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WIP screens: a new technology for fish protection at water intakes

M. Fillon, P. Jackson & J. Lindsay E. Beaudrey & Cie, France

Abstract

Changing legislation in the United States and Europe has required the development of new screening systems. Screen manufacturers recognise that water intake systems have to address the challenge of drastically reducing or suppressing their impact on nature without reducing their efficiency or industrial reliability. This paper describes the development of Beaudrey’s Water Intake Protection (WIP) system and application at Omaha North Power Station in the USA, as well as describing other environmentally friendly systems developed by Beaudrey. The results of the Omaha North Power Station application of the WIP recovery and return system suggest that little if any mortality could be attributed to impingement and that fish impinged, removed and recovered from the WIP screen exhibited survival rates consistently at or above the performance standard of the USA’s suspended Clean Water Act Phase II rule of 80 to 95 percent reduction in impingement losses, and therefore is progressing towards becoming classified as ‘best available technology’ (BAT) for fish protection at water intakes. Keywords: water intakes, best available technology, fish recovery and return, screening systems, fish survival.

1 Introduction

Beaudrey is a fourth generation family owned business established in 1912, with over 4850 screening systems installed in over 80 countries worldwide. Beaudrey’s focus on fish-friendly equipment dates back to 1978. Recently, changing legislation in the USA and in Europe has required further development of existing water screening systems and a radically new approach to the development of fish recovery and return (FRR) systems.

International Fish Screening Techniques 2011 79

doi:10.2495/978-1-84564-849-7/007

www.witpress.com, ISSN 1755-8336 (on-line) WIT Transactions on State of the Art in Science and Engineering, Vol 71, © 2013 WIT Press

In the USA, the Environmental Protection Agency (EPA) is developing regulations under The Clean Water Act 316(b) which require that, “the location, design, construction and capacity of cooling water intake structures reflect the best technology available for minimising adverse environmental impact. Impacts are defined as impingement (where aquatic organisms are pinned against screens or other parts of a CWIS) and entrainment (when organisms are killed or injured as they are drawn through cooling water systems).” In the UK, the Environment Agency’s “Screening for Intake and Outfalls: a best practice guide” [1] published in 2005 provides an overview of relevant legislation and current methods and technologies that are common and work best for fish screening, while also identifying the gaps, where effectiveness of techniques has not been fully evaluated. Also, a guidance document published by the Environment Agency in 2010, ‘Cooling Water Options for the New Generation of Nuclear Power Stations in the UK’ [2], details the environmental issues associated with cooling water abstraction and acceptable mitigation techniques for fish protection. The most recent guidance developed by the Environment Agency concerns the screening against European eel as required under the Eel (England & Wales) Regulations 2009, which is described elsewhere in these conference proceedings (see Apprahamian et al., this volume). The examples mentioned demonstrate that the requirement to achieve demanding ecological status objectives will strengthen rather than weaken existing powers, and is likely to mean that owners will be required to ensure that any new developments meet sustainability criteria and that they do not lessen the existing ecological status of a water body but if anything improve it.

2 Beaudrey’s solution

Beaudrey recognises that water intake systems have to address the challenge of drastically reducing or suppressing their impact on natural resources without reducing their efficiency or industrial reliability by achieving the following criteria:

• minimizing the impingement time (e.g. 30 seconds) and therefore substantially reducing the biota mortality;

• minimizing entrainment of smaller organisms,

and that: • aquatic life must not be exposed to air; • aquatic life must not be subjected to skin injury; • aquatic life must not be subjected to e injurious water pressure

decreases nor to negative relative pressure; • aquatic life must not fall from a height greater than 500 mm (an extra

recommendation in some countries); • there must be sufficient water to provide adequate return capability.

