Air flotation equipment is a type of air flotation equipment that enters or generates a large number of fine air bubbles in the water, so that the air adheres to the suspended particles in the form of highly dispersed tiny air bubbles, resulting in a state where the density is lower than that of water. Water treatment equipment for solid-liquid separation. Through the dissolved air and release system, a large number of fine air bubbles are generated in the water, making them adhere to the solid or liquid particles in the wastewater whose density is close to that of water, resulting in a state where the overall density is lower than that of water, and relying on buoyancy to make them rise to the water surface, thereby To achieve the purpose of solid-liquid or liquid-liquid separation.
The air flotation effect is very important to the water quality of the effluent. In order to obtain a good air flotation effect, it is necessary to recognize the air flotation process and comprehensively analyze the factors that can cause changes in the effluent quality.
1. Sewage flow
The influence of sewage flow on the treatment effect cannot be ignored. During the operation of the dissolved air flotation machine, it is necessary to ensure that the water distribution of each air flotation tank is uniform. The change in flow rate means the change in the amount of pollutants. Effect.
When the sewage flow 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 flocculation separation; When the water volume is too large, the height of the outlet weir should be adjusted in time to prevent sewage from entering the scum system.
2. Influence of flocculant and pH value on air flotation effect
Generally speaking, the higher the COD concentration of the raw water, the more chemicals need to be added; the higher the concentration of suspended solids in the raw water, the more chemicals need to be added. For the occurrence of flocculation, there is a dosing amount. When this amount is exceeded, the flocculation effect will decrease, and if it exceeds too much, it will have the opposite protective effect. In addition, it is also necessary to pay attention to the proportion and order of dosing.
The coagulant (such as PAC) can break the hydrophobic group during the hydrolysis process, so that the suspended solids and oil can flocculate each other, and at the same time, part of the dissolved protein can be precipitated in the form of small particles.
The flocculant PAM has a large molecular weight, and has the functions of adsorption, bridging, coupling, 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 with PAM.
Most of the flocculants PAM used now are acidic flocculants and have a suitable pH value. When the pH value of the sewage exceeds the suitable pH value, it will cause the dissolution or fragmentation of the floc, which will have a very adverse effect on the air flotation separation of the dissolved air flotation machine. Therefore, in the process of operation, the pH value of the influent water should be monitored and controlled.
