The Potential for
Recirculation Aquaculture
Dr Mark Burdass

Recirculation Systems
• Systems used worldwide
• Production capacity depends on treatment
system
• Defining Recirculation Systems:
– System that recycles and renovates water for
the culture of aquatic organisms!

Global Perspective
• Successful large scale recirculation
aquaculture facilities in UK, Norway,
Europe, US, Canada & Australia.
• Highly intensive recirculation facilities used
in Scotland to produce salmon smolts

Definition
• Original definition 95% recycle (based on
flow), means 5% exchange per pass
• More recent systems defined by daily
volumetric exchange rates (10% per day)
• Lots of challenges with systems
recirculating water at < 5% per day

Advantages
• Controlled Environment
– Controlled temperature environment
– Allows controlled product growth rates
– More efficient food conversion
– Predictable harvest routines
– Allows production all year round
– Biosecurity advantages
– Enclosed environment means production free of
predators and other damaging wildlife
– Allows efficient inventory control
• The systems designed to conserves heat and
water through water reuse
– Reconditions the water through filtration processes
• Allows effective economies of scale
– This results in high production per unit area
– Save on handling equipment as used more
intensively.

Advantages
• Environmentally sustainable
– Use up to 99% less water than a conventional
aquaculture facility
– Less than 1% of the land area
– Allows waste to be managed in an
environmentally safe manner
– Allows waste to be further processed or used
for hydroponics
– Producing tropical fish locally has low carbon
footprint because of low food foodmiles in
production

Advantages
• Not restricted to traditional aquaculture
production locations
• Not restricted to traditional UK aquaculture
species
– Species such as barramundi, tilapia and
catfish possible in UK
• Allows production to be placed near to
market

Why Recirculation Systems
• Challenges
– High Initial Investment
• Compared to other production methods
– Financing can be an issue because investors often
want fast returns
– Technology is not well known
• Getting better
– Very short response time
– Reliability of electricity supply critical
– Lack of track record
• Failures common
• Hard to finance

Challenges
• Not as yet able to compete with large
scale aquaculture production
• Most Recirculation farms are under 500
tonnes in size
• Don’t have the economies of production
volume
– Supermarket product volume requirements
often above production of a single unit

Other Challenges
• There have been a number of high profile failure
in UK and across Europe
• Often difficult to determine why they failed,
however:
• The reasons are various but have included:
– Technology was labour intensive and therefore
running costs were too high
– Poor Design
• Often under-capitalised
– Poor management decisions
– Over optimistic market forecasts for product sales
– Inexperienced staff

System Comparison
• Conventional
intensive tilapia • Recirculation tilapia
farm farm
• 17.4 tonnes per ha • 1,340 tonnes per ha
per year per year
• Water use: 21 m3 per • Water use: 0.5m3 per
kg of production kg of production

Uses for Recirculation Systems
• Hatchery
• Nursery
• Quarantine
• Advanced fingerling production
• Purging market sized product
• Grow-out table production
• Near market site holding system

Running Costs
• Food and labour are the still the two main
costs
• Heating and pumping often amount to less
than ¼ of the above
• Initial capitalisation is a very significant
cost compared to conventional
aquaculture
• Possibility for large units of using
renewable energy supplies thereby
reducing costs in the long term

Systems
• High Stocking densities do not constitute
an efficient recirculation system!
• High feed rates per day do!
• It takes feed to grow fish!
• Food is the main consideration when
designing and predicting the capacity of a
system.
• An intensive recirculation system has a
high capacity to grow fish rather than hold
them

Technology
• The technology has been available for
over 30 years
• Reliable
• Efficient
• Most failures are down to mismanagement
of systems or producing inappropriate
species

Filtration System must:
• Remove solid wastes
– Settleable, suspended and dissolved
• Convert ammonia and nitrite to nitrate
• Remove CO2
• Add oxygen
• Maintain acceptable pH
• Control Pathogens
• Keep up with the generation of waste

Recirculation Process Diagram
MAKE-UP
WATER
BIOFILTER NH3
CO2 REMOVAL AIR BLOWER
REMOVAL
OZONE
DESTRUCTION O3
BY UV MONITOR
O2 ADDITION
O3 ADDITION
CULTURE TANKS
CLEAN WATER FROM BOTTOM DRAIN
UPPER LEVEL IN TANK 15%
(SIDE BOX) 85%
DRUM FILTER SWIRL
SEPARATOR
PUMP SUMP
FILTRATE
BOTTOM DRAIN
15%
SLUDGE TO SEPTIC TANK
WASTE

Key Water Quality Parameters
• Dissolved Oxygen
+
• Ammonia-Nitrogen (NH3 & NH4 )
-
• Nitrite-Nitrogen (NO2 )
• pH
• Alkalinity
• Carbon dioxide (CO2)
-
• Nitrate-Nitrogen ( NO3 )

Misperceptions
• Overly complicated
• Prone to catastrophic failure
• Only suitable for high value species
• Needs highly educated staff to run

Key Issues for success
• Use proven technology in system
construction
• Ensure system has effective monitoring
systems
• Build in back up systems to key processes
• Most success has come from small units
which have scaled up
• Use species with a track record in
recirculation systems
• Be sure of the market

Key Issues for success
• Business plan assumes market prices will
drop once production starts
• Grow species with a short production time
to improve cash flow
• Ensure product is fit for market
• Ensure have the trained staff to operate
the systems