Activated Sludge Aeration Tank Calculations - S.I. Units
Workbook Contents
NOTE: The cells containing formulas are locked (protected) to avoid the possibility of inadvertently typing over any of the formulas. You may, however, adjust the number of decmal places for any of the cells.
(Parameter values entered here will be used in the other worksheets)
(tank volume based on volumetric loading, HRT, or F:M ratio)
(waste activated sludge and recycle activated sludge rates)
NOTE: The cells containing formulas are locked (protected) to avoid the possibility of inadvertently typing over any of the formulas. You may, however, adjust the number of decmal places for any of the cells.
Activated Sludge Waste Water Treatment Calculations - U.S. units
Input of Values for Wastewater Parameters
Enter values in yellow cells only.
INPU
T IN
FOR
MA
TIO
N
Note that these parameter values will be used in the other worksheets.
Activated Sludge Waste Water Treatment Calculations - S.I. units References and Equations
Aeration Tank Sizing Calculations A flow diagram of the activated sludge process is shown below along with the equations used in this worksheet. For more details and background information on the activated sludge process and its design and operation calculations, see the following references:
The symbols used in the flow diagram at the left andthe equations below are as follows:
Enter values in yellow cells only.
Values of other Design Parameters
hr
waste activated sludge and recycle activated sludge
are taken to be equal to that in the effluent stream.
hr
Equations Used for These Calculations:
Values of other Design Parameters
Water and Wastewater Engineering Design Principles and Practice, Sec 23.7 Suspended Growth Design Practice
Standard Handbook of Environmental Engineering, 2nd Ed, Sec 6.5.1 Activated Sludge
Handbook of Environmental Engineering Calculations, 2nd Ed, Sec 1.7.21 Activated Sludge Process
Design of Municipal Wastewater Treatment Plants, WEF MOP No. 8, 5th Ed., Sec. 14.1.3 Activated Sludge Environment
Q is volumetric flow rate in m3day
S is BOD5 concentration in g/m3
kg BOD5/day/m3 X is total suspended solids concentration in g/m3
The subscript o refers to the primary effluent stream.
The subscript e refers to the secondary effluent stream.
The subscript w refers to the waste act. sludge stream.
The subscript r refers to the recycle act. Sludge stream. kg BOD5/day/kg MLVSS NOTE: Based on an assumption of no biological
degradation in the secondary clarifier, the BOD5 in the V is the volume of the aeration tank in m3.X is the mixed liquor suspended solids concentration
in the aeration tank in g/m3.
Volumetric Loading: VL = [(So*Qo)/V]/(1000 g/kg)
kg BOD5/day/m3 hydraulic Loading: HRT = 24*V/Qo
kg BOD5/day/kg MLVSS F:M Ratio: F:M = (So*Qo)/(%Vol*X*V)
NOTE: The conversion factors in these equations are: 1000 g/kg and 24 hr/day
A flow diagram of the activated sludge process is shown below along with the equations used in this worksheet. For more details and background information on the activated sludge process and its
The symbols used in the flow diagram at the left andthe equations below are as follows:
Water and Wastewater Engineering Design Principles and Practice, Sec 23.7 Suspended Growth Design Practice
Standard Handbook of Environmental Engineering, 2nd Ed, Sec 6.5.1 Activated Sludge
Handbook of Environmental Engineering Calculations, 2nd Ed, Sec 1.7.21 Activated Sludge Process
Design of Municipal Wastewater Treatment Plants, WEF MOP No. 8, 5th Ed., Sec. 14.1.3 Activated Sludge Environment
is volumetric flow rate in m3day
concentration in g/m3
is total suspended solids concentration in g/m3
The subscript o refers to the primary effluent stream.
The subscript e refers to the secondary effluent stream.
The subscript w refers to the waste act. sludge stream.
The subscript r refers to the recycle act. Sludge stream.
is the volume of the aeration tank in m3. is the mixed liquor suspended solids concentration
in the aeration tank in g/m3.
: The conversion factors in these equations are: 1000 g/kg and 24 hr/day
NOTE: In Calculating Qw, the effluent flow rate, Qe is taken to be equal to the influent flow
rate, Qo, based on the assumption that liquid streams separated from the waste
Activated Sludge Waste Water Treatment Calculations - S.I. units References and Equations
Aeration Tank Operation Calculations A flow diagram of the activated sludge process is shown below along with the equations used in this
worksheet. For more details and background information on the activated sludge process and its design and operation calculations, see the following references:
days
Parameter Values Transferred from Worksheet 2:
degradation in the secondary clarifier, the soluble
is taken to be equal to that in the effluent stream.
kg BOD/day/kg MLVSS
Water and Wastewater Engineering Design Principles and Practice, Sec 23.7 Suspended Growth Design Practice
m3 Standard Handbook of Environmental Engineering, 2nd Ed, Sec 6.5.1 Activated Sludge
Handbook of Environmental Engineering Calculations, 2nd Ed, Sec 1.7.21 Activated Sludge Process
Operation of Municipal Wastewater Treatment Plants, MOP No. 11, 6th Ed., Sec. 20.1 Activated Sludge
A flow diagram of the activated sludge process is shown below along with the equations used in this
worksheet. For more details and background information on the activated sludge process and its design and operation calculations, see the following references:
The symbols used in the flow diagram at the left andthe equations below are as follows:
degradation in the secondary clarifier, the soluble
is taken to be equal to that in the effluent stream.
