NC0067342_Worksheets_20180921

WASTEWATER TREATMENT PLANT DESIGN
PRACTICAL
Sources:
1) Metcalf & Eddy: Wastewater Engineering, 1979
2) NCDENR Guidance
Daily Design Flow (DDF)
32000 gpd
Influent (mg/1)
Effluent (mg/1)
BOD 350
BOD 30
Ammonia 35
Ammonia 20
TSS 250
TSS 30
BOD Loading 93.408
lb/day
Ammonia Loading 9.341
lb/day
Solids Loading 66.720
lb/day
BOD Removal 85.4
lb/day
Ammonia Removal 4.0
lb/day
Solids Removal 58.7
lb/day
Flow Equalization Requirements
Volume = 25% of DDF =
8000 gal.
Req'd Air = Volume x 2 cfm/1000
gal. = 16.0 cfm
Aeration Basin Requirements
For Extended Air Plants:
Tank Volume = 24 hrs DDF
32000
gal
BOD Oxygen requirement = 1.5lbs/lb BOD =
140.11
lb/day
NH3 Oxygen Requirement = 4.5lb/lb NH3 =
42.03
lb/day
Total Oxygen Requirment =
182.15
lb/day
Aeration Required with 10% efficiency =
84.33
cfm
Mixing Rqmt = 25 cfm/1,OOOcf vol x aeration vol =
106.95
cfm
Clarifier Requirements
For Surface Loading Rate (gpd/sf) <300 =
107
Surface Area s.f.
Sludge Holding Basin Requirements
Daily Sludge Production = .65lb/lb BOD Removed
55.51
lb/day solids
Volume of Thickened Sludge at 2%
332.8
gal/day
30 days Storage Rqmt.
9984.0
gal
Post -Air Requirements
PAR = 30 minutes detention timexQ
NA
gal
Brooks Engineering Associates, PA p.1 9/17/2018

Chlorine Contact Requirements
Contact chamber vol / peak flow (>30 min) 1333 gal
Total Plant Air Requirements
1. For EQ Basin = 2 cfm/1000 gal.
16.0
cfm
2. For SHT = 20 cfm/1000 ft3 (mixing minimum)
199.7
cfm
3. For Post -Aeration Basin = 20 cfm/1000 ft3
NA
cfm
4. For Aeration Basin = 2100 cfm/lb.BOD/min
84.3
cfm
5.OR For Aeration Mixing = 25 cfm/1000 ft3
107.0
cfm
6. For air lift = 10 cfm/return
40
cfm
TOTAL
362.6
cfm
Brooks Engineering Associates, PA p.2 9/17/2018