- Email: [email protected]
Design of a rapid-flow seawater supply system for the university of Connecticut's marine laboratory at Noank
Ocean Engng, Vol. 17, No 1/2, pp. 171-178, 1990. Printed in Great Britain.
0029--8018/90 $3.00 + .00 Pergamon Press plc
DESIGN OF A RAPID-FLOW SEAWATER SUPPLY SYSTEM FOR THE UNIVERSITY OF CONNECTICUT'S MARINE LABORATORY AT NOANK ALAN C. CAOLO General Dynamics, Electric Boat Division, 75 Eastern.Point Road, Groton, CT 06340, U.S.A.
and STEPHEN SPOTIE Sea Research Foundation and Marine Sciences Institute, The University of Connecticut, Noank, CT 06340, U.S.A. Abstract--Seawater supply systems serving coastal laboratories typically are affected by two maladies: reduced flow caused by biofouling, and gas supersaturation of the influent stream. The first results in unpredictable supplies and extended maintenance; the second increases the mortality of the experimental animals. We describe the design of a system installed at the University of Connecticut's Noank laboratory on Long Island Sound. Biofouling has been eliminated by uninterrupted rapid flow (> 2.5 m/sec); simple degassing units seem to have solved the gas supersaturation problem. Engineering features of the system are described in detail. Potential problems and future improvements are discussed.
INTRODUCTION BIOFOULING and gas supersaturation are common occurrences in marine laboratories that rely on continuous seawater supplies (Bouck et al., 1984; McLeod, 1978; Spotte, 1979; Sprague, 1966). The accumulation of fouling organisms reduces the flow rate of the influent stream. Captive fishes and invertebrates are susceptible to gas-bubble disease if the water is supersaturated with oxygen or nitrogen (Colt et al., 1986; Mathias and Barica, 1985; Marking, 1987; Fickeisen and Schneider, 1976). To control biofouling, Sprague (1966) recommended that a seawater supply system be duplicated from start to finish. A portion can be shut down periodically and allowed to become anoxic (Sprague, 1966), or flushed with freshwater (Bouck, 1981; Lindsay, 1964). Degassing of freshwaters and seawater can be accomplished by several processes (see the review of Colt, 1986), including vacuum flow (Fuss, 1983), packed-column aeration (Bouck et al., 1984; Marking et al., 1983), and surface agitation (Penrose and Squires, 1976; Wold, 1973). Duplicate seawater supply systems are costly to install and often labor-intensive afterward. Conventional degassing devices may consume considerable space. The system we describe has been operational at the University of Connecticut's marine laboratory at Noank for several months. Biofouling and gas supersaturation are no longer evident. The system was economical to install and has been easy to maintain, because duplication is unnecessary and the low maximum operating pressure (3.835 x 105 N/m z) and rapidflow rate permit the use of thin-walled pipe of small diameter. As a side benefit, the amount of pipe inside the building was reduced substantially. Degassing is accomplished 171
172
A . C . CAOLO and S. SPOTI'E
in simple overhead devices that induce turbulence of the influent stream near the discharge point. METHODS The key design feature is rapid, continuous flow. Seawater velocities approaching 1.03 m/sec prevent the attachment of most fouling organisms (Benson et al., 1973). Doubling this velocity suppresses the growth of developing barnacles and removes recently settled larvae (Benson et al., 1973). We selected a velocity of 2.5 m/sec to be conservative, although the actual minimum velocity obtained was 2.7 m/sec. All pipe is PVC (polyvinyl chloride, U.S. schedule 40); valves are high-impact plastic. The design flow rate of the influent stream is 1.278 × 10 - 2 m3/sec, apportioned equally to three laboratories in the building at design flow rates of 4.259 × 10 3 m3/sec. The enclosed pump station is located at the end of the dock, 41 m from the building (Fig. 1). Seawater from Long Island Sound is drawn through an open-ended suction pipe [0.076 m inside diameter (ID)]. The intake is - 1.5 m below the surface at mean low water (tidal range < 1 m). The intake pipe is bifurcate, and each end is fitted with a coarse-mesh strainer (0.0035 x 0.0015 m sieve size). The dual arrangement allows maintenance personnel to remove and clean the strainers one at a time without