Download History of Recirculation Aquaculture Systems (RAS) in European

History of Recirculation Aquaculture Systems (RAS) in European Aquaculture
Focus on Technology and Fish Welfare
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Statement
Recirculation technology is not about fish farming,
it is about managing the water for the well-being
of the fish.
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Fish welfare in the EU
STANDING COMMITTEE OF THE EUROPEAN CONVENTION FOR THE PROTECTION OF ANIMALS KEPT FOR
FARMING PURPOSES (T-AP)
RECOMMENDATION CONCERNING FARMED FISH
adopted by the Standing Committee on 5 December 2005
(In accordance with Article 9, paragraph 3 of the Convention, entered into force on 5 June 2006)
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Example from the recommendation
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Norwegian salmonid welfare
Parameter
Level
pH level in inlet to fish tanks
6,2 – 7,8
Oxygen level in fish tanks
Not more than 100% *
Oxygen saturation in outlet of fish tanks
Not less than 80%
Carbondioxide level - Salmon
Less than 15 mg/L
Carbondioxide level - Rainbows
Less than 10 mg/L
Nitrite – fresh water
Less than 0,1 mg/L
Nitrite - saltwater
Less than 0,5 mg/L
Total-N
Less than 2 mg/L
Ammonia
Less than 0,002 mg/L
*) Super-saturated zones in fish tanks must be avoided when dissolving pure oxygen in tank inlets
Norway, Mattilsynet 17.06.2008
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Mechanical Filtration
First step in the treatment of
water coming from the fish tanks
The purpose is to clean the
water for faeces from the fish
The filter removes particles
larger than 40-50 micron (µm)
Mechanical filtration is important
for the biofilter performance
The dirty fraction is washed out
of the RAS for external water
treatment
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Biofilter
The biofilter is most often split into multiple
chambers to ensure optimal conditions for different
biological processes
Fixed bed technology or moving bed technology or
a combination between the two types
Organic material is consumed by heterotrophic
bacteria in the first chambers
The following chambers will perform optimally for
nitrification (converting ammonia to nitrate)
Ammonia (NH4)
Nitrite (NO2)
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Nitrate (NO3)
Degasser ꞊ CO2-stripper ꞊ trickling filter
Effective CO2 removal is crucial for fish
welfare, optimal growth and reduced feed
conversion rate (FCR)
CO2 degasser must be extremely efficient, and
can be dimensioned to any CO2 concentration
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UV-disinfection
UV treatment is especially recommended
when growing small fish – 100% treatment
In grow-out systems, the concept of partly
UV treatment will stabilise bacterial dynamics
The harmless bacteria will be favoured and
outcompete pathogenic bacteria that might
enter the system (pro-biotic concept)
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Oxygenation
Pure oxygen is injected to the process water to
enhance the availability of oxygen for the fish
Sufficient oxygen levels are needed for the wellbeing of the fish and for optimal feed conversion
High oxygen saturation throughout the RAS is
crucial for overall system performance
Injection is most often done by the use of high
pressure oxygen cones
Other oxygenation methods are available: Low
head oxygenation, venturi injection etc.
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Pumps
Only one point of lifting the entire water volume
of process water saves energy
Custom designed for each project to optimise
efficiency and reduce running cost
Pumps also necessary for injection of pure
oxygen, back-washing of biofilters and pressurised
cleaning of the mechanical filter
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RAS cost distribution – portion trout
Note: Energy costs are 7% only
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Principle lay-out of a RAS
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Desktop and mobile Client
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16
Continous logging
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17
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System configuration
Growout
0.400.
System Data Sheet
Item Group
Item Name
Specification
System
Primary tanks
Circular Fish tank, ø9m
standard version
10 pc at
170,0 m3
2,06 exchanges/hr
Total system volume (excluding reservoir)
2.550 m3
Total system flow
3.500 m3/hr
Total tank flow
3.500 m3/hr
Total biofilter flow
2.900 m3/hr
Total biomedia surface area
510.000 m2
Performance
Peak feed capacity (according to specified comp.)
Peak water exchange
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1.802 kg/day
14,7 m3/hr
Concluding remarks
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The technology works
Complete control of the production environment
Good water quality for both fresh water and saltwater systems
Fish are growing well and have good health standards
Need for better understanding of conditions for fish welfare
More applied research needed
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Thank you for your attention
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