Novel Bioreactors for Culturing Marine Organisms 12.7 Fluidized Bed and Moving Bed Bioreactors (FBBR and MBBR) 367
Part B | 12.8
which tank water was used. Sludge and backwash water were collected in a rectangular tank (volume 0:3 m
3 )
packed with 0:1 m
3 beads that provided a means for
solids removal, as well as a substrate for bacterial colonization. Water from the sludge tank was pumped
back into the system through the anaerobic biofilter,
and high-density sludge was collected and removed. In
view of stricter environmental regulations for effluent
discharge from aquaculture facilities there is increasing emphasis on closing the nitrogen cycle in the water
treatment system by utilizing the anammox process as
a preferred alternative to heterotrophic denitrification,
especially in marine recirculating systems in order to
reduce effluent volumes as well as nitrogen loads. The
results of this study show that anammox bacteria and
their activity are associated with the consortia of a denitrifying biofilter, which makes this approach feasible
for implementation.
Enhanced biological phosphorus removal (EBPR)
in wastewater treatment is based on the fact that phosphorus accumulating organisms (PAOs) can accumulate
intracellular phosphorus as polyphosphate (poly-P). In
EBPR, the biomass is exposed to cyclically occurring anaerobic and aerobic/anoxic conditions. Under
anaerobic conditions, PAOs store rapidly biodegradable substrate in their cells as poly-ˇ-hydoxyalkanoates
(PHA) by using intracellular poly-P and glycogen as
energy sources. Under aerobic/anoxic conditions, PAOs
use PHA as a carbon source to refill poly-P and glycogen stocks. Poly-P synthesis allows bulk phosphate
to accumulate in the biomass. The phosphate is then
removed with the biomass during aerobic/anoxic conditions. Another group of bacteria, the glycogen accumulating organisms (GAOs), also grow under cyclic
alternation of anaerobic and aerobic/anoxic conditions,
using only glycogen as energy source and therefore
consuming substrate but not removing phosphorus.
Thus to optimize EBPR, anaerobic conditions must
be strictly controlled, poly-P storage maximized, and
GAOs growth minimized. Poly-P storage is maximized
by using acetate as a carbon source because it increases the production of poly-P compared to other
volatile fatty acids during aerobic periods. Environmental conditions known to favor PAOs over GAOs are
temperature < 25
ı C and pH > 7:5. Aquariums and fish
farms run in closed circuit face major accumulation of
phosphate and nitrate which cause, respectively, excessive algal growth and toxicity to aquatic fauna. As an
alternative to regularly changing the water that causes
highly polluted discharge to the surroundings, denitrifying biological phosphorus removal (DN-BPR) may
be applied to this system without producing excessive
sludge.
The Montreal Biodome operates a 3250 m
3 , closed
circuit, cold (10
ı C) marine mesocosm named St.
Lawrence Mesocosm (SLM) containing very high nitrate and phosphate levels. Earlier workers (e.g., Labelle et al. [12.66], Dupla et al. [12.67]) have demonstrated the feasibility of denitrifying the SLM water
using an MBBR with methanol as the C-source. Vallet et al. [12.69] modified the process to implement
DN-BPR to promote the anaerobic growth of PAOs in
the reactor – and additional C-source was required in
view of low concentration of organic matter in the SLM
water (24 mg C=L). The process developed is based
on the alternation of anaerobic and aerobic/anoxic conditions in the MBBR with biofilm growth occurring on
the surfaces of plastic carriers. A sequential complete
exchange of two waters thus takes place in the MBBR –
(1) the influent containing nitrate and phosphate and (2)
the anaerobic water stored in a stock tank. Therefore,
the environmental conditions in the MBBR selectively
favor the growth of PAOs only. An additional advantage
is the accumulation of phosphate in a stock tank thereby
allowing an easy recovery of P for use as fertilizer.
Two identical reactor setups (used earlier by Labelle et al. [12.66]) were operated in parallel under
identical conditions. Each setup comprised a wellmixed bioreactor (volume 110 L) filled with 35 L of
plastic carriers, and a stock tank (volume 220 L).
The packed bed was moved using a circulation pump
thereby allowing operation as an MBBR. Water was
pumped from the stock tank to the MBBR through
a three-way transfer valve, while the MBBR was
filled with the pressurized influent through a solenoid
valve. A pH probe, a redox-potential probe, an oxygen probe, and a UV nitrate analyzer were installed
on the recirculation line. This study demonstrated the
inhibition of BPR by seawater presumably due to the
high calcium levels in seawater. However, in freshwater, a biofilm was developed with a phosphorus
removal efficiency rate of 20% of which 80% was attributed to biological removal and 20% to chemical
precipitation.
