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SVWM System Nutrient
Removal -- Nitrification/Denitrification
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Nitrification/Denitrification
and BOD5 and Solids Removal :
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This is accomplished without
the addition of methanol
as an organic carbon source.
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The influent serves as
a natural, internal organic
carbon source. |
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In addition, denitrification
enhances alkalinity recovery.
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This prevents a pH drop
which could contribute to
filamentous growth and bulked
sludge. |
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Alkalinity recovery is
particularly advantageous
in areas with low natural
alkalinity. |
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The Nitrification and Denitrification
Cycle :
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During
nitrification (aeration),
excess oxygen is present,
and Nitrosomonas oxidize
the Ammonium (NH4) to
Nitrite (NO2). |
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Nitrobacter further oxidize
the Nitrite (NO2) to Nitrate
(NO3). |
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During
denitrification (non-aerated
periods) (sedimentation
and decantation), the
dissolved oxygen level
in the sludge blanket
approaches zero. |
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Nitrate
dissimilation takes place
in two steps :
First, Nitrate is reduced
to Nitrite.
Second, Nitrite is reduced
by the bacterial dissimilation
process to form Nitric
Oxide (NO), Nitrous Oxide
(N2O), or Nitrogen Gas
(N2). |
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The
lack of molecular oxygen
encourages Pseudomonas
and other denitrifying
bacteria to attack the
oxygen bound up in the
Nitrate (NO3) molecules.
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The bacteria reduces the
nitrate molecules to N2
and O2. |
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The molecule, nitrogen
(N2, a gas), is released
to the atmosphere, while
the bacteria utilize the
liberated O2. |
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Intermittent
aeration periods in the
SVWM System basin promotes
nitrogen removal from
the waste stream. (NH3
removal of 95% or better). |
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F/M RATIONS :
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Food to microorganism
ratio (F/M) may vary from
0.04 to 0.3 lb of BOD5 /lb
of MLSS/day. |
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Mixed Liquor Suspended
Solids (MLSS) range from
1,000 to 15,000 mg/l. |
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Actual
practice has shown that
systems with MLSS concentrations
in the 2,000 to 6,000
mg/l range to be most
effective. |
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With
a hydraulic retention
time (HRT) targeted for
18 to 36 hours, and a
sludge age of twenty to
seventy days, the system
is sized according to
extended aeration conventional
standards. |
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Sludge Wasting :
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With
standard design parameters,
typical excess solids
(waste sludge) production
ranges from 0.5 to 1.0
lb/lb of BOD5 removed.
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The sludge produced is
very stable with an O2 uptake
rate of less than 10mg/l
of O2/gm of MLSS/hr. |
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The
SVWM System offers sludge
production of 0.2 to 0.5
lb/lb of BOD5 removed
with an even higher degree
of stability.
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When
excess sludge is dissipated
from the SVWM System basin,
additional nitrogen removal
is accomplished through
assimilation of nitrogen
into a bacterial cell
mass in satisfaction of
metabolic needs. |
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Actual
operating data have shown
the concentration of nitrogen
in the sludge mass to
be between 5% and 8% by
weight of the dry solids.
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Copyright
© 2000 -
2011 Unitech Water Systems Corp. All Rights Reserved |
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