With the expansion and development of the aquaculture industry, several challenges arise. The intensification of production systems increases the pressure on the environment, which can severely affect water quality and as a consequence fish or shrimp performance and the incidence of diseases.

1. I N C O R P O R AT I N G
f i s h far m ing t e c h no l og y
March | April 2013
The role of bioremediation in water quality
management
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3. FEATURE
The role of
bioremediation in water
quality management
by Goncalo A. Santos, MSc, technical manager – aquaculture, Biomin
Holding GmbH, Austria
W
ith the expansion and devel- decreased anaerobic conditions in pond soil example, the formation of glutamine in the
opment of the aquaculture and reduced sludge accumulation. brain to detoxify ammonium to urea, to
industry, several challenges Moreover, enzymes can be an effective protect themselves from toxic ammonia levels
arise. The intensification of tool in the degradation of organic matter (Randall and Tsui, 2002). Nitrite (NO2-) is
production systems increases the pressure in very intensive production systems. These usually present below dangerous concentra-
on the environment, which can severely positive changes in the environment are sup- tions in fresh and marine water.
affect water quality and as a consequence ported by proven benefits for the perform- However, prolonged exposure to high
fish or shrimp performance and the inci- ance and survival of shrimp from the larval to nitrite levels, especially when oxygen is limited,
dence of diseases. grow-out stages. leads to anoxia and slow suffocation of the
animals, because nitrite changes hemoglobin
In aquaculture, the application of beneficial Toxicity of nitrogenous into methemoglobin, a form that is not able to
bacteria (probiotics) is not only associated compounds bind oxygen (Lewis and Morris, 1986).
with gut health (feed probiotics), but also Nitrogen compounds, such as nitrite, Nitrate (NO3-) is the least dangerous
with bioremediation improving the environ- nitrate and ammonium ions / ammonia are compound and low concentrations are not
ment (water and soil) in which the animals toxic when their concentrations exceed a problematic. Similar to nitrite, nitrate converts
are reared. The effects of biodegrading strains certain level in the rearing water. Ammonium hemoglobin, into a non-binder for oxygen.
(such as Bacillus sp., Paracoccus sp., Thiobacillus nitrogen that occurs partly in the form of Permanent exposure to high nitrate levels
sp.) added directly to the water involve the ammonium ion (NH4+) and ammonia causes weight loss and a higher occurrence of
modulation of the microbiology profile in (NH3+) originates from decomposing organic infectious diseases. To avoid these complica-
ponds, degradation of undesirable waste com- waste and animal excretions in the farm. The tions, excess nitrate needs to be removed
pounds (ammonia, nitrite, hydrogen sulfide), sensitivity to ammonium nitrogen depends to reach lower, non-toxic concentrations
enhanced mineralization of organic matter, largely on the species. (Camarga et al., 2005). This is often achieved
Some fish have developed strategies, for by water renewal at the farms.
Bioremediation in aquaculture
Watewater management in aquaculture
systems is crucial to maintain a good health
status of the animals as well as to counteract
the negative impacts on the environment.
Bioremediation, the application of micro-
organisms like bacteria to remove dangerous
waste products, is a promising tool for onsite
treatment of watewater and contaminated
sediments. For the bioremediation of nitrog-
enous compounds, bacteria have to perform
nitrification and denitrification. Bacterial nitrifica-
tion is the oxidation of ammonium / ammonia
Figure 1: Nitrification and denitrification (NH4+, NH3+) to nitrate (NO3-) via hydroxyl
processes in aquatic environments amine and nitrite (NO2-). Denitrification
28 | InternAtIonAl AquAFeed | March-April 2013

5. FEATURE
FEATURE
duced on a large scale it could bring fish uniqueness of the technology is based on its carbon dioxide. In particular, oversaturation
production to the place where the fish is ability to perform three critical functions in of nitrogen, even in relatively small quantities,
actually consumed. one system - dissolving oxygen in the water, can endanger the wellbeing of fish stock, slow-
The Marine Harvest Group, the world's producing the correct marine hydrodynamics ing growth and increasing the possibility of
largest private fish producer, is building ever- and stripping out potentially harmful nitrogen disease, and ultimately, even mortality. With
larger tanks. At Kårstø, Norway, the company - and all this via a very low energy require- the installation of OxyStream, external degas-
has plans to produce 6,000 tons of salmon ment. The system is easily installed, as a new sing units to prevent inert gas build-up will, in
per year, onshore, to an average size of 1 set-up or as a retrofit to existing fish farm many cases, become obsolete.
