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Nitrifying Bioreactor
Technology
Introduction
India's National Center for Aquatic Animal
Health and Cochin University of Science and Technology have
developed a bacterial consortium delivery system for aquaculture
hatcheries that removes or neutralizes nitrous waste including
ammonia thus avoiding common industry use of chemical disinfectants
and antibiotics. This organic aquaculture system enhances
spawning and the survival rate of the shrimp larvae. Initial
studies show an increase in shrimp spawn rates of approximately
20% and an increase in larval survival of 46%. This new system
has been developed for management of a larval prawn seed production
system in prawn/shrimp hatcheries and comprises two bacterial
consortium delivery systems known in the industry as bioreactors,
and a pond or tank water recirculation system. The water recirculation
or closed system hatchery is designed to avoid the introduction
of deadly bacteria and viruses that are often pumped from
infected waters of the wild into open system hatcheries. This
recirculation system enables more consistent water quality
management and fewer incidents of diseases typically leading
to an increased larval survival rate. The system of nitrifying
bioreactors allows the waters of a closed system hatchery
to remain inhabitable by neutralizing the rapid buildup of
waste that exists in a packed shrimp tank or pond.
The Nitrifying Bioreactor can be used as a stand-alone product
or as a component of an Organic Recirculation Prawn Seed Production
System (ORPSPS) designed to improve the health of shrimp and
eliminate most viral and bacterial pathogens problematic to
shrimp hatcheries.
Potential Benefits of The Technology
Dr. Tzachi Samocha, Professor, Shrimp
Mariculture, Texas Agricultural Experiment Station (TAES),
and Corpus Christi, Texas: "We did extensive research
here on closed hatchery systems and indeed found that post-larval
shrimp produced in a closed hatchery outperform those in an
open system in terms of strength."
Two major components in a hatchery are
the maturation system and the larval rearing tank. In the
maturation system male and female shrimp mate. When their
eggs have hatched, the tiny larvae known as nauplii are transferred
to the larval rearing tank in which they grow for about 21
days. In the course of just seven days, the water becomes
very dirty due to organic matter and is not conducive for
healthy growth. Organic matter accumulation leads to secretion
of ammonia and nitrites which are harmful to shrimps even
at very low concentrations. To overcome this problem, hatcheries
practice water exchange, i.e., removal of water in the tank
and addition of fresh sea water. At approximately 21-days
old, shrimps called seeds are sold to shrimp farmers who grow
it for between 2 - 3 months till they attain a certain size
and weight and are then sold to seafood companies.
Dr. Samocha, "In both closed maturation
and larvae rearing systems we definitely saw improvement of
reproductive performance and the post-larvae's ability to
sustain a stress test. The information out there suggests
you will do much better working with closed systems than an
open system's continuous water exchange if you can indeed
develop the bacteria that can control the bacteria detrimental
to shrimp health."
Sometimes a single virus can travel and
hit all of the shrimp in one pond. Because water from an open
system flows from one pond to another, it is easy for a blight
to hit and severely damage the shrimp farming industry for
a year or two. Bob Rosenbury, editor of Shrimp News International
for 31 years, "I have seen reports that in the last two
years India has lost $500 million to the white spot virus."
To avoid the introduction of deadly diseases into their hatcheries,
there are specific pathogen free (SPF) certified brood stock
owners may purchase. SPF helps to address a very severe problem,
but it does a hatchery little good if what they pump into
their open systems is water from the wild that is infected
or contains carriers of these diseases. Dr. Samocha, "Thousands
of hatcheries would use the post-larvae from a controlled
closed system larval rearing facility rather than collecting
them from the wild and running the risk of introducing diseased
animals that will wipe out all of your population in a matter
of days." Bob Rosenbury, "Two years ago virus free
brood stock was selling for $25 an animal, today they are
selling for $100 - $1000 each, and you need hundreds of these
per ten ton tank (shrimp hatcheries in India may have 40 to
50 such tanks each with typically larger numbers in Thailand
and the U.S.)." Over 95% of larval rearing hatcheries
are open system.
Although having low manufacturing costs
is very important, a shrimp farmer or a hatchery owner can
justify additional investment if it reduces the inconsistent
performance and losses associated with running an open system
hatchery. Significant operating expenses associated with chemical
treatment, water temperature maintenance and other issues
would be reduced or eliminated.
Additionally, exposing post-larval shrimp to sudden changes
in water temperature, pH, salinity, different concentrations
of oxygen and other environmental factors have a significant
impact on their survival rate. The stronger the animal, the
better their survival is. These inherent challenges with open
hatchery systems are kept significantly more manageable in
closed hatchery systems.
External growth stimulating media such as vaccines can be
added to stimulate healthy growth. A closed circuit system
ensures that these helpful media directly reach the shrimps
rather than being expelled during water exchange. Similarly,
in the maturation system, the male and female shrimps are
attracted by pheromones. When water exchange is carried out,
the pheromones get diluted and have an impact of reduced spawning
rate.
- Nitrifying bioreactor cost:
- The average hatchery in
India produces approximately 100 million seeds (shrimp)
per year. This number is somewhat larger in Thailand
and China, respectively first and third in worldwide
shrimp production.
- A hatchery producing 100 million
shrimp a year would need approximately 350 tons of water
for a closed system hatchery. Each hatchery would need
about 30 packed bed bioreactors (PBBR) and 500 stringed
bed suspended bioreactors (SBSBR).
- Although the bioreactors are designed
to be integrated into hatcheries without much difficulty,
there would be an expense for the civil and plumbing
work to physically accommodate the reactors.
- Hatcheries using tanks or fully
enclosed ponds should see very minimal switching costs.
Hatcheries that are partially open to a water source
would need to establish a barrier to block any accidental
flow of water from the water source to the pond.
- Open system hatcheries converting
to closed system ones should realize savings in water
consumption and pumping expenses.
- OABIP states the hardware should
last many years. The bacterial consortium does not require
recharging unless it is removed from the water.
- OABIP states that tests done in
small hatcheries and labs comparing test systems having
the bioreactor and control systems without the bioreactor
show larval relative survival percent to average 46.4%
higher in the test systems with the bioreactor than
the control system without the bioreactor for both penaeid
and non-penaeid varieties. If at least one-half of this
higher production can be duplicated in larger commercial
hatcheries, the annual revenue for the hatchery example
given would increase $145,000 ($625,000 x 23.2%).
The OABIP system is completely organic-no
chemicals are used as is common in most hatcheries to control
the growth of unwanted bacteria and the spread of viruses.
Agricultural commodities that are organically
produced typically command a premium of 20% to 30% in the
market place. Environmental benefits of a closed system are
also significant. The need to continually replenish ocean
water in open system shrimp farms has spoiled ground water
resources in nearby communities. This salinized water is also
detrimental to traditional forms of agriculture.
Source:
Mohan Kandaswamy,
Oriental Aquamarine Biotech India P Ltd
E-mail:
orpsps@vsnl.net
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