Treatment Plants for Nitrification
f.lmax,At Ks,NH4 (= Ks), Ks,oz,A and bA can be found in Table 3.10 (the column for
Nitrosomonas or for the entire process), 9x,A can be found in Fig 6.2, after which
SNH4,2can be determined.
Example 6.1
The critical point of a nitrifying activated sludge treatment plant is the low temperatures in winter. In the case of an ideally mixed tank we know that the aerobic sludge age
is 25 days and that the oxygen concentration is 1.6 g/m 3 .
What will the effluent concentration of ammonium be at a temperature of soc?
The following is known (see values in Tables 3.10 and 3.6):
llmax,A = 0.7 d- 1 (20°C)
1( = o.o9° c- 1
Ks.NH4,A = 0.5 g N/m 3
Ks.o2,A = O.S g 02/m 3
bA = 0.05 d- 1
llmax,A (S°C) calculated by Expression (3.16).
llmax,A (SoC)= llmax,A (20°C) · exp (K · (T-20)) = 0.7 · exp (0.09 · (8-20)) = 0.24 d- 1
Likewise bA (S°C) = 0.02 a 1 iS found.
When substituting known values into Expression (6.4), the ammonium concentration
of the aeration tank, SNH4,2. is found:
SNH4,2
So2,2
b
1
llmaxA
- A=-' SNH4,2 + l ex,A
(6.4)
0.24
SNH4,2
1.6
0 02
1
SNH4,2 + 0.5 O.S + 1.6 - . = 25
hence:
SNH4,2 - 0.3 g NH,t-N/m 3
Biofilm plants
Nitrification consists of the removal of soluble materials: NHt and 02. Therefore,
the condition of the biofilm theory, as described in previous sections, has been
satisfied, and the theory has shown its practical applicability. Fig 6.3 shows the
observed nitrification rate per surface area as a function of the concentration in the
bulk water.
The nitrogen mass balance of a nitrifying filter (Fig 6.1b) is as follows, see Expression
(5.3):
(6.5)
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