80 International Fish Screening Techniques 2011


Field experience, application and the subsequent improvement of Beaudrey screens have led to the development of the WIP (Water Intake Protection) screening system. The WIP system provides:

• minimum impingement time; • an efficient sealing system (for rotating-screens, ≤0.5 mm), minimising

entrainment; • continuous screen rotation; • a recovery and return system that meets the above requirements.

3 The water intake protection (WIP) system

Beaudrey’s WIP screen was born from these considerations. Its design (Figures 1 and 2) combines proven screening technologies and the fish-recovery “Scoop-a-fish” system. The machine can fit into most new or existing intake channels.

Figure 1: Isometric illustration of WIP screen.

The system fits without civil structure modifications into any standard band screen pit. It essentially consists of:

• A “WIP” module slid into the existing screen guides and resting on the floor.

• Each “WIP” module is in fact a plate-mounted “W” debris filter with a Hidrostal fish pump drawing out the backwash water.

• Each module consists of a carrying plate with a large circular aperture fitted into the existing wall guides.

One rotating screening wheel divided in a number of radial, deep storage compartments. The downstream side of the compartments is fitted with the



Figure 2: Details of WIP screen and “Scoop-a-fish” system.

Figure 3: “No-Cling” fish screening panel.

patented Beaudrey “Nocling” fish-friendly, jelly-fish and fibre-proof screening panel (Figure 3). The Nocling panel offers a smooth and flat resting surface designed to minimise fish skin damage and surface trauma.

• The wheel shaft is held by radial arms to the support plate. • The drive wheel is located on the screened water side. • A number of wall-plates are positioned into the wall guides on top of

the “WIP” modules to prevent the water from by-passing the “WIP” modules.



• The wall-plates support the vertical backwash pipes that run up to the deck.

• A fixed backwash suction scoop secured to the carrying plate. The Hidrostal pump is of a special fish and eel friendly type.

The Hidrostal pump has a single spiral vane and large free passage and is a fish and eel friendly pump that avoids exposing aquatic organisms to the air and to potentially injurious changes in water pressure.

Figure 4: “Scoop-a-fish” system (left) and Hidrostal fish pump (right).

4 Testing and application

4.1 Omaha North Power Station

The first WIP screen was installed at Omaha North Power Station (USA: Figure 5), for an evaluation that would allow the station to meet the forthcoming Cleaning Water Act (CWA), paragraph 316(b) regulations. The study was carried out between April 2007 and August 2008 by an independent third party, EA Engineering Science and Technology, Inc.

4.1.1 Site description

The site is a coal fired generating station located in Omaha, Nebraska on the Nebraska bank of the Missouri River at river mile 625.2. The station has five generating units with a combined capacity of 663 MW. It utilizes a once-through cooling system that draws water from the Missouri River.



4.1.2 Missouri River data • Plant located 185 miles downstream of Gavins Point Dam. • Average Flow = 28,850 cfs. • Average Slope = 1ft/mile. • Normal Flow Velocity = 7 ft/s. • Bedrock Elevation = 958 feet. • Low Water Level = 963 feet. • Normal Water Level = 972 feet. • High Water Level = 1,000 feet.

Figure 5: Omaha North Power Station.

4.1.3 Power station data There are three cooling water intake structures. The total intake flow f is 1,130 cubic feet per second (730.4 MGD) and is 3.9% of the average Missouri River flow. There is one trash rack, inlet bay, sluice gate, and travelling screen for each circulating water pump. Intake Structure No. 1 contains five circulating water pumps that provide condenser cooling water for Unit 1 and Unit 2. Intake Structure No. 2 contains five circulating water pumps that provide condenser cooling water for Unit 3 and Unit 4. There is one trash rack, inlet bay, sluice gate, and travelling screen for each circulating water pump. Intake Structure No. 3 contains three circulating water pumps that provide condenser cooling water for Unit 5. There are two sets of trash racks, inlet bays, sluice gates, and travelling screens for each circulating water pump.



