RECIRCULATION TECHNOLOGY
From: VASUDEVAN hiline@xlweb.com
To: shrimp@yahoogroups.com
Sent: 28 August 2004
QUESTION:
Can anybody suggest the best recirculation
aquaculture technology to
produce shrimp post larvae in hatcheries and also adult shrimp in ponds?
I would like to know any short term practical courses that are being
offered on the above subject.
Dr. S. Vasudevan - Managing Director
HI-LINE AQUA PVT. LTD.,
28//1, Third Main Road, Kasturba Nagar, Adyar, Chennai-600 020.INDIA
Tel : 91-44-24416108 / 24416311 Res: 24463176 / 24462850,
Tel / Fax : 91-44-24420591, Mobile : 98403 95110.
Dr. S. Vasudevan - General Manager
AL KHAT AL RAFIEE FISHES TRADING,
P.O. Box 38061, 1 B, Fifth Floor, Flat No. 506, Sheeba Building, Al
Qasmia, Sharjah, U.A.E.
Tel : 971-6-5746988 Fax:971-6-5746989 Mobile: 971-50-5877824.
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The "best" recirculation aquaculture
technology will be site-
specific. There are economic trade-offs relating land cost, water
cost, water quality, weather conditions, system intensity, labor
costs, energy costs, oxygen costs, interest rates on capital cost,
feed costs and quality, species, life stage, and technology in
determining the "best".
Sorry, no simple answer.
Dallas E. Weaver, Ph.D.
Scientific Hatcheries
5542 Engineer Dr.
Huntington Beach, Ca 92649, USA
714-890-0138
Fax 714-890-3778
deweaver@surfcity.net
http://www.ScientificHatcheries.com
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COMMENTS 2:
We have developed a recirculation system for
shrimp/prawn hatcheries named Organic Recirculation Prawn Production System
(ORPSPS). The process of commercialisation of the technology is on.
Dr. I.S. Bright Singh
Reader & Coordinator
Centre for Fish Disease Diagnosis and Management
Cochin University of Science and Technology
Fine Arts Avenue
Cochin 682 016
Phone /Fax0484 –2381120
e-mail: bsingh@md3.vsnl.net.in
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comments 3:
As Dallas has mentioned, practical and working RAS
design would be site-specific as there are so many
variable design parameters. RAS in shrimp maturation
and larval rearing could bring in improved performance
but at what cost? RAS are bound to be expensive.
My question to Dr.Singh, what do you mean by
"Organic"? Have these systems been tried in commercial
hatcheries?
Ramraj
e-mail: padlab@yahoo.com
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COMMENTS 4:
Be careful when going for re-circulation system for
shrimp grow-out. You will probably end up with small shrimp, which has
limited market. Especially for India, it is better to do away with
re-circulation technology as the producers already struggle with low market
conditions. Go for extensive, closed cycle system with probiotics.
M.Chandrasekar
Aquaculture Manager
Oman Fisheries Co SAOG
PO Box 2900
PC 112, Ruwi
Sultanate of Oman
Phone: +968 597805
Fax:
597804
Mobile: 9523620
Email: aqua@omanfisheries.com
Web: www.omanfisheries.com
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comments
5:
In the case of maturation, larval rearing, the
advantages of recycle
are very significant for most sites. With recycle, you can have
biosecurity, temperature control, salinity control and pH control.
At most sites, these parameters are not as well controlled, year
around, as desired for maturation/larval rearing.
Relative to the cost of having your facility shut down or not
producing properly for a time during a rain event (low salinity),
recycle -- in this application -- is cheap. Opportunity cost of not
having PL when you want them can be much greater than the cost of a
recycle system.
Dallas E. Weaver
e-mail: deweaver@surfcity.net
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COMMENTS 6:
We are running a large P. indicus hatchery in Saudi
Arabia, producing over 100 million per month (12 months a year
- trying for flat line in production) and here the temperature will
fluctuate in winter, so do our productions in winter. So we are considering
to utilize solar energy to heat the sea water in reservoirs in winter season
from 22° to 30°, for water exchange and them maintain the tank temperature
at 30° with titanium heater.
Now with this discussion, I am also thinking the possibility of doing the
cost benefit analysis for recycle systems to be adapted starting with
maturation unit.
BONDADA
Manager - Hatcheries
National Prawn Company
Saudi Arabia
www.robian.com.sa
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COMMENTS 7:
A way to get a feel for this problem is to look at
the relative costs and impacts of alternatives for temperature control.
