Pounds Formula

1. Pounds Formula Prepared By Michigan Department of Environmental Quality Operator Training and Certification Unit

2. CALCULATION OF POUNDS We often need to know how many pounds of material we are dealing with. 1. Loading on treatment system. 2. Calculating pounds of a chemical to add. 3. Calculating pounds of a material being discharged.

3. Pounds Formula mg/L (Metric) To Pounds (English)

4. CALCULATION OF POUNDS Three things must be known to calculate the POUNDS of material in a quantity of water. 1. The Quantity of water must be known. (The flow of the water stream or the volume of the tank containing the water.) 2. TheConcentration of material in water must be known. (Lab analysis) 3. The Weight of a gallon of water The Weight of a gallon of water is a constant. 1 gallon of water weighs 8.34 pounds

5. CALCULATION OF POUNDS Pounds = Conc. x Flow (or Volume) x 8.34 Lbs/gallon Quantity Of Water The STUFF Is In Concentration Of STUFF In the Water Weight Of The Water X X

6. Flow (volume) and concentration must be expressed in specific units. Flow or Volume must be expressed as millions of gallons: gallons = MG 1,000,000 gal/MG i.e.) A tank contains 1,125,000 gallons of water. How many million gallons are there? 1,125,000 gal = 1.125 MG 1,000,000 gal/MG

7. Concentration must be expressed as parts per million parts. Concentration usually reported as milligrams per liter. This unit is equivalent to ppm. 1 mg = 1 mg = 1 mg = ppm liter 1000 grams 1,000,000 mg Lbs. Mil Lbs. Parts Mil Parts ppm = = mg/L =

8. When Flow (volume) is expressed as MG and Concentration is in ppm, the units cancel to leave only pounds. Lbs. = Concentrationx Flow (or Volume) x8.34 Lbs/gallon Lbs. Lbs. X X M gal M Lbs. gal = Lbs.

9. Lbs./Day = Concentration (mg/L)x Flow (MGD) x8.34 Lbs/gal. If we enterflowrate in M gal per day (MGD), the answer will be inLbs/day. M gal Lbs. Lbs. X X Day M Lbs. gal = Lbs./Day

10. POUNDS/day = Conc. (mg/L) X Flow (MGD) X 8.34 pounds/gallon EXAMPLE POUNDS CALCULATIONS Calculate the POUNDS of suspended solids discharged to the receiving stream if the suspended solids concentration was 15 mg/L and the plant flow was 1.2 MGD. 1. POUNDS/day = X X8.34 #/gal 15 mg/L 1.2 MGD = 150 Lbs./day Suspended Solids

11. POUNDS/day = Conc. (mg/L) X Flow (MGD) X 8.34 pounds/gallon 2. Calculate the POUNDS of Phosphorus discharged from a system if the Phosphorus concentration was 0.75 mg/L and the flow was 500,000 gallons/day. POUNDS/day = 500,000 gal/day X8.34#/gal 0.75 mg/L X 1,000,000 = 0.75 mg/L X 0.50 MGD X 8.34 #/gallon = 3.1 Lbs./day Phosphorus

12. POUNDS = Conc. (mg/L) X Flow (MG) X 8.34 pounds/gallon 3. Calculate the POUNDS of Mixed Liquor Volatile Suspended Solids, (MLVSS) in a 250,000 gallon aeration tank if the MLVSS concentration is 2500 mg/L.

13. POUNDS = Conc. (mg/L) X Q (MG) X 8.34 pounds/gallon 3. Calculate the POUNDS of Mixed Liquor Volatile Suspended Solids, (MLVSS) in a 250,000 gallon aeration tank if the MLVSS concentration is 2500 mg/L. POUNDS = 250,000 gallons X8.34#/gal 2500 mg/L X 1,000,000 = 2500 mg/L X 0.25 MG X 8.34 #/gallon = 5200 Lbs MLVSS

14. The Pounds formula can be rearranged to calculate flow or concentration: a. M gal = Lbs _ 8.34 Lbs/gal x conc. (mg/L) What volume may be discharged to meet a pounds limit? b. conc. (mg/L) = Lbs _ 8.34 Lbs/gal x M gal. What is the concentration if this amount of chemical was added?

15. CALCULATION OF POUNDS Pounds = Conc. x Flow (or Volume) x 8.34 Lbs/gallon Quantity Of Water The STUFF Is In Concentration Of STUFF In the Water Weight Of The Water X X

16. Practice Problems Work Calculations on Separate Paper Answers Given on Next Slides 1. Calculate the POUNDS of suspended solids discharged to the receiving stream if the suspended solids concentration was 18 mg/Land the plant flow was0.20 MGD. 2. Calculate the POUNDS of BOD going to a treatment system if the influent BOD concentration was 195 mg/Land the flow was 86,000 gallons/day. 3. Calculate the CONCENTRATION of Alum added if 43 poundswere fed into a flow of0.125 MGD. 4. Calculate the number of GALLONS that may be discharged per day from a lagoon if the permit limit is 30 poundsof BOD per day and the BOD concentration is 20 mg/L.

17. POUNDS CALCULATIONS POUNDS/day = Conc. (mg/L) X Flow (MGD) X 8.34 pounds/gallon 1. Calculate the POUNDS of suspended solids discharged to the receiving stream if the suspended solids concentration was 18 mg/L and the plant flow was 0.20 MGD. POUNDS/day = Conc. (mg/L) X Flow (MGD) X 8.34 pounds/gallon 18 mg/L X 8.34 #/gal 0.20 MGD X POUNDS/day = = 30 Lbs./day Suspended Solids

18. 2. Calculate the POUNDS of BOD going to a treatment system if the influent BOD concentration was 195 mg/L and the flow was 86,000 gallons/day. POUNDS/day = Conc. (mg/L) X Flow (MGD) X 8.34 pounds/gallon 86,000 gal/day 195 mg/L X X8.34#/gal POUNDS/day = 1,000,000 = 195 mg/L X 0.086 MGD X 8.34 #/gallon = 140 Lbs./day BOD

19. Conc. (mg/L) X Flow (MGD) X 8.34 pounds/gallon POUNDS/day = 43 0.1325 X 8.34 3. Calculate the CONCENTRATION of Alum added if 43 pounds were fed into a flow of 0.125 MGD. X 8.34#/gal X Conc. (mg/L) 0.125 MGD 43 #/day = 0.125 X 8.34 0.125 X 8.34 = Conc. (mg/L) = 41.25 mg/L Alum

20. 4. Calculate the number of GALLONS that may be discharged per day from a lagoon if the permit limit is 30 pounds of BOD per day and the BOD concentration is 20 mg/L. 30 20 X 8.34 Conc. (mg/L) X Flow (MGD) X 8.34 pounds/gallon POUNDS/day = X8.34#/gal Flow MGD 30 #/day = 20 mg/L X 20 mg/L X 8.34 #/gal 20 X 8.34 Flow MGD = 0.18 = Flow MGD 0.18 MGD X 1,000,000 = 180,000 gallons/day

21. Pounds Formula Prepared By Michigan Department of Environmental Quality Operator Training and Certification Unit