Maths - Q&A Flashcards
Water is being pumped from a water source with an elevation of 290ft to an elevation of 365ft. What is the total head if friction or minor head losses are 12ft?
87ft
= (365-290)+12
Determine a pump’s total output in million gallons per day if it is pumping 1,550gal/min
2.23MGD
Find the total head in feet for a pump with a total static head of 22ft and a head loss of 2ft
24 ft
total (dynamic) head = total static head + loss
An aeration tank has a volume of 1.4 million gallons. The MLSS are 2,100 mg/L. What are the mixed liquor suspended solids (MLSS) in pounds under aeration?
a) 1,840
b) 16,490
c) 18,390
d) 24,520
d) 24,520
How many gallons of wastewater are contained in 100ft of 10-inch force main
a) 40,800
b) 4,080
c) 408
d) 40.8
c) 408
A settling basin has a length of 60ft, width of 20ft, and a depth of 12ft. At a flow rate of 6 mgd. What is the retention time of this basin? (Detention time=(volume, gal)/ (flow, gpd)
a) 15 min
b) 26 min
c) 1.1 hr
d) 3hrs
b) 26 min
… check
Using a labor cost of $12.50 man-hour, what is the labor cost of a job that takes two people 10 hours to complete?
$250
$12.50 * 2 persons * 10hrs
A sewer has failed and 127 ft (39m) of 8 in. (200mm) pipe must be replaced. How many 5ft (1.5m) sections of pipe will be replaced?
a) 5
b) 16
c) 25
d) 26
d) 26
127 ft / 5 ft = 25.4 ft so 26 ft sections of pipe
If a pump discharges 8,750 gal in 2hrs and 45min, how many gallons per minute is the pump discharging?
2hrs 45 min = 2*60min + 45min = 165 min
8,750 gal / 165min =53.03 gal / min = 53 gal/min
How long will take it in hours for a pump to discharge 86,400 gal if it is pumping at a rate of 30 gpm?
86,400 gal / 30gpm = 2880 min
2880 min / 60min per hr = 48hrs
A pump’s output is averaging 36 gpm. How many gallons will it pump in one day?
1 day = 24 hrs = 24hrs * 60min = 1440min
36gpm * 1440min/day = 51,840 gpd
A pump discharges 680 gpm. How many gallons will it discharge in 8hrs?
a) 5,440 gal
b) 130,560 gal
c) 326,400 gal
d) 408,000 gal
c) 326,400 gal
8hrs = 8hrs * 60min = 480min
480min * 680 gpm = 326,400 gal
Ho many gallons will a pump discharge if it pumps an average of 65gpm for 1hr and 42 min?
65gpm * (1hr*60min + 42min)
= 65gpm * 102min = 6,630 gal
Given the following data, calculate the average in pounds per day for chlorine used.
Monday (34), Tuesday (28), Wed (26), Thursday (29), Friday (31), Saturday (32) and Sunday (35)
a) 26.0 lb/day
b) 30.7 lb/day
c) 107.5 lb/day
d) 214.9 lb/day
(34+28+26+29+31+32+35) / 7 = 30.7 lb/day
Determine a pump’s total output in million gallons per day if it is pumping 1,550 gal/min
1 day = 1440min
1,550 gal/min * 1440min = 2,232,000 gpd = 2.23MGD
Note: Check units in question
FORMULA
Lbs/day = Conc. (mg/L) x Flow (MGD) x 8.34 Lbs/gallon
How many pounds of suspended solids leave a facility each day if the flow rate is
150,000 gal/day and the concentration of suspended solids is 25 mg/L?
Lbs/day = 25 mg/L x 150,000 gal/day x 8.34 Lbs / gal
————————-
1,000,000 gal/MG
= 25 x 0.15 x 8.34
= 31 Lbs/day
Pounds of Volatile Solids in the Aeration Tank
Lbs MLVSS = Volume Aeration Tank, MG X MLVSS, mg/L X 8.34 Lbs/gal
Calculate the pounds of volatile solids in an aeration tank that has a volume of 0.471 MG and the concentration of volatile suspended solids is 1700 mg/L.
Lbs = 0.471 MG X 1700 mg/L X 8.34 lbs/gal
= 6678 lbs MLVSS
Food to Microorganism Ratio = Lbs of BOD / Lbs of MLVSS = F / M
The 7-day moving average BOD is 2002 lbs and the mixed liquor volatile suspended solids is 6681 pounds. Calculate the F/M ratio of the process.
F / M = 2002 lbs BOD / 6681 lbs MLVSS = 0.30
Typical Range:
Conventional Activated Sludge - F:M 0.25-0.45
Extended Aeration Activated Sludge - F:M 0.05-0.15
Food to Microorganism Ratio Calculations
F/M Ratio is Used to Determine the Lbs of MLVSS Needed at a Particular Loading Rate
F/M = Lbs BOD / Lbs of MLVSS
Suppose F/M of 0.30 is desired
and BOD loading is 1200 lbs/day. What is M = Lbs MLVSS?
F / M = 0.30
F / 0.30 = M
1200 lbs / 0.30 = 4000 lbs MLVSS
Food to Microorganism Ratio Calculations
If we Know the Pounds of MLVSS Needed and the Volume of the Aeration Tank We Can Calculate MLVSS, mg/L.
Calculate the MLVSS, mg/L given
an Aeration Tank Volume of 0.20 MG.
4000 lbs = 0.20 MG X 8.34 lbs/gal X ? mg/L
4000 lbs / (0.20 MG X 8.34 lbs/gal) = 2398 mg/L
How many pounds of MLVSS should be maintained in an aeration tank with a volume of 0.105 MG receiving primary effluent BOD of 630 lbs/d ? The desired F:M is 0.3.
F/M
F / (F/M) = M
= 630 lbs/d / 0.3
= 2100 lbs MLVSS
Cell Residence Time
The Average Length of Time in Days that an Organism Remains in the Secondary Treatment System
Cell Residence Time, CRT
CRT, days = (Total MLVSS, lbs) / (Total MLVSS Wasted, lbs/d)
MLVSS = 6681 lbs
MLVSS Wasted = 835 lbs/d
Calculate the CRT
CRT, days = (Total MLVSS, lbs) / (Total MLVSS Wasted, lbs/d)
CRT = 6681 lbs / 835 lbs/d
CRT = 8.0 days