If you recycle a maturation system with a 800 l/min high performance
filtration system (90+% removal of ammonia, nitrite, bod and anything else
that is biodegradable), that is equivalent to 720 l/min of clean filtered
seawater. Now to heat that 720 l/min. 8ºC requires a 1.4 mbtu
(million BTU) per hr of heat in the water. Full sun light might peak
at about 3,500 btu/m2 hr which you may be able to collect 50% and if you are
getting an average of 20000 btu/m2/day, you could net about 10,000
btu/m2/day. However, you need 1.37 *24 = 33 mbtu/day which would mean
that you need somewhere in the range 3,000 m2 of solar greenhouse or
equivalent. I don't know what construction costs are in Saudi
Arabia, but 30$/m2 may be towards the extreme low end (including reservoirs)
for the solar collector which means that you are looking at a capital cost
in the $90,000 range just for the basic heat for 800 l/min recycle flow
equivalent. This is excluding the cost of cleaning up the raw seawater
and emergency heating systems for when the sun doesn't shine, etc.
A recycle filtration system for 90% removal at about 800 l/min costs about
$25,000 for all the hardware (fob San Diego) which would make the system
about $35,000 to $40,000 installed in place with operator training. A
real high end system with full automation and lots of instrumentation and
consulting may get you into the $60K range per system.
In other words, recycle is much cheaper and you can also get salinity
control and pH control along with the temperature.
All of the above rough numbers and calculation above are only meant to be
instructive and were pulled off the top of my head -- this is not a
consulting job. The cost of the solar system is totally an educated
guess at the low end of the cost -- a covered lined pond (it has to be very
deep to get the required volume). Note that greenhouses in the USA
cost > $100/m2 for well designed units.
As you are probably talking several hundred thousand dollars in lost
production at the PL stage and possibly even 5 times that amount if the lack
of PL's impacts production, the cost of not having thermal control can be
very high. I don't know the water flow/ million nauplii for P. indicus
maturation systems, but if you want flat line production, recycle maturation
is the way to go.
Dallas
PS: You may have very cheap natural gas that you can use in Saudi Arabia
(may be site specific).
Dallas E. Weaver
e-mail: deweaver@surfcity.net
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comments 8:
We installed some pretty large area high laminar flow
solar heaters in Mexico and Dallas is correct. This type of solar
heating works best when the water from a reservoir is recirculated
constantly through the PE laminar cross flow panels but that then means
additional cost. Further, in the cooler months, the Delta T. overnight
was still less than optimal since you need a large heat sink reservoir to
maintain the heat.
We found solar to be a good supplemental tool wherein we used it in such
fashion to heat the boiler feed water by 11-12° C thereby reducing the
Delta T requirements of the boiler itself rather than the hatchery water.
In a closed system, you can control your heat loss as well so the overall
heat maintenance (only 25% of the BTU's required to heat the flow- through
water up to desired) was more cost effective.
Leland Lai
Aquafauna Bio-Marine, Inc.
e-mail: lelandlai@aquafauna.com
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comments 9:
The difference in heat between recycle and flow
through is usually a lot less than 25%. With very well insulated indoor
systems, the heat loss is determined by the need to vent air from the
building to keep the CO2 level from getting too high. That means cold
air coming in at a rate of approximately 10 or so liters of air/ liter of
flow -- depending upon the loop strength (ratio of feed to recycle flow
rate) you are running. Heating 10 liters of air is nothing relative to
heating 1 liter of
water.
Dallas E. Weaver
e-mail: deweaver@surfcity.net
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comments 10:
You are right but in context of just water
consideration, it only takes
about 25% of the total caloric requirements when compared to heating once
through water in an open system. In fine tuning this, we often
suggest heating the air (as you suggested) for water temp. maintenance and
this can be done at way less than the 25% heat factor applied to water.
When doing air heating, however, the facility has to be designed with this
in mind in terms of insulation, structure design (for fine tuning the actual
BTU's expended for air heating), ceiling height, etc. In such systems,
we get a much smaller primary water boiler system to bring the water up to
desired temp. then through valving, switch over to fan driven radiators that
are situated around the room or facility to be heated. Hence, if the
calculations are done properly, the same boiler can service both water heat
exchanger and air heater systems.
Since air heating is so much cheaper than water heating, other unique
options become available in co-generation using exhaust heat from generators
if located appropriately. This is often done in hotel applications to
preheat boiler intake water as we spoke about yesterday
except using solar to preheat the boiler intake water. Most of these unique
applications for use and reuse or conservation of the fuel management are
not that costly to implement or maintain, yet the cost savings that result
just from applying these could be more than made up in less than a single
year burning a heafty boiler to raise water 8° C for the winter season.
e-mail: lelandlai@aquafauna.com