kilogram, in fish tanks 40 metres in diameter tanks, and is maintenance-free because it is Depending on the application, pumping
and 10 metres high, with volumes of water as not associated with any ancillary equipment pressures as low as 0.05 to 0.2 bar are nor-
high as 12,000 cubic metres. Marine Harvest to manage water pressure. mally sufficient to oxygenate the incoming
also intends to explore the possibility of SOLVOX ® OxyStream significantly water, strip nitrogen and create optimal tank
building a land based fish farm in a quarry at increases fish production volume, optimises hydrodynamics. This low operating pressure
Mjølkevikvarden, in 2: Pond Norway, where fish meat quality and considerably improves
Figure Askøy, interactions without the addition of Figure 3: Pond interactions with the
makes the system very energy efficient.
the company believes there is potential to beneficial bacteria
operations from an environmental standpoint. The addition of beneficial bacteria were
capabilities of this technology
build a plant big enough to produce 50,000 It is a combined oxygenation and flow system proved during trials conducted at a Marine
tons per year of 1 kilogram salmon. nitrous
describes the reduction of nitrate to compounds is more likely to ensure a amount
that not only dissolves the optimal stable are constantly exposed Results showed that
Harvest facility in 2011. to and challenged
This is equal to 5 percent of the total
oxide and finally to nitrogen gas, which returns performance.in the inlet water flow, but also
of oxygen OxyStream was the only oxygenation source
by micro-organisms from the surrounding
into the atmosphere (Chávez-Crooker trout
biomass production of salmon and and distributes it evenly at an adjustable flow pat- environment. rearing young salmon hatched in
suitable for
Obreque-Contreras, — currently about range
in Norway today 2010). Although a 1 mil- Beneficial bacteria and enzymes
tern throughout the tank, ensuring that the tanks running on fresh water, before gradually
These environmental challenges are
of bacterial species are Theoretically, if 20 of
lion tons per year. capable of nitrification to improve water and soil exercise
fish stock benefit from the physical transitioning them to seawater. This creates
obviously influenced by different factors,
these plants where in operation today, all of
and / or denitrification, not all species are appli- quality in aquaculture ponds The
involved in swimming against the flow. an optimum environment in and to rear
including farm management which rearing
Norway’s salmon production to full slaughter
cable for bioremediation products. Recently flow key factor for successful aquaculture is
A regime can be fully tailored according salmon, ensuring the correct oxygen levels
methods. Aquaculture operations generally
size could be accomplished on land. Key
strains such as Paracoccus sp. and Thiobacillus sp. to understand stock density and fish species,
to fish size, the interactions between the throughout the entire production period and
involve the stocking and feeding of shrimp
parameters associated with this installation
have gained interest due to its degrading capa- such as salmon or cod. The system comprises
microbial environment, gut flora and immune in open fish semi-closed water systems.
keeping or stress levels to an absolute
are 20,000 cubic metre fish tanks, 35 metres
bilities. Also Bacillus sp. is also well suited to a standalone unit, allowing water flow and
system of the shrimp, as well as the factors minimum.
