Treahnent Plants for Nitrification
' ' ' ' '
f!!
::::1
0
::c
C')
'
'
'
'
'
' ' '
D
1 Hour
A
c
1 Hour
B
N nitrification
S settling
SG screen and grit chamber
Fig 6.15
Operational cycle for single sludge system with alternating operation for nitrification.
In phases A and C the former nitrification tank is prepared to become a settling tank.
While this is carried out, raw wastewater is directed into one end of the functioning
settling tank (the wastewater will not have time to nm out, before the switch to phase
B or D occurs).
Example 6.4
Find the necessary tank volume for a plant as shown in Fig 6.14 having an operational
cycle as shown in Fig 6.15.
The wastewater volume is 1,700 m 3 /d with 0.25 kg BOD/m 3 . The yield constant is 0.6
kg SS/kg BOD. The plant is to observe an effluent criteria of 0.02 kg BOD/m 3 (20 mg
BOD/I). The lowest plant temperature is estimated at soc.
The sludge production is calculated from Expression (4.13)
Fsp = Y obs (C1 - C3) · 01 = 0.6 (0.25- 0.02) · 1,700 = 235 kg SS/d
On the basis of Table 4.5, the sludge concentration in the aeration tanks is estimated
at 5 kg SS/m 3 . From Fig 6.2 the necessary aerobic sludge age can be estimated at 14
days. With an operational cycle as shown in Fig 6.9, where the aerobic sludge age is
3/8 of the total sludge age (only aeration and nitrification in 3 out of each 8 hours), the
necessary total sludge age will be:
ex= 14 ~ = 37 d
The total volume of the two aeration tanks can be calculated from Expression (4.14)
213
' ' ' ' '
f!!
::::1
0
::c
C')
'
'
'
'
'
' ' '
D
1 Hour
A
c
1 Hour
B
N nitrification
S settling
SG screen and grit chamber
Fig 6.15
Operational cycle for single sludge system with alternating operation for nitrification.
In phases A and C the former nitrification tank is prepared to become a settling tank.
While this is carried out, raw wastewater is directed into one end of the functioning
settling tank (the wastewater will not have time to nm out, before the switch to phase
B or D occurs).
Example 6.4
Find the necessary tank volume for a plant as shown in Fig 6.14 having an operational
cycle as shown in Fig 6.15.
The wastewater volume is 1,700 m 3 /d with 0.25 kg BOD/m 3 . The yield constant is 0.6
kg SS/kg BOD. The plant is to observe an effluent criteria of 0.02 kg BOD/m 3 (20 mg
BOD/I). The lowest plant temperature is estimated at soc.
The sludge production is calculated from Expression (4.13)
Fsp = Y obs (C1 - C3) · 01 = 0.6 (0.25- 0.02) · 1,700 = 235 kg SS/d
On the basis of Table 4.5, the sludge concentration in the aeration tanks is estimated
at 5 kg SS/m 3 . From Fig 6.2 the necessary aerobic sludge age can be estimated at 14
days. With an operational cycle as shown in Fig 6.9, where the aerobic sludge age is
3/8 of the total sludge age (only aeration and nitrification in 3 out of each 8 hours), the
necessary total sludge age will be:
ex= 14 ~ = 37 d
The total volume of the two aeration tanks can be calculated from Expression (4.14)
213