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Recirculating Aquaculture Systems
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Recirculating Aquaculture Systems
Recirculating aquaculture systems (RAS) are systems in which
aquatic organisms are cultured in water which is serially
reconditioned and reused.
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Why recirculate?
Conserves water Permits high density culture in locations
where space and or water are limiting Minimizes volume of effluent, facilitating
waste recovery Allows for increased control over the
culture environment, especially indoors Improved biosecurity Environmentally sustainable
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Water Reuse Rates
Open orFlow-throughSystem
ClosedSystem
0% 100%50%25% 75%
Semi-Closed System
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Characteristics of Culture Tank Effluent
High concentrations of suspended
and dissolved solidsHigh ammonia levelsHigh concentration of CO2
Low levels of dissolved oxygen
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Recirculating System Applications
Broodstock maturation Larval rearing systems Nursery systems Nutrition and health research systems Short-term holding systems Ornamental and display tanks High density growout of food fish
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Scientific HatcheriesHuntington Beach, California
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Scientific HatcheriesHuntington Beach, California
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Seagreen TilapiaPalm Springs, California
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Seagreen TilapiaPalm Springs, California
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Kent SeaTechSouthern California
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Kent SeaTechPalm Springs, California
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Southern Farm TilapiaRaleigh, North Carolina
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Southern Farm TilapiaRaleigh, North Carolina
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Mote Marine LabSarasota, FL
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Mote Marine LabSarasota, FL
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Harbor Branch ShrimpFort Pierce, Florida
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Harbor Branch ShrimpFort Pierce, Florida
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Classification of Culture Systems
Trophic LevelTemperatureSalinity
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Classification of Culture Systems
Recirculating Systems
Freshwater
Marine
Warmwater
Warmwater
Coldwater
Coldwater
Oligotrophic
Mesotrophic
Eutrophic
Oligotrophic
Mesotrophic
Eutrophic
Oligotrophic
Mesotrophic
Eutrophic
Oligotrophic
Mesotrophic
Eutrophic
ExamplesTropical RainforestTropical Display & Breeding
Warmwater growout
Hardy warmwater
Salmonid spawning
Coldwater growout
Null
Marine reef
Marine growout
Null
Coldwater aquaria
Coldwater growout
Null
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Salinity
Major effect on the oxygen saturation level
FreshwaterLess than 10 ppt
MarineGreater than 10 ppt
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Temperature
Impacts the rates of chemical and biological process at the most fundamental level
Affects: bacterial growth, respiration, nitrification efficiency
Cool-water species: below 20º CWarm-water species: above 20º C
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Trophic Level
Distinguishes the level of nutrient enrichment
•Oligotrophic•Mesotrophic•Eutrophic
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Oligotrophic
Excellent water quality Very Clear Used in display aquaria Most frequently used for
breeding purposes Some species are kept in these
conditions all of their lives, while others for a period of time
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Mesotrophic
Describes the bulk of high-density production systems where risk and economics must be carefully balanced to achieve profitability
Some deterioration in aesthetics Water quality at safe levels Dissolved Oxygen- above 5 mg/L TAN & Nitrite – less than 1mg-N/L Total suspended solids – less than 15 mg/L
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Eutrophic
Exist for the grow out of the most tolerant species that show vigorous growth under moderately deteriorated water quality conditions
Dissolved oxygen levels- economic optimum level Ammonia & Nitrite – less than 2mg-N/L Water quality – marginal Species evolved under similar natural conditions
prosper in these conditions
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Integrated Treatment
An assembly of components that creates an artificial environment suitable for production, breeding or display of aquatic animals• Must be reliable• Must be cost effective• Must be compatible with the intended user
group
Fine & Dissolved
Solids Removal
Solids
CaptureWaste Mgmt
Biofiltration
& Nitrification
Hydraulics
CO2 Removal
Water Quality, Loading, Culture Units, Species
Aeration & Oxygenation
Disinfection & Sterilization
System Components
SystemControl
System Design & Construction
Monitoring & System Control
Economics
Biosecurity
Nutrition
Management Decisions
Water Quality, Loading, Culture Units, Species
System Components
Circular Tank Flow Pattern
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Alternative Drainage Strategies
Two DrainsTwo Drains
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Dual Drains
• Cornell Dual-Drain Design• Tank depth - 1.0 m• Tank diameter - 3.0 m• Tank volume - 7.4 m3
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Commercial Dual Drains
Aqua Optimas Aquatic EcoSystems
Raceway - Plug Flow
Racetrack Configuration
Fine & Dissolved
Solids Removal
Solids
CaptureWaste Mgmt
Water Quality, Loading, Culture Units, Species
System Components
100 75 50 30 10
Course Screen
Sedimentation
Tube Settler
Microscreens
Granular Filter
Foam Fractionati on
Particle Size in an Intensive Aquaculture System
DE or Cartridge Filter
PRETREATMENT MAIN TREATMENT POLISHING TREATMENT
(After Chen & Malone, 1991)
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SludgeRemoval
INFLOW OUTFLOW
SludgeRemoval
Tube Settler
Settling Media
Tube Settler