1. Sewage flow
The flow of sewage has a great influence on the treatment results. When the dissolved air flotation machine is working, it is necessary to ensure that the water distribution of each air flotation tank is uniform. The change of the flow rate means the change of the amount of pollutants, and it is necessary to immediately change the dosage of additives to obtain ideal effect.
When the flow rate of sewage is too large, the horizontal flow rate of the flotation tank will increase, and the residence time will be reduced, which is not conducive to the floating and separation of flocs; When the water flow is too large, the position of the outlet weir should be adjusted immediately to prevent sewage from entering the scum system.
2. Dissolved air and water volume, reflux ratio and dissolved air tank pressure
The turbidity of the dissolved gas water source should be small, the cleaner the water source, the more fully dissolved the gas, and the reflux ratio of dissolved gas and water should be determined according to the specific situation.
The higher the pressure of dissolved air and water, the more fully the oxygen is dissolved. The optimal pressure range is 4.0-5.0kg/cm2. The pressure in the container is regulated by the air-floating dissolved air and water outlet valve. After closing, the pressure rises, and when released, the pressure decreases. . If the flocs in the raw water increase, the reflux ratio can be appropriately increased, but the pressure of the dissolved air and water must be taken into account; at the same time, the normal working state of the reflux pump can be ensured.
3. Intervention of flocculant and pH value on air flotation
The higher the COD concentration of the raw water, the more pharmaceuticals need to be added; the higher the concentration of the suspended solids in the raw water, the more pharmaceutical doses need to be added. For the occurrence of flocculation, there is a proportional dosage. If the amount is excessive, the flocculation effect will decline, and if it exceeds a certain upper limit, it will have a contradictory effect. In addition, it is also necessary to pay attention to the order in which the additives are added and the appropriate ratio.
Coagulants (such as PAC) can break up hydrophobic groups during the hydrolysis process, so that suspended solids and oils can flocculate each other, and at the same time, part of the dissolved protein can be discharged as small particles.
The flocculant PAM has a large molecular volume and has the functions of adsorption, bridging, connection and sweeping. It makes the small particles initially formed under the action of the coagulant adsorb and connect with each other, thereby forming large flocs that are quickly separated from water. In this way, under the combined action of PAC and PAM, larger flocs are formed. The wastewater needs to be added with PAC in advance and then PAM.
The currently used flocculant PAM is mostly acidic flocculant, which is a certain proportion of pH value. When the pH value of the sewage exceeds the proportion, it will lead to the rupture of the floc, which will seriously affect the working results of the dissolved air flotation machine. Therefore, in the process of operation, the pH value of the influent water should be monitored and controlled.
4. Scraping frequency
The frequency of the scraper affects the amount of slag on the air flotation. The more slag, the smaller the water content, which will reduce the fluidity of the sludge, block the sewage pipe, and also make the sludge concentration in the pool too high, the viscosity is too high, and it is not easy to improve. Too much scum will cause the average density to be too high, making it difficult to separate the mud and water, and reducing the water quality after treatment, so the frequency of mud scraping should be adjusted according to the amount of slag filtered out.
5. Cleaning of air flotation system
Because industrial wastewater and other sewage mostly contain excessive Ca2+, SO42-, and appropriate flotation additives are added during the air flotation process, after the dissolved air flotation system works for a period of time, the air flotation wheel and bearing will produce a layer of Dirt can reduce the efficiency of the air flotation system. Therefore, regular maintenance and cleaning of the air flotation swash plate and releaser should be carried out. Also regularly check the state of the releaser, whether it is aging, whether the pipeline is leaking, and whether it is blocked.
