the conventional ones’. Let us take a look at its structure first.


When water or any other liquid gets sucked into the pump with air or other gas, it will be accelerate by the high-speed rotation impeller and the sucked air will be sheared be the impeller's blades and form it into micro bubble. As you can see in the above diagram, the impeller of this regenerative turbine pump is different from the ones of conventional centrifugal pumps. Instead of vanes, this impeller has radially oriented blades.


What is unique about this machine is that it can generate a high pressure in its compact structure and it can also absorb the ambient air be the negative pressure cause at its inlet. The pump's wetted components are all made of stainless steel. The suction port of the gas-liquid mixing pump can draw in gas by the negative pressure, so there is no need to use a gas compressor and an atmospheric injector. The high-speed rotating impeller agitates the liquid with the gas, so no compressor and mixers are needed. Due to the pressurized mixing in the pump, the gas and the liquid are fully dissolved, and the dissolution efficiency can reach 80 to 99%. Therefore, a high-pressure solution can be obtained without a large pressurized gas tank or an expensive reaction tower. A gas-liquid mixing pump can be used for gas-liquid attraction, mixing, dissolution and direct delivery of highly dissolved liquid to the point of use. Therefore, the use of a gas-liquid mixing pump can improve the efficiency of the dissolved gas production, simplify the preparation device, save the space, greatly reduce the initial investment, save operating costs and maintenance costs.


Like the multi-stage pump, when applied in the dissolved air application, the pressure with this pump usually set to 90-120 psi. 


Other advantages of regenerative turbine pumps are: it can overcome the difficulty of dissolving and pressurizing gas into the liquid and can evenly mix the two different kinds of liquid. The gas liquid mixing pump, compared to the conventional mixing machine, greatly simplifies the mixing process and maximally miniaturize the equipment so as to save the investment cost. One typical use of gas-liquid mixing pump is with dissolved air flotation system. With our gas-liquid mixing pump (micro nano bubble generator), not only can the parts like pressure pump, air compressor, ejector, high-pressure container tank and releaser be eliminated, but so are the problems like releaser clogging, large bubble tumbling and pressure pump failure which are the problem inevitably and difficultly to solve with the conventional dissolved air flotation system. Gas-liquid mixing pump can generate micro bubbles which can greatly and efficiently improve the quality of water.


Other applications of this pump:


Air flotation treatment. When the reflux ratio is 1:1, the water treatment capacity is 1~45m3/h.

Removal of impurities in well water, such as pre-engineering for semiconductor pure water manufacturing.

Wastewater treatment with grease, for example kitchen wastewater.

Urine treatment after screening, such as excrement treatment of livestock.

Resource recycling, such as recycling and recycling of paper fibers.

Front-end treatment of plant wastewater, for example for the recovery of food, crystallization, pharmaceuticals.

Sediment, floats, fouling sludge, algae recovery, for example for ponds, lakes.

A tiny bubble bath like a cow's milk, such as a milk bath for hotels and restaurants.

Water surface projection in a large celebration, like a water screen.

Decoration of the water surface

High concentration ozone water treatment (use example)  The water preparation capacity can be up to 54m3/h. The ozone concentration can reach 30mg/L.

Water quality improvement. Sterilization. Deoxidation, for example, for drinking water, beverages, underground well water

Fresh food sterilization and preservation, for example, in food factories, restaurants, canteens

Medical institutions, such as for instruments, wounds, white clothes, bedding, sterilization of wastewater, disinfection, decolorization, deodorization

Sterilization of drinking water, water towers, water pipe descaling

Sterilization of circulating water. Deodorization, for example, for swimming pools. Hot springs. Baths

Reduce BOD.COD, decolorization of dye drainage, such as wastewater treatment in factories

Laundry room. Paper mill, for example for sterilization, bleaching, deodorization, drainage and bleaching


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