Recycling Aquaculture System

Topics: Oxygen, Water pollution, Water Pages: 13 (2877 words) Published: May 18, 2011
A simplest definition of a recirculating aquaculture system would be: “Recirculating aquaculture encompasses systems used for the rearing of aquatic organisms where 90% or more of system water is recycled.” Why Recirculating Aquaculture?

Low water Requirements
* consume considerable less water than other types of culture systems * Suited to areas with limited water supplies.
* Requires a minimum daily input of water, just enough to clean the waste from the filters and to replace water lost to evaporation. Less Land Requirements
* Fish can be safely stocked and grown at high densities. * The goal which designers are striving to attain is 1 pound of fish per gallon of water. * Can be located in areas where large amounts of level land are not available. Control of Water Temperature

* Produce species which could not normally be raised in a given geographic area. * maximize food conversion
* provide optimum growth,
* Growth can also occur throughout the year, maximizing production. Control of Water Quality
* To the benefit of the live fish stock to the final product and the environment. * maintaining dissolved oxygen at optimum levels
* fish have better food conversion and are less stressed, * greater disease resistance,
* less wasted feed
* Faster stock growth.
* Isolated from potential environmental contaminants such as off-flavor caused by algal blooms.   Protection From The Elements and Potential Predators
* Protection from cold weather because tank can be equipped with heater * Having the fish indoors also permits harvest at times when heavy rain, snow or ice * Indoor RAS farms are designed to prevent stock escapement and mitigation of potential conflicts. ADVANTAGES * Increase in growing season * Decrease labor costs: automation * Increase stock security (predators, disease, theft, pollution) * Decrease dependency on natural resources * Increase production control * Increase marketing control| DISADVANTAGES * Increase construction costs * Increase production costs * Increase complexity (Elect., Mech., Hydraulic) * Increase need for trained operators * Electrical reliability * Increase back-up components * Increase biological risks| Recirculating Aquaculture System Components:

1. Holding tank
2. Construction materials
3. Biological filters for nitrification
4. Protein skimmers/foam fractionators for removal of dissolved protein 5. Bead filters/screens/sedimentation tanks for solids removal 6. Aeration/oxygenation systems
7. CO2 removal (diffusers)
8. UV system for disinfections
9. Pump(s)
10. Heaters/coolers
11. Monitoring systems
1. Holding tank
Holding tank is the vessel within which the cultured organism is maintained. Tanks are constructed in such a way that they are ergonomics. (Safety interaction and most efficient) The design of individual components of the tank is estimated by the number of fish (fish biomass) and it’s mass which is used to calculate the feeding rates. Types of holding tanks that are used in RAS:

* Circular
* Raceway
* D-ended
* Octagonal/hexagonal
* Square/hybrid
* Conical/Silo tank

1. Circular/oval
Advantages * Big and large cost savings * Good water circulation * Reasonable sludge collectionFor oval:Advantages same as circular| Disadvantages * Difficult to capture fish * Poor use of footprint * Difficult to remove dead fishFor oval: * More expensive * Hydrodynamic performance may be poor (dead spaces)| 2. Raceway/Rectangular

Advantages * Good foot printing * Easy to harvest fish | Disadvantages * Hydrodynamic (plug flow) problemsCross-flow racewaySolves the problems associated with poor hydrodynamic flow | 3. Square/hybrid

Advantages * Good footprint * Easy harvesting * Easy mort removal| Disadvantages * Hydrodynamic performance may be...
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