Transcript ภาพนิ่ง 1 - Coastalaqua

การออกแบบระบบนา้ หมุนเวียน
นิคม ละอองศริ วิ งศ ์
ั นา้ ชายฝั่ง
้ งสตว์
สถาบ ันวิจ ัยการเพาะเลีย
สาน ักวิจ ัยและพ ัฒนาประมงชายฝั่ง กรมประมง
Recirculating Aquaculture Systems
Recirculating aquaculture systems
(RAS) are systems in which aquatic
organisms are cultured in water
which is serially reconditioned and
reused.
source : Wik et al. (2009)
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

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

Fish Food has an Impact (usually
negative) on Water Quality
0.25 - 1.0 kg
Oxygen
0.35 – 1.38 kg
CO2
1 kg Feed
0.25 - 0.5 kg
Waste Solids
0.18 - 0.4 kg
Alkalinity
0.025 - 0.055 kg
NH3 & NH4
Characteristics of Culture Tank
Effluent
High concentrations of suspended
and dissolved solids
 High ammonia levels
 High concentration of CO2
 Low levels of dissolved oxygen

Basic Components
Recirc systems maintain fish at high
densities: 61-122 kg/m3
 Water treated by several processes prior
to recirc to culture units
 Question exists: which method is
proven and economical?
 Main ones: screening, sedimentation,
media filtration, biological filtration,
aeration, disinfection

Production Capacity Depends
Upon Treatment System Design & Scale
Fish
Culture
Tank
Waste
Solids
Removal
Oxygenation
&
Degassing
Biological
Filtration
(Nitrification)
Your Technology Maintains Life
Support and Must:
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Remove Solid Wastes
– Settleable, Suspended, and Dissolved
Convert Ammonia and Nitrite to Nitrate
Remove Carbon Dioxide
Add Oxygen
Maintain Proper pH
Control Pathogens
Keep up with generation of waste
Bacteria Are Important in a
Recirculating System

Bacteria Can Cause Trouble
– Consume Oxygen
– Create Toxic Ammonia
– Cause Disease

Bacteria Also Make the System Run
– Biological Filtration
Bacteria Eat Wastes and Cause Changes
in Water Quality

Bacteria Break Down Uneaten Feed and
Waste to Create:
– Ammonia (toxic to fish)
– Consumes Oxygen (often referred to as BOD,
BioChemical Oxygen Demand)

These Bacteria are called Heterotrophic
Ammonia is also Consumed and
Converted by Bacteria

Bacteria (Nitrosomonas) Convert Ammonia to
Nitrite (NO2)
– Nitrite is also toxic to Fish

Other Bacteria (Nitrobacter) Convert Nitrite to
Nitrate (NO3)
– Nitrate is not generally very toxic to fish

The Process is called Nitrification
– The Bacteria are called Nitrifying Bacteria

Also referred to as Autotrophic Bacteria
Very Important Water Quality
Parameters
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Dissolved Oxygen (continuously monitor)
+
Ammonia-Nitrogen (NH3 & NH4 )
Nitrite-Nitrogen (NO2-)
pH
Alkalinity
Biological Nitrification is a Two
Step Process
Nitrosomonas
Bacteria
NO2
(un-ionize ammonia)
NH3 &
NH 4+
(ionize ammonia)
(nitrite)
Nitrobacter
Bacteria
NO3
(nitrate)
Biological Nitrification
Is All About:
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Surface Area
Living Space for the Nitrifying Bacteria
Competition for that Space
Food (ammonia or nitrite) > 0.07 mg / L
Good Living Conditions
– DO going into the biofilter > 4 mg / L
– pH (7.2 – 8.8 for nitrosomonas;
7.2 – 9.0 for nitrobacter)
– Alkalinity > 200 mg / L as CaCO3
Required Unit Processes
Carbon Dioxide
Removal
Fine & Dissolved
Solids Removal
Fish Culture Tank
Foam Fractionation
Round, Octagonal
Rectangular or
D-ended
Aeration or
Oxygenation
Air Stone Diffuser
Packed Column
Down-flow Contactor
Low Head Oxygenator
U-tube
Waste Solids Removal
Sedimentation
Swirl Separators
Screen Filters
Bead Filters
Double Drain
Air Stone Diffuser
Packed Column
Disinfection
Ultraviolet Light
Ozone Contact
Biological Filtration
(Nitrification)
Fluidized Bed Filters
Mixed Bed Filters
Trickling Filters
Rotating Bio-Contactors
Unit Processes : Waste Solids
Removal
WASTE SOLIDS
GENERATION
UNEATEN FEED
&
FECES
Suspended Solids
Solids that will not settle out in
1 hour under quiet conditions
Settleable Solids
Sedimentation
Swirl Separators
Screen Filters
Bead Filters
Double Drain
Removal Mechanisms

