CONTINUOUS FLOW DENITRIFICATION IN CLOSED SEAWATER AQUARIA

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CONTINUOUS FLOW DENITRIFICATION IN CLOSED
SEAWATER AQUARIA

• Robert Mort, Melbourne Aquarium, cnr Queenswharf
  Rd King St, Melbourne Vic 3000,Australia
• rmort_at_underwaterworld.com.au

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Melbourne Aquarium external photoraph
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Nitrogen Cycle in Aquaria (Source Adrian R.
Tappin)
1st AQUALITY Symposium, April 2 - 7, 2004,
Oceanario de Lisboa, Portugal
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Inorganic nitrogen forms found in aquaria (in
order of their toxicity to fish)

• Ammonia (Un-ionised and ionised)(NH3,NH4)
• Nitrite (NO2 -)
• Nitrate (NO3-)

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Denitrification is the process of the reduction
of nitrates and nitrites by bacteria to gaseous
nitrogen.
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Different methods for reducing nitrates in
aquaria

• Algal turf scrubbers
• Coil denitrifiers
• Electrochemical devices
• Natural systems (live rock)
• Jaubert (plenum) systems
• Batch denitrification systems
• Continuous flow denitrification systems

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Continuous flow denitrification systems inject a
carbon source to significantly increase the
bacterial population accelerating
denitrification.
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Mangrove display

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Oceanarium display
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Table 1. Typical fish feed composition at
Melbourne Aquarium (Garman, 2000)
 
 
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Pilot-scale denitrification system

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Pilot-scale denitrification plumbing diagram
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Denitrification tank plastic carrier

1st AQUALITY Symposium, April 2 - 7, 2004,
Oceanario de Lisboa, Portugal
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ORP controller used to deliver carbon source

1st AQUALITY Symposium, April 2 - 7, 2004,
Oceanario de Lisboa, Portugal
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Chemical relationships in a continuous flow
denitrification system.
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Disadvantages of excessive carbon dosing

• Production of undesirable compounds such as
  nitrite, hydrogen sulfide, and nitrous oxide
• Promotion of eutrophic conditions favouring
  parasitic organisms
• Reduced clarity in aquarium display

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Advantages of continuous flow denitrification
systems

• Reduction of nitrates
• pH control
• Promotes better fish health

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A comparison of nitrates between two aquaria
with (Mangroves) and without (Oceanarium) a
denitrification system
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Full-scale denitrification unit at Melbourne
Aquarium