shutting down the system. The design specifies three electrically-driven (5.59 kW), self-priming centrifugal pumps plumbed in parallel. The pump housings are polypropylene; the impellers are fiberglass-reinforced plastic. All internal metallic parts (e.g. screws, washers, bushings) are stainless steel or titanium. Seawater is drawn into the system through a suction header (0.051 m ID) with isolation valves. The pumps discharge through check valves integral with their housings into a discharge header (0.051 m ID) with isolation valves. Two pumps operating simultaneously provide the design flow rate of 1.278 x 10 -2 m3/ sec (6.39 × 10 -3 m3/sec each) at a total dynamic head of 38.1 m. The third pump is on standby. The static head is 6.1 m from mean low water to the final delivery elevation inside the laboratories. A dynamic head of 32 m is required to overcome viscous frictional losses and velocity head differences in the piping system on the suction and discharge sides of the pump station. The pumps are sized to provide the required flow rate, but the design includes a 10% safety margin against the design system resistance with all valves open. Seawater is delivered to a central distribution manifold inside the building through a main influent pipe (0.076 m ID) 64.7 m long (Fig. 1). Flow balancing is regulated from the central manifold with globe throttle valves (Fig. 2). A pipe (0.041 m ID) with globe throttle valves extends from the manifold to each laboratory supply branch. This line can also be used to discharge the entire flow if a laboratory must be shut down. A laboratory arrangement is shown in Fig. 3. Pipe sizes are reduced continuously at every branch to maintain velocities that exceed the minimum design value of 2.5 m/sec. Downstream of the manifold the system branches to the three laboratory networks by means of piping (0.041 m ID) that delivers the design flow rate of 4.259 x 103 m/sec. Final reduction (0.025 m ID) is reached at the inlet to the degassers (Fig. 4). The degassers are PVC pipes 1.918 m long (0.304 m ID), capped at the ends, with longitudinal saw cuts for exposing influent seawater to the atmosphere (Figs 4 and 5).
Design of a rapid-flow seawater supply system
Laboratory No 1
f
Laboratory No 2
]
173
Laboratory No 3
e
g°,io,o"
,i ° ,] Pump No 1
I o.ost m
$YMBOL LIST
(~ N ~,
BALLVALVE
ID
Pump No 2 t0.051 m ID
]
Pump No 3
I o.os, m
ID
.076 m ID
CHECKVALVE STRAINER
Fro. 1. Pump station and distribution manifold.
The area of each saw cut is 0.304 m2. The units are mounted in raised wood frames 1.12 m above the wet tables. One degasser serves two wet tables. The influent stream entering a degasser is dispersed through a perforated pipe 1.12 m long (0.041 m ID) to reduce impingement velocities. Supersaturated gases are brought rapidly to steadystate, after which the water is discharged by surface overlow to the wet tables below through vertical feed pipes 0.178 m long (0.076 m ID, one feed pipe per table). Eight threaded ball valve ports (0.0127 m) inserted in the bottom of each degasser permit the attachment of hoses with threaded ends. We consider this is an important design
174
A . C . CAOt.O and S. SPOrrE
0.025 m ID
(
~ . l l = t m )76 m I0
Flush I connection
TI 0.025 m ID
0076 m ID
E Supply to E
Laboratory
E 0.025 m ID
Flush connection I
(
,76 m IO v
-
0.025 m IO
SYMBOL LIST ~ I N I 0.076 m ID
Valve
(D
Ball
~
H o s e Conn
I0
~ O l Degasser
F]~. 3. Laboratory arrangement showing supply and discharge lines. Wet tables are represented by shaded
rectangles.
feature, because experiments that require low flow rates can be conducted simultaneously in several small aquarium tanks without compromising the flow rate of the main supply system. The wet tables are constructed of plywood (0.0127 m thick) coated with clear polyester resin and supported 1.0 m above the floor on wood frames. The tables are 2.13 m long × 0.914 m wide x 0.152 m deep. The tables are drained continuously by surface overflow through single drain pipes (0.076 m ID) 0.102 m high. The influent feed pipes and drain pipes are located at opposite ends of the tables to enhance mixing. Effluent seawater is removed by gravity flow (Fig. 3). The drainage system consists of a discharge header (0.152 m ID) arranged peripherally around the laboratories. The
Fie;. 2. Central manifold with globe valves.
