Treatment Plants for Denitrification
k%A,N03 = k%V,Nosfro
= 1.2 g N03-N%m-%d- 1
This is less than stated in Table 7.2 because only a certain part of the biofilm is exposed to free-flowing water.
'li
k%A,N03 = (2 DN03 · koVt,N03) 2
2
ko
_ (k%A,N03)
Vf,N03 -
2 DN03
10 kg N03-N/(m 3 ·d)
2·0.7·10-4
[32 = 1 = 2 DN03 · SN03
2
kovt,N03 · l
2
S
_ kovt,N03 · L
N032 DN03
SN03 = 2.9 g N03-N/m 3
10000 · (2 · 10-4) 2 gNm- 3 d- 1 m 2
2 · 0.7 · 10-4
m 2 d- 1
7.1.2 Combined nitrification and denitrification
This type of plant is normally found in activated sludge plants, see the schematic
representation in Fig 7.4. The mass balances for the plant can be written when a
process matrix is known. An example is shown in Table 4.7.
Among the biomass balances, especially the balance for nitrifying bacteria is interesting. This balance can be used to examine whether a washout of the nitrifying
bacteria takes place. The mass balance for the nitrifying biomass fully corresponds
to the balance set out in Expression (6.1). By using the symbols, defined in Fig 7.4,
the balance is:
Q1 · Xa,A,l + rv,xa · V 3- b A · Xa,A,3 · V 3 = Q4 · Xa,A,4 + Q6 · Xa,A,6
(7.8)
Fig 7.4
Schematic representation of a combined nitrification and denitrification, activated
sludge plant.
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