What are the reasons for the poor performance of dissolved air flotation machines?

The main body of the equipment is a rectangular carbon steel structure. The main components are composed of a dissolved air pump, air compressor, dissolved air tank, rectangular box, air flotation system, mud scraping system, etc.
1. The gas tank produces small bubbles with a particle size of 20-40um, and the adhesive flocculent is firm, which can achieve good air flotation effect;
2. Less use of flocculants and reduced costs;
3. The operating procedures are easy to master, the water quality and quantity are easy to control, and the management is simple.
4. Equipped with a backwash system, the release device is not easily blocked.
What are the reasons for the poor effectiveness of air flotation?
1. Release device failure: The release device generally does not block, and in case of blockage, large bubbles will appear in the contact area of the air flotation, which will cause damage to the air flotation and impact the scum, causing the scum to lose stability and resulting in turbid production water.
2. Scraping problem: The scraping machine moves too fast when scraping, causing the lower layer of scum to be sheared, broken, and turbulent, and to come out with the water. Of course, not scraping in time and accumulating too much mud at the bottom can also lead to poor air flotation effect.
3. Sewage flow rate: The impact of sewage flow rate on treatment efficiency cannot be ignored. During the operation of air flotation equipment, it is necessary to evenly distribute water in each air flotation tank. The change in flow rate means a change in the amount of pollutants, so it is necessary to adjust the dosage of reagents in a timely manner to achieve optimal results.
When the sewage flow rate is too high, the horizontal flow rate of the air flotation tank accelerates, the residence time shortens, and it is not conducive to the floating separation of the flocs; If the flow rate is too high, the turbulence of the water flow in the separation area will be too high, resulting in the breaking of the foam flocculation combination. When the water volume is too large, the height of the outlet weir should be adjusted in a timely manner to prevent sewage from entering the scum system.
4. Influence of flocculant and pH on flotation: generally speaking, the higher the Chemical oxygen demand concentration of raw water is, the more chemicals need to be added. The higher the concentration of suspended solids in the raw water, the greater the dosage of drugs that need to be added. There is an optimal dosage for flocculation. Exceeding this dosage will reduce the flocculation effect, and exceeding it too much will have the opposite protective effect. In addition, attention should also be paid to the proportion and sequence of administration.
Coagulants (such as PAC) can destroy hydrophobic groups during hydrolysis, make Suspended solids and oil flocculate each other, and make some dissolved proteins precipitate in the form of small particles.
The flocculant PAM has a large molecular weight and has functions such as adsorption, bridging, connection, and cleaning. It causes small particles initially formed under the action of coagulants to adsorb and connect with each other, forming large flocs that quickly separate from water. In this way, under the joint action of PAC and PAM, larger flocs are formed, and PAC needs to be added to the wastewater before PAM.
At present, most flocculants PAM are acidic flocculants with appropriate pH values. When the pH value of sewage exceeds the optimal pH value, it can cause the dissolution or fragmentation of flocs, which has a very adverse impact on the air flotation separation of air flotation equipment. Therefore, during operation, the acidity and alkalinity of the incoming water should be monitored.
5. Dissolved water volume, reflux ratio, and pressure of the dissolved air tank: The turbidity of the dissolved water source should be lower, and the lower the turbidity, the easier the air is to dissolve; The dissolved water volume and reflux ratio (dissolved water volume/raw water volume) are determined based on the water quality situation.
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