Optimisation of clarifier-thickeners processing stable suspensions for turn-up/turn-down

Area of Science:

• Environmental Engineering
• Chemical Engineering
• Water Treatment Technology

Background:

• Wastewater solid-liquid separation equipment rarely operates at steady state.
• Variable feed loads challenge the performance of clarifiers and thickeners.
• Controlling solids residence time is critical to prevent issues like hydrolysis and rising sludge.

Purpose of the Study:

• To address the design of clarifiers and thickeners for minimum solids residence time.
• To optimize equipment performance under dynamic operating conditions.
• To develop a robust design methodology for efficient wastewater treatment.

Main Methods:

• Utilized a one-dimensional force balance theory of sedimentation for optimal design.
• Incorporated turn-up and turn-down scenarios directly into the optimization process.
• Developed a robust algorithm for solving design equations and optimizing solids residence time.

Main Results:

• Identified and illustrated three types of controlling phenomena in sedimentation.
• The optimized designs resulted in taller units with smaller plan areas compared to traditional methods.
• Demonstrated the effectiveness of the developed algorithm in practical design cases.

Conclusions:

• The proposed design methodology effectively minimizes solids residence time in wastewater clarifiers and thickeners.
• Optimized designs offer improved performance and space efficiency.
• The study provides a robust approach for the design of efficient solid-liquid separation equipment.