How to Keep Fish and Eel Screens from Clogging and Blocking

Ever more stringent regulations for the protection of fish and eels when abstracting raw water have added greatly to the maintenance costs of screening raw water. Fish and eel screening requires fine mesh, which, even in averagely clean river or lake water, can quickly become blocked blinded and clogged. This can affect irrigation, cooling water intakes, water treatment works, power plants and many more industrial sectors.

Here are some steps to ensure efficient operation of raw water intakes. These measures will ensure compliance to regulations, help to prevent fish and eel screens from clogging and minimise their maintenance.

1. Install Self-Cleaning Eel Screens:

Opt for self-cleaning filters like those manufactured and supplied by Rotorflush Filters Ltd. Designed for use directly in the water source, these filters have a continuous self-cleaning backwash system that keeps their mesh clear, preventing blockages before they occur.

The self-cleaning mechanism ensures that debris is cleared off the mesh continuously, maintaining optimal flow rates while protecting wildlife.

2. Choose Appropriate Filter Mesh:

Select screens with mesh sizes of 2 mm or less to comply with regulations for fish protection and eel screening. The smaller mesh prevents young eels, fish fry, and other aquatic life from passing through while allowing water to flow effectively. Wedge wire screens are to be avoided if possible; their structure offers a low open area, meaning larger screens are required for a given flow rate.

Woven mesh on Rotorflush screens are designed to handle high volumes of water while maintaining a clear mesh due to their in-built self-cleaning mechanism. They have a high open area to minimise their size for a given rate of flow.

3. Low Intake Velocities:

Choose filters and screens that offer low intake velocities to protect aquatic life from being entrained or impinged on the intake system. Current UK Eel protection Regulations and US EPA cooling water intake Rules stipulate low intake approach velocities.

Rotorflush filters are matched to flow rates and low intake velocities, ensuring that water flows at a rate that allows aquatic organisms to free themselves if caught.

4. Use Baffles or Screens

Installing baffles or screens upstream of the fish and eel screens can deflect large items of debris before they reach the screens. This can help prevent damage to screens and help stop screens clogging and blocking.

5. Regularly Inspect Screens:

Regularly inspect the fish and eel screens for any signs of blinding or blockage, particularly after extreme weather events. If you notice any issues, take action to clean or unclog the screens to prevent damage to your intake system.

Our user manuals provide details of how to look after our low-maintenance screens; typical inspection intervals are 4 - 6 months

By following these steps and using specialised self-cleaning filters with appropriate mesh sizes and low intake velocities, you can effectively prevent clogging and blocking in fish and eel screens, maintaining the efficiency of your water intake systems, and complying with current regulatory requirements.

Rotorflush Filters limited have many years’ experience of manufacturing and supplying self-cleaning intake screens. Our screens are used for eel protection ahead of raw water intakes for the water industry, for fish screening on vertical pumps providing cooling water and protecting irrigation and water monitoring equipment. Our screens enable compliance with UK and EU regulations to protect fish and eels, and compliance with EPA Rule 316(b) for cooling water.

This Article made reference to:

Rotorflush Filters Ltd: Information provided by Rotorflush Filters Ltd was instrumental in understanding the features and benefits of their self-cleaning filters for fish and eel screening applications.
National Geographic: Insights from National Geographic’s coverage on the American eel migration patterns and conservation challenges helped highlight the importance of protecting eels from obstacles like hydroelectric power plants.
Natel Energy: Details from Natel Energy’s research on turbine design for hydropower plants shed light on the impact of traditional turbines on fish populations, including vulnerable species like eels.