River Blackwater (Langford)

Chosen Solution for the Langford Mill Eel Screen

To meet the legal requirements of 'The Eels (England and Wales) Regulations 2009' Essex & Suffolk Water have an obligation to install fine screening at our main raw water intakes to prevent eel entrapment within pumping systems. At the Langford Mill, the chosen option is a static 'Eco-Screen' which will sit in the river in front of the intake and water will filter through the fine mesh panels to the original pumps inside the Mill building. If the screen starts to block with the debris in the river, sensors will detect the difference in levels and will initiate an automated cleaning operation. This activates a wiper arm with bristles (like a large toothbrush) that will draw the debris up the screen to a trough and a wash water system in the trough will flush the debris into a catchment trolley which will be regularly cleared by our Operatives.

For the Eels Regulations, the key parameter is the speed at which the water engages with the screen, called the 'approach velocity'. This needs to be low enough to enable eels and fish to swim away rather than being drawn towards the screen and unable to escape. To achieve the right approach velocity the screen needs a large surface area. This meant that some screening types were not suitable for the Mill as the number of units and overall footprint would have been excessively large in this location, we therefore selected the most compact solution available to minimise the visual impact. The photomontage below depicts how the screen will fit with the existing structures. It will be a dark colour to blend in with the surroundings as much as possible.