Gravity separation
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Filtration
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Settling tanks, tube settlers and hydrocyclones
Screen, Granular meda, or porous media filter
Flotation

Foam Fractionation
Settling Basins Sedimentation:
Advantages

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Simplest technologies
Little energy input
Relatively inexpensive to install and operate
No specialized operational skills
Easily incorporated into new or existing facilities
Settling Basins Sedimentation:
Disadvantages
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Low hydraulic loading rates
Poor removal of small suspended solids
Large floor space requirements
Resuspension of solids and leeching
Granular Media Filters
• Sand Filters
–
–
–
–
effective at removing fine solids
relatively expensive
large backwash requirements
not often used unless required by effluent
regulations
Recirculating Aquaculture Systems Short Course
HydroTech Drum Screen Filter
Backwash Spray
Nozzles
Waste Drain
Unit Processes: Biofiltration
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Biofilter operation for aquaculture production
systems has only been studied for about 25 years
Earliest types were submerged filters, soon replaced
by trickling filters, but same principles apply to all
biofilters
Various types: submerged, trickling, rotating
biodisks, biodrums, fluidized beds, low-density
media filters
Submerged biofilters are the simplest and come
directly from the sewage treatment industry
Lately shown to be somewhat inefficient
Submerged Biofilters
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Characterized as downflow filters (top to bottom)
Relegated to novice culture systems
Bacteria grow on a film at the surface of a sand
substrate within a tank
The medium is continuously submerged
Most common medium is limestone rock (helps pH,
until covered by bacteria)
Others: oyster shell, clam shell, crushed coral,
ceramic/plastic modules, glass/plastic beads
Particle must be large than 19-25 mm or will clog
Trickling Filters
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Similar in design as submerged filters with one major
exception: medium is not submerged
Bacteria adhering to medium are kept moist and in a
semi-aerobic environment
Seldom clog
Can only function in downflow mode
Media currently consist of plastic modules (light, large
surface area)
Sand cannot be used due to small void area
Submerged vs. Trickling Filters
Rotating Media Filters
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Also referred to as rotating biocontactors (RBC’s)
biodisks or biodrums
Biodisks: series of flat or corrugated disks mounted
on a horizontal shaft
40% of disk surface is submerged at a time, shaft
and bearings above the water surface
Disks separated from each other by at least 13 mm
(0.5 in.)
Most disks constructed from flat or corrugated
fiberglass or plastic sheet material
Rotating Media Filters