175
FIG. 5. Photograph
of one of the operating
laboratories
showing degasm~
and water
tables.
Design of a rapid-flow seawater supply system
177
1.916m
i~ 0"152 m't'i I
/i
•
. . . . . . . I . ! t 0 . o . i . . . ~ , . . , e.---e-~ e,.--.,~,---.e- t-o. 0 1 - - t - - .
°"'-m--;4 !
i
=~_
0.826m
i
~'.~. 0.559m-~l~ : PLAN VIEW Degasser supply
Water
l
e
v
e
' ~'-
Coupling
l
~
To laboratory tanks
B Pipe joint seal
ELEVATION
~ ,
VIEW
Degasser supply Water level ~
~?''t
"m'~'i~6 Pipe joint
mID
seal SECTION VIEW
FIG.4.Degasserdetails. header has 0.152 m nominal, vertically-oriented tee fittings, which provide openings for access to the discharge header as required for each wet table. The effluent from each wet table is drained by gravity through a pipe (0.076 m ID) to an access port on the discharge header. Each header carries the discharge outside the building, where it empties into Long Island Sound. DISCUSSION The rapid-flow concept is well known in the marine shipping industry: the hulls of vessels kept in motion are notably less susceptible to fouling than are the hulls of stationary vessels. The principles of rapid-flow are also amenable to the design of inexpensive seawater supply systems for coastal laboratories. Our design contains at least three flaws. First, the continuous demand on the pumps may lead to future maintenance problems. Second, the rapid flow rate may not prevent
178
A. (~. CAOI.Oand S. SI,olq~
t h e f o r m a t i o n o f s l i m e layers in the p i p e s a n d e x c e s s i v e algal g r o w t h s in t h e d e g a s s e r s , a l t h o u g h n e i t h e r has b e e n t r o u b l e s o m e so far. T h i r d , t h e d e g a s s e r s are p r o b a b l y i n a d e q u a t e to d e a l w i t h s e r i o u s i n c i d e n c e s of gas s u p e r s a t u r a t i o n , a n d d i f f e r e n t units o f p r o v e n d e s i g n (e.g. p a c k e d c o l u m n s ) m a y be n e e d e d e v e n t u a l l y . F u t u r e i m p r o v e m e n t s i n c l u d e the a d d i t i o n o f filtration e q u i p m e n t to c o n t r o l s i l t a t i o n in the d e g a s s e r s a n d w e t tables. Acknowledgements--Gary Adams provided useful suggestions during the design phase. Patricia M. Bubucis took the photographs. The system was assembled by Arthur Lima and his staff. This is Contribution No. 74 of Sea Research Foundation and No. 223 of the Marine Sciences Institute.
