Optimizing Secondary Settling Performance through Dye Testing
Authors:
- Dan Miklos - Hazen and Sawyer
Optimizing secondary settling performance involves evaluating major performance limiting factors.
Typically areas of the evaluation involves considering operating parameters such as:
• Sludge quality (optimize settleability).
• Hydraulic loading or hydraulic throughput.
• Methods of controlling solids loading to the clarifiers.
• Optimizing sludge withdrawal based on the existing mechanical design.
The presentation will focus on responding to design limitations in:
• Tank geometry including depth.
• Velocity currents.
• Limitations of particle collision in a flocculation zone.
• Opportunities for baffling to improve clarifier performance.
The “Coanda Effect” on clarifier performance will be highlighted and explained in regards to clarifier operation. A sodium florescent dye study was performed in Peru, Indiana. Existing rectangular settling tanks were used as part of the wet weather design approach to the new plant design. The dye study was used to:
• Establish hydraulic efficiencies of secondary clarifiers.
• Establish “Coanda” signature.
• Profile clarifier “velocity currents.”
• Provide baseline information for any additional baffling that would improve dry weather and peak flow performance.
Baffling was installed in the secondary settling tanks and the dye study repeated to evaluate performance:
• Low cost baffling improved performance clarifier performance on both tank designs.
• Maximum dye concentrations were reduced while retention time was increased.
• Settling tanks modifications would be provided if the existing tanks were operated as part of the wet weather requirements.
To request a copy of the full presentation, please contact the author at .(JavaScript must be enabled to view this email address).