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Rotational speed: 2-6
rpm, but no faster than
1ft/sec (peripheral
speed)
This is the generator of
the previously
mentioned “biofloc”
Rotating Media Filters
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Biodrums are variations
of biodisks
Cylindrical cages filled
with media = more
surface area
Downside: more energy
required to turn them
Fluidized Bed Reactors
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Contained within a vertical plastic
tube
Sand media is supported by coarse
gravel, supported by a perforated
plate
Media kept in various degrees of
suspension by upward flow of water
Usually pressurized and driven by a
pump
Only used for NH3 removal (not
solids)
Primary design criterion is upward
flow rate and oxygen demand
Capacity is 10x that of static filters
Downside: requires high
upward Q (60-65 gpm/m2)
Floating Bead Filters
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Low-density media filter
Use 3-5 mm poly beads in
pressurized upflow mode
Beads float above injection point
Capable of solids capture and
biofiltration
Traps suspended particles while
enhancing nitrification
Can nitrify 270 mg TAN per m2 per
day
1.0 m3 of beads can provide
complete water treatment of wastes
generated from 12-16 kg feed per
day (400-530 kg fish/m3 media)
Design Nitrification Rate
Trickling Filter Typical
ExpoNet
BioBlock 200
0.45 g TAN / m2 / day
90 g TAN / m3 / day
(Losordo et al.)
0.55m x 0.55m
x 0.55 m each
Approx. 3 kg feed per day
per cubic meter of media
200 m2 / m3
($212 - $353 / cubic meter)
Net 200
Biological Nitrification
Moving Bed Reactors
Design Nitrification Rate
0. 10 - 1.0 g TAN / m2 / day
50 - 500 g / m3 / day
1.66 - 16.66 kg feed / day
(Media Cost = US$1000 - $1500 / m3 )
(RBC)
KMT Copy
SSA =
850 / m2 / m3 ??
B-Cell
KMT
SSA =
SSA =
500 / m2 / m3 650 / m2 / m3
Biofilters Come in All Shapes and Sizes
Fluid Sand
Beds are the
most compact
biofilter
Moving Bed
Filters are
low energy
and compact
An RBC
specifically
designed for
aquaculture
Bead Filters
combine
nitrification
with solids
removal
Rotating Water
Distribution
Arm
Trickling
Filters are
the “work
horse” of
aquaculture
Water Inflow
from Culture
Tank
Biofilter
MediaPlastic Blocks
or Plastic Rings
(RBC)
Low
Pressure
Air
Inflow
Water
Return to
Culture
Tank 7/17/2015
Biofilter Chemical Factors
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pH: nitrification inhibition commences below pH 7;
optimum slight > 7.0
Alkalinity: 20-50 mg/L
NH3 and NO2: NH3 inhibits Nitrosomonas sp. and
Nitrobacter sp. at 10-150 and 0.1-1.0 mg/L,
respectively
O2: biofilter effluent > 2.0 mg/L
Solids: 1.4-2.7 µM best
Salinity: normal culture ranges are OK, no sudden
changes
Temperature: 30-35C
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)
Design Assumptions
For any design, some
assumptions need to be
made, hopefully based
either on actual
experience or reputable
research.
Design Assumptions
Assuming: 454,000 kg/yr production
• 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)
System Biomass Estimation
Estimate of system’s average feeding biomass :
Biom asssystem

annualproduction  ( FCR)

rfeed
454,000kg fish / yr 1.3 kg feed / kg fish 1yr


(0.012kg feed / day) / kg fish
365day
 129,600kg fish in system / day
Total Oxygen Requirements
• Estimate the oxygen demand of system’s 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
RDO water
biom asssystem  rfeed  aDO
0.012 kg feed 0.75 kg DO
 129,600kg fish 

kg fish  day kg feed
 11,66 kg O2 consum ed/ day
Total Flow Requirement –
Oxygen Load
• Estimate water flow (Q) required for fish’s O2
demand:
• Assuming oxygen:
• DOinlet = 18 mg/L
• DOeffluent= 4 mg/L (@ steady state)
QTotal
1
 rDO 
DOinlet  DOeffluent 
1166kg O2 106 m g
L
1




day
kg 18  4 m g 1440min/day
 57.84 m / min (15,280gal / min)
3
Total Tank Volume
Requirements
Assume an average fish density across all culture
tanks in the system:
• culture density = 80 kg fish/m3
Volum eTotal  biom asssystem / Culture Density
129,600kg fish

