Fish Protection Systems
20 December 2007, News release from Eimco Water Technologies Limited
Preventing fish from entering water intakes is a common problem facing many users abstracting large volumes of water from rivers, lakes, reservoirs, estuaries, the seas and oceans.
Fish protection has traditionally been achieved by using physical screen panels. However, where positive fish exclusion is impractical, or as a supplement to, behavioural barrier and guidance technologies have been effectively used.
Fish Protection Systems
Passive intake screens provide a reliable and robust physical barrier, separating aquatic life and debris from large volumes of water withdrawn from streams, lakes and reservoirs. Behavioural guidance systems stimulate the natural senses of fish to guide them away from a stimulus. These protection systems presently include:
• Acoustic-The most widely used behavioural system. Suitable for deflecting migrating fish, resident coarse fish, estuarine and marine fish.
• Strobe light-Used in conjunction with other behavioural systems. Suitable for deflecting fish less sensitive to sound, such as eels.
• Bubble curtains-Suitable for guiding fish to a point downstream.
• S.I.M.P.L.E.®-Fish handling band screens for marine life recovery and return.
Driven by legislation and environmental requisites, Eimco Water Technologies has developed some of the best land-based and marine engineered water and wastewater treatment systems. Today we offer a range of systems to treat raw water from intakes to wastewater prior to discharge at the outfall.
Our portfolio extends further to include some of the world's leading technologies in fish protection systems from physical screen barriers to behavioural, non-physical, screens and fish handling technologies. This unique range of technologies allows us to present a portfolio of methods that are known to work best for different species and life stages of fish in different situations.
Whilst safeguarding the natural habitat and future of aquatic species, fish protection systems have the added benefit of eliminating handling costs, disposal of fish kills, and maintenance of mechanical plant and processes.
Passive Screens-physical screens
Profiled Passive Screens exclusively distributed by Eimco Water Technologies provides a fish friendly, reliable and robust physical barrier, separating marine life and debris from large volumes of water being abstracted.
Behavioural Systems-non-physical fish guidance screens
Deterrent methods, commonly known as behavioural barriers or screens, use the natural response of fish to a stimulus, which may deflect the fish away from the stimulus. These systems are particularly favourable where physical fish screening is impractical, owing to the risk of fouling, either by attached biofouling or by waterborne organisms or debris.
Fish have a number of well developed senses, and are able to detect and react to a number of stimuli; light, sound, vibration, electrical, etc. For example herring or salmon smolt are more responsive to sound than eels who respond better to light stimuli.
The unique range of behavioural fish deflection systems produced by Fish Guidance Systems Ltd exclusively distributed worldwide by Eimco Water Technologies, offer a range of stimuli to deter fish from the immediate area of water intakes or to guide them into by-pass channels to a point downstream. Effective fish guidance systems include:
• Acoustic screens
• Bio-acoustic screens
• Strobe light
• Bubble curtains
Acoustic Screens are up to 95% Efficient
We offer two methods for Acoustic Fish Deterrents (AFD).
• SPA (Sound Projector Array) uses an array of underwater low frequency sound projectors to produce a diffused field of sound.
• BAFF (Bio-Acoustic Fish Fence) The BAFF is used primarily for diversion of fish. It employs sound sources coupled to a bubble curtain to produce a discreet wall of sound that can be used for more precise guidance of fish e.g. into a bywash channel.
Both systems operate between a frequency spectrum of 10 Hz - 3 KHz, producing a blend of signals applied as a pulse or crescendo, or a chirp across a frequency band.
Bubble & Strobe Light Screens
Bubble screens are one of the most basic behavioural barrier types. The screen works on the principal of a curtain of bubbles being generated via a submerged perforated tube through which compressed air is released. The wall of released bubbles is used to guide approaching fish into a bywash. Bubble curtains can achieve greater efficiency when combined with other deterrent systems such as sound or light.
Strobe lights generally give better results than continuous illumination. They are particularly effective in repelling eels and salmon. However, the success of strobe lighting remains site specific.
Combined with bubble curtains the strobe lights work well for some species, e.g. alewife, smelt, and gizzard shad.
Fish Handling S.I.M.P.L.E.
Our fish handling band screens using the S.I.M.P.L.E. process for marine life recovery are available in Dual Flow, Dual Flow Conversion or Thru Flow patterns. The advanced process has proven both reliable and effective regarding the significant increase in marine life survivability on raw water intakes and effectively contributes to achieving the 316(b) requirements (USA EPA legislation). The combination of the S.I.M.P.L.E. system and Fish Guidance Systems' acoustic system meet UK Best Practice Requirements.
Travelling fish buckets incorporated into the rotating band screen design provide a natural shelter for fish, that may become trapped, allowing them to be elevated to deck level where a series of gentle sprays sluice them into a return trough system back to their natural habitat, away from the intake flow.
• Power Stations
• Hydro-electric Stations
• Pulp & Paper
• Drinking Water Abstraction
• Flood Relief
• Inland Waterways
• Fish Farming
• Irrigation Schemes
Selecting the Best Available Technology
Eimco Water Technologies are a multi-disciplined international company offering a comprehensive product range of: screening equipment, water and wastewater, and water reuse technologies. The fish protection technologies complements our product portfolio in offering complete water abstraction solutions.
For further information please visit our website www.glv.com
For further information please email Eimco Water Technologies Limited