REFERENCES BENSON, P.H., BRINING, D.L. and PERRIN, D.W. 1973. Marine fouling and its prevention. Mar. Technol. 10, 30-37. BOUCK, G.R. 1981. Easily constructed, economical seawater intake and supply system. J. WId Maricult. Soc. 12, 51-58. BOUCK, G.R., KING, R.E. and BOUCK-SCHMIDJ,G. 1984. Comparative removal of gas supersaturation by plunges, screens and packed columns. Aquacult. Engng 3, 15%176. COLT, J. 1986. Gas supersaturation - - impact on the design and operation of aquatic systems. Aquacuh. Engng 5, 4%85. COLT, J., BOUCK, G. and FIm, ER, L. 1986. Review of current literature and research on gas supersaturation and gas bubble trauma. Special Publication No. l, Bioengineering Section, American Fisheries Society, Portland, Oregon (52 pp.). FICKEISEN, D.H. and SCHNEIDER, M.J, (eds) 1976, Gas bubble disease. CONF-741033, National Technical Information Service, U.S. Department of Commerce, 123 pp. Springfield, Virginia. Fuss, J.T. 1983. Effective flow-through degasser for fish hatcheries. Aquacult. Engng 2, 3(11-307. LINDSAY, C.E. 1964. Sea-water system at the Point Whitney Shellfish Laboratory. In Sea-water Systems )br Experimental Aquariums, CLARK, J.E. and CLARK, R.L. (eds), pp. 147-153. Research Report No. 63, U.S. Fish and Wildlife Service, Bureau of Sport Fisheries and Wildlife, Washington, DC. MARKING, L.L. 1987. Gas supersaturation in fisheries: causes, concerns, and cures. Fish and Wildlife Leaflet No. 9, U.S. Fish and Wildlife Service, Washington, D.C. (10 pp.). MARKING, L.L., DAWSON, V.K. and CROWTHER,J.R. 1983. Comparison of column aerators and a vacuum degasser for treating supersaturated culture water. Prog. Fish-Cult. 45, 81-83. MATHIAS,J.A. and BARICA,J. 1985. Gas supersaturation as a cause of early spring mortality of stocked trout, Can. J. Fish. Aquat. Sci. 42, 268-279, McLEOD, G.C. 1978. The gas bubble disease of fish. In The Behaviour of Fish and Other Aquatic Animals. MOSTOVSKY, D.I. (ed.), pp. 319-339. Academic Press, New York. PENROSE, W.R. and SQUIRES. W.R. 1976. Two devices for removing supersaturating gases in aquarium systems. Trans. Am. Fish. Soc. 105, 1t6-118. SPOrrE, S. 1979. Seawater Aquariums: the Captive Environment. Wiley, New York. r~ SPRAGUE, J.B. 1966. Filtration of sea-water for marine biological laboratories. Manuscript Report Series (Biological) No. 851, Fisheries Research Board of Canada, Ottawa (22 pp.). WOLD, E. 1973. Surface agitators as a means to reduce nitrogen gas in a hatchery water supply. Prog. FishCult. 32, 14.3-146.
0029--8018/90 $3.00 + .00 Pergamon Press plc
DESIGN OF A RAPID-FLOW SEAWATER SUPPLY SYSTEM FOR THE UNIVERSITY OF CONNECTICUT'S MARINE LABORATORY AT NOANK ALAN C. CAOLO General Dynamics, Electric Boat Division, 75 Eastern.Point Road, Groton, CT 06340, U.S.A.
and STEPHEN SPOTIE Sea Research Foundation and Marine Sciences Institute, The University of Connecticut, Noank, CT 06340, U.S.A. Abstract--Seawater supply systems serving coastal laboratories typically are affected by two maladies: reduced flow caused by biofouling, and gas supersaturation of the influent stream. The first results in unpredictable supplies and extended maintenance; the second increases the mortality of the experimental animals. We describe the design of a system installed at the University of Connecticut's Noank laboratory on Long Island Sound. Biofouling has been eliminated by uninterrupted rapid flow (> 2.5 m/sec); simple degassing units seem to have solved the gas supersaturation problem. Engineering features of the system are described in detail. Potential problems and future improvements are discussed.
