Math Flashcards
Convert 18 degrees Fahrenheit to Celsius.
-7.8˚C
7.8˚C
21.9˚C
-21.9˚C
-7.8 C
˚C = 0.56 (˚F – 32)
˚C = 0.56 (18 – 32)
˚C = -7.8˚C
The elevation of water in the tank is 1,100 feet, the pump elevation is 850 feet. What is the gauge pressure at the pump?
108.2
78.4
577.5
274.3
108.2
1100 ft – 850 ft = 250 ft (difference in elevation)
250 ft / (2.31 ft/psi) = 108.2 psi
Calculate the filtration rate in gpm/ft2 for a filter with a length of 75 feet and a width of 17 feet when the flow is 2 MGD.
3.75 gpm/ft²
1.08 gpm/ft²
0.72 gpm/ft²
6.11 gpm/ft²
1.08 gpm/ft
Step 1:
Q (gpm) = 2 MG X 1,000,000 gal X 1 day
1 day 1 MG 1440 min
Q (gpm) = 1388.89 gpm
Step 2 (Area):
A (ft²) = l (ft) x w (ft)
A (ft²) = 75 ft x 17 ft
A (ft²)= 1275 ft²
Step 3:
Filtration Rate (gpm/ft²) = Q (gpm)
A (ft²)
Filtration Rate (gpm/ft²) = 1388.89 gpm
1275 ft²
Filtration Rate (gpm/ft²) = 1.08 gpm/ft²
How much chlorine is required to treat 2 MGD if the chlorine demand is 5 mg/L and you want to maintain a residual of 0.8 mg/l?
137.3 lbs/day
96.74 lbs/day
45.72 lbs/day
102.6 lbs/day
96.74 lbs/day
Step 1:
Dose = Demand + Residual
Dose = 5 mg/l + 0.8 mg/l
Dose = 5.8 mg/l
Step 2:
Feed (lbs/day) = Dose (mg/l) x Flow (MGD) x (8.34 lbs/gal.)
Feed = (5.8 mg/l) (2 MGD) (8.34 lbs/gal)
Feed = 96.74 lbs/day
A treatment plant uses 23 gallons of solution when treating 220,000 gallons of water. What is the dosage?
1.88 mg/L
0.188 mg/L
1.45 mg/L
2.38 mg/L
1.88 mg/L
Dosage (mg/L) = Solution fed (gal) x 18,000 mg/L
Capacity (gpd)
= 23 gal x 18,000 mg/L
220,000 gal
= 414,000 mg/L
220,000 gal
= 1.88 mg/L
A flow of 1.5 MGD is equal to ____ gpm?
427 gpm
694 gpm
1,042 gpm
90 gpm
1042 gpm
1.5 MGD X (694.4 gpm/1 MGD) = 1041.6 gpm
If you need 100 feet of head on the discharge side of a pump, the pressure gauge should read ____ psi.
57.2
43.3
231
123.1
43.3 psi
100 ft / (2.31 ft/psi) = 43.3 psi
Convert 10 mg/L to grains per gallon.
0.24 gpg
1.71 gpg
171 gpg
0.58 gpg
0.58 gpg
10 mg/L X (1 gpg/17.12 mg/L) = 0.58 gpg
How many lbs/day of Chlorine is required to achieve a chlorine dosage of 4.0 mg/L when pumping 600 gpm?
6.4 lbs/day
17.8 lbs/day
2.7 lbs/day
28.7 lbs/day
28.7 lbs/day
600 gpm x (1MG/694.4 gpm) =0.86 MG
Feed (lbs/day) = Dose (mg/L) X Flow (MGD) X 8.34 lb/gal
= 4.0 mg/L X 0.86 MGD X 8.34 lb/gal
= 28.69 lb/day
20 feet of head equals a pressure of ____ psi.
46.2
8.7
6.8
24.7
8.7
Pressure (psi) = 20 ft X 1 psi
2.31 ft
psi = 8.66 psi
Calculate the filtration rate in gpm/ft² for a filter measuring 60 feet by 25 feet with a the flow of 1.3 MGD.
