Water Operation Certification Guide Math
ACTUAL QUESTIONS AND CORRECT
ANSWERS
What is the hardness in mg/L of a treatment plant's well water if the hardness is 18.44 grains per
gallon (gpg)? - Correct answers✔B. 315.7 mg/L
Hardness,mg/L=(Hardness,gpg)(17.12mg/L)/(1 gpg)
(18.44)(17.12)/1 = 315.69 mg/L
Find the specific yield in gpm/ft if a well produces 105 gpm and the drawdown for the well is
16.3 ft - Correct answers✔B. 6.44 gpm/ft
specific yield, gpm/ft=(well yield, gpm)/(drawdown, ft)
(105 gpm)/(16.3 ft) = 6.44 gpm/ft
If the static level in the well was 138.6 ft below ground level and the drawdown was 21.1 ft,
what was the pumping water level in the well? - Correct answers✔D. 159.7 ft
drawdown = pumping water level - static level
What is the pressure in lb/ft², 189 ft below a lake's surface if the lake is 386 ft in depth? - Correct
answers✔C. 11,790 lb/ft²
pressure = (depth, ft)(density, 62.4 lb/ft³)
,(189 ft)(62.4 lb/ft³) = 11,793.6 lb/ft²
A circular clarifier has a weir lenth of 162 ft. What is the weir overflow rate in gpd/ft, if the flow
is 2,330,000 gallons per day? - Correct answers✔B. 14,380 gpd/ft
weir overflow rate = (flow, gpd)/(weir length,ft)
Convert 35.1 cfs to gpm - Correct answers✔B. 15,800 gpm
(35.1 cfs)(60 s/min)(7.48 gal/ft³)=15752 gpm
Convert 7.7 mgd into cfs - Correct answers✔B. 12 cfs
How many million gallons are there in 318 acre-ft? - Correct answers✔A. 104 mil gal
(318 acre-ft)(43560 ft³/acre-ft)(7.48 gal/ft³)=
1,036,100=1.04 mil gal
Convert 68° F to Celsius - Correct answers✔A. 20° C
°C=(°F-32)/1.8
Calculate 81.5% of 316 - Correct answers✔C. 258
, If 8.25 lbs of soda ash are mixed into 45 gal of water, what is the percent of soda ash in the
slurry? - Correct answers✔C. 2.2% soda ash slurry
1 gal water=8.34 lbs
(8.25)/[(8.25)+45gal(8.34lbs/gal)]
Calculate the area of a circular reservoir in ft², with a diameter of 411 ft - Correct answers✔D.
133,000 ft²
area=πr²
(3.14)(205.5ft)²=132,602
Determine the circumference of a clarifier, if the radius is 95 ft. - Correct answers✔D. 600 ft
circumference=2πr
95(2)(3.14)=596.6
Determine the volume in gallons for a pipe completely full of water given the following data:
Diameter=1.5 ft
Length=1.09 miles - Correct answers✔D. 76,000 gallons
(5,280 ft/mile)(1.09 miles)=5,755 ft
(.75)²(π)(5,755 ft)(7.48 gal/ft²)=76,035 gal
ACTUAL QUESTIONS AND CORRECT
ANSWERS
What is the hardness in mg/L of a treatment plant's well water if the hardness is 18.44 grains per
gallon (gpg)? - Correct answers✔B. 315.7 mg/L
Hardness,mg/L=(Hardness,gpg)(17.12mg/L)/(1 gpg)
(18.44)(17.12)/1 = 315.69 mg/L
Find the specific yield in gpm/ft if a well produces 105 gpm and the drawdown for the well is
16.3 ft - Correct answers✔B. 6.44 gpm/ft
specific yield, gpm/ft=(well yield, gpm)/(drawdown, ft)
(105 gpm)/(16.3 ft) = 6.44 gpm/ft
If the static level in the well was 138.6 ft below ground level and the drawdown was 21.1 ft,
what was the pumping water level in the well? - Correct answers✔D. 159.7 ft
drawdown = pumping water level - static level
What is the pressure in lb/ft², 189 ft below a lake's surface if the lake is 386 ft in depth? - Correct
answers✔C. 11,790 lb/ft²
pressure = (depth, ft)(density, 62.4 lb/ft³)
,(189 ft)(62.4 lb/ft³) = 11,793.6 lb/ft²
A circular clarifier has a weir lenth of 162 ft. What is the weir overflow rate in gpd/ft, if the flow
is 2,330,000 gallons per day? - Correct answers✔B. 14,380 gpd/ft
weir overflow rate = (flow, gpd)/(weir length,ft)
Convert 35.1 cfs to gpm - Correct answers✔B. 15,800 gpm
(35.1 cfs)(60 s/min)(7.48 gal/ft³)=15752 gpm
Convert 7.7 mgd into cfs - Correct answers✔B. 12 cfs
How many million gallons are there in 318 acre-ft? - Correct answers✔A. 104 mil gal
(318 acre-ft)(43560 ft³/acre-ft)(7.48 gal/ft³)=
1,036,100=1.04 mil gal
Convert 68° F to Celsius - Correct answers✔A. 20° C
°C=(°F-32)/1.8
Calculate 81.5% of 316 - Correct answers✔C. 258
, If 8.25 lbs of soda ash are mixed into 45 gal of water, what is the percent of soda ash in the
slurry? - Correct answers✔C. 2.2% soda ash slurry
1 gal water=8.34 lbs
(8.25)/[(8.25)+45gal(8.34lbs/gal)]
Calculate the area of a circular reservoir in ft², with a diameter of 411 ft - Correct answers✔D.
133,000 ft²
area=πr²
(3.14)(205.5ft)²=132,602
Determine the circumference of a clarifier, if the radius is 95 ft. - Correct answers✔D. 600 ft
circumference=2πr
95(2)(3.14)=596.6
Determine the volume in gallons for a pipe completely full of water given the following data:
Diameter=1.5 ft
Length=1.09 miles - Correct answers✔D. 76,000 gallons
(5,280 ft/mile)(1.09 miles)=5,755 ft
(.75)²(π)(5,755 ft)(7.48 gal/ft²)=76,035 gal
