1. Recirculation Aquaculture

2. Why Recirculation Water use Climate Quality Predation
Environmental impact
Land
Disease
Exotic species (or control thereof…

3. Cost of Labor : $7/day
Solids Siphon
Near Ensenada, Mexico; 2002

4. Near Ensenada, Mexico; 2002

5. Near Ensenada, Mexico; 2002

6. Raise a lot of fish with Little Labor

7. Definitions 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

8. Five Major Processes 1) Circulation 2) Clarification (Solids capture)
3) Biofiltration (BOD reduction/nitrification)
4) Aeration (Oxygen replacement)
5) Degasification (CO2 stripping)

9. The Five Major Processes in a Recirculating System
Five Major Treatment Objectives
The Five Major Processes in a Recirculating System
Feeding
Circulation
Aeration
Fish Tank
Degasification
Biofiltration
Solids Capture

10. Return to
Tank
Double Drain at Center of Tank

11. Inlet
Outlet
Sludge outlet
From Under-drain

12. Over-Drain Flow

13. Captured Solids

14. Microscreen Cleaning Jets

15. From Microscreen
Micro-Bead Filter

16. 1 mm Styrene Beads

17. Centrifugal Pumps

18. Pressure line from Centrifugal
Pumps
Oxygen
Bubbles
02 Flow Meter
Pressure Gauge
Water
Return to Tanks

19. Degasification Biofiltration
Solids Capture
Feeding
Circulation
Aeration
Fish Tank
Degasification
Biofiltration
Solids Capture

20. Impact of Solids on Recirculating Systems
Solids Capture
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)
Aside from their direct physical impact, suspended solids generated in culture systems are highly organic. Most of the suspended solids generated in a recirculating system are feces, reflecting the undigested residuals of feed. Additional solids are generated as bacterial colonies (biofloc) grow from dissolved organic materials found in the water. Both feces and biofloc are mostly organic matter and are thus are subject to further breakdown by bacteria. Over two-thirds of the Biochemical Oxygen Demand (BOD) generated is attributed to suspended solids. It is not surprising, therefore, that clarification was the first wastewater treatment component added to extend water re-use and the first to be used to treat effluents. If allowed to remain in a culture system, solids encourage heavy bacterial growths that can clog (biofoul) a wide variety of treatment units. Excessive growths of bacteria can rapidly deplete oxygen in isolated pockets within a system. Heavy organic loads can inhibit critical nitrification processes in biofilters (Bovendeur et al., 1990). These localized, oxygen depleted zones can stimulate the development of a wide variety of anaerobic reactions that produce odor and contribute to off-flavor development. The bacteria will utilize large amounts of oxygen and produce TAN as they breakdown the solids. Additionally, these enriched conditions tend to cause population explosions of less desirable bacteria, leading to disease outbreaks.

21. Particle Size Distribution (microns)
Solids Capture
Particle Size Distribution (microns)
Settleable
Dissolved
Colloidal
Suspended

22. Tilapia
No Fine Solids Capture

23. SOLIDS REMOVAL PROCESSES AND PARTICLE SIZES
Foam Fractionation
Granular Filter
Microscreen
Tube Settler
Cartridge Filter
Coarse
Screens
Plain
Sedimentation
100 75 30 10
Particle Size, microns

24. SEDIMENTATION INFLOW OUTFLOW Solids Capture Vh Vs Settling Zone
Inlet Zone
Outlet Zone
Settling basins have been the clarifier of choice for a number of years. A settling basin is designed to provide an area of quiescent water where the solids can settle out into a cone, from which they can then be removed. More advanced configurations, tube settlers, use a media to shorten settling distances, reducing the size of the settling basin. Performing superbly on systems with high water replacement rates, settling provides poor control of fine suspended solids (< 80 microns in diameter), which tend to accumulate as replacement rates are reduced. This problem, coupled with labor issues, has prompted some to search for a more efficient, yet cost-effective approach.
(Vs > Overflow Rate
to settle)
Sludge Zone

26. Solid Removal Technologies
Solids Capture
Solid Removal Technologies
Effective for selected particle size
Differ in headloss…energy $$$
Differ in labor for upkeep
Sensitive to organic loading

27. Floor Plan

28. “BYPASS” FILTRATION
TANKS
Pump
Liquid O2
Bead Filter
Packed Column
Fluidized Bed
Packed Column
Lime Addition

29. “IN-LINE” FILTRATION
TANKS
Shrimp Maturation in South America
Pump
Bead Filter
Fluidized Bed
Packed Column

