Transcript Document 7620892

Coldwater Biofilter
Design Examples
M.B. Timmons, Ph.D.
Biological & Environmental Engineering
Cornell University
Ithaca, NY
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Coldwater Design Example

Production Goal: 1.0 million lb/yr (454 mton/yr)
Arctic char
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Large Operations Dominate
Commercial Trout & Salmon Culture

Both culture technologies
face tough environmental
challenges.
6 m3/s flows to some farms
1,000-20,000 m3 per cage

There are few large water
resources available for
aquaculture development.
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Large Production Systems
are More Cost Effective

Economies of Scale
Reduce fixed costs per MTON produced
Reduce variable costs per MTON produced
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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)
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System Biomass Estimation

Estimate of system’s average feeding biomass :
Biomass system 
annual production   (FCR )
rfeed
454,000 kg produced
1.3 kg feed


yr
kg fish produced
100 kg fish in system  day
yr


1.2 kg feed
365 day
 129,600 kg fish in system
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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
R DO  biomass system  rfeed  a DO
1.2 kg feed
0.4 kg DO
 129,600 kg fish 

100 kg fish  day 1 kg feed
 622 kg DO consumed / day
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Oxygen Requirements

Estimate the mass and volume of oxygen required:
Account for oxygen transfer efficiency
622 kg DO consumed
100
Mass O 2 Gas 

day
O 2 transfer efficiency
622 kg DO consumed 100


day
70%
 890 kg O 2 gas sup plied / day
Volume of O 2 Gas  465 L / min O 2 sup plied
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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
1
Q  rDO 
DOinlet  DOeffluent 
622 kg DO 106 mg
L
day




day
kg
16  9 mg 1440 min
 61,700 L / min (16,320 gal / min)
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Flow Requirement

traditional trout culture rule of thumb
50 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
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Tank Volume Requirements

Assume an average fish density across all culture
tanks in the system:
culture density = 60 kg fish/m3
Culture Volume  Biomass system  Culture Density
1m3
 129,600 kg fish 
60 kg fish
 2,160 m3 (570,000 gal )
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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 .
3
EXCH tan k  2,160 m 
min
61.7 m
3
 35 min
 Assuming ideal tank mixing.
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Tank Requirements

Assuming 30 ft dia tanks

Assuming 50 ft dia tanks
 water depth
 water depth
 2.3 m
 7.5 ft
 3.7 m
 12 ft
 culture volume per tank
 150 m3
 40,000 gal
 14-15 culture tanks required
 culture volume per tank
 670 m3
 177,000 gal
 3-4 culture tanks required
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Ammonia Production Estimate

Calculate TAN production in system
R TAN  a TAN  rfeed  biomass 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
RTAN
0.032 kg TAN
1.2 kg feed


129,600 kg fish
kg feed
100 kg fish  day
 46.7 kg TAN Produced / day
( Assumes 32% P feed )
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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.
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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
46.7 kg TAN day  m
Vstatic sand 

day
0.7 kg TAN
 67 m
3
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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
46.7 kg TAN 103 g day  m 2
m3
Vstatic sand 



day
kg 0.06 g TAN 11,500 m 2
 67 m3
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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.
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Biofilter Sizing

Biofilter cross-sectional area can be calculated from
the required flow rate (Q) and water velocity (v):
A biofilter
 Q biofilter / v
61,700 L min
sec 100 cm m3





min
60 sec 1.0 cm
m 1000 L
 103 m 2
Twelve biofilters that are each 11 ft dia
(or other geometries could be used)
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Static Sand Depth

Static sand depth can be calculated from the biofilter
cross-sectional area (Q) and sand volume requirement:
Static Sand Depth
 Vsand / Area biofilter
103 m3
12 biofilers

8.8 m 2
 1.0 m static sand in each biofilter
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Assume a Fully-Recirculating
System (no water exchange)
Example 2: Trickling Filter

Size biofilter to remove all of daily TAN production
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Trickling Filter Sizing
The volume of packing required to remove the PTAN can be
estimated using an areal TAN removal rate.
TAN removal rate, g/d/m2

(Nitrification data at 15°C from Bovendeur. 1989.)
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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
46.7 kg TAN 103 g day  m 2
m3
Vpacking 



day
kg 0.25 g TAN 200 m 2
 934 m3
(approximately $170,000 of ACCUPAC structured packing)
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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):
A biofilter
 Q biofilter / v
61.7 m3 1440 min m 2  day



min
day
300 m3
 296 m 2
Six biofilters that are each 7.0 m x 7.0 m (23 ft x 23 ft) square
(or other geometries could be used)
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Trickling Filter

Packing depth can be calculated from the biofilter
cross-sectional area (Abiof) and packing volume
(Vpacking) requirement:
Packing Depth
 Vpacking / Area biofilter

934 m3
296 m 2
 3.2 m packing depth in each biofilter
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Trickling Filter

Must also design:
flow distribution manifold above packing
packing support structure
sump basin below packing to provide cleanouts and
overflow back to pump sump
air inlet and outlet structures

Select air handler/fan to provide G:L = 5:1 (vol:vol)
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Stripping Column Design

Design criteria used for the forced-ventilation
cascade column:
hydraulic fall of about 1.0-1.5 m
hydraulic loading of 1.0-1.4 m3/min per m2
61,700 L min  m 2 m3
plan area  


min
1.4 m3 1,000 L

44 m 2
Six stripping columns each with diameter = 3.0 m = 10 ft
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Stripping Column Design

Design criteria used for the forced-ventilation
cascade column:
volumetric G:L of 5:1 to 10:1
air flow
61,700 L water 10 L air
m3



min
1L water 1,000 L

617 m3 / min  21,800 scfm
Each stripping columns will ventilate 3,630 scfm
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Ozone Requirements

Estimate the ozone requirement of system’s
feeding fish:
where:
 aozone = kg ozone added per 100 kg feed
mass ozone  biomass system  rfeed  a ozone
1.2 kg feed
2 kg ozone
 129,600 kg fish 

100 kg fish  day 100 kg feed
 31 kg ozone sup plied / day
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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
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