Detention Time

1.  A circular clarifier is 65 feet in diameter and 12 feet deep.  The flow rate into
     the clarifier is 1800 gpm.  What is the detention time in hours?     

a.  2.8 hrs b.  8.8 hrs c.  27 hrs d.  188 minutes

2.  Your storage tank contains 1.5 million gallons of water.  The tank's influent line
      just broke so you have to close the valve.  Your community is consuming water
      at 350 gpm.  How many hours before you run out of water?

a.  22.2 hrs b.  58.8 hrs c.  71.4 hrs d.  14,388 minutes

3.  A storage tank measuring 75 feet high and 25 feet in diameter is being refilled
     after service at a rate of 300 gpm.  How many hours will it take to fill the tank?

a.  9.62 hrs b.  15.3 hrs c.  91.1 hrs d.  919 minutes

Chemical Feed

4.  Determine the chlorine setting necessary to inject 2.1 ppm of 100% chlorine into
     a 500,000 gpd flow.

a.  2.2 lbs b.  8.99 ppm c.  5.2 lbs d.  8.76 lbs

5.  A well is going to run at 1400 gpm for a period of 24 hours.  What would you set 
    the feed rate on the chlorinator at to obtain 1.5 ppm?

a.  22.2 ppm b.  16.1 lbs/day c.  25.22 lbs/day d.  35.6 lbs/day

6.  Fluoride is added at a concentration of 1.2 mg/l.  The flow rate at the treatment
     plant is 2 MGD.  How many lbs/day of fluoride are added?

a.  200.2 minutes b.  20.02 lbs/day c.  48.6 lbs/day d.  202.2 lbs/day

A.  How many pounds are added if you have a natural fluoride residual of .8 mg/l?

a.  5.67 lbs/day b.  10 lbs/day c.  6.67 lbs/day d.  5 lbs/day

7.  Hydrofluosilicic acid obtained from the supplier is 25% pure acid.  Of that 25%,
    79% is pure Fluoride.  If you require 100 gallons of pure Fluoride to meet your
    treatment needs, how many gallons must you order?

a.  125 gal b.  179 gal c.  358 gal d.  506 gal

8.  A standpipe measuring 40 feet high and 35 feet in diameter is being disinfected
     at 50 ppm for 24 hours after service work.  How many pounds of 70% HTH
     will be required?

a.  101 lbs b.  120 lbs c.  155 lbs d.  172 lbs

9.  How many pounds of Hydrofluosilicic acid must be fed each day to maintain a 
     residual of 1.2 mg/l in 1200 gpm?  The solution is 25% pure acid and of that, 
    78% is pure fluoride.

a.  33.8 lbs/day b.  52.6 lbs/day c.  71.5 lbs/day d.  88.7 lbs/day

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