طرق حساب سعة وقدرة وحدات ومحطات معالجة الصرف الصناعى

PART 6 - STANDARD DESIGN AND CALCULATION FORMS

6.8

WASTEWATER TREATMENT PLANT DESIGN CALCULATION SHEET

Municipality, County & Sewer District __________________________________________________
Address of Treatment Facility _______________________________________________________
Original Lot & Tract No. ___________________________________________________________
Engineer _______________________________________________________________________
Date __________________________________________________________________________
Name & Address of Governmental Agency for Approval ___________________________________
__________________________________________________________

____________________
Design period: _________________________ First phase

_______________________________
Ultimate _______________________________

Number of persons to be served: ___________ First phase

_______________________________
Ultimate _______________________________

Average Daily Design Hydraulic Flow (ADDF): ___________ gal./day

Design BOD5 loading: _________lbs. BOD5/day

Significant Runoff Period (SRP): __________ hours

Peak Factor (PF): ____________ unitless

Peak Influent Flow Rate (PIR
):

ADDF gal./day x PF

______________________________ = _____________ gal./min
SRP hours x 60 min.

If an equalization basin is to be used, its volume will be ________________ gal.

Air to be supplied: ____________ cu. ft./min. (with largest blower out of service)

Plant influent pumping station: Yes ____________ No ______________

Number of pumps _____________ Type of pumps _______________

Influent Pumping Rate (IPR): _____________ gal./min. (with largest pump out of service)

NOTE: Influent pumping facilities shall be capable of pumping the Peak Influent Rate

(PIR) with the
largest pump out of service, unless a flow equalization basin is installed.

Include here the wet

well calculations for the pumping station - 7.601.
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6-24

Pretreatment devices:

Trash trap: Yes _____________ No ____________ Capacity ___________ ga

l.
Comminutor with bar screen bypass: Yes _____________ No ____________
Other

_________________________________________________________________________
Design capacity of comminutor _____________ gal./min.

Method of flow division where parallel aeration unit arrangements are planned. Describe:
_______________________________________________________________________________
_______________________________________________________________________________
Aeration chamber volume: (based on 80 cu. ft./lb. BOD5
)
___________ lb. BOD5/day x 80 cu. ft. x 7.48 gal./cu. ft. = __________ gal.

_____________
gallons supplied

Aeration detention time:

Chamber volume gal. x 24 hours
_____________________________ = ______________ hours
ADDF ___________ gal./day

Are the dimensions and proportions of the aeration tanks such as to maintain effective mixture and utilization
of air, to prevent unaerated sections and noticeable channeling, and to maintain velocities sufficient to
prevent deposition of solids?

Yes __________ No ___________

Are inlets and outlets for each aeration tank provided with valves, gates, stop-planks, weirs, or other
devices to permit flexibility in controlling the flow to any unit to maintain a reasonable constant water level
and to permit cleaning of individual units?

Yes __________ No ___________

Amount of air required: (based on 2600 cu. ft./lb. BOD5/day)
lbs. BOD5 /day x 2600 cu. ft.
____________________________ = _____________ cu. ft./min.
min./day
Amount of air supplied: ______________cu. ft./min. (with largest blower out of service)
NOTE: Additional capacity should be provided to operate airlifts and skimmers.
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6-25

Are the aeration plates, tubes, or jets used for the introduction of air to mixed liquor removable for
inspection, maintenance, and replacement without de-watering the tank?

Yes _________ No ___________ N/A ___________

If mechanical aerators are to be used, the oxygen required will be:

____________ lbs.BOD5/day x 2 = ______________lbs. 02/day
NOTE: Calculations and data should be included to verify the 02 transfer rate used to compute the
supplied amount of 02/day.

Settling chamber volume: _____________ gallons

Settling chamber detention time:

Chamber volume gal. x 24 hours
______________________________ = _____________ hours
ADDF_____________ gal./day
NOTE: Non-mechanical hoppered tanks only may include the upper 1/3 (by height) of the hopper(s)
in computing detention time.

