Recirculation Aquaculture

Why Recirculation• Water use

• Climate

• Quality

• Predation

• Environmental impact

• Land

• Disease

• Exotic species (or control thereof…

Cost of Labor : $7/day

Solids Siphon

Near Ensenada, Mexico; 2002

Near Ensenada, Mexico; 2002

Near Ensenada, Mexico; 2002

Raise a lot of fish with Little Labor

Recirculating System:

A production system that reconditions water to extend it’s reuse

A technique that increases the value of a limited resource

An artificial well that never ceases to flow

A stable platform forming a reliable base for commercial production

Definitions

• Five Major Processes1) Circulation2) Clarification (Solids capture)3) Biofiltration (BOD reduction/nitrification)4) Aeration (Oxygen replacement)5) Degasification (CO2 stripping) DENITRIFICATION

ION BALANCE

GAS STRIPPING

ALKALINITY ADDITION

DISSOLVED

REFRACTORY

MANAGEMENT

AERATION

SOLIDS REMOVAL

SOLIDS

TAN

BOD

SOLIDSB A C TE R IA

N

NO

CO

O

INERT

NO2

2

3

--

2

2

CO2

O2

FEED

BOD REDUCTION

NITRIFICATION

H+

Solids Capture

Circulation Aeration

Biofiltration

Fish Tank

The Five Major Processes in a Recirculating System

Feeding

Degasification

Five Major Treatment Objectives

Double Drain at Center of Tank

Return toTank

Sludge outlet

Inlet

Outlet

From Under-drain

Over-Drain Flow

Captured Solids

Microscreen Cleaning Jets

From Microscreen

Micro-Bead Filter

1 mm Styrene Beads

Centrifugal Pumps

Pressure line from CentrifugalPumps

02 Flow Meter

Pressure GaugeWater

OxygenBubbles

Return to Tanks

Solids Capture

Circulation Aeration

Biofiltration

Fish Tank

Feeding

Degasification

Solids Capture

Impact of Solids on Recirculating Systems

Impact of Solids on Recirculating Systems

• Increased BOD load (organic solids) causes problems with Biofilters

• Increased system turbidity (fine particles)

• Gill damage in fish (fine particles)

Solids Capture

Particle Size Distribution (microns)Particle Size Distribution (microns)

10-4 10-3 10-2 10-1 1 10 100

Dissolved Colloidal Suspended

Settleable

Solids Capture

No Fine Solids Capture

Tilapia

Foam Fractionation

Granular Filter

Microscreen

Tube Settler

Cartridge Filter

CoarseScreens

PlainSedimentation

100 75 30 10Particle Size, microns

SOLIDS REMOVAL PROCESSES AND PARTICLE SIZES

INFLOW

OUTFLOW

Inle

t Zon

e

Out

let Z

oneVs

Vh

Sludge Zone

Settling Zone

(Vs > Overflow Rate to settle)

SEDIMENTATION

Solids Capture

Solid Removal Technologies

• Effective for selected particle size

• Differ in headloss…energy $$$

• Differ in labor for upkeep

• Sensitive to organic loading

Solids Capture

Floor Plan

TANKS

Pump

Bead Filter

Fluidized Bed

Lime Addition

Liquid O2

Packed Column

Packed Column

““BYPASS” FILTRATIONBYPASS” FILTRATION

TANKS

Pump

Bead Filter

Fluidized Bed

Packed Column

Shrimp Maturation in South America

“IN-LINE” FILTRATION

Solids Capture

Circulation Aeration

Biofiltration

Fish Tank

Feeding

Degasification

Types of Biofilters

Biofiltration

PlasticBead

Heterotrophic Biofilm

Embedded NitrifyingBacteria

Oxygen

Organic Wastes

Carbon Dioxide

BOD

Decay

Nitrite

Oxygen

Carbon Dioxide

Bicarbonates

Nitrate

Nitrification

Ammonia

Biofiltration

TSS

BOD Bacteria

NH + NH

Nitrobacter sp.

Nitrosomonas sp.

NO

NO (Nitrate)

(Nitrite)

O

O

CO

CONitrification

(Total Ammonia)

TAN

HCO

HCO

3 4+

2

2

2

2

2

3

3

3

HeterotrophicBiofiltration

Inert M aterials

N itrifier rich

H eterotrop hs

B ound ary L ayer

B u lk W ater

M aterial S u rface

Inert M aterials

N itrifier rich

H eterotrop hs

B ound ary L ayer

B u lk W ater

M aterial S u rface

Biofiltration

0

100

200

300

400

500

TA

N C

onve

rsio

n (g

ms/

m3 -d

ay)

Beads Modified Beads Tubes

0.45 kg/m0.45 kg/m33

USDA - SBIR/AST, 97USDA - SBIR/AST, 97

Production Units

Propellor-washed Floating Bead Filters

Filtration Backwashing

Sludge

Return

Bypass

Pressure GaugeSludge View Port

Anti-siphon valve

Intake

Broodstock

ADM Tilapia System

Solids Capture

Circulation Aeration

Biofiltration

Fish Tank

Feeding

Degasification

Gas Exchange

Different Behavior

• Oxygen– 21% of air

– Saturation 10 mg/l

– Poorly soluble

– Transfer H20 limited

• Carbon Dioxide– 0.035% of air

– Saturation 0.5 mg/l

– Highly soluble

• 50 mg/l +

– Transfer gas limited

Oxygen goes in easier than CO2 comes out

Gas Exchange

Enrichment Devices

•Commonly used for large scale applications•Self-generates pressure (150-200 psi)•1 m3 liquid860 m3 gas•Dependent on local source of liquid oxygen•Not impacted by power failure •15-35cents/kg typical

Timmons and Lorsordo (1994) pg. 188Liquid Oxygen

Gas Exchange

No CO2

Removal

• Air stones

• Paddle wheels

• Surface Agitators

• Spray nozzles

• Packed columns

Gas Exchange

Ambient Air –Oxygen Addition and Carbon Dioxide removal are balanced

Gas Exchange

Ambient Air Options

Solids Capture

Circulation

Aeration

Biofiltration

Fish Tank

Feeding

Degasification

Circulation

Circulation Options

Airlift

Air

Air

Pump

Circulation

Air

Air

Airlifts Perform Several Functions– Circulation

– Aeration

– C02 stripping

– Foam control

B

D

E

(1)

(3)

(6)

A

Water

(2)

(7)

AirWater

Patent # 5,770,080

Water Flow

(4)C

(5)

Air Flow

Sludge

Water Flow

Air Bleed Builds Charge

Settled BackwashWaters returned to

system

Filter Mode Drop Filters : Low Water LossFloating Bead Bioclarifiers

E

(1)

(3)

(4)

(6)C

(2)

(7)

Water

(5)

Air

Patent # 5,770,080

Air Flow

Water Flow

Internal Sludge Capture

Drop Filters : Low Water LossFloating Bead Bioclarifiers

Released Air Washes Beads

Backwashmode

Fish Tank

Feeding

FAS 1012C: Recirculation Aquaculture Quiz Name:_________________List the five major treatment objectives and explain what they do.