Part B | 12.8
which tank water was used. Sludge and backwash water were collected in a rectangular tank (volume 0:3 m
3 )
packed with 0:1 m
3 beads that provided a means for
solids removal, as well as a substrate for bacterial colonization. Water from the sludge tank was pumped
back into the system through the anaerobic biofilter,
and high-density sludge was collected and removed. In
view of stricter environmental regulations for effluent
discharge from aquaculture facilities there is increasing emphasis on closing the nitrogen cycle in the water
treatment system by utilizing the anammox process as
a preferred alternative to heterotrophic denitrification,
especially in marine recirculating systems in order to
reduce effluent volumes as well as nitrogen loads. The
results of this study show that anammox bacteria and
their activity are associated with the consortia of a denitrifying biofilter, which makes this approach feasible
for implementation.
Enhanced biological phosphorus removal (EBPR)
in wastewater treatment is based on the fact that phosphorus accumulating organisms (PAOs) can accumulate
intracellular phosphorus as polyphosphate (poly-P). In
EBPR, the biomass is exposed to cyclically occurring anaerobic and aerobic/anoxic conditions. Under
anaerobic conditions, PAOs store rapidly biodegradable substrate in their cells as poly-ˇ-hydoxyalkanoates
(PHA) by using intracellular poly-P and glycogen as
energy sources. Under aerobic/anoxic conditions, PAOs
use PHA as a carbon source to refill poly-P and glycogen stocks. Poly-P synthesis allows bulk phosphate
to accumulate in the biomass. The phosphate is then
removed with the biomass during aerobic/anoxic conditions. Another group of bacteria, the glycogen accumulating organisms (GAOs), also grow under cyclic
alternation of anaerobic and aerobic/anoxic conditions,
using only glycogen as energy source and therefore
consuming substrate but not removing phosphorus.
Thus to optimize EBPR, anaerobic conditions must
be strictly controlled, poly-P storage maximized, and
GAOs growth minimized. Poly-P storage is maximized
by using acetate as a carbon source because it increases the production of poly-P compared to other
volatile fatty acids during aerobic periods. Environmental conditions known to favor PAOs over GAOs are
temperature < 25
ı C and pH > 7:5. Aquariums and fish
farms run in closed circuit face major accumulation of
phosphate and nitrate which cause, respectively, excessive algal growth and toxicity to aquatic fauna. As an
alternative to regularly changing the water that causes
highly polluted discharge to the surroundings, denitrifying biological phosphorus removal (DN-BPR) may
be applied to this system without producing excessive
sludge.
The Montreal Biodome operates a 3250 m
3 , closed
circuit, cold (10
ı C) marine mesocosm named St.
Lawrence Mesocosm (SLM) containing very high nitrate and phosphate levels. Earlier workers (e.g., Labelle et al. [12.66], Dupla et al. [12.67]) have demonstrated the feasibility of denitrifying the SLM water
using an MBBR with methanol as the C-source. Vallet et al. [12.69] modified the process to implement
DN-BPR to promote the anaerobic growth of PAOs in
the reactor – and additional C-source was required in
view of low concentration of organic matter in the SLM
water (24 mg C=L). The process developed is based
on the alternation of anaerobic and aerobic/anoxic conditions in the MBBR with biofilm growth occurring on
the surfaces of plastic carriers. A sequential complete
exchange of two waters thus takes place in the MBBR –
(1) the influent containing nitrate and phosphate and (2)
the anaerobic water stored in a stock tank. Therefore,
the environmental conditions in the MBBR selectively
favor the growth of PAOs only. An additional advantage
is the accumulation of phosphate in a stock tank thereby
allowing an easy recovery of P for use as fertilizer.
Two identical reactor setups (used earlier by Labelle et al. [12.66]) were operated in parallel under
identical conditions. Each setup comprised a wellmixed bioreactor (volume 110 L) filled with 35 L of
plastic carriers, and a stock tank (volume 220 L).
The packed bed was moved using a circulation pump
thereby allowing operation as an MBBR. Water was
pumped from the stock tank to the MBBR through
a three-way transfer valve, while the MBBR was
filled with the pressurized influent through a solenoid
valve. A pH probe, a redox-potential probe, an oxygen probe, and a UV nitrate analyzer were installed
on the recirculation line. This study demonstrated the
inhibition of BPR by seawater presumably due to the
high calcium levels in seawater. However, in freshwater, a biofilm was developed with a phosphorus
removal efficiency rate of 20% of which 80% was attributed to biological removal and 20% to chemical
precipitation.