TCEQ Wastewater Exam A Questions And
Accurate answers
Explain proper design of force main wastewater lines - ANSWER Minimum 2 fps velocity
with the smallest pump operating alone.
Minimum 4 inch diameter pipe
150 psi rating.
What is Standard Dimension Ratio? - ANSWER Ratio of outside pipe diameter (OD) to
wall thickness (PVC)
Explain proper design of gravity wastewater lines. - ANSWER Designed to flow half full
under normal conditions at a minimum of 2 fps
maximum of 10 fps.
Primary clarifier shall remove how much BOD and TSS? - ANSWER 30% to 40% BOD
50% to 70 % TSS
What is a wastewater outfall line? - ANSWER Main line that carries the wastewater to the
treatment plant.
What are the minimum slopes for pipe sizes six, eight, ten, and 12 inches? What are
these slopes designed to do? - ANSWER 6 inch - 0.50 ft slope per 100 ft
8 inch - 0.33 ft slope per 100 ft
10 inch - 0.25 ft slope per 100 ft
12 inch - 0.20 ft slope per 100 ft
,You have 3900 feet of 10-inch pipe on a grade of 0.25. What is the elevation difference
from one end to the other? - ANSWER 3900/100 = 39 sections of pipe 39 ( 39 x 0.25 =
9.75 ft = 9 ft 9 in
A 12-inch line is on a 0.20 foot/100 foot grade. Point A is at an elevation of 127.6 feet.
Point B is 600 feet downstream of point A and point C is 500 feet downstream of point B.
What is the elevation of points B and C? - ANSWER A = 127.6
600
600 x (.2 ft / 100 ft) = 1.2 ft
B = 127.6 - 1.2 = 126.4 ft
500 x (.2ft/100ft) = 1 ft
C = 126.4-1= 125.4
Name two methods of establishing grades when laying wastewater lines? - ANSWER a.
string and rod
b. batter boards
c. lasers
A 20-inch pipe is flowing at 4000 GPM. What is the velocity in the pipe? - ANSWER CFS =
(pipe area (sq^2)) x (Velocity (fps))
4000 gpm / 449 gpm/cfs = 8.91 cfs
R = (20/12)/2 = 0.833
sq ft = 3.14 (0.833)^2 = 2.18 ft^2
8.91 =2.18 ft x V=
V = 8.91/2.18
V(FPS) = 4.09
Define infiltration and inflow. Give some examples of each. - ANSWER Infiltration is
water entering wastewater lines around joints, bad taps, or other small holes in the pipe
caused by roots, etc. Infiltration usually occurs from ground water. Inflow is the direct
flow of storm water into the system from direct connections of roof drains, etc., bad
, manholes, large openings in pipe such as old concrete pipe, or direct connections to
storm water lines.
What are some typical techniques used to locate leaks in a wastewater collection
system? - ANSWER a. infiltration/exfiltration testing
b. low pressure air
c. smoke testing
d. television
e. dye testing
Manholes shall have a minimum opening of _________ and be at least _________ wide. The
invert depth shall be at least ________ the diameter of the pipe. - ANSWER 24 inches
4 ft
1/2
What is the normal DO range in the aeration basin of an activated sludge plant? -
ANSWER 2.0 to 4.0 mg/L absolute minimum of 1.0 mg/L
Which activated sludge process can operate the aeration basin below 2.0 mg/L D.O.?
Explain why. - ANSWER Extended aeration or racetracks. This process keeps the bugs
starving and holds them for a longer time. (Endogenous growth phase)
List several methods of wastewater flow measurements - ANSWER a. V notch or
rectangular weirs
b. Parshall flumes
c. Ultrasonic
d. Venturi
e. Magmeter
What size pipe is needed to carry 6.5 MGD at a velocity of 2.0 FPS flowing half full? -
Accurate answers
Explain proper design of force main wastewater lines - ANSWER Minimum 2 fps velocity
with the smallest pump operating alone.
Minimum 4 inch diameter pipe
150 psi rating.
What is Standard Dimension Ratio? - ANSWER Ratio of outside pipe diameter (OD) to
wall thickness (PVC)
Explain proper design of gravity wastewater lines. - ANSWER Designed to flow half full
under normal conditions at a minimum of 2 fps
maximum of 10 fps.
Primary clarifier shall remove how much BOD and TSS? - ANSWER 30% to 40% BOD
50% to 70 % TSS
What is a wastewater outfall line? - ANSWER Main line that carries the wastewater to the
treatment plant.
What are the minimum slopes for pipe sizes six, eight, ten, and 12 inches? What are
these slopes designed to do? - ANSWER 6 inch - 0.50 ft slope per 100 ft
8 inch - 0.33 ft slope per 100 ft
10 inch - 0.25 ft slope per 100 ft
12 inch - 0.20 ft slope per 100 ft
,You have 3900 feet of 10-inch pipe on a grade of 0.25. What is the elevation difference
from one end to the other? - ANSWER 3900/100 = 39 sections of pipe 39 ( 39 x 0.25 =
9.75 ft = 9 ft 9 in
A 12-inch line is on a 0.20 foot/100 foot grade. Point A is at an elevation of 127.6 feet.
Point B is 600 feet downstream of point A and point C is 500 feet downstream of point B.
What is the elevation of points B and C? - ANSWER A = 127.6
600
600 x (.2 ft / 100 ft) = 1.2 ft
B = 127.6 - 1.2 = 126.4 ft
500 x (.2ft/100ft) = 1 ft
C = 126.4-1= 125.4
Name two methods of establishing grades when laying wastewater lines? - ANSWER a.
string and rod
b. batter boards
c. lasers
A 20-inch pipe is flowing at 4000 GPM. What is the velocity in the pipe? - ANSWER CFS =
(pipe area (sq^2)) x (Velocity (fps))
4000 gpm / 449 gpm/cfs = 8.91 cfs
R = (20/12)/2 = 0.833
sq ft = 3.14 (0.833)^2 = 2.18 ft^2
8.91 =2.18 ft x V=
V = 8.91/2.18
V(FPS) = 4.09
Define infiltration and inflow. Give some examples of each. - ANSWER Infiltration is
water entering wastewater lines around joints, bad taps, or other small holes in the pipe
caused by roots, etc. Infiltration usually occurs from ground water. Inflow is the direct
flow of storm water into the system from direct connections of roof drains, etc., bad
, manholes, large openings in pipe such as old concrete pipe, or direct connections to
storm water lines.
What are some typical techniques used to locate leaks in a wastewater collection
system? - ANSWER a. infiltration/exfiltration testing
b. low pressure air
c. smoke testing
d. television
e. dye testing
Manholes shall have a minimum opening of _________ and be at least _________ wide. The
invert depth shall be at least ________ the diameter of the pipe. - ANSWER 24 inches
4 ft
1/2
What is the normal DO range in the aeration basin of an activated sludge plant? -
ANSWER 2.0 to 4.0 mg/L absolute minimum of 1.0 mg/L
Which activated sludge process can operate the aeration basin below 2.0 mg/L D.O.?
Explain why. - ANSWER Extended aeration or racetracks. This process keeps the bugs
starving and holds them for a longer time. (Endogenous growth phase)
List several methods of wastewater flow measurements - ANSWER a. V notch or
rectangular weirs
b. Parshall flumes
c. Ultrasonic
d. Venturi
e. Magmeter
What size pipe is needed to carry 6.5 MGD at a velocity of 2.0 FPS flowing half full? -
