Sedimentation Tanks

Stainless Steel Equipment for Primary and Secondary Clarifiers - Circular and Rectangular

The inflow into primary clarifiers is a raw wastewater arriving from the grit trap. Organic and mineral solids are separated in the primary clarifier by sedimentation and removed as primary sludge. Secondary clarifiers should remove as much as possible of the biological sludge,activated sludge or trickling filter sludge, from the wastewater.

To achieve a clear effluent and an superior effluent quality meeting all standards, virtually all floating and suspended solids must be removed from the effluent and retained in the clarifier. The peak flow during storm events is critical for the design of the clarifiers. If the sludge layer rises too high there is a risk of sludge overflowing with the effluent. Sludge overflowing must be prevented in any case to comply with the consent standards.

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The hydraulic pattern of the inflow into secondary clarifiers are very important for their performance. Unsuited flow distribution can cause problems leading to high concentrations of suspended solids in the effluent.

A main problem is that the kinetic inflow energy is often too high in centrally fed clarifiers. This problem leads to eddies and recirculating flow patterns and results in reduced separation efficiency of the clarifier. The kinetic energy can be significantly reduced by feeding the clarifier at its circumference, as it is done with the HUBER Opti-Flow System.

A further determining factor for clarifier performance is a uniform and slow outflow of the effluent from the clarifier which can be guaranteed with a HUBER Submerged Effluent Pipe.