Surface settling rate:
ADDF gal./day
_______________________________ = ___________ GPD/sq. ft.
Surface area _____________ sq. ft.
At peak flow:

PIR gal./min/ x 1400
________________________________ = ___________ GPD/sq. ft.
Surface area _____________ sq. ft.
NOTE: If the Influent Pumping Rate (IPR) exceeds the peak Influent Flow Rate (PIR), then it should be
substituted in the above equation for (PIR
).
Weir overflow rate:

a. At peak flow:
PIR gal./min/ x 1400
________________________________ = __________ GPD/lin. ft.
Total weir length _____________feet

NOTE: If the Influent Pumping Rate (IPR) exceeds the Peak Influent Flow Rate (PIR), then it should
be substituted in the above equation for (PIR).

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6-26

b. Are the weirs adjustable? Yes __________ No ___________
Describe method of scum removal and disposal: ____________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Scum storage capacity ______________________________________________________________
Describe method and frequency of sludge removal and method and location of sludge disposal:
______________________________________________________________________________
______________________________________________________________________________
Amount of sludge to be removed ____________ lbs./day.
If a sludge storage tank is to be installed, the volume of the tank(s) will be: (based on at least 10% of design
loading).

Design BOD5 loading lbs./day x 100 x 10%
_____________________________________ = _____________ gal. (minimum)
0.167

lbs. BOD5/population equivalent
Aeration tank vol. x 10% _____________ gallons supplied

a. Air supply: ____________ cu. ft./min. (with largest blower out of service
)
Note: A minimum storage volume of 1,000 gallons will be required for plants with a design flow of less
than 10,000 gal. day.

If aerobic digestion of sludge is to be utilized, the volume of the tank(s) will be:

(based on three cubic feet
per population equivalent
)
Design BOD5 loading lbs./day x 3 x 7.48
_____________________________________ = _____________ gal. (minimum)
0.167 lbs. BOD5/population equivalent
_____________ gallons supplied
a. Air supply: (based on 20 cu. ft./min. per 100 cu. ft. of volume)
gallons supplied x 20 cu. ft./min.
_____________________________________ = _____________ cu. ft./min.
7.48 gal./cu. ft. x 1,000 cu. ft.
Air supplied: ____________ cu. ft./min. (with largest blower our of service
)
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6-27

If anaerobic digestion of sludge is to be utilized, the volume of the tank(s) will be:
______________ gal.

NOTE: Basis of design and calculations must be submitted for the above volume.

If sludge drying beds are to be installed, the area provided shall be: (based on one square foot per
population equivalent

)
Design BOD5 loading lbs./day
_____________________________________ = _____________ sq. ft.
0.167 lbs./population equivalent
___________square feet provided ______________ number of beds
NOTE: Where phosphate removal or other chemical treatment processes are to be utilized, design of
sludge handling facilities must take into account possible increased sludge production.

Check which of the following modes of advanced treatment of effluent disposal are to be installed:
___________ Surface slow sand filter
___________ Rapid sand gravity filter
___________ Microstrainers
___________ Lagoons
___________ Other:

If surface slow sand filters are to be installed, the area provided shall be: (Based on 11.5 gallons per square
foot per day)
ADDF gal./day
_____________________________________ = _____________ sq. ft
11.5 gal./sq. ft./day

_____________square feet provided _______________ number of beds
a. Capacity of dosing chamber shall be: _____________ gallons

b. Size of dosing pumps: _____________ gal./min. (with largest pump out of service)
NOTE: Dosing chamber and pumps must be sized to dose half of the total filter to depth of three (3)
inches within 10 to 15 minutes.
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6-28

c. Dosing siphon height above sand beds: _____________ feet
If rapid sand gravity filters are to be installed, the area provided shall be: (based on 3.33 gpm/sq. ft. at the
peak flow rate)
Peak flow rate* gal./min.
_____________________________________ = _____________ sq. ft
3.3 gpm/sq. ft.
_____________square feet provided ______________ number of cells
*NOTE: The peak flow rate shall be equal to the maximum rate of the pumping facilities preceding

filtering.

