HighlandReefer
Team RC
Trying to wrap my head around this article. 
How are the implications provided in this article related to using a solid biopellet like PHA for reducing nitrate?
Denitrification in recirculating systems:
Theory and applications
Jaap van Rijn a,*, Yossi Tal b, Harold J. Schreier b,c
growfishanywhere.com/media/3849/denitrification__2_.pdf
From it in part:
"4. Denitrifiers and phosphate removal
Enhanced biological phosphorus removal (EBPR)
from domestic wastewater in activated sludge plants is
accomplished by alternate stages, where sludge is
subjected to anaerobic and aerobic conditions.
Phosphorus is released from bacterial biomass in
the anaerobic stage and is assimilated by these bacteria
in excess as polyphosphate (poly-P) during the aerobic
stage. Phosphorus is removed from the process stream
by harvesting a fraction of the phosphorus-rich
bacterial biomass (Toerien et al., 1990). Some of
these polyphosphate accumulating organisms (PAO)
are also capable of poly-P accumulation under
denitrifying conditions, i.e. with nitrate instead of
oxygen serving as the terminal electron acceptor
(Barker and Dold, 1996; Mino et al., 1998). Studies on
poly-P accumulating organisms have revealed the
involvement of specific metabolic properties under
anaerobic, aerobic and anoxic conditions (Mino et al.,
1998). Under anaerobic conditions, acetate or other
low molecular weight organic compounds are converted
to polyhydroxyalkanoates (PHA), poly-P and
glycogen are degraded and phosphate is released.
Under aerobic and anoxic conditions, PHA is
converted to glycogen, phosphate is taken up and
poly-P is synthesized intracellularly. Under the latter
conditions, growth and phosphate uptake is regulated
by the energy released from the breakdown of PHA.
Some heterotrophic denitrifiers exhibit phosphorus
storage in excess of their metabolic requirements
through poly-P synthesis under either aerobic or
anoxic conditions, without the need for alternating
anaerobic/aerobic switches (Barak and van Rijn,
2000a). Unlike PAO, these denitrifiers were unable
to use PHA as an energy source for poly-P synthesis
and derived energy from oxidation of external carbon
sources. The feasibility of this type of phosphate
removal was demonstrated for freshwater as well as
marine recirculating systems (Barak and van Rijn,
2000b; Shnel et al., 2002; Barak et al., 2003; Gelfand
et al., 2003). In the culture water of these systems,
stable orthophosphate concentrations were found
throughout the culture period. Phosphorus immobilization
took place in the anoxic treatment stages of the
system where it accumulated to up to 19% of the
sludge dry weight."
How are the implications provided in this article related to using a solid biopellet like PHA for reducing nitrate?
Denitrification in recirculating systems:
Theory and applications
Jaap van Rijn a,*, Yossi Tal b, Harold J. Schreier b,c
growfishanywhere.com/media/3849/denitrification__2_.pdf
From it in part:
"4. Denitrifiers and phosphate removal
Enhanced biological phosphorus removal (EBPR)
from domestic wastewater in activated sludge plants is
accomplished by alternate stages, where sludge is
subjected to anaerobic and aerobic conditions.
Phosphorus is released from bacterial biomass in
the anaerobic stage and is assimilated by these bacteria
in excess as polyphosphate (poly-P) during the aerobic
stage. Phosphorus is removed from the process stream
by harvesting a fraction of the phosphorus-rich
bacterial biomass (Toerien et al., 1990). Some of
these polyphosphate accumulating organisms (PAO)
are also capable of poly-P accumulation under
denitrifying conditions, i.e. with nitrate instead of
oxygen serving as the terminal electron acceptor
(Barker and Dold, 1996; Mino et al., 1998). Studies on
poly-P accumulating organisms have revealed the
involvement of specific metabolic properties under
anaerobic, aerobic and anoxic conditions (Mino et al.,
1998). Under anaerobic conditions, acetate or other
low molecular weight organic compounds are converted
to polyhydroxyalkanoates (PHA), poly-P and
glycogen are degraded and phosphate is released.
Under aerobic and anoxic conditions, PHA is
converted to glycogen, phosphate is taken up and
poly-P is synthesized intracellularly. Under the latter
conditions, growth and phosphate uptake is regulated
by the energy released from the breakdown of PHA.
Some heterotrophic denitrifiers exhibit phosphorus
storage in excess of their metabolic requirements
through poly-P synthesis under either aerobic or
anoxic conditions, without the need for alternating
anaerobic/aerobic switches (Barak and van Rijn,
2000a). Unlike PAO, these denitrifiers were unable
to use PHA as an energy source for poly-P synthesis
and derived energy from oxidation of external carbon
sources. The feasibility of this type of phosphate
removal was demonstrated for freshwater as well as
marine recirculating systems (Barak and van Rijn,
2000b; Shnel et al., 2002; Barak et al., 2003; Gelfand
et al., 2003). In the culture water of these systems,
stable orthophosphate concentrations were found
throughout the culture period. Phosphorus immobilization
took place in the anoxic treatment stages of the
system where it accumulated to up to 19% of the
sludge dry weight."
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