Treatment Plants for Denitrification
The figure shows the reduced denitrification rate, rA,N031 in relation to the denitrification rate if no oxygen was present: kl/2A,N03 · SN03 112 , as a function of the ratio
between the concentration of oxygen and nitrate in the wastewater.
The penetration of nitrate can be expressed by the penetration of oxygen and nitrate:
PN03,red = Pb2 + P~03
where 13m
13N03
13N03,red
is the degree of penetration of oxygen
is the degree of penetration of nitrate
is the degree of penetration of nitrate when oxygen is present
A2
_ 2 DmSm
PN03,red - ko
2
Vf,02 · L
Example 7.3
2 DNo3· SNo3
kovf,N03 · L 2
In the effluent from an ideally mixed filter, the following concentrations are measured:
Oxygen
Methanol
Nitrate
3
So2 = 2 g02/m
3
SMe = 20 g CH30H/m
SN03 = 5 g N03-N/m 3
What is the removal of methanol and nitrate per m 2 of filter medium?
For the processes, the following constants are chosen (Tables 5.1, 5.2 and 7.2 which
are calculated in g CH30H, not as g COD).
Methanol and oxygen:
kovt,Me = 90 kg CH30H m 3 /d
DMe
= 1.0 · 10-4 m 2 /d
Do2
= 1.7 · 10-4 m 2 /d
VMe,02 = 1.1 g 02/g CH30H
Methanol and nitrate:
kot,N03 = 30 kg N03-N m 3 /d
- % -% -1
k%A,N03 = 3 g NOa-N m
d
DN03
= 0.7 · 10-4 m 2 /d
VN03,Me = 3 g CH30H/g NO:r-N
So2
2
DMe
1.0
SMe = 20 < Do2. VMe,02 = U. 1.1 = 0.65
The oxygen is limiting for the removal.
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