INTRODUCTION BIOFOULING and gas supersaturation are common occurrences in marine laboratories that rely on continuous seawater supplies (Bouck et al., 1984; McLeod, 1978; Spotte, 1979; Sprague, 1966). The accumulation of fouling organisms reduces the flow rate of the influent stream. Captive fishes and invertebrates are susceptible to gas-bubble disease if the water is supersaturated with oxygen or nitrogen (Colt et al., 1986; Mathias and Barica, 1985; Marking, 1987; Fickeisen and Schneider, 1976). To control biofouling, Sprague (1966) recommended that a seawater supply system be duplicated from start to finish. A portion can be shut down periodically and allowed to become anoxic (Sprague, 1966), or flushed with freshwater (Bouck, 1981; Lindsay, 1964). Degassing of freshwaters and seawater can be accomplished by several processes (see the review of Colt, 1986), including vacuum flow (Fuss, 1983), packed-column aeration (Bouck et al., 1984; Marking et al., 1983), and surface agitation (Penrose and Squires, 1976; Wold, 1973). Duplicate seawater supply systems are costly to install and often labor-intensive afterward. Conventional degassing devices may consume considerable space. The system we describe has been operational at the University of Connecticut's marine laboratory at Noank for several months. Biofouling and gas supersaturation are no longer evident. The system was economical to install and has been easy to maintain, because duplication is unnecessary and the low maximum operating pressure (3.835 x 105 N/m z) and rapidflow rate permit the use of thin-walled pipe of small diameter. As a side benefit, the amount of pipe inside the building was reduced substantially. Degassing is accomplished 171
172
A . C . CAOLO and S. SPOTI'E
in simple overhead devices that induce turbulence of the influent stream near the discharge point. METHODS The key design feature is rapid, continuous flow. Seawater velocities approaching 1.03 m/sec prevent the attachment of most fouling organisms (Benson et al., 1973). Doubling this velocity suppresses the growth of developing barnacles and removes recently settled larvae (Benson et al., 1973). We selected a velocity of 2.5 m/sec to be conservative, although the actual minimum velocity obtained was 2.7 m/sec. All pipe is PVC (polyvinyl chloride, U.S. schedule 40); valves are high-impact plastic. The design flow rate of the influent stream is 1.278 × 10 - 2 m3/sec, apportioned equally to three laboratories in the building at design flow rates of 4.259 × 10 3 m3/sec. The enclosed pump station is located at the end of the dock, 41 m from the building (Fig. 1). Seawater from Long Island Sound is drawn through an open-ended suction pipe [0.076 m inside diameter (ID)]. The intake is - 1.5 m below the surface at mean low water (tidal range < 1 m). The intake pipe is bifurcate, and each end is fitted with a coarse-mesh strainer (0.0035 x 0.0015 m sieve size). The dual arrangement allows maintenance personnel to remove and clean the strainers one at a time without shutting down the system. The design specifies three electrically-driven (5.59 kW), self-priming centrifugal pumps plumbed in parallel. The pump housings are polypropylene; the impellers are fiberglass-reinforced plastic. All internal metallic parts (e.g. screws, washers, bushings) are stainless steel or titanium. Seawater is drawn into the system through a suction header (0.051 m ID) with isolation valves. The pumps discharge through check valves integral with their housings into a discharge header (0.051 m ID) with isolation valves. Two pumps operating simultaneously provide the design flow rate of 1.278 x 10 -2 m3/ sec (6.39 × 10 -3 m3/sec each) at a total dynamic head of 38.1 m. The third pump is on standby. The static head is 6.1 m from mean low water to the final delivery elevation inside the laboratories. A dynamic head of 32 m is required to overcome viscous frictional losses and velocity head differences in the piping system on the suction and discharge sides of the pump station. The pumps are sized to provide the required flow rate, but the design includes a 10% safety margin against the design system resistance with all valves open. Seawater is delivered to a central distribution manifold inside the building through a main influent pipe (0.076 m ID) 64.7 m long (Fig. 1). Flow balancing is regulated from the central manifold with globe throttle valves (Fig. 2). A pipe (0.041 m ID) with globe throttle valves extends from the manifold to each laboratory supply branch. This line can also be used to discharge the entire flow if a laboratory must be shut down. A laboratory arrangement is shown in Fig. 3. Pipe sizes are reduced continuously at every branch to maintain velocities that exceed the minimum design value of 2.5 m/sec. Downstream of the manifold the system branches to the three laboratory networks by means of piping (0.041 m ID) that delivers the design flow rate of 4.259 x 103 m/sec. Final reduction (0.025 m ID) is reached at the inlet to the degassers (Fig. 4). The degassers are PVC pipes 1.918 m long (0.304 m ID), capped at the ends, with longitudinal saw cuts for exposing influent seawater to the atmosphere (Figs 4 and 5).
