Warm Water System Design

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Warm Water System Design

• James M. Ebeling, Ph.D.
• Research Engineer
• Aquaculture Systems Technologies, LLC
• New Orleans, LA

M.B. Timmons, Ph.D. Biological Environmental
Engineering Cornell University Ithaca, NY
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Overview of System Design
Aeration Air/Oxygen
Carbon Dioxide Removal
Fish Culture Tank
Monitoring System Control
Disinfection
Fine Dissolved Solids Removal
Biofiltration Nitrification
95
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Suspended Solids
Settable Solids
Sludge
Biosecurity Program
Sludge
Sludge
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Design Requirements

• The Following Unit Process are required in any
  design
• Culture Tank Design
• Circulation
• Solids Removal
• Biofiltration / Nitrification
• Gas Transfer (Aeration / Oxygenation / CO2
  Removal)

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Design Assumptions
For any design, some assumptions need to be made,
hopefully based either on actual experience or
reputable research.
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Design Assumptions

• Assuming 454,000 kg/yr production (1 million
  pounds/year)
• Mean feeding rate rfeed 1.2 BW/day
• Feed conversion rate FCR 1.3 kg feed/kg fish
  produced
• Culture Density 80 kg fish/m3
• Oxygen Demand 0.75 kg O2/ kg feed

(these rates are an average over entire year)
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System Biomass Estimation

• Estimate of systems average feeding biomass

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Total Oxygen Requirements

• Estimate the oxygen demand of systems feeding
  fish
• where
• RDO average DO consumption Rate
• kg DO consumed by fish per day)
• aDO average DO consumption proportionality
  constant
• kg DO consumed per 1 kg feed
• Ranges from 0.4 to 1.0 kg O2/kg feed cold
  water to warm water

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Total Flow Requirement Oxygen Load

• Estimate water flow (Q) required for fishs O2
  demand
• Assuming oxygen
• DOinlet 18 mg/L
• DOeffluent 4 mg/L (_at_ steady state)

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Total Tank Volume Requirements

• Assume an average fish density across all culture
  tanks in the system
• culture density 80 kg fish/m3

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Check Culture Tank Exchange Rate

• Rule of Thumb

a culture tank exchange every 30-60 minutes
provides good flushing of waste metabolites while
maintaining hydraulics within circular culture
tanks
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Number of Tanks Required

• Assuming 9 m (30 ft) dia tanks
• water depth
• 2.3 m
• 7.5 ft
• culture volume per tank
• 150 m3
• 40,000 gal
• 10-11 culture tanks required

• Assuming 15 m (50 ft) dia tanks
• water depth
• 3.7 m
• 12 ft
• culture volume per tank
• 670 m3
• 177,000 gal
• 2-3 culture tanks required

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Tanks Design Summary

• Ten Production Tanks
• Diameter
• 9.14 m ( 30 ft )
• Water depth
• 2.3 m (7.5 ft)
• Culture volume per tank
• 150 m3 (40,000 gal)
• Oxygen Demand
• 117 kg O2/day (257 lbs/day)

• Flow Rate (30 min exchange)
• 5,000 Lpm (1,320gpm)
• Biomass Density
• 86 kg/m3 (0.72 lbs/gal)

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Options for Solids Capture
Solids Capture

• Dual-drain System
• Settling Basin
• Swirl Separator
• Microscreen Filter
• Propeller Washed Bead Filter

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One Options for Solids Capture
Solids Capture
Dual-drain System (15 bottom Drain) Bottom Drain
??To a Swirl Separator Combine Flow (Swirl
Separator Side-wall Drain) ?? To Microscreen
Filter

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Terms Used To Describe Biofilters
Biofiltration/Nitrification

• Void Space / porosity
• Cross-sectional Area
• Hydraulic Loading Rate
• Specific Surface Area

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Biofilter Design Step 1
Step 1 Calculate the dissolved oxygen
requirement (RDO).
Assume a DO consumption of 1.0 kg/kg feed Both
the MBB and Trickling Tower provide O2 for
Nitrification or approximately 0.25 kg. Thus
0.75 kg O2 /kg feed.

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Biofilter Design Step 2
Step 2 Calculate water flow requirement (Qtank)
required for fish DO demand. Assume DOinlet
18 mg/L (pure oxygen aeration system) DOtank
4 mg/L (warm water 24 Deg. C, Tilapia!!)  