4.1.4 Unit 5 intake structure data • 3 Circulating Water pumps (58,750 gpm each). • Total water intake = 176,250 gpm. • Each pump supplied by two concrete intake cells w/ Link Belt traveling

screens. o 8’-8” Wide x 46’ deep. o 29,375 gpm per cell. o Normal water depth in cell = 14 feet. o Normal Thru Screen Velocity = 1.3 ft/s. o Low Water Level Approaching Velocity = 3.64 ft/s.

One of the six travelling screens in Intake Structure No. 3 was replaced by a Beaudrey WIP screen. For this application, the WIP screen consists of one rotating screen wheel and Hidrostal fish-friendly backwash pump mounted in a frame at the bottom of the inlet bay. The WIP screen openings are 0.24 inch (6mm) x 0.24 inch (6mm). The space above the screen wheel is blocked by wall plates forcing all incoming water to pass through the screen. The screening wheel is divided into pie-shaped sections by plates on the inlet side of the screen, with the Nocling panels. Fish and debris impinged on the wheel in these sections are vacuumed off as they rotate under a stationary scoop mounted over one section of the wheel by the Hidrostal pump. The pump impeller is designed to separate the water into “pockets” thus providing a safe place for the fish to remain as the water is moved through the pump. The pump created a backwash flow that removed fish, sand, rocks, and debris off the screen wheel and pumped it through a discharge pipe, for test purposes to a collection tank which overflowed back into the river. During operation, the screen wheel rotates at a constant two revolutions per minute for a maximum impingement time of fish on the screen of 30 seconds. The backwash pump has a variable speed drive that optimises the flow rate through the pump in response to river stage. This allows the pump to remain at peak operating efficiency for fish survival. Impinged fish are continuously submerged in water as they are pumped from the screen to the collection tank. The objectives of the study were to:

• To evaluate the impingement mortality reduction against CWA 316(b) performance standards.

• Evaluate 48-hour latent survival of fish removed by the Beaudrey WIP screen.

The trials used a combination of hatchery fish and native Missouri River fish. The results are summarised in Figure 6 and can be found detailed in full in publication [3]. The findings indicate little mortality observed during the survival studies Omaha North could be attributed to impingement.



Figure 6: Summary of fish impingement survival data from Omaha North Beaudray WIP screen trials (see [3]).

The studies show that fish impinged, removed, and recovered from the Beaudrey WIP screen exhibited survival rates at or above the performance standard of the suspended Phase II rule of 80 to 95 percent reduction in impingement losses.

4.2 EPRI Alden Research Laboratory

Testing of the Beaudray WIP screen at the Alden Research Laboratory (Massachusetts) is being carried out by the Electric Power Research Institute (EPRI), on freshwater species and further tests are planned on finer screening sizes.

5 Conclusion

To conclude, Beaudrey recognises that recently, changing legislation in the US and in Europe has required further development of existing systems and a radically new approach to the development of recovery and return screening systems. Beaudrey have developed and continue to develop fish- and eel-friendly systems in response to these changing requirements. The results of practical testing of the WIP recovery and return system suggest that little if any mortality could be attributed to impingement and that fish impinged, removed and recovered from the Beaudrey WIP screen exhibited survival rates consistently at or above the performance standard of the suspended CWA 316(b) Phase II rule of 80 to 95 percent reduction in impingement losses, and therefore en route to meeting BAT requirements for fish survival in water intakes under the USA’s requirements.



References

[1] Turnpenny, A.W.H. & O’Keeffe, N.J., Screening for intake and outfalls: a best practice guide. Environment Agency Science Report SC030231, 2005.

[2] Turnpenny, A.W.H., Coughlan, J., Ng, B., Crews, P. & Rowles, P. Cooling water options for the new generation of nuclear power stations in the UK. Environment Agency Science Report SC070015/SR, Environment Agency, Bristol (2010).

[3] Survival of Fish Impinged on a Rotary Disk Screen. North American Journal of Fisheries Management; 30: 1420–1433, 2010.



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