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