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Biofilter Design Step 2 (cont)
Step 2 Check the Exchange rate (2-4
exchanges/hr)

A tank exchange rate of 2 exchanges per hour is
OK!
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Biofilter Design Step 3
Step 3 Calculate TAN production by fish
(PTAN) (Note Feed is 35 protein)
PTAN F PC 0.092 F 0.35 0.092
0.032 where PTAN Production rate of total
ammonia nitrogen, (kg/day) F Feed
rate (kg/day) PC protein concentration in
feed (decimal value)

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Ammonia Assimilation Rates

 
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Biofilter Design Step 4 (MBB)
Step 4 Calculate volume of media, Vmedia based
on the Volumetric nitrification rate (VTR)
Consider a Moving Bed BioReactor (MBB) Curler
Advance X-1 has a 605 g TAN/m3 (17.14 g TAN/ft3).

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Biofilter Design Step 4 (MBB)
Step 4 Calculate volume of biofilter, Vbiofiler
based on a fill ratio of 65.

This would require a tank (3200 gal) 7 ft in
diameter and 11 ft tall.
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Biofilter Design Step 4 (Trickling Tower)
Step 4 Calculate the surface area (Amedia)
required to remove PTAN from the Areal TAN
removal rate (ATR) (0.45 g TAN/m2 day) 

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Biofilter Design Step 5 (Trickling Tower)
Step 5 Calculate volume of media based on the
specific surface area (SSA), example BioBlock
200 m2/m3 (61 ft2/ft3)  

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Biofilter Design Step 6 (Trickling Tower)
Step 6 Calculate the biofilter cross-sectional
area from required flow for the fish oxygen
demand (Qtank) and the hydraulic loading rate,
HLR of 250 m3/m2 day (4.4 gpm/ft2).

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Biofilter Design Step 7 (Trickling Tower)
From high school math class area ? (Dia)2
/ 4 diameter 4 area / ?1/2
The diameter of a two trickling towers,
Dbiofilter, with this cross sectional area is

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Biofilter Design Step 8 (Trickling Tower)
Step 8 Calculate the biofilter depth
(Depthmedia) from the biofilter cross-sectional
area (Amedia) and volume (Vmedia).

The final Trickling Tower is 15 ft in diameter
and 12 ft tall plus distribution plate, etc.
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Aeration / Oxygenation Options

• Multi-staged low head oxygenators (LHO)
• Packed or spray columns
• Pressurized columns
• Enclosed mechanical surface mixers

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Tank Oxygen Requirements

• Estimate the oxygen demand of system
• where
• RDO average DO consumption Rate
• kg DO consumed by fish per day)
• aDO average DO consumption proportionality
  constant
• kg DO consumed per 1 kg feed
• Ranges from 0.4 to 1.0 kg O2/kg feed cold
  water to warm water

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Tank Oxygen - Speece Cones
(Design Requirement 117 kg O2 / day or 4.88 kg
/ hr)
From Aquatic Eco-Systems, Inc. Catalog A
single Speece Cone OY140F is rated at 4.5 kg O2
/hr _at_ 10 psi, 600 gpm, 40 mg/L Or two Speece
Cones OY60F is rated at 2.3 kg O2 /hr _at_ 15 psi,
260 gpm, 46 mg/L
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CO2 PRODUCTION

• Molar basis
• 1 mole of CO2 is produced for every1 mole O2
  consumed
• Mass basis
• 1.38 g of CO2 is produced for every1 g O2
  consumed

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CO2 Control Options

• Packed Tower Stripping
• Sodium Hydroxide Addition
• Water Exchange
• In-tank Surface Aeration
• Side-stream Surface Aeration
• In-tank Diffused Aeration
• Side-stream Diffused Aeration

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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

one stripping columns with diameter 2.0 m 6.6
ft
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Stripping Column Design

• Design criteria used for the forced-ventilation
  cascade column
• volumetric GL of 51 to 101

Fan requirement 1770 scfm
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Ozone Requirements

• Estimate the ozone requirement of systems
  feeding fish
• where
• aozone kg ozone added per 100 kg feed

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Putting It All Together
Aeration Air/Oxygen
Carbon Dioxide Removal
Fish Culture Tank
Disinfection
Fine Dissolved Solids Removal
Biofiltration Nitrification
Sludge
Waste Solids Removal
Monitoring System Control
Sludge