Semi-closed pond systems have a low
in diameter.
perform several functions in the water cleanup that determine the be individually microbial
oxygen dosing to persistence of controlled Importantly, the technology makes it pos-
water turnover and can accumulate gases,
application (Nakano et al., 1998). for each tank.
species in the internal and external microbial nutrients, precisely predict flow etc., which
sible to metabolites, waste, velocity and
Pioneering technology all desired
A single strain, rarely harbours The micro-bubbles created by SOLVOX®
ecosystems. While natural environments are can adjust this velocity in the circular on-land
to deteriorate the water quality and
qualities necessary for an efficient degradation
One of the most pioneering technologies balanced, the farming environment favours
OxyStream create the additional benefit of create anoxic conditions in state of matu-
tanks, Depending on their the soil. This
of toxic compounds, therefore a combination
to be introduced to the industry has been the growth of micro-organisms as it is rich
helping to reduce the concentration of dis- rity, fish need a certain water velocity to
can strongly affect the performance of the
Linde’s SOLVOX® OxyStream system. The
of strains that perform best for one or several in nutrients and feed waste. Farmed species
solved inert gases such as nitrogen, argon and remain healthy. If the velocity is not correct,
farmed species. Thus, good pond manage-
Extruder OEE for the Production of Fish Feed
-
AMANDUS KAHL GmbH & Co. KG, Dieselstrasse 5-9, D-21465 Reinbek / Hamburg,
Phone: +49 40 727 71 0, Fax: +49 40 727 71 100, info@amandus-kahl-group.de www.akahl.de
March-April 2013 | InternAtIonAl AquAFeed | 29
March-April 2013 | InternAtIonAl AquAFeed | 11

7. FEATURE
Table 1: A diverse range of enzymes used as
bioremediation agents in aquaculture
enzyme substrate
amy;lase ß-Glucoside
Cellulase Cellulose
lipase lipids and fat
Protease Protien
Xylanase Xylan, Hemicellulose
Peectinase Pectin
ment is crucial for high production and
a healthy crop. Since water quality plays
an important role, it is of great value to
understand the various interactions taking
place within the ponds. These are quite
complex and depend directly on the pond
environment, stocked biomass, input of
nutrients and pond management. pathogens to grow and affecting the condition the level of such toxic compounds. Some
As can be seen in Figure 2, the accumula- of the shrimp. Under these poor conditions, beneficial bacteria can also degrade toxic H2S,
tion and degradation of organic waste in the the shrimp faces higher levels of stress and improving water quality and odor. The com-
pond will result in an increased consumption is more susceptible to diseases, which could bination of all these factors will improve water
of oxygen (O2) and production of waste result in poor growth or a failed crop through quality and the condition of the pond soil,
compounds such as ammonia (NH3), nitrites disease outbreaks. resulting in a better environment for shrimp
(NO2 -) and hydrogen sulfide (H2S), which With the inclusion of beneficial bacteria with better growth and health status.
can lead to a phytoplankton bloom. Massive (Figure 3), organic matter is utilized as a In the bioremediation process, enzymes
growth of phytoplankton can further deplete source of nutrients by the bioremediation play the role of catalysts that accelerate
oxygen during the night and contribute to a bacteria, which reduces the amount of waste biochemical reactions in pond soil and water.
phytoplankton bloom crash. All these factors accumulating in the pond. Additionally, specific When added to the culture water or spread
contribute to the contamination of water nitrifying and denitrifying bacteria will convert on top of the pond soil, enzymes are able
and soil, creating favourable conditions for NH3 and NO2- into nitrogen gas, reducing to degrade the major organic constituents
normally found in shrimp and fish ponds. Each
enzyme has its mode of action and is very
specific in the chemical reaction it catalyzes
(Table 1).
Enzymes are also naturally produced and
excreted by some microbes. These extracel-
lular enzymes, such as cellulase, protease and
amylase, are produced during the aerobic fer-
mentation of organic matter by micro-organ-
isms, for example by some Bacillus species.
Bacilli are commonly found in pond sediments
and can also be added to the pond water for
bioremediation purposes. Some Bacillus sp. are
also able to degrade nitrogenous compounds.
