Recirculating Aquaculture Systems

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Recirculating Aquaculture Systems
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Definition
Recirculating aquaculture encompasses systems
used for the rearing of aquatic organisms where
90 or more of system water is recycled
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Why Recirculating Aquaculture?

• Good quality water resources for aquaculture are
  scarce
• Land is expensive, especially near good markets
• Problems relating to biosecurity are more complex

• Greater control over effluent production and
  quality
• Permits the culture of aquatic organisms outside
  of natural range

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Why Recirculating Aquaculture?

• ADVANTAGES
• Ý growing season
• ß labor costs automation
• Ý stock security (predators, disease, theft,
  pollution)
• ß dependency on natural resources
• Ý production control
• Ý marketing control

• DISADVANTAGES
• Ý construction costs
• Ý production costs
• Ý complexity (Elect., Mech., Hydraulic)
• Ý need for trained operators
• Electrical reliability
• Ý back-up components
• Ý biological risks

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Components of a Recirculating Aquaculture System
1. Holding tank
The vessel within which the cultured organism is
maintained
ERGONOMICS The study of workplace equipment
design or how to arrange and design devices,
machines, or workspace so that people and things
interact safely and most efficiently

• Shape determined by
• economics
• ergonomics
• system components
• species under culture
• self-cleansing demands

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Components of a Recirculating Aquaculture System
continued
1. Holding tank continued
Number of fish and mass determines feeding rates
Feeding rates will determine the design of
individual system components
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Components of a Recirculating Aquaculture System
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1. Holding tank continued

• Engineered forms
• Circular
• Raceway
• D-ended
• Octagonal/hexagonal
• Square/hybrid
• Conical

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Components of a Recirculating Aquaculture System
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1. Holding tank continued
Circular/oval Big large cost savings Uniform
water quality Range of operational
velocities Rapid flush of settleable
solids Problems Mort removal Harvesting and
grading Footprint
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Components of a Recirculating Aquaculture System
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1. Holding tank continued
Raceway/rectangular Good footprint Easy
harvesting Easy mort removal Problems Hydrodynami
c flow
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Components of a Recirculating Aquaculture System
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1. Holding tank continued
Cross-flow raceway Solves the problems associated
with poor hydrodynamic flow
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Components of a Recirculating Aquaculture System
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1. Holding tank continued
D-ended raceways
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Components of a Recirculating Aquaculture System
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1. Holding tank continued
Square/hybrid Good footprint Easy harvesting Easy
mort removal Problems Hydrodynamic flow
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Components of a Recirculating Aquaculture System
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1. Holding tank continued
Hexagonal/octagonal Uniform water quality Good
hydrodynamics Rapid solids collection Okay
footprint Problems Mort removal Harvesting and
grading
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Components of a Recirculating Aquaculture System
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1. Holding tank continued

• Construction materials
• Fiberglass
• Plastic
• Concrete
• Wood
• Steel

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Components of a Recirculating Aquaculture System
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2. Biofiltration
A filtration system that uses biological organisms
to convert ammonia to nitrate
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Components of a Recirculating Aquaculture System
continued
2. Biofiltration continued

• Engineered forms
• Submerged
• Fluidized beds
• Emerged
• Trickling/RBC
• Combinations

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Recirculating Aquaculture System Components
continued
2. Biofiltration continued

• Ideal characteristics
• Large surface area volume ratios
• Long-lasting
• Cheap
• Light

Kaldnes
B-cell
198 ft2/ft3
152 ft2/ft3
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Recirculating Aquaculture System Components
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2. Biofiltration continued
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Components of a Recirculating Aquaculture System
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3. Particulate removal

• Removal by
• Gravity separation
• Filtration
• Flotation

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3. Particulate removal continued
Most effective solids removal processes and
particle range
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3. Particulate removal continued
Major source of water loss due to
back-washing Bead filters sold as
biofilter-solids removal combo
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3. Particulate removal continued

• Sedimentation tanks

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3. Particulate removal continued
Hydrocyclones/swirl separators

• Relatively expensive
• Dont remove fine solids
• Effective at removing TSS
• May remove 85 of gt 75 mm particles
• Good footprint

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3. Particulate removal continued

• Physical filtration

• Minimal labor
• Good footprint
• Low head loss
• Screen strains water
• 15000
• Similar disc and belt filters

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4. Removal of solubles
Foam fractionation

• Airlift foam fractionators
• Venturi foam fractionators
• Essential for some species and larval rearing

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Recirculating Aquaculture System Components
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5. Oxygenation

• Oxygen depletion caused by
• Respiration
• Biological oxygen demand
• Chemical oxygen demand
• Nitrification

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Recirculating Aquaculture System Components
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5. Oxygenation continued

• Addition by
• Aerators
• agitators
• blowers
• Oxygen
• cones
• packed towers
• U-tubes

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Recirculating Aquaculture System Components
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5. Oxygenation continued
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Recirculating Aquaculture System Components
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6. Disinfections
Ultraviolet light
Ozone
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Recirculating Aquaculture System Components
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6. Disinfections continued

• ADVANTAGES of OZONE
• Control of fungal, bacterial and viral pathogens
• Pre-treatment of POPs
• Reduced biofouling
• Improved fine solids removal
• Control of water color
• Control of off-flavors
• Reductions in TSS, COD
• Removal of nitrite

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Recirculating Aquaculture System Components
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7. Pumps

• Water circulation
• Air-lift
• Propeller pumps

• Other needs
• Moving fish
• Food propulsion
• Side systems (skimmers)

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Recirculating Aquaculture System Components
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7. Miscellaneous

• On-line monitoring
• Temperature
• Depth
• pH
• Salinity
• Oxygen

Heater systems Coolers Larval rearing
systems Feeders Motors (e.g. mech. filter)