3
80 kg fish / m
 1,620 m (428,000gal)
3
Check Culture Tank
Exchange Rate
EXCHTANK  Volum eTotal / QTotal
min
 1,620m 
3
57.84 m
 28 min
3
Rule of Thumb
a culture tank exchange every 3060 minutes provides good flushing
of waste metabolites while
maintaining hydraulics within
circular culture tanks
Number of Tanks Required
Assuming 9 m (30 ft) dia
tanks
Assuming 15 m (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
• 10-11 culture tanks
required
• culture volume per tank
• 670 m3
• 177,000 gal
• 2-3 culture tanks
required
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)
Removal solids design
• Settling Basin
• Dual-drain System
• Swirl Separator
• Microscreen Filter
• Propeller Washed Bead Filter
Biofiltration/Nitrification
Terms Used To Describe Biofilters:
• Void Space / porosity
• Cross-sectional Area
• Hydraulic Loading Rate
• Specific Surface Area
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.
RDO  biom assTANK  rfeed  aDO
0.012 kg feed 0.75 kg DO
 12,960kg fish 

kg fish  day kg feed
 117 kg O2 consumed/ day
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!!)
QTANK
1
 rDO 
DOinlet  DOeffluent 
6
117 kg O2 10 m g
L
1




day
kg 18  4 m g 1440min/day
 5,800 L / min (1,530gal / min)
Biofilter Design – Step 2 (cont)
Step 2: Check the Exchange rate (2-4
exchanges/hr)
EXCHTANK  Volum eTANK / QTANK
150m 3

3
5.8 m / min
 26 min
A tank exchange rate of 2 exchanges per hour is OK!
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)
PTAN  aTAN  BiomassTANK  rfeed
 0.032kg TAN / kg feed 12,960kg fish  0.012kg feed / kg fish
 5.0kg TAN
Ammonia Assimilation Rates
TAN Conversion
TAN Conversion
Basis
Rate
TAN Conversion
Media Type
Trickling or RBC
(100 – 300
m2/m3)
Rate
(25 to 30 Deg. C)
Surface area of
media
Granular
(bead/sand)
Volume of media
(> 500 m2/m3)
(15 to 20 Deg. C)
0.2 to 1.0 g/m2 day
1.0 to 2.0 g/m2 day
0.6 to 0.7 kg/m3
1.0 to 1.5 kg/m3
day
day
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).
PTAN
Vmedia 
VTR
5.0kg TAN

 8.23m3
kg TAN
0.605
m3
Biofilter Design – Step 4 (MBB)
Step 4: Calculate volume of biofilter, Vbiofiler based on a fill ratio
of 65%.
Vmedia
Vbiofilter 
Fill%
8.23m 3

 12.66m 3
0.65
This would require a tank (3200 gal): 7 ft in diameter and 11 ft tall.
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)
PTAN
Amedia 
ATR
kgTAN 1,000g
5.0

day
kg

 11,100m 2
0.45gTAN
m 2 day
2
10
.
76
ft
2
11,100m 2 

120,000
ft
m2
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)
Amedia
Vmedia 
SSA
11,100 m 2
3


55
.
5
m
m2
200 3
m
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).
Qtank
Abed 
HLR
L 1m3
1
1,440min
 5800



3
min 1,000L 250m
day
m2
2
2
 33.4 m  360 ft
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:
4  Abed
4 16.7m2
Dbiofilter 

 4.61m  15 ft

3.14
Biofilter Design – Step 8 (Trickling
Tower)
Step 8: Calculate the biofilter depth (Depthmedia) from
the biofilter cross-sectional area (Amedia) and volume
(Vmedia).
Vmedia 16.7m3
Depthmedia 

 3.62m  11.9 ft
2
Amedia 4.61m
The final Trickling Tower is
15 ft in diameter
and 12 ft tall
plus distribution plate, etc.