Design of a rapid-flow seawater supply system
Laboratory No 1
f
Laboratory No 2
]
173
Laboratory No 3
e
g°,io,o"
,i ° ,] Pump No 1
I o.ost m
$YMBOL LIST
(~ N ~,
BALLVALVE
ID
Pump No 2 t0.051 m ID
]
Pump No 3
I o.os, m
ID
.076 m ID
CHECKVALVE STRAINER
Fro. 1. Pump station and distribution manifold.
The area of each saw cut is 0.304 m2. The units are mounted in raised wood frames 1.12 m above the wet tables. One degasser serves two wet tables. The influent stream entering a degasser is dispersed through a perforated pipe 1.12 m long (0.041 m ID) to reduce impingement velocities. Supersaturated gases are brought rapidly to steadystate, after which the water is discharged by surface overlow to the wet tables below through vertical feed pipes 0.178 m long (0.076 m ID, one feed pipe per table). Eight threaded ball valve ports (0.0127 m) inserted in the bottom of each degasser permit the attachment of hoses with threaded ends. We consider this is an important design
174
A . C . CAOt.O and S. SPOrrE
0.025 m ID
(
~ . l l = t m )76 m I0
Flush I connection
TI 0.025 m ID
0076 m ID
E Supply to E
Laboratory
E 0.025 m ID
Flush connection I
(
,76 m IO v
-
0.025 m IO
SYMBOL LIST ~ I N I 0.076 m ID
Valve
(D
Ball
~
H o s e Conn
I0
~ O l Degasser
F]~. 3. Laboratory arrangement showing supply and discharge lines. Wet tables are represented by shaded
rectangles.
feature, because experiments that require low flow rates can be conducted simultaneously in several small aquarium tanks without compromising the flow rate of the main supply system. The wet tables are constructed of plywood (0.0127 m thick) coated with clear polyester resin and supported 1.0 m above the floor on wood frames. The tables are 2.13 m long × 0.914 m wide x 0.152 m deep. The tables are drained continuously by surface overflow through single drain pipes (0.076 m ID) 0.102 m high. The influent feed pipes and drain pipes are located at opposite ends of the tables to enhance mixing. Effluent seawater is removed by gravity flow (Fig. 3). The drainage system consists of a discharge header (0.152 m ID) arranged peripherally around the laboratories. The
Fie;. 2. Central manifold with globe valves.
175
FIG. 5. Photograph
of one of the operating
laboratories
showing degasm~
and water
tables.
Design of a rapid-flow seawater supply system
177
1.916m
i~ 0"152 m't'i I
/i
•
. . . . . . . I . ! t 0 . o . i . . . ~ , . . , e.---e-~ e,.--.,~,---.e- t-o. 0 1 - - t - - .
°"'-m--;4 !
i
=~_
0.826m
i
~'.~. 0.559m-~l~ : PLAN VIEW Degasser supply
Water
l
e
v
e
' ~'-
Coupling
l
~
To laboratory tanks
B Pipe joint seal
ELEVATION
~ ,
VIEW
Degasser supply Water level ~
~?''t
"m'~'i~6 Pipe joint
mID
seal SECTION VIEW
FIG.4.Degasserdetails. header has 0.152 m nominal, vertically-oriented tee fittings, which provide openings for access to the discharge header as required for each wet table. The effluent from each wet table is drained by gravity through a pipe (0.076 m ID) to an access port on the discharge header. Each header carries the discharge outside the building, where it empties into Long Island Sound. DISCUSSION The rapid-flow concept is well known in the marine shipping industry: the hulls of vessels kept in motion are notably less susceptible to fouling than are the hulls of stationary vessels. The principles of rapid-flow are also amenable to the design of inexpensive seawater supply systems for coastal laboratories. Our design contains at least three flaws. First, the continuous demand on the pumps may lead to future maintenance problems. Second, the rapid flow rate may not prevent
178
A. (~. CAOI.Oand S. SI,olq~
t h e f o r m a t i o n o f s l i m e layers in the p i p e s a n d e x c e s s i v e algal g r o w t h s in t h e d e g a s s e r s , a l t h o u g h n e i t h e r has b e e n t r o u b l e s o m e so far. T h i r d , t h e d e g a s s e r s are p r o b a b l y i n a d e q u a t e to d e a l w i t h s e r i o u s i n c i d e n c e s of gas s u p e r s a t u r a t i o n , a n d d i f f e r e n t units o f p r o v e n d e s i g n (e.g. p a c k e d c o l u m n s ) m a y be n e e d e d e v e n t u a l l y . F u t u r e i m p r o v e m e n t s i n c l u d e the a d d i t i o n o f filtration e q u i p m e n t to c o n t r o l s i l t a t i o n in the d e g a s s e r s a n d w e t tables. Acknowledgements--Gary Adams provided useful suggestions during the design phase. Patricia M. Bubucis took the photographs. The system was assembled by Arthur Lima and his staff. This is Contribution No. 74 of Sea Research Foundation and No. 223 of the Marine Sciences Institute.
