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Equalization Tank Sizing Calculator

Calculate equalization tank volume, dimensions, and retention time for flow balancing in water and wastewater treatment plants. Accounts for peak flow factors, surge volumes, and tank geometry.

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Equalization Tank Sizing Calculator

Enter your process parameters below to calculate design values. All calculations follow industry-standard methodologies.

m³/day
Peak / Average ratio (1.5-3.0 typical)
m³/day
hours at average flow
metres (typical 3-5m)
metres (typical 0.3-0.6m)
Length to width ratio (1.5-3.0 typical)

Equalization Design Principles

Equalization tanks smooth out diurnal flow and load variations to protect downstream biological treatment from shock loads. Typical retention times are 2-8 hours for municipal wastewater and 4-12 hours for industrial effluents with batch discharge patterns. The tank should be mixed to prevent solids settling and septicity.

  • Municipal: 2-6 hours at average dry weather flow
  • Industrial batch: 8-24 hours or one full batch cycle
  • Minimum HRT at peak flow should exceed 1 hour
  • Provide mixing (0.003-0.005 kW/m³) to prevent settling
  • Consider odour control for long retention times

Tank Configuration

Rectangular tanks with length-to-width ratios of 1.5:1 to 3:1 are common for process tanks. Circular tanks are efficient for smaller volumes. The inlet and outlet should be positioned to maximise plug flow characteristics and minimise short-circuiting. Baffled or compartmentalized designs improve flow distribution. Online equalization (variable level) provides more volume flexibility than offline (constant level) designs.

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