Reasons for the floating of alum flowers

Thread Content

1. The speed of the mixer in the clarifier was too high, which crushed the floc and reduced the flocculation effect; as a result, the strength of the sludge decreased and the flocs floated to the surface.     Solution: In such cases, it is necessary to control the straightness of the outer edge of the mixer impeller so that it does not exceed the specified design values. And appropriately increase the amount of coagulant to re-form a suspended sludge layer. 2. The return pipe in the clarifier is blocked, preventing the activated sludge from flowing back; flocs rise along the walls of the tank.     Solution: At this point, it is necessary to activate the backflow seam flushing pipeline to clear any blockages, carry out appropriate central sewage discharge, and increase the mixing machine’s flow rate to 4–5 times the amount of water discharged; this will help prevent the phenomenon of floating.     3. Sludge is not removed regularly in a timely manner, or the height of the sludge layer fluctuates greatly; in such cases, an excessive sludge layer causes the alumina flocs to float to the surface.     Solution: Sludge should be removed promptly, and the height of the sludge layer should be adjusted or controlled properly.  4. The amount of coagulant used is low, making it difficult to form flocs; as a result, the coagulation effect is poor, and the suspended solids fail to be separated and settled ； Alternatively, if too much coagulant is used, a counterion effect occurs, making it difficult to achieve aggregation; this also leads to the floccules floating to the surface.     Solution: Control the dosage of polyaluminum chloride (PAC) and polyacrylamide (PAM).     5. Sudden changes in water temperature disrupt the water flow, causing the sediment layer to rise to the surface.     Solution: The mixing speed can be appropriately reduced, the amount of coagulant used can be increased, and the water output can be adjusted to stabilize the water flow. If possible, the active mud or clay can be appropriately withdrawn.     6. In a clarifier where lime slurry is added, an excessive amount of it can result in the formation of CaCO3 colloids, causing the floc to be large in size and low in density, which facilitates their floating to the surface. However, if the amount added is too small, the resulting CaCO3 precipitates are small, the size of the floc particles is small as well, which reduces the strength of the sludge layer at the upper part of the reaction zone and causes it to float.     Solution: Adjust the mixer speed appropriately, maintain stable alkalinity, and increase the coagulant dosage as needed.     7. Due to the presence of a small amount of unpolymerized aluminum chloride in polyaluminum chloride, this aluminum chloride undergoes hydrolysis to form white flocculent colloids of AL(OH)3—alumina.     Solution: To remove these substances, simply add hydrochloric acid! But the main reason for this is that you chose poor-quality polyaluminum chloride