Why is the dissolved air flotation machine ineffective sometimes in the wastewater treatment process?

News 2022年7月21日 21

dissolved air flotation manufacturers

Dissolved Air flotation is mainly used to remove suspended impurities with a density similar to that of water. These impurities cannot settle naturally and are difficult to float naturally. DAF has the advantages of high separation efficiency and simple structure. The dissolved air flotation will directly affect the effluent quality. The poor effect of the dissolved air flotation machine is mainly manifested as: the water from the DAF machine is not clear enough with color , or the water still entrains suspended matter. So, what caused the poor treatment effect of the dissolved air flotation machine? Hope you can find the answer by reading the following aspects.

1.Stability of sewage flow

The influence of the change of sewage flow on the treatment effect cannot be ignored. Changes in flow mean changes in the amount of pollutants, and it is necessary to adjust the dosage of chemicals in time to obtain better results.

When the flow rate of sewage is too large, the horizontal flow rate of the air flotation tank is accelerated, and the residence time is shortened, which is not conducive to the flotation and separation of flocs. Excessive flow rates can cause excessive turbulence in the separation zone and disrupt bubble-floc binding. When the water volume is too large, the height of the outlet weir should be adjusted in time to prevent sewage from entering the sludge bucket.

2.Dissolved air water volume, reflux ratio and dissolved air tank pressure

The turbidity of the dissolved air water source should be low. The lower the turbidity, the more easily the air dissolves; the dissolved air water volume and the reflux ratio (dissolved air water volume/raw water volume) are determined according to the water quality.

The higher the dissolved air water pressure is, the easier the oxygen is to dissolve in the water. The optimum pressure range is 4.0-5.0kg/cm2. The pressure of the dissolved air tank can be adjusted through the dissolved air water outlet valve. When the outlet valve is closed, the pressure rises, and when it is released, the pressure drops. If the raw water flocs increase, the reflux ratio can be appropriately increased, but the pressure of the dissolved air water must be taken into account; at the same time, the normal working state of the reflux pump should be guaranteed.

3.Influence of flocculant and pH value on the effect of dissolved air flotation machine

In general, the dosage of the chemicals is proportional to the COD concentration of the raw water. However, when we add chemicals to the dissolved air flotation machine, it is not that the more flocculant is added, the better the flocculation effect will be. There is a suitable dosage value. If too much chemicals is added beyond the range of this value, then the flocculation effect will be reduced. In addition, we should also pay attention to the dosage order of the chemicals, which will also affect the effect.

4.Scraping frequency

The frequency of the scraper directly affects the thickness of the scum on the surface of the air flotation tank. When the frequency is slow, the thickness of the scum will be thicker and the water content will be less. so that the fluidity of the sludge layer is poor, it is easy to block the sludge discharge pipeline, and will lead to the subsequent sludge tank concentration is too high, which is not easy to improve. At the same time, the density of scum will increase, which increases the difficulty of solid-liquid separation, so that the incomplete separation will affect the effluent quality of the air flotation machine. If this situation is found, the frequency of the skimmer can be adjusted according to the actual situation of the scum.

5.Cleaning of DAFsystem

The cleaning of the DAF system is relatively easy to overlook. Generally, the industrial wastewater treated by DAF machine contains certain oils, calcium elements, etc., as well as the chemicals added during the air flotation process. After long-term use, a layer of dirt will adhere to the air-floating wheels, bearings, air-floating swash plates, releasers and other components, causing the releaser to block, thereby reducing the air-floating efficiency.Therefore, after the user uses the DAF machine for a period of time, it is necessary to clean and inspect the equipment to ensure that it is in good condition.

dissolved air flotation process
dissolved air flotation for water clarification

Jorsun has 18 years of experience in dissolved air flotation machine manufacturing, and continuously optimizes the design and function of air flotation machines. Each machine is strictly inspected before it is delivered to the customer. Jorsun has developed the following series of dissolved air flotation machines according to the different needs of customers.

We have standarized DAF products ,have 5 types in total.The left picture is our DAF series.It  has thoese main features:

1.Very stable in operation as our 1st generation DAF

2.Flat bottom design for easier fabrication .The first choice for limited budget project

3.Suitable for low SS project (<1500ppm)

4.Design hydraulic loading rate:4-6m3/m2/h

We have standarized DAF products ,have 5 types in total.The left picture is our DAF2 series.It  has thoese main features:

1.Upgrade based on our 1st generation DAF series

2.”W” type sludge hopper design.So sediments can be discharged more smoothly

3.Suitable for  higher SS project (>1500ppm)

4.Design hydraulic loading rate:4-6m3/m2/h

We have standarized DAF products ,have 5 types in total.The left picture is our IDAF (flat bottom) /IDAF2 (slant bottom) series.It  has thoese main features:

1.Perfect combination of chemical reaction device and DAF unit

2.Compact design for smaller footprint, and easier installation

3.The most cost-effective solution and the best seller series

4.Design hydraulic loading rate:4-6m3/m2/h

We have standarized DAF products ,have 5 types in total.The left picture is our SDAF series.It  has thoese main features:

1.Inclined plates installed can enhance the separation efficiency

2.Full coverage skimmer design

3.Suitable for high concentration solids

4.Design hydraulic loading rate:5-12m3/m2/h

5.Disadvantage is higher porice than other series

We have standarized DAF products ,have 5 types in total.The left picture is our RF-DAF series.It  has thoese main features:

1.Perfect solution for large flowrate project

2.Design capacity from 200m3/h to 1200m3/h

3.Air dissolved water are distributed to the whole tank equally with patent design

4.Design hydraulic loading rate:15-25m3/m2/h