30. Degasification Biofiltration
Feeding
Circulation
Aeration
Fish Tank
Degasification
Biofiltration
Solids Capture

31. Biofiltration
Types of Biofilters

32. Biofiltration

33. Biofiltration
The classification of heterotrophic bacteria encompasses a great number of genera/species which share the common characteristics of extracting their nourishment from the breakdown (decay) of organic matter. Biochemical oxygen demand (BOD) is largely an indirect measure of the biodegradable organic material in water. Heterotrophic bacteria reduce BOD levels, consuming oxygen in the process. About 60 percent of the organic matter consumed is converted to bacterial biomass; whereas, the balance (40 percent) is converted to carbon dioxide, water, or ammonia. Heterotrophic bacteria grow very fast, capable of doubling their population every ten to fifteen minutes. If the BOD in the water being treated is very high (> 20 mg -O2/l), the heterotrophs will quickly dominate the bead bed, overgrowing the slower growing nitrifying bacteria and consuming tremendous amounts of oxygen.
The second, yet more important, classification of bacteria is the nitrifying bacteria. These bacteria are specialists, extracting energy for growth from the chemical conversion of ammonia to nitrite and from nitrite to nitrate (Figure 3.6). Nitrate is a stable end product which, although a valuable nutrient for plants, displays little of the toxic impacts of ammonia and nitrite. Composed principally of two genera (Nitrosomonas and Nitrobacter), nitrifying bacteria are very slow growing and sensitive to a wide variety of water quality factors. It is not surprising that most bead filters used for biofiltration are managed to optimize conditions for nitrification.

35. Biofiltration

36. 0.45 kg/m3
USDA - SBIR/AST, 97

38. Production Units

42. Propellor-washed Floating Bead Filters

43. Broodstock Return Anti-siphon Bypass valve Sludge View Port
Pressure Gauge
Sludge
Intake

44. ADM Tilapia System

45. Degasification Biofiltration
Gas Exchange
Feeding
Circulation
Aeration
Fish Tank
Degasification
Biofiltration
Solids Capture

46. Different Behavior Oxygen goes in easier than CO2 comes out Oxygen
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

47. No CO2 Removal Enrichment Devices
Gas Exchange
No CO2
Removal
Enrichment Devices
Commonly used for large scale applications
Self-generates pressure ( psi)
1 m3 liquid860 m3 gas
Dependent on local source of liquid oxygen
Not impacted by power failure
15-35cents/kg typical
Liquid Oxygen
Timmons and Lorsordo (1994) pg. 188

48. Air stones Paddle wheels Surface Agitators Spray nozzles
Gas Exchange
Air stones
Paddle wheels
Surface Agitators
Spray nozzles
Packed columns
Ambient Air –Oxygen Addition and Carbon Dioxide removal are balanced

49. Ambient Air Options Gas Exchange
Carbon dioxide can be stripped from culture waters by the use of large amounts of air in traditional blown air systems usually consisting of a large rotary blower and banks of airstones. The most efficient approach identified so far involves the use of a packed column aerator (Colt and Bouck, 1984). A packed column degasifier consists of a tall column filled with a porous packing media. Water cascades down through the media as air is forced upwards. When operated with a high air to water ratio, the unit effectively strips excess carbon dioxide gas. Unfortunately, early units were subject to biofouling problems.

50. Circulation Fish Tank Biofiltration Degasification Circulation Feeding
Aeration
Circulation
Fish Tank
Biofiltration
Degasification
Solids Capture

51. Airlift Pump Circulation Options Circulation Air
Low head centrifugal or airlift pumps are the most common choices for recirculation of waters through the water treatment block in a recirculating system. Centrifugal pumps are extremely efficient at water movement, but, they must matched with the treatment components through their pump curve that relates flow deliver (liter per minute) with the expected headloss (meters of water). The best pumps are expensive but realize considerable savings over the long run generally drawing less than half the amperage of less expensive units commonly marketed for pool applications. Most recirculating systems operate well with head delivery pressures below 5 meters. Additional savings in energy can be realized by use of 220 or 440 V units. Airlift pumps consist in their simplest form of a partially submerged piece of pipe fitted with a air injection line near the bottom. When air is injected the density of the air/water mixture drops allowing water to enter from the bottom of the pipe eventually overflowing the above water lip of the pipe. Airlift pumps are capable of delivering large quantities of water, but, usually only at a few inches of lift. The lift is usually limited to about 30 percent of the submerged depth. Serially placed airlift pumps can lift water several feet but they are not particularly efficient. Airlift pumps are generally used only in systems specifically designed for their use. Their principle advantage is their substantial contribution to the reaeration needs of the system. Once their design variables are understood, they are easily constructed from standard PVC piping.
Pump

53. Airlifts Perform Several Functions
Circulation
Aeration
C02 stripping
Foam control

54. Drop Filters : Low Water Loss Floating Bead Bioclarifiers
Filter Mode
Drop Filters : Low Water Loss
Floating Bead Bioclarifiers
Air Bleed
Builds Charge
Settled Backwash
Waters returned to
system

55. Drop Filters : Low Water Loss Floating Bead Bioclarifiers
Backwash
mode
Drop Filters : Low Water Loss
Floating Bead Bioclarifiers
Released Air Washes Beads
Internal Sludge Capture

56. FAS 1012C: Recirculation Aquaculture Quiz Name:_________________
List the five major treatment objectives and explain what they do.
Feeding
Fish Tank