REFERENCES BENSON, P.H., BRINING, D.L. and PERRIN, D.W. 1973. Marine fouling and its prevention. Mar. Technol. 10, 30-37. BOUCK, G.R. 1981. Easily constructed, economical seawater intake and supply system. J. WId Maricult. Soc. 12, 51-58. BOUCK, G.R., KING, R.E. and BOUCK-SCHMIDJ,G. 1984. Comparative removal of gas supersaturation by plunges, screens and packed columns. Aquacult. Engng 3, 15%176. COLT, J. 1986. Gas supersaturation - - impact on the design and operation of aquatic systems. Aquacuh. Engng 5, 4%85. COLT, J., BOUCK, G. and FIm, ER, L. 1986. Review of current literature and research on gas supersaturation and gas bubble trauma. Special Publication No. l, Bioengineering Section, American Fisheries Society, Portland, Oregon (52 pp.). FICKEISEN, D.H. and SCHNEIDER, M.J, (eds) 1976, Gas bubble disease. CONF-741033, National Technical Information Service, U.S. Department of Commerce, 123 pp. Springfield, Virginia. Fuss, J.T. 1983. Effective flow-through degasser for fish hatcheries. Aquacult. Engng 2, 3(11-307. LINDSAY, C.E. 1964. Sea-water system at the Point Whitney Shellfish Laboratory. In Sea-water Systems )br Experimental Aquariums, CLARK, J.E. and CLARK, R.L. (eds), pp. 147-153. Research Report No. 63, U.S. Fish and Wildlife Service, Bureau of Sport Fisheries and Wildlife, Washington, DC. MARKING, L.L. 1987. Gas supersaturation in fisheries: causes, concerns, and cures. Fish and Wildlife Leaflet No. 9, U.S. Fish and Wildlife Service, Washington, D.C. (10 pp.). MARKING, L.L., DAWSON, V.K. and CROWTHER,J.R. 1983. Comparison of column aerators and a vacuum degasser for treating supersaturated culture water. Prog. Fish-Cult. 45, 81-83. MATHIAS,J.A. and BARICA,J. 1985. Gas supersaturation as a cause of early spring mortality of stocked trout, Can. J. Fish. Aquat. Sci. 42, 268-279, McLEOD, G.C. 1978. The gas bubble disease of fish. In The Behaviour of Fish and Other Aquatic Animals. MOSTOVSKY, D.I. (ed.), pp. 319-339. Academic Press, New York. PENROSE, W.R. and SQUIRES. W.R. 1976. Two devices for removing supersaturating gases in aquarium systems. Trans. Am. Fish. Soc. 105, 1t6-118. SPOrrE, S. 1979. Seawater Aquariums: the Captive Environment. Wiley, New York. r~ SPRAGUE, J.B. 1966. Filtration of sea-water for marine biological laboratories. Manuscript Report Series (Biological) No. 851, Fisheries Research Board of Canada, Ottawa (22 pp.). WOLD, E. 1973. Surface agitators as a means to reduce nitrogen gas in a hatchery water supply. Prog. FishCult. 32, 14.3-146.