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Formula Sheet for all Wastewater Operator Exams Revised 8/
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Surface area of a pond, acres = Length, ft x Width, ft
43560
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Volume of a pond, MG =
Depth,ft 2
Surfacearea,sf Bottomarea,sf
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BOD removal efficiency, % =
InfluentBOD, mg/L
InfluentBOD,mg/L EffluentBOD,mg/L X 100%
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Theoretical detention time of a pond, days = Volume of the pond, MG Flow rate, MGD
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Removal efficiency, % = 100% Influentconcentration
Influent concentration Effluentconcentration
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Solids, lbs= (Volume, MG) x (MLSS, mg/L) x (8.34)
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Average flow rate, MGD = (Final flow, MG) - (Initial flow, MG)
Time elapsed, days
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BOD loading, lbs/day = (Flow rate, MGD) x (BOD, mg/L) x 8.
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TSS removal efficiency, % = 100% InfluentTSS
Influent TSS EffluentTSS
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Volume of sample needed for a BOD test bottle, mL = EstimatedBODofthesample,mg/L
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BOD, mg/L = (Initial D.O., mg/L - Final D.O., mg/L) x 300 mL Sample volume, mL
Chlorine feed rate, lbs/day = (Flow, MGD) x (Dosage, mg/L) x (8.34)
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TSS test results, mg/L =
Samplevolume, mL
Netdry weight,mg X 1000 mL/L
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Pump capacity, gpm = (Width, ft) x (Length, ft) x (Draw-down, ft) x 7.
Time of draw-down in minutes
F030B
Increased flow = (New pipe diameter, inch)^2
(Old pipe diameter, inch) 2
F030C
Flow rate in a pipe, gpd =
0.785 Velocity,ft/sec 60 sec/min 1440 min/day 7.48gal/cf
12 in/ft
Pipe diameter,inches 2
2 ^
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Desired suspended solids, lbs = (Sludge age, days) x (Primary effluent solids, lb/day)
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Volume per stroke, gal/stroke =
Stroke,inches 7. 12
0.785 Diameter,inches 2 2
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Total dry solids, lbs = (Raw sludge, gal) x (Total solids, %) x (8.34) 100%
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MLSS, lbs = (Aeration volume, MG) x (MLSS conc, mg/L) x (8.34)
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Digestion time, days = Digester volume, gal
Flow, gpd
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Phosphorus (P) removal, % =
InfluentP, mg/L
InfluentP,mg/L EffluentP,mg/L x 100%
Dry polymer, lbs = 8.34 lb/gal
Polymerconcentration,% Volume ofsolution,gal
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Pumping rate, gpm = (Volume, cf) x (7.48 gal/cf) Time, min
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Surface loading, gpd/sf = Surfacearea,sf
Flow,gpd
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Solids loading, lbs/day/sf = (Flow, MGD) x (TSS, mg/L) x (8.34)
Surface area, sf
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Sludge age = TSSinprimaryeffluent,lbs/day
TSSinaerator,lbs
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F/M = lbs BOD/day to aeration tank
lbs of MLVSS under aeration
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Waste sludge pumping rate, MGD =
RASconcentration,mg/L 8.
Differenceinaeratorsludgeinventory,lbs Currentpumprate,MGD
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MCRT, days =
TSS wasted,lbs/day TSSineffluent,lbs/day
MLSSinaerationtiontank,lbs
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MLVSS, mg/L =
F/M Ratio Aeratorvolume,MG 8.34
BODLoadingfromprimary,lbs/day
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Return sludge rate, MGD = Settled solids, mL x (Flow, MGD)
(1000 mL - Settled solids, mL)
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S0 2 feed, lbs/day =(Flow, MGD) x (Residual chlorine, mg/L + SO 2 overdose, mg/L) x (8.34)
Chlorine demand, mg/L = (Chlorine dose, mg/L) - (Chlorine residual, mg/L)
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Polymer dose, mg/L = (Polymer delivery rate, gpm) x (Polymer, lbs/gal) x (1,000,000)
(Flow, gpm) x (8.34)
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Polymer dose, mg/L = (Polymer feed rate, lbs/day) x (1,000,000)
(Flow, gpm) x (1440) x (8.34)
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Volume of seed sludge, gal = (Volume of digester, gal) x (% seed)
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Solid loading, lbs/day = (Raw sludge volume,gal)x(Solid conc,%)x(Volatile fraction,%)x(8.34)
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Total settleable solids to pump to digester, gpd = (Sludge removed, mL) x (Flow, MGD) x (1000)
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% reduction of volatile matter, % = (In - Out) x (100)
In - [(In) x (Out)] ( “ in ” and “ out ” in fraction, not in %)
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% reduction of volatile matter, % =
Initialvolatilematter,lbs
Initial volatilematter,lbs Finalvolatilematter,lbs
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Seed correction per 1.0 mL of seed = Initial D.O. – Final D.O.
mL of seed in bottle and
BOD 5 , mg/L =
300 mL Samplevolume,mL
Initial DO,mg/L FinalDO,mg/L Seedcorrection,mg/L
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Volume diluted, mL = (Target normality) x (Target volume, mL)
Stock acid normality
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Sludge flow, MGD = (Thickener loading, lbs/day/sf) x (Surface area, sf)
(8.34) x (10,000) x (% solids)
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Desired lbs of solids in aeration tank = (Daily solids addition, lbs/day) x (Sludge age, days)
Desired COD loading, lbs/day = (COD loading rate, lbs COD/lbs VS) x (VS, lbs)
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Sludge produced, lbs/day =
(Flow, MGD) x (Influent BOD, mg/L - Effluent BOD, mg/L) x (8.34 x yield factor)
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Thickened sludge volume, gal/day =
Sludgesolidsconcentration, %
8.34lbs/gal
Sludge,lbs/day
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Solids loading, lbs/hr/sf = (Flow, gpm) x (60) x (8.34 lbs/gal) x (SS%)
(Liquid surface area, sf) x (100%)
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Air to solids ratio =
Solids feedrate,gpm Sludge conc,% 8.34 lbs/gal
Airsupplyrate,cfm 0.075lb/cf 100%
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Feed time to a centrifuge, min = (Storage volume, cf) x (Basket sludge conc, %) x (62.4 lbs/cu ft)
(Flow, gpm) x (Influent solids, %) x (8.34 lbs/gal)
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Increase of detention time, days =
Initial sludgeflow,gpd Initial sludgeconc.,%
Aerobicdigestervolume,gal Increaseinsludgeconc.,%
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Polymer dosage, lbs/ton = (Polymer solution conc, %) x (Polymer added, gpm) x (2,000 lbs/ton)
(Sludge conc, %) x (Sludge flow rate, gpm)
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Vacuum filter yield, lbs/hr/sq ft =
Duration offilteroperation,hr/day Filter area,sf
Recovery,% Sludgeloading,lbs/day
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Required filter run time, hr/day = Sludge solids loading, lbs/day x Solids recovery, %
(Filter yield, lbs/hr/sf) x (Filter area, sf) x (100%)
