There are many reasons for the floating of alum in the clarifier. It will directly affect the quality of the effluent, so attention should be paid. The manufacturer has summarized the following points where a large amount of alum blooms in the clarification tank:

　　1. The speed of the mixer in the clarifier is too fast to break up the alum blooms, and it is more difficult for the broken alum blooms to agglomerate again, causing the strength of the sludge to decrease and the alum blooms to float. When encountering this kind of situation, it is necessary to control the alignment of the outer edge of the mixer impeller and not exceed the design regulations. And appropriately increase the amount of coagulant to form a suspended sludge layer again.

　　2. The backflow of the clarification tank is blocked, the active mud cannot flow back, and the alum blooms float up along the wall of the tank. At this time, open the backflow joint to flush the pipeline, clear the blockage, properly carry out the central drainage, and increase the flow rate of the mixer to 4~5 times of the outlet water volume, so as to avoid the phenomenon of floating.

　　 3. Sludge is not discharged regularly in time, or the height of the sludge layer fluctuates greatly. It is classified that the sludge layer is too high, causing the alum blooms to float up. At this time, the sludge should be discharged in time, and the height of the sludge layer should be adjusted or controlled.

　　 4. Small addition of coagulant makes it difficult to form alum blooms, poor coagulation effect, and the suspended solids cannot be separated and settled; or if the addition of coagulant is too large, counter-ion phenomenon occurs, which is difficult to agglomerate, and it will also cause alum blooms to float up.

　　 5. The water temperature changes suddenly, and the water flow is disturbed as a result, and the mud layer floats up. At this time, you can appropriately reduce the stirring speed, appropriately increase the amount of coagulant, and adjust the amount of water to stabilize the water flow. If possible, the activated mud or slime can be properly withdrawn.

　　6. If it is a clarification tank with lime slurry, CaCO3 colloid will be formed due to the excessive increase, which makes the alum flower large in volume and small in density and easy to float. However, if the dosage is too small, the CaCO3 produced will be small, the volume of the alum is small, and the strength of the sludge layer in the upper part of the reaction zone will decrease and rise. At this time, the mixer speed should be adjusted appropriately, and the alkalinity should be controlled stably, and coagulant should be appropriately increased dose.

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