0.60 gpm/ft²
0.95 gpm/ft²
4.25 gpm/ft²
1.63 gpm/ft²
0.60 gmp/ft
Step 1:
Q (gpm) = 1.3 MG X 1,000,000 gal X 1 day
1 day 1 MG 1440 min
Q (gpm) = 902.78 gpm
Step 2:
A (ft²) = length x width
A (ft²) = 60 ft x 25 ft
A (ft²) = 1500 ft²
Step 3:
Filtration Rate (gpm/ft²) = Q (gpm)
A (ft²)
Filtration Rate (gpm/ft²) = 902.78 gpm
1500 ft²
Filtration Rate (gpm/ft2) = 0.60 gpm/ft²
How many pounds of 65% HTH chlorine are needed to disinfect 400 feet of 8-inch water main at 50 ppm?
0.88 lbs
2.47 lbs
0.68 lbs
6.80 lbs
0.68 lbs
8 inch x (1 ft/12 inch) = 0.67 ft
Volume = 0.785 d2 h X (7.48 gal/ft3)
= 0.785 X 0.67 ft X 0.67 ft X 400 ft X 7.48 gal/ft3
= 1054 gal X (1MG/1,000,000 gal)
= 0.001054 MG
Feed (lbs/day) = Dose (mg/L) X Flow (MGD) X (8.34 lbs/gal)
= 50 mg/L X 0.001054 MGD X 8.34 lbs/gal
= 0.43 lbs/day
= 0.43 lbs/day / 0.65
= 0.68 lbs/day
What is the pressure in psi at the bottom of a tank if the water level is at 34 feet?
124.2 psi
14.7 psi
18.7 psi
78.5 psi
14.7 psi
Given: Need:
h = 34 ft Pressure (psi)
Pressure = (34 ft) X (1 psi)
(2.31 ft)
Pressure = 14.7 psi
The static pressure in a pipe is 120 psi. This is equivalent to _____ feet of head.
51.9
277.2
64.3
164.5
277.2
120 psi X (2.31 ft/1 psi) = 277.2 ft
A stream has a flow of 14 cfs. What is the flow of the stream in MGD?
4.82 MGD
6.12 MGD
9.03 MGD
21.5 MGD
9.03 MGD
14 cfs X (1 MGD/1.55 cfs) = 9.03 MGD
A treatment plant produces 0.50 MGD and has less than 0.1 mg/L of natural fluoride. What is the needed fluoride feed rate to provide 1.0 mg/L of fluoride in the water?
18.11 gpd
13,45 gpd
27.78 gpd
2.78 gpd
27.78 gpd
Fluoride Feed rate (gpd) = Dose (mg/L) x Capacity (gpd)
18,000 mg/L
= 1.0 mg/L x 500,000 gpd
18,000 mg/L
= 500,000 gpd
18,000
= 27.78 gpd
How many pounds of available chlorine are there in 50 pounds of 65% calcium hypochlorite?
24 lbs
50 lbs
35 lbs
32.5 lbs
32.5 lbs
Part = whole x percent (as decimal)
= 50 pounds X 0.65
= 32.5 pounds available chlorine
What is the volume of a tank measuring 25 feet long, 13 feet wide, and 20 feet high when the water level is 12 feet?
47,013 gal
24,813 gal
12,340 gal
29,172 gal
29172 gal
Volume = L x W x H x 7.48 gal/ft3
= 25 ft x 13 ft x 12 ft x 7.48 gal/ft3
= 29,172 gal
Convert 38 degrees Celsius to Fahrenheit.
112.4˚ F
100.4˚ F
36.4˚ F
76.4˚ F
100.4 F
˚F = (1.8 X ˚C) + 32
˚F = (1.8 X 38) + 32
˚F = 100.4˚ F
Convert 8.8 grains per gallon to mg/L of hardness.
47 mg/L
151 mg/L
122 mg/L
15 mg/L
151 mg/L
8.8 gpg X (17.12 mg/L/1 gpg) = 150.66 mg/L