Equations Used for These Calculations
Water and Wastewater Engineering Design Principles and Practice, Sec 23.7 Suspended Growth Design Practice
Standard Handbook of Environmental Engineering, 2nd Ed, Sec 6.5.1 Activated Sludge
Handbook of Environmental Engineering Calculations, 2nd Ed, Sec 1.7.21 Activated Sludge Process
Operation of Municipal Wastewater Treatment Plants, MOP No. 11, 6th Ed., Sec. 20.1 Activated Sludge
Q is volumetric flow rate in m3dayS is BOD5 concentration in g/m3
X is total suspended solids concentration in g/m3
The subscript o refers to the primary effluent stream.The subscript e refers to the secondary effluent stream.
The subscript w refers to the waste act. sludge stream.The subscript r refers to the recycle act. Sludge stream.
: Based on an assumption of no biological V is the volume of the aeration tank in m3.
X is the mixed liquor suspended solids concentration
in the waste and recycle activated sludge in the aeration tank in g/m3.
Observed Yield (with recycle), Yobs = kg VSS/kg BOD5
Required O2 flow rate =
Act. O2 transfer Efficiency, AOTE* =
O2 required per day =
Act. O2 transfer Efficiency, AOTE* =
* NOTE: The calculation of actual oxygen transfer efficiency (AOTE) considers the mean bubble position to be half the diffuser
Activated Sludge Waste Water Treatment Calculations - S.I. units
Oxygen Requirements/Blower Sizing Calculations A flow diagram of the activated sludge process is shown below along with the equations used in this worksheet. For more details and background information on the activated sludge process and its design and operation calculations, see the following references:
and average ww flow rates be identified and that the oxygen requirement rates be calculated for each.
Enter values in yellow cells only
35
0.50
1.014 bar (ambient pressure at site)
Design wastewater Temperature = 10
0.67
70%
Ratio of oxygen transfer rate in wastewater
0.9
Ratio of D.O. saturation in wastewater to that
1.0
D.O saturation conc. for clean water at
11.28 waste activated sludge and recycle activated sludge
D.O conc. to be maintained are taken to be equal to that in the effluent stream.
2.0
0.8
0.021 bar (due to filter, silencer, etc.)
: To aid in setting the design WW flow rate for these calculations, it is recommended that the maximum, minimum
Water and Wastewater Engineering Design Principles and Practice, Sec 23.7, Suspended Growth Design Practice
User Input Information - See Tables below right for typical values of kd and Y and of oxygen transfer parameters Standard Handbook of Environmental Engineering, 2nd Ed, Sec 6.5.1. Activated Sludge
Influent TKN, TKNo = g/m3 Handbook of Environmental Engineering Calculations, 2nd Ed, Sec 1.7.21. Activated Sludge Process
Design of Municipal Wastewater Treatment Plants, WEF MOP No. 8, 5th Ed., Sec. 14.1.3. Activated Sludge Environment
Effluent NH4-N Concentration, Ne = g/m3
Design Barometric Press., Patm =
oC
Ratio of BOD5/BODu, f =
Blower efficiency, h =
to that in clean water, a =
in clean water at same T & P, B = NOTE: Based on an assumption of not biological
degradation in the secondary clarifier, the BOD5 in the
wastewater temp. & 1 atm, Cs = g/m3
for WW trtmt operation, CL = g/m3
Diffuser fouling factor, F =
Pressure drop at blower inlet, DPin = Temperature correction for kd: kd at temp. T = (kd at 20oC)q(T - 20) ( T is in oC )
B. Oxygen Requirement/Blower Specifications (BOD Removal and Nitrification)
Air Requirement/Blower Design Calculations/Results
30.96
21.63 (at delivery point) The sources for the information in the above table are:
1.402 bar
Company, 2003.
submergence depth. Oxygen depletion due to transfer from rising bubbles is not considered, thus the AOTE is then slightly For an example calculation of oxygen and air requirement, see:
overstated. Hence the the air delivery requirement is then slightly underestimated.
A flow diagram of the activated sludge process is shown below along with the equations used in this worksheet. For more details and background information on the activated sludge process and its design and operation calculations, see the following references:
The symbols used in the flow diagram at the left, in
the equations below, and in the worksheet calculations
are as follows:
waste activated sludge and recycle activated sludge
are taken to be equal to that in the effluent stream.
Equations Used for These Calculations See descriptions of the parameters above and in the User Entry section to the left.
Water and Wastewater Engineering Design Principles and Practice, Sec 23.7, Suspended Growth Design Practice
Standard Handbook of Environmental Engineering, 2nd Ed, Sec 6.5.1. Activated Sludge
Handbook of Environmental Engineering Calculations, 2nd Ed, Sec 1.7.21. Activated Sludge Process
Design of Municipal Wastewater Treatment Plants, WEF MOP No. 8, 5th Ed., Sec. 14.1.3. Activated Sludge Environment
Q is volumetric flow rate in m3day
S is BOD5 concentration in g/m3
X is total suspended solids concentration in g/m3
The subscript o refers to the primary effluent stream.
The subscript e refers to the secondary effluent stream.
The subscript w refers to the waste act. sludge stream.
The subscript r refers to the recycle act. Sludge stream.
NOTE: Based on an assumption of not biological
degradation in the secondary clarifier, the BOD5 in the V is the volume of the aeration tank in m3.
X is the mixed liquor suspended solids concentration
in the aeration tank in g/m3.
Temperature correction for kd: kd at temp. T = (kd at 20oC)q(T - 20) ( T is in oC )
