The decisive intake-screen design driver — holding through-slot approach velocity at or below 0.15 m/s to minimise fish impingement and larval entrainment under US EPA CWA §316(b) and equivalent rules.
Intake Screening for Water & Desalination Plants
Approach velocity is the single most important environmental design parameter for an intake screen. Holding the through-slot velocity at or below 0.15 m/s lets most fish swim away (reducing impingement) and, combined with fine slots, excludes eggs and larvae (reducing entrainment). It is the basis of US EPA Clean Water Act §316(b) compliance and equivalent rules worldwide, and it drives screen type, slot size and total screen area.
Velocity, slots and area set by ecology
The benchmark through-slot velocity for fish protection.
1–3 mm slots exclude eggs and larvae (entrainment).
Screen area = design flow ÷ allowable velocity.
Low velocity lets fish detect and swim away (impingement).
Fine slots physically exclude eggs and larvae.
Sampling and reporting demonstrate 316(b) performance.
| Parameter | Target | Why |
|---|---|---|
| Through-slot velocity | ≤0.15 m/s | Minimise impingement |
| Slot opening | 1–3 mm | Exclude eggs / larvae |
| Screen area | Flow ÷ 0.15 m/s | Sets number/size of screens |
| Regulation | CWA §316(b) / WFD | Permitting driver |
| Verification | Entrainment sampling | Compliance evidence |
Continue across the screening knowledge base
316(b) fish protection and low-entrainment design.
Read MoreLow-velocity, no moving parts — 316(b) benchmark.
Read MoreCylindrical passive screens parallel to the flow, outside-to-inside.
Read MorePassive wedge-wire screens on a submerged pipe end.
Read MoreThe screening hub for the seawater intake series.
Read MoreOur engineers select, size and material-match intake screening — approach velocity & 316(b) and the full train — for your debris load, fish-protection duty and downstream desalination process.
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