Formula 
Math Toolbox Example 
Mass Load (kg/day) = Flow {MGD} x Concentration {mg/L} x 3.785 
V6 * V46 * 8.34
Where: V6 is flow in MGD, V46 is concentration in mg/L 

V452 / V450 * 1000
Where: V452 is 30 min settleometer, V450 is MLSS


V102/V460
Where: V102 is BOD primary effluent lbs, V460 is MLSS lbs 

V460 / V101
Where: V460 is MLSS lbs, V101 is TSS lbs in primary effluent 

V460 / ( (V350 * V351 * 8.34) + (V131 * V101 * 8.34))
Where: V460=MLSS lbs, V350= WAS Flow (MGD), V351 = RAS/WAS SS {mg/L} V131= Eff TSS {mg/L}, V101=Effluent Flow {MGD}
Note: Typically SRT does not include the Solids in the Secondary Clarifiers

Method #1 
(V460+V413) / (V399+V132)
Where: V460=MLSS lbs, V413=secondary clarifier lbs, V399=WAS lbs, V132=effluent TSS lbs 
Method #2 
(V461*2.5*8.34) / (( V350*V352*8.34) + (V132*V101*8.34)
Where: V461 = MLVSS, 2.5 Vol of Aeration in MG, V350 = WAS Flow (MGD), V352 RAS/WAS VSS (mg/L)V132 = Eff VSS (mg/L), V101 = Eff Flow (MGD)


V399/(V102V131)
Where: V399=WAS lbs, V102= BOD primary effluent lbs, V131= BOD effluent lbs 

(V50*8.34*V2)/0.167
Where: V50=Influent BOD, V2=Influent flow 

1.8 * V92 + 32
Where: V92 is Influent Water Temperature {C} 

(V91 32) / 1.8
Where: V91 is Influent Water Temperature {F} 

V2 * 0.00144
Where: V2 is Flow {GPM} 

(1.23*7.48*24) / V7
Where: 1.23 is Tank Volume in Cu Ft
7.48 is gal/Cu Ft
24 is hours in day
V7 is Flow in gals/day 

(V1021*1.23*8.34)  (V11 * V1 * 8.34) / V1071
Where:
V1021 = MLSS
1.23 = Aeration Volume
8.34 = lbs/gal
V11 = Inf BOD
V1 = Inf Flow
V1071 = Target F:M 
See calculating percent removal for more information on percent removal calculations. 
(V11  V4011) / V11 * 100
Where:
V11=Inf BOD
V4011=Eff BOD 
Solids Loading Rate in lbs/sqft = MLSS{mg/L} X (Inf Flow{MGD} + RAS FLow{MGD}) X 8.34{lbs/gal} / Clarifier Surface are in Sq Ft 
(V1021 (V1+V1001)8.34) / V4065
Where:
V1021 = MLSS
V1 = Inf Flow
V1001=Ras Flow
8.34 = lbs/gal
V4065 = Clarifier Surface area in Sqft 

V14 / 890
V14 = Flow in gpd
890 = Surface area in SqFt 
Chlorine Demand in mg/L = Chlorine Dose{mg/L}  Chlorine Residual{mg/L} 
V4062  V4063
Where:
V4062 = Chlorine Dose
V4063 = Chlorine Residual 
Lab: Seeded BOD {mg/L} = (Initial DO{mg/L}  Final Do{mg/L})  (Initial Seed Control DO{mg/L}  Final Seed Control DO{mg/L}) X Volume of Seed Added{mg/L} / Sample Volume {mL/bottle volume mL}
* Volume of Seed added is Seed Material that has been added directly to sample or to seed control bottles 
(V4013V4014)(V4023V4024) * 2 / 300
Where:
V4013= Eff BOD Initial DO
V4014= Eff BOD Final DO
V4023=Seed Control Sample Intial DO
V4024=Seed Control Sample Final DO
2= Volume of Seed added
300 = mL / bottle 
Lab: Suspended Solids in {SS} mg/L = Weight of Filtered dry Solids{mg}  Weight of the filter{mg} / Sample volume{ml}X 1000000
* See Custom Data Entry TSS Bench Sheet 
1.08752  1.06619 / 100 * 1000000
Where:
1.08752 = Weight of Filter Dry and Tara Weight
1.06619 = Tara weight
100 = amount of Sample in mililiters
1000000 = Liters 
Lab: Volatile Suspended Solids {VSS} mg/L = Weight of filter and Dry Solids{mg}  Weight of Filter and Ash{mg} / Sample volume {ml} * 1000000 
1.08750  1.0687 / 100 *1000000
Where:
1.08750 = Weight of Filter Dry and Dry Solids
1.0687 = Weight of Filter and Ash
100 = amount of Sample in mililiters
1000000 = Liters 
Langelier Saturation Index = pH  pHs
where pHs = (9.3 + A + B)  (C + D)
Where:
A = (Log 10 [TDS]  1) / 10
B = 13.12 x Log10 (oC + 273) + 34.55
C = Log10 [Ca2+ as CaCO3]  0.4
D = Log10 [alkalinity as CaCO3] 
V101 = LSI(V102,V103,V104,V105,V106)
Where:
V102: is the measured water pH V103: is the TDS V104: is the Temperature in Deg C V105: is the Hardness in mg/L
V106: is the Alkalinity in mg/L 