Treabnent Plants for Nitrification
Design based on sludge load
Design based on sludge load is the design most frequently used. It is characteristic
of this design that it does not in any way involve the ammonium content of the
wastewater or the content of nitrifying bacteria in the sludge.
When designing based on the sludge load:
(4.11)
the volume of the aeration tank, V'b can be found from the expression:
(4.21)
If a sufficiently small sludge load is required ( 0.15 kg BOD/(kg SS ·d)), it can be
seen from Table 6.5 that nitrification is expected to be achieved. In Denmark, many
plants have been designed based on sludge stabilization, that is, with a considerably
lower load than required with regard to nitrification. In such plants, nitrification is
normally achieved without problems.
Sludge load, kg BOD(S)/(kg SS(B) · d)
0.05
0.15
0.3
0.6
Effluent concentration of BOD, g/m 3
5-10
10-20
15-25
20-40
Nitrification
yes
yes
no
no
Aerobic sludge stabilization
yes
no
no
no
Table 6.5
Design of activated sludge treatment plants based on sludge load at 10°C.
Design based on aerobic sludge age
A somewhat more advanced design can be made based on the aerobic sludge age.
In this case attention is focused on the living conditions of the nitrifying bacteria in
the plant; but it is still the content of organic matter in the wastewater and the total
mass of sludge which are used for the design.
Design based on the aerobic sludge age is calculated from Expression (4.14):
9x,aerobic= Mx/Fsr = V2 · X2/Fsr
V2 = 9x,aerobic· Fsr/X2
(6.9)
When the sludge content and the form of operation of the aeration tank have been
established, the necessary tank volume can be found based on the requirements for
the aerobic sludge age. Fig 6.2 shows the curve normally used for the determination
of ex,aerobic·
Example 6.4
Design of nitrification plants. Fig 6.23 shows the layout and operational cycle of two alternative designs of nitrification plants. An estimate of
the necessary plant volume for the two plants is required, based on a criterion of full ni219
Design based on sludge load
Design based on sludge load is the design most frequently used. It is characteristic
of this design that it does not in any way involve the ammonium content of the
wastewater or the content of nitrifying bacteria in the sludge.
When designing based on the sludge load:
(4.11)
the volume of the aeration tank, V'b can be found from the expression:
(4.21)
If a sufficiently small sludge load is required ( 0.15 kg BOD/(kg SS ·d)), it can be
seen from Table 6.5 that nitrification is expected to be achieved. In Denmark, many
plants have been designed based on sludge stabilization, that is, with a considerably
lower load than required with regard to nitrification. In such plants, nitrification is
normally achieved without problems.
Sludge load, kg BOD(S)/(kg SS(B) · d)
0.05
0.15
0.3
0.6
Effluent concentration of BOD, g/m 3
5-10
10-20
15-25
20-40
Nitrification
yes
yes
no
no
Aerobic sludge stabilization
yes
no
no
no
Table 6.5
Design of activated sludge treatment plants based on sludge load at 10°C.
Design based on aerobic sludge age
A somewhat more advanced design can be made based on the aerobic sludge age.
In this case attention is focused on the living conditions of the nitrifying bacteria in
the plant; but it is still the content of organic matter in the wastewater and the total
mass of sludge which are used for the design.
Design based on the aerobic sludge age is calculated from Expression (4.14):
9x,aerobic= Mx/Fsr = V2 · X2/Fsr
V2 = 9x,aerobic· Fsr/X2
(6.9)
When the sludge content and the form of operation of the aeration tank have been
established, the necessary tank volume can be found based on the requirements for
the aerobic sludge age. Fig 6.2 shows the curve normally used for the determination
of ex,aerobic·
Example 6.4
Design of nitrification plants. Fig 6.23 shows the layout and operational cycle of two alternative designs of nitrification plants. An estimate of
the necessary plant volume for the two plants is required, based on a criterion of full ni219