Water Resources and Environmental Engineering — Quiz 5

Questions in this quiz (10)

1. A sanitary sewer delivers flow from a sump to a lift station through a $$400$$-ft long, $$30$$-in diameter concrete pipe with Manning roughness coefficient $$n=0.013$$. The sump invert elevation is $$101.00$$ ft and the lift station invert elevation is $$100.00$$ ft. For full pipe flow with water surface elevations in the upstream sewer sump and lift station wet well of $$105.00$$ ft and $$103.50$$ ft, respectively, determine the discharge.

   • $$46.1\ \mathrm{cfs}$$
   • $$25.1\ \mathrm{cfs}$$
   • $$25.1\ \mathrm{cfs}$$
   • $$13.8\ \mathrm{cfs}$$
   • $$5.1\ \mathrm{cfs}$$

2. To provide a minimum velocity of $$2.0$$ ft/s, when half full, in a $$12$$-inch diameter sewer pipe with $$n=0.013$$, determine the required drop per $$100$$ feet.

   • $$0.02$$
   • $$0.15$$
   • $$0.20$$
   • $$0.44$$

3. An open trapezoidal channel has a bottom width of $$8$$ ft, water depth of $$4$$ ft, and side slopes that make an angle of $$60^\circ$$ with the horizontal. Determine the hydraulic radius.

   • $$2.4$$
   • $$4.8$$
   • $$13.0$$
   • $$41.0$$

4. A $$24$$-inch diameter sewer pipe is running one-half full. Determine the hydraulic radius in inches.

   • $$5$$
   • $$6$$
   • $$12$$
   • $$18$$

5. A centrifugal pump delivers $$0.15\ \mathrm{m^3/s}$$ of water against a total head of $$25\ \mathrm{m}$$. The pump efficiency is $$78\%$$. Using $$\gamma=9.81\ \mathrm{kN/m^3}$$, determine the required shaft power input to the pump.

   • 36.8 kW
   • 28.7 kW
   • 47.2 kW
   • 58.4 kW

6. Soil testing indicates the presence of an unconfined aquifer with a depth of $$180$$ ft above an impermeable layer. Three wells are installed $$400$$ ft apart. One well is pumped at $$50$$ gpm, and the other two are observation wells. At steady state, the drawdown is $$15$$ ft at $$400$$ ft and $$11$$ ft at $$800$$ ft from the pumping well. Determine the hydraulic conductivity in ft/day.

   • $$1.1$$
   • $$1.6$$
   • $$1.9$$
   • $$2.2$$

7. A wastewater sample has an ultimate BOD $$L_0$$ of $$280\ \mathrm{mg/L}$$. The first-order decay rate constant is $$0.23\ \mathrm{day^{-1}}$$. Using the first-order BOD model, calculate the 5-day BOD $$(BOD_5)$$.

   • 88.7 mg/L
   • 191.3 mg/L
   • 280.0 mg/L
   • 145.6 mg/L

8. Water flows in an open channel at a velocity of $$3.5\ \mathrm{m/s}$$ with a flow depth of $$0.8\ \mathrm{m}$$. Calculate the Froude number and determine the flow regime. Use $$g=9.81\ \mathrm{m/s^2}$$.

   • Fr = 0.80; subcritical flow
   • Fr = 1.56; supercritical flow
   • Fr = 1.25; supercritical flow
   • Fr = 0.45; subcritical flow

9. Water flows through a $$0.2$$ m diameter pipe at a velocity of $$2.5\ \mathrm{m/s}$$. The pipe is $$300$$ m long with a Darcy friction factor of $$0.022$$. Using the Darcy-Weisbach equation, calculate the head loss due to friction. Use $$g=9.81\ \mathrm{m/s^2}$$.

   • 21.0 m
   • 10.5 m
   • 5.25 m
   • 15.8 m

10. Two tanks are connected by a $$500$$-ft length of $$1$$-inch inside-diameter PVC pipe. The Hazen-Williams coefficient is $$150$$. Water at $$60^\circ\mathrm{F}$$ flows through the pipe at $$10$$ ft/s. The tanks are open to the atmosphere, and entrance, exit, and minor losses are negligible. Determine the difference in water surface elevation between the tanks.

    • $$81$$
    • $$167$$
    • $$182$$
    • $$447$$