BEAUDREY has pioneered in the field of fish protection over the past 60 years. Many systems have been developed over the years; they have been constantly adapted to meet the evolving constraints with regards to environmental protection.
It is common knowledge that water intakes and cooling circuits are detrimental to some extent, to all forms of life carried by the water. For the purpose of screening, two categories of living matter are to be considered:
Adult fishes defined as having passed through all larval stages and reached full swimming capacity (called “swimmers”).
Their conservation first received attention from fishing sport and fishing industry lobbies as well as for the reproduction potential of adult fish.
Large plankton, eggs, larvae and juvenile fish with reduced swimming capacity, crustaceous animals (called “non-swimmers”).
Fish in general, are especially vulnerable to skin injuries and require particularly smooth screening mesh. They are also very sensitive to brutal pressure decreases and to physical shocks. They must not remain impinged on the mesh for long periods nor be forced to swim to exhaustion.
All swimmers proceed from non-swimmer phases.
MAIN EXISTING PROTECTION SYSTEMS
They are of two types:
The “Dissuasive Systems” which all tend to use the natural reactions of fish to divert them from the screens and return them to safety.
Electrical field barriers, sound, light or bubble barriers, louvered screens are available with variable case-by-case results. Such systems only concern swimmers. None are capable of turning all the fish away.
BEAUDREY can supply reliable sound and light barriers in association with a reputed specialist.
The “Last Ditch Defenses” which concern both non-swimmers and swimmers that have managed to pass through the upstream dissuasive systems.
Such systems are invariably the combination of traditional rotating screens with special features for saving water life.
The best known of these devices are:
All such systems use BEAUDREY’s special fish-friendly screening media.
HOW TO DESIGN A FISH-FRIENDLY SCREENING PLANT
Such intakes are the subject of various regulation which you must find out. Getting in contact with the authorities concerned at an early stage is important. For instance, the maximum approach velocity of a screen is very often imposed.
Some general rules apply to all cases:
The lower the approach velocity, the better as the fish can swim away.
By continually rotating the screens, reduce the amount of time the fish remain impinged on the mesh and lower the head-loss. This avoids fish exhaustion.
Dissuasion systems, if used, should be located right by the intake, not at the end of a long channel or pipe.
Determine how water life captured on the screens can be returned safely to their environment. Recirculation and predators must be avoided.
Whatever is done for the fish must not in any way impair the efficiency and reliability of the screens.
Remember that the civil engineering cost is generally much higher than that of the machines.
Whenever the regulatory, biological and hydraulic conditions are overly complex, calling in an experienced consulting engineer helps greatly.
There are two specific cases to consider:
(1) THE WATER INTAKE IS NEW
It can be designed to be the best possible from both fish and screening standpoints. Ask BEAUDREY: we can help you select the most cost-effective solutions and cooperate with your engineer.
Using the WIP or SWIFF screening systems is generally the best all-round solution as the civil structure is much reduced.
Optimized fish return circuit in an intake plant
(2) THE PLANT EXISTS AND NEEDS TO BE MADE FISH-FRIENDLY TO MEET LEGAL REQUIREMENTS
This is never easy and each case is special. Modifications to the civil structure should be minimal as they are both costly and structurally delicate.
Call in BEAUDREY from the start as the solution consists in finding what fits into the available space and meets the requirements.
The main alleys in this case are:
Improve the existing equipment by installing a BEAUDREY “Bio-flush”™ trash rake.
Add a low-pressure spray/lift tray kit to the existing travelling band screens or drum screens.
Implement continuous rotation to reduce impingement time.
Increase screen size if there is enough space.
Install a BEAUDREY “Scoop-a-fish”™ system on the rotating screens. This gives the best possible results with existing screens.
Replace the existing rotating screens with a BEAUDREY WIP or SWIFF screen. This gives the highest possible survival rate (“Best Available Technology” according to EPRI) and a totally reliable screening plant.
More details on the available BEAUDREY systems is given in the product list.