Protection of Fish at Freshwater and Saltwater Cooling Water Intake Structures Using Electricity

The search for successful and cost-effective solutions to fish impingement and entrainment at cooling water intake structures (CWIS) in freshwater, brackish water and full strength sea water continues unabated in line with the demands of 316(b) legislation in the USA. However, the focus continues on the management of the problem (fish collection-return systems) rather than the elimination of the problem (fish impingement / entrainment). Recent advances in our understanding of electric fields in water of different conductivities have convinced us that through the use of appropriate electrode configurations, voltage gradients and pulsed DC settings (pulse shape, frequency and width), relatively large intakes may be screened successfully by deploying innovative circuitry to reduce peak current while improving reliability. Electric fields may also be programmed to deter fish species, which have proven vulnerable to fish collection – return systems, by adjusting applied voltage, pulse shape, pulse width and pulse frequency on a daily or seasonal basis in accordance with the presence of target fish species’ life stages. Finally, where fish collection – return systems are in operation, electric fields may also be deployed at the fish return location(s) with the objective of excluding large predatory fish from these zones.