a. Clearwell capacity: _____________ gallons
b. Rate of backwash: _____________ gpm/sq. ft.
c. Duration of backwash: ____________ minutes
d. Number of backwash pumps: ____________ @ _____________ gal./min.
e. Mudwell capacity: ____________ gallons
NOTE: Please refer to Part II of Ohio EPA's "Recommended Engineering Procedures and Design
Guidelines Relative to Advanced Wastewater Treatment" in designing rapid sand gravity filters.

If microstrainers are to be installed, the net submerged effective area of the microstrainer fabric shall be:

(based on 3.33 gpm/sq. ft. at the peak flow rate).
Peak flow rate* gal./min.
_____________________________________ = _____________ sq. ft
3.3 gpm/sq. ft.
_____________submerged square feet provided
_____________total square feet provided
_____________number of microstrainers
*NOTE: The peak flow rate shall be equal to the maximum rate of the pumping facilities preceding the
microstrainers.
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6-29

a. Continuous backwash rate: ____________ gal./min./ft. of microstrainer length.
b. Number of backwash pumps: ____________ @ ____________ gal./min
.
NOTE: Please refer to Part II of Ohio EPA's "Recommended Engineering Procedures and Design
Guidelines Relative to Advanced Wastewater Treatment" in designing microstrainers.

If lagoons are to be utilized, their total volume will be: (based on five (5) days detention)
Design hydraulic flow _____________ gal./day x 5 = ________ gal.
________ gallons supplied
Average design flow depth: ____________ feet
Number of cells: _______________
Minimum freeboard of _____________ feet will be provided.

The embankments of the lagoons shall have a minimum slope of ________________ vertical to
__________________ horizontal.

Does the overflow structure provide flexible water depth control and operation of facilities?

Yes ____________ No ____________
NOTE: Prior to designing tertiary lagoons, contact the Division of Waste Management and Engineering
in the appropriate District Office for information relative to the acceptability of the proposal.

What type of disinfection process will be employed?

Chlorination ______________ Ozone ______________ Other ________________
Describe: ________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
If chlorination is to be used, in what form will it be?
Gas ____________ Powder ____________ Tablet ______________
Volume of contact tank(s): (based on 15 minutes retention at the peak flow rate)
Peak flow rate* _____________ gal./min. x 15 min. = _____________ gal.
_____________ gallons supplied
*NOTE: The peak flow rate shall be equal to the maximum rate of the pumping facilities preceding the
contact chamber.
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6-30
Are the tank(s) baffled or so constructed as to reduce short circuiting of flow to a minimum?
Yes ____________ No ______________
Describe provisions for cleaning tank(s) and for maintaining adequate disinfection during cleaning operations:
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Chlorine dosage rate: _____________ mg/l (at peak flow rate)
Will duplicate chlorinators be providers? Yes _____________ No ______________
Will the chlorinator be housed? Yes _____________ No ______________
Describe: _________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
What type of flow measurement device, if any, will be installed?
Describe: (indicating, recording, totalizing, etc.) ___________________________________________
______________________________________________________________________________
______________________________________________________________________________
What laboratory facilities or other types of monitoring equipment will be provided? Describe:
______________________________________________________________________________
______________________________________________________________________________
What is the estimated cost of the above proposed wastewater treatment facility? $ ________________
Will a certified operator be employed to run the proposed treatment works?
Yes _____________ No ___________ If yes: full-time __________________
part-time __________________
Grade certification level __________________
Is the site for the proposed treatment works subject to flooding?
Yes _____________ No ___________ If yes, what measures will be taken to protect mechanical
equipment?
6-31
What provisions, if any, will be made to provide standby power for electrical equipment?
Describe: _________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Should include capacity.

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