Water Resources and Environmental Engineering — Quiz 6

Questions in this quiz (10)

1. A $$36$$-inch diameter sewer pipe is running three-quarter full. Determine the hydraulic radius in inches.

   • 9
   • 12
   • 15
   • 18

2. Which of the following statements is correct regarding specific energy in open-channel flow?

   • Specific energy is defined as the energy of fluid flowing in a channel when the base of channel is taken as the datum.
   • Specific energy is defined as the energy of fluid flowing in a channel when the centerline of channel is taken as the datum.
   • Specific energy is defined as the energy of fluid flowing in a channel when the top water level in channel is taken as the datum.
   • Specific energy is defined as the energy of fluid flowing in a channel with respect to a selected horizontal line taken as the datum.

3. The primary purpose of the federal National Discharge Pollutant Elimination System in the United States is which of the following?

   • Limit and control pollutants from point source discharges to waters of the United States
   • Develop new technologies to research and mitigate impacts of deleterious pollutants
   • Establish standards for maximum contaminant levels for safe drinking water
   • Provide aid to communities to construct and maintain treatment plants for elimination of pollutants

4. You are designing an aerobic system to biodegrade benzene $$\left(C_6H_6\right)$$. The benzene concentration is $$500\ \mathrm{mg/L}$$. Balance the reaction $$C_6H_6+O_2\rightarrow CO_2+H_2O$$ and determine the oxygen consumed to completely biodegrade the benzene.

   • 200
   • 500
   • 800
   • 1,600

5. A centrifugal pump is located $$3.5$$ m above the water surface in a suction tank. The atmospheric pressure is $$101.3$$ kPa, the vapor pressure of water is $$2.34$$ kPa, and the head loss in the suction pipe is $$0.8$$ m. Using $$\gamma=9.81\ \mathrm{kN/m^3}$$, calculate the Net Positive Suction Head Available $$(NPSH_a)$$.

   • 6.59 m
   • 12.79 m
   • 5.79 m
   • 8.45 m

6. At a stream monitoring station, the dissolved oxygen saturation concentration at the current water temperature is $$9.2\ \mathrm{mg/L}$$. The measured dissolved oxygen is $$6.5\ \mathrm{mg/L}$$. Calculate the dissolved oxygen deficit.

   • 6.5 mg/L
   • 9.2 mg/L
   • 15.7 mg/L
   • 2.7 mg/L

7. A trapezoidal channel has a bottom width of $$4.0\ \mathrm{m}$$, a flow depth of $$1.8\ \mathrm{m}$$, and side slopes of $$2H:1V$$. Calculate the cross-sectional flow area.

   • 7.20 m^2
   • 10.80 m^2
   • 13.68 m^2
   • 6.84 m^2

8. A circular concrete storm sewer with Manning's $$n=0.013$$ has diameter $$0.9\ \mathrm{m}$$ and slope $$0.005$$. Calculate the full-flow capacity. For full circular pipe $$R=D/4$$.

   • 0.85 m^3/s
   • 2.03 m^3/s
   • 1.28 m^3/s
   • 1.65 m^3/s

9. Which of the following statements is correct about hydraulic jump?

   • Depth upstream at or above critical
   • Depth upstream less than critical
   • Specific energy maximum upstream
   • No energy loss

10. Lime-soda softening removes calcium carbonate hardness. Lime with purity of $$80\%$$ Ca(OH)₂ is used. The dosage of lime required to combine with $$50\ \mathrm{mg/L}$$ of calcium is most nearly:

    • 74 mg/L
    • 92 mg/L
    • 115 mg/L
    • 162 mg/L