In addition, their large variety of excreted
(extracellular) enzymes helps to speed up the
degradation of organic matter and toxic com-
pounds such as ammonia. The efficient removal
of nitrogenous compounds can also be carried
out by nitrifying and denitrifying bacteria such as
Figure 4: Average growth rate (g/day) of shrimp during the production period
Thiobacillus and Paracoccus.
30 | InternAtIonAl AquAFeed | March-April 2013

8. FEATURE
While some micro-organisms proliferate in breaking apart large sludge particles, thus the soil of the control ponds in Picture 2
a narrow range of environmental conditions creating wider surface areas which can then exhibited a dark black colour, an indica-
(pH, oxygen, availability, etc.), certain enzymes be fermented by microbes. This reduction tion of the accumulation of dead organic
are able to act in multiple environments. of sludge and dead organic matter can be matter.
Nevertheless, some products combining seen visually not only through better water Results suggested that with the combined
the positive effects of beneficial bacteria and quality, but also through better soil quality. use of beneficial bacteria and enzymes, pond
enzymes are already being used as bioreme- soils containing black and glutinous organic
diation agents in aquaculture. Field trial sludge turned into a more yellow soil.
In a field study in China, it was observed In terms of performance, the average daily
Efficacy of enzymes in that the combined application of the weight gain of shrimp in the AquaStar® group
bioremediation bioremediation products AquaStar® Pond increased by 36 percent and feed conversion
Enzymes have the capacity to stabilize (Bacillus sp., Enterococcus sp.,Pediococcus ratio improved by 9 percent compared with
the soil organic matter and can be used sp., Paracoccus sp., Thiobacillus sp) and the control (no probiotic inclusion). The
effectively to manage soil quality and rear- AquaStar® PondZyme (beneficial bacteria results are shown in Figure 4 and 5.
ing conditions for aquatic species. There is and a blend of amylases, xylanases, cellulases Based on these results, it was concluded
not one specific enzyme that works best and proteases) to the water, according to that in the search for more effective and
in all cases. A blend containing a variety of a specific application programme, improved environmentally-friendly treatments, benefi-
enzymes may be the most effective means water quality, soil condition and ultimately, cial bacteria have emerged as a viable alter-
for bioremediation in aquaculture. Enzymes shrimp performance. native. The application of bioremediation
greatly reduce sludge accumulation and Four earth shrimp ponds (0.7 – 0.8 ha/ solutions in aquaculture can also benefit
anaerobic conditions in pond bottoms. pond) with a depth of 1 – 1.2 m were from the inclusion of enzymes, especially in
They promote a faster degradation of stocked with juvenile shrimp (approximately intensive productions. AquaStar® positively
the accumulated organic matter especially 1.4 g/shrimp) with a density of 50 shrimp/ affects the performance of shrimp while
under intensive production conditions. m². The trial was carried out for a period maintaining a stable environment in the
This organic matter comprises uneaten of 57 days with a dosage of 500 g/ha of pond, proving to be an effective manage-
feed, dead plankton, mineral soils, faeces product applied once a month to the ment tool in aquaculture.
and pathogenic micro-organisms in the soil treatment group (two ponds). The control
where the conditions are often anaerobic. ponds consisted of two ponds with normal
However, for all these bioremediation proc- production operations.
esses catalyzed by enzymes, the presence The soil of the AquaStar® ponds in More InforMatIon:
of beneficial bacteria is important as well. Picture 1 was of yellow colour which is Website: www.biomin.net
Enzymes accelerate microbial processes by regarded as the best bottom type, while
Ecobiol Aqua
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sit
VI Bo NO
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A highly effective new generation probiotic
Pathogenic bacteria antagonist
Enhances friendly intestinal microflora
Improves Feed Conversion Ratio and growth
Helps mantain optimal health status
Reduces mortality in the ponds
Controls water quality
Central Office and Orders
Jesús Aprendiz, 19. 1º A-B 28007 Madrid
T. +34 915 014 041 norel@norel.es www.norel.es
March-April 2013 | InternAtIonAl AquAFeed | 31

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