Recirculating Aquaculture Systems Short Course
Coldwater Biofilter Coldwater Biofilter Design ExamplesDesign Examples
M.B. Timmons, M.B. Timmons, Ph.D.Ph.D.
Biological & Environmental Biological & Environmental EngineeringEngineering
Cornell UniversityCornell UniversityIthaca, NY Ithaca, NY
Recirculating Aquaculture Systems Short Course
Coldwater Design Example
Production Goal: 1.0 million lb/yr (454 mton/yr)Arctic char
Recirculating Aquaculture Systems Short Course
Large Operations Dominate Commercial Trout & Salmon Culture
Both culture technologies face tough environmental challenges.
There are few large water resources available for aquaculture development.
1,000-20,000 m3 per cage
6 m3/s flows to some farms
Recirculating Aquaculture Systems Short Course
Large Production Systems are More Cost Effective
Economies of ScaleReduce fixed costs per MTON producedReduce variable costs per MTON produced
Recirculating Aquaculture Systems Short Course
Design Assumptions
Assuming for the growout system:Mean feeding rate: F = 1.2% BW/day; Feed conversion rate: FCR = 1.3 kg feed/kg fish produced;
(these rates are an average over entire year)
Recirculating Aquaculture Systems Short Course
System Biomass Estimation Estimate of system’s average feeding biomass :
systeminfishkg600,129
day365yr
feedkg2.1daysysteminfishkg100
producedfishkgfeedkg3.1
yrproducedkg000,454
r)FCR(productionannual
Biomassfeed
system
Recirculating Aquaculture Systems Short Course
Oxygen Requirements Estimate the oxygen demand of system’s feeding fish:
where: RDO = average DO consumption rate
= kg DO consumed by fish per day (about 0.4)
aDO = average DO consumption proportionality constant
= kg DO consumed per 100 kg feed
day /consumed DO kg 622
feedkg 1DO kg 4.0
dayfish kg 100feed kg 2.1
fishkg600,129
arbiomassR DOfeedsystemDO
Recirculating Aquaculture Systems Short Course
Oxygen Requirements Estimate the mass and volume of oxygen required:
Account for oxygen transfer efficiency
pliedsupOmin/L465 GasOofVolume 22
day /pliedsupgas O kg 890
%70100
dayconsumed DO kg 622
efficiencytransferO100
dayconsumed DO kg 622
GasOMass
2
22
Recirculating Aquaculture Systems Short Course
Flow Requirements Estimate water flow (Q) required to meet fish O2 demand:
Assuming culture tank: DOinlet = 16 mg/L
DOeffluent= 9 mg/L (@ steady state)
DOsaturation = 10 mg/L
min)/gal320,16(min/L 700,61
min 1440day
mg 916L
kgmg 10
dayDO kg 622
DODO1
rQ
6effluentinlet
DO
Recirculating Aquaculture Systems Short Course
Flow Requirement
traditional trout culture rule of thumb50 lb/yr production in 1 gpm of water flow (correct water
temp.) 76,000 L/min for 454 MTON/yr production 20,000 gal/min for 1 million lb (500 TON) annual production
Recirculating Aquaculture Systems Short Course
Tank Volume Requirements Assume an average fish density across all culture
tanks in the system:culture density = 60 kg fish/m3
)gal000,570(m 160,2
fishkg60m1
fishkg600,129
DensityCultureBiomassVolumeCulture
3
3
system
Recirculating Aquaculture Systems Short Course
Culture Tank Exchange Rate At a Q of 61.7 m3/min, the culture tank volume of 2160 m3
would be exchanged on average every 35 minutes .
Assuming ideal tank mixing.
min35m 7.61
minm160,2EXCH
33
ktan
Recirculating Aquaculture Systems Short Course
Tank Requirements
Assuming 30 ft dia tankswater depth
2.3 m 7.5 ft
culture volume per tank 150 m3
40,000 gal
14-15 culture tanks required
Assuming 50 ft dia tankswater depth
3.7 m 12 ft
culture volume per tank 670 m3
177,000 gal
3-4 culture tanks required
Recirculating Aquaculture Systems Short Course
Ammonia Production Estimate Calculate TAN production in system
where: RTAN = TAN production rate
= kg TAN produced by fish per day
aTAN = TAN production proportionality constant
= kg TAN produced per 100 kg feed
systemfeedTANTAN biomassraR
)%32(
/Produced 7.46
600,129 100
2.1
032.0
feedPAssumes
dayTANkg
fishkgdayfishkg
feedkg
feedkg
TANkgRTAN
Recirculating Aquaculture Systems Short Course
Assume a Fully-Recirculating System (no water exchange)
Size biofilter to remove all of daily TAN production
Example 1: Fluidized-bed biofilters with fine sand, i.e., D10 = 0.2-0.25 m.
