Desalination Plant Intakes - WateReuse Association

Table 1 – Potential Open Intake Impingement and Entrainment Reduction TechnologiesImpact Reduction PotentialType ofHow Do They Work?TechnologiesI&EReductionImpingement EntrainmentMeasuresPhysicalBarriersCollection&ReturnSystemsDiversionSystemsBehavioralDeterrentDevicesBy Blocking Fish Passageand Reducing IntakeVelocityEquipment is Installed onFine Screens for FishCollection and Return tothe OceanDevices Which Divert Fishfrom the Screens and DirectBack to the OceanRepulsing Organisms fromthe Intake by IntroducingChanges that Alert Them• Wedgewire Screens• Fine Mesh Screens• Microscreening Systems• Barrier Nets• Aquatic Filter Barriers• Ristroph TravellingScreens• Fine Mesh TravellingScreens• Angled Screens withLouvers• Inclined Screens• Velocity Caps• Acoustic Barriers• Strobe Lights• Air Bubble CurtainsYesYesYesYesYesNoYesNoAn example of the synergistic use of I&E reduction technologies is the previously referenced 40MGD Beckton desalination plant in London. Besides wedgewire screens, the intake structure ofthis plant is equipped with an acoustic fish deflection system. This system includes eight lowfrequency sound generation units that deflect fish movement away from the wedgewire intakestructure (Figure 12). The scale at the bottom of this figure indicates the sound level of theacoustic fish deflection system in decibels (dB). The low frequency (25 – 400 Hz) sound level ismaintained at a level of 150 dB or more, which gives a clear cue for danger to fish entering thearea of the intake. This acoustic system is only operated for short periods, twice daily, duringpump startup. At this time, no published data are available regarding the I&E reductionefficiency of this technology.Seawater Desalination Plant Intakes – Impingement and Entrainment Page 17