The Rise of Alum Flowers After Using Polyaluminum Chloride

Polyaluminum Chloride (PAC), as a highly efficient water-soluble inorganic polymer coagulant, is widely used in wastewater treatment. However, operators often encounter various issues during its application, among which the rise of large floc particles on the surface of sedimentation tanks is a common problem.

I. Problem Description and Causes

During wastewater treatment using polyaluminum chloride, operators may observe a significant number of large floc particles rising to the surface of the sedimentation tank. These flocs not only degrade effluent quality but also reduce the operational efficiency of the sedimentation tank and may even clog downstream treatment equipment.

The primary cause of this phenomenon is excessive polyaluminum chloride dosage. When the dosage exceeds the treatment capacity of the wastewater, surplus PAC rapidly binds with suspended solids to form large flocs. These flocs exhibit a fast upward velocity in the sedimentation tank, preventing effective settling and leading to surface accumulation.

Additionally, sludge discharge practices may contribute to floc rise. If sludge is not discharged promptly or in sufficient quantities, the sludge layer in the sedimentation tank thickens over time. Fine particles within the sludge may then ascend with the water flow, exacerbating the floc rise phenomenon.

II. Solutions

Adjust polyaluminum chloride Dosage:

Determine the optimal polyaluminum chloride dosage through bench-scale and pilot-scale tests based on actual wastewater quality and treatment requirements.

Continuously monitor floc formation and effluent quality during operation, adjusting the dosage as needed.

Reduce polyaluminum chloride dosage appropriately if floc rise is observed to slow down floc formation.

Enhance Sludge Discharge:

Perform regular sludge discharge to prevent excessive sludge layer thickness.

Schedule sludge discharge intervals and durations according to sludge generation rates and tank workload.

Control discharge volumes to avoid over- or under-removal of sludge.

Optimize Sedimentation Tank Design:

Improve the structural design and layout of the sedimentation tank to enhance settling efficiency and treatment capacity.

Consider increasing tank volume or modifying internal structures to accommodate varying water quality and treatment demands.

Strengthen Operational Management:

Conduct routine inspections and maintenance to ensure normal tank operation.

Strictly manage PAC storage, preparation, and application to ensure quality and safety.

Provide operator training to improve technical skills and safety awareness.

In summary, the rise of large floc particles in sedimentation tanks is a common challenge during PAC application. By optimizing dosage, improving sludge discharge practices, refining tank design, and strengthening operational management, this issue can be effectively mitigated, thereby enhancing wastewater treatment efficiency and effluent quality.