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BIOFILTRATION
Basic components of biofiltration in a RAS:
• Mechanical filter
• Biological filter
• Pump
• Aeration
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BIOFILTRATION (Cont.…)Basic components of biofiltration in a RAS:
• The mechanical filter is used to remove the suspended
solids (feacal matter) from the system water flow.
• The removal of suspended solids is required to
maintain good water quality.
Type of mechanical filter:
• Sedimentation filter (Sump).
• Drum filter.
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MECHANICAL FILTER• Sedimentation filter (Sump)
Solids are allowed to settle on
special adapted filters (Matala
filter).
Nitrate present in the waste is
denitrified into nitrogen gas.
Sump must be cleaned regularly.
After the mechanical filter, the water
is pumped to biological filter.
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MECHANICAL FILTER (Cont…)• Drum filter
Waste water from the fish tank
passes the filter screen.
Due to filter clogging the water
inside the drum rises – rotates
Clean water is sprayed
through the filter cloth while
flushing the waste particles
through the gutter.
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BIOLOGICAL FILTER• Ammonium (toxic) is the waste
produced by fish during
digestion.
• Bacteria converts NH4 to NO2
and later to NO3
• Re-using water after
mechanical and biological
filtration and recirculation
provides local healthy food
that can support the local
economy
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SWIRL FILTER/ SOLID REMOVER
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A swirl filter is a solid filter called settler,
where the heavier solids are allowed to
settle out of suspension by gravity.
• It involves movement of wastewater
through special designed pipe in spiral,
creating centrifugal force to bring solids
together to bottom.
• It removes particles of fish waste in the
form of fish poop, floating debris, food to
clarify the water.
• Only cleaner water taken from the top of
the barrel flows onto grow beds and
back to fish tank.
• It also stops clogging the plant roots in
the grow bed units, improving absorption
of oxygen and dissolved nutrients.
BIOFILTRATION PROCESS
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GROW MEDIA BED BELL SIPHON
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A bell siphon is used in ebb and flow (flood
and drain) aquaponics systems to
regulate water flow automatically without
human intervention. The bell siphon
maintains a minimum water level in the
grow bed as it drains the excess water
automatically when it reaches a certain
level..
• As benefits, it is automatic, increases
root oxygenation and consistent water
circulation.
• Plants need drain cycle not so long to
dry out the roots and flood cycle not so
long that the roots don't get any oxygen
and aerobic bacteria to start growing.
SUMP TANK IN AQUAPONICS
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Broadly, a “sump” is an area where liquid run-
off accumulates and in aquaponics system,
the sump sits at lowest point than the grow
beds for easy draining.
• It enables the fish tank water height to
remain constant regardless of how full or
empty grow beds are.
• This becomes possible because the
fluctuating water height shifts from the fish
tank to the sump.
• In aquaponics, the water flows in and out
of the grow beds via the sump tank and
the water level in the fish tank remains
undisturbed.
• It should be big enough to handle all grow
beds to simultaneously fill.
HANDS-ON PRACTICAL ON SYSTEM SETUP
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CONSTANT HEIGHT ONE PUMP (CHOP) SYSTEM AND WATERF LOW
CHOP system
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• The CHOP system (Constant Height One Pump) is popularly employed for
aquaponics (Fig. 1).
• It reduces the number of water pumps required and uses the fish tank overflow
to fill the grow beds.
UKZN AQUAPONIC SYSTEMS
DESIGN MODEL
• What is
wrong with
this figure
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CHOP system cont.……
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• The advantage of this design is that the farmer does not need to have perfectly levelled
grow-beds to function.
• Siphons can function properly with the presence of ball valves to regulate water flow-
rate.
• This design can help the farmer to add as many grow-beds as possible with
consideration to the economics of scale of course.
Water flow in the system
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• Water from the sump will be pumped using water pumps to the swirl filter (blue drum) to
remove all the suspended solids.
• The water from the swirl filter will gravitational flow through four T pipes connected to
grow beds:
Three grow-beds which will be almost at different levels and provided with tap
valves to regulate water flow and,
The other pipe goes to the fish tanks. The fish tank will not receive water from any
of the grow-beds to prevent solid particles that might be washed from the grow-
beds to the fish tank.
The water overflow from the swirl filter will be drained through line 3 back to the
sump.
All the suspended solids in the swirl filter will be washed out of the filter through
line 4.
Water outflow in the CHOP system
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• All the systems should be constructed above the sump in different levels because all
the outflows of these systems including the fish tank discard effluents into the sump,
which is situated at the lowest level. All the outflows must be situated above the sump.
Outflow in
the CHOP
System
Equipment required for the bell
siphon design:
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• 5 cm below grow bed depth
• 2 end caps
• 50 – 40 mm reducer • 40 mm pipe to 40 mm adapter bush
to 40 mm valve socket
• To 40 mm Bulkhead fitting 30 mm
higher than pipe
Figure 2: Constructing a bell siphon
(https://www.youtube.com/watch?v=Ia1BQF
TaG7c)
System Specifications (Sump)
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1. Sump (1000 L, Fig. 3) = 1:3 ratio grow-bed volume to fish tank volume. The
sump should be able to be drained to 40% capability but still have sufficient
water to supply the whole system. IBC tank will be used as a sump and
equipped with an outflow valve that passes through the water pump to the
swirl filter and an inflow pipe at the top (line 13) with waste effluents from
grow-beds and fish tank. Tubes: 110 mm X 3m = 0.11403981332531
meters3.
System Specifications (Swirl)
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• The swirl filter is often used to remove solid waste in aquaponics system. It
is basically a tool to help maintain water clarity so that fish can survive and
thrive. The swirl filter mechanism is all about calming the whirlpool of the
water. Inside the swirl filter drum there are three pipes, that is,
The incoming pipe with water wastes from the sump (Line 1) which is
purposely bent 90° to the walls of the filter,
Outflow pipe which sends water to the grow-beds.
The excess solids can then be drained off from the bottom (Line 4). The
excess fish solids can then be drained off from the bottom.
How to construct the swirl filter Movement of water and solid waste in swirl filter
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