Recirculating Aquaculture Systems Short Course
Biofilter Sizing The volume of static sand required to remove the
PTAN can be estimated using either volumetric or areal TAN removal rates:0.7 kg TAN removed per day per m3 static sand volume
3
3
sand static
m 67
TAN kg 7.0mday
dayTAN kg 7.46
V
Recirculating Aquaculture Systems Short Course
Biofilter Sizing The volume of static sand required to remove the
PTAN can be estimated using either volumetric or areal TAN removal rates:0.06 g TAN removed per day per m2 bed surface area
(Sb) and Sb=11,500 m2/m3
3
2
323
sand static
m 67
m 500,11
mTAN g 06.0mday
kgg 10
dayTAN kg 7.46
V
Recirculating Aquaculture Systems Short Course
Selecting a Sand for FSB
Select a fine graded filter sand that expands 50-100% at a velocity of 0.7-1.0 cm/s (10-15 gpm/ft2). a sand with D10=0.23 mm and a uniformity coefficient of
1.3-1.5 would expand about 50% at v = 1.0 cm/s.
Recirculating Aquaculture Systems Short Course
Biofilter Sizing Biofilter cross-sectional area can be calculated from
the required flow rate (Q) and water velocity (v):
2
3biofilterbiofilter
m103
L 1000m
mcm100
cm 0.1sec
sec60min
minL700,61
v/QA
Twelve biofilters that are each 11 ft dia(or other geometries could be used)
Recirculating Aquaculture Systems Short Course
Static Sand Depth Static sand depth can be calculated from the biofilter
cross-sectional area (Q) and sand volume requirement:
biofiltereachinsandstaticm
m
biofilersm
AreaVDepthSandStatic biofiltersand
0.1
8.8
12103
/
2
3
Recirculating Aquaculture Systems Short Course
Assume a Fully-Recirculating System (no water exchange)
Size biofilter to remove all of daily TAN production
Example 2: Trickling Filter
Recirculating Aquaculture Systems Short Course
Trickling Filter Sizing The volume of packing required to remove the PTAN can be
estimated using an areal TAN removal rate.T
AN
rem
ova
l ra
te, g
/d/m
2
(Nitrification data at 15°C from Bovendeur. 1989.)
Recirculating Aquaculture Systems Short Course
Trickling Filter Sizing
The volume of packing required to remove the PTAN can be estimated using 0.25 g TAN removed per day per m2 bed surface area (Sb); Sb=200 m2/m3
3
2
323
packing
m 934
m 200
m
TAN g 25.0
mday
kg
g 10
day
TAN kg 7.46V
(approximately $170,000 of ACCUPAC structured packing)
Recirculating Aquaculture Systems Short Course
Trickling Filter Biofilter cross-sectional area can be calculated from the
required flow rate (Q) and hydraulic loading rate (HLR=300 m3/day per m2):
2
3
23biofilterbiofilter
m296
m300
daym
day
min1440
min
m7.61
v/QA
Six biofilters that are each 7.0 m x 7.0 m (23 ft x 23 ft) square(or other geometries could be used)
Recirculating Aquaculture Systems Short Course
Trickling Filter Packing depth can be calculated from the biofilter
cross-sectional area (Abiof) and packing volume (Vpacking) requirement:
biofiltereachindepthpackingm2.3
m296
m934
Area/VDepthPacking
2
3
biofilterpacking
Recirculating Aquaculture Systems Short Course
Trickling Filter
Must also design:flow distribution manifold above packingpacking support structuresump basin below packing to provide cleanouts and
overflow back to pump sumpair inlet and outlet structures
Select air handler/fan to provide G:L = 5:1 (vol:vol)
Recirculating Aquaculture Systems Short Course
Stripping Column Design Design criteria used for the forced-ventilation
cascade column:hydraulic fall of about 1.0-1.5 mhydraulic loading of 1.0-1.4 m3/min per m2
2
3
3
2
m 44
L 000,1m
m4.1
mminmin
L 700,61areaplan
Six stripping columns each with diameter = 3.0 m = 10 ft
Recirculating Aquaculture Systems Short Course
Stripping Column Design Design criteria used for the forced-ventilation
cascade column:volumetric G:L of 5:1 to 10:1
scfm800,21min/m617
L 000,1m
waterL1airL10
minwaterL 700,61
flowair
3
3
Each stripping columns will ventilate 3,630 scfm
Recirculating Aquaculture Systems Short Course
Ozone Requirements Estimate the ozone requirement of system’s
feeding fish:where:
aozone = kg ozone added per 100 kg feed
day /pliedsupozone kg 31
feedkg 100ozone kg 2
dayfish kg 100feed kg 2.1
fishkg600,129
arbiomassozonemass ozonefeedsystem
Recirculating Aquaculture Systems Short Course
Overall Conclusions
Use appropriate level of intensification. Risk of failure higher for commercial reuse systems. Trends towards larger and more intensive reuse systems
for smolts and coldwater food-fish production: reduced capital costs per MTon produced reduced variable costs per MTon produced
especially labor and electric cost savings.
Technologies must scale functionally and cost effectively:certain technologies are better suited than others at large scales