Recommendations
Thin mechanized step screen
Downflow

Input data

Flow

Width (b)

Trashrack width (W)

Distance between trashracks (d)

Downflow level (y)

Inclination (º)

β - Kirschmer

Output data

Upflow level

Upflow velocity

Energy

Velocity between bars

Head loss

Upflow level at 50%

Upflow velocity at 50%

Velocity between bars at 50%

Upflow energy at 50%

Head loss at 50%

Description

The thin mechanized step screen is designed for debris removal in hydraulic flows, using calculation methods based on variables like flow rate and specific channel geometries.

Downflow calculation:

ParameterStandard UnitsDescription
Flowm³/sVolume of water passing through the section
Width (b)mChannel width
Trashrack width (W)mThickness of the trashrack bar
Distance between trashracks (d)mSpacing between the bars
Downflow level (y)mWater level at the downstream side
Inclination (º)ºAngle of the bars relative to the flow
β - Kirschmer-Kirschmer coefficient for calculation

Calculated results:

ParameterStandard UnitsDescription
Upflow level (ym)mWater level at the upstream side
Upflow velocity (Um)m/sVelocity of flow at the upstream side
Energy (Em)JEnergy associated with the upstream flow
Velocity between bars (Ubb)m/sFlow velocity between the trashrack bars
Head loss (Hl)mPressure drop or head loss
Upflow level at 50% (ym50)mUpstream level calculated with 50% of the flow
Upflow velocity at 50% (Um50)m/sUpstream velocity at 50% of the flow
Velocity between bars at 50% (Ubb50)m/sVelocity between bars with 50% of the flow
Upflow energy at 50% (Em50)JEnergy with 50% of the flow
Head loss at 50% (Hl50)mHead loss with 50% of the flow
Flow output (Qout)m³/sVolume of water exiting the system

References

  • WEF, ASCE, EWRI (2010). Design of municipal wastewater treatment plants. Volume 2: liquid treatment processes. New York, McGraw Hill.