# Streamline - Spring 2013 - (Page 41)

Wastewater Math
QUESTIONS
BY DONNA LAWSON, WASTEWATER TECH II
1.
Water is flowing through a pipe
at a rate of 3.5 ft/sec. What is the
flow rate in ft3/sec given that the pipe
diameter is 16 inches?
a. 4.6 ft3/sec
b. 7.0 ft3/sec
c. 4.86 ft3/sec
d. 43.96 ft3/sec
4.
Find the total weight in pounds of
ferric chloride (SG 1.47) in a storage
tank that has a diameter of 3.2 feet and
with a useable height of 5.7 feet?
a. 2,000 lbs
b. 3,200 lbs
c. 4,000 lbs
d. 4,201 lbs
7.
2.
5.
8.
A centrifugal pump is able to
produce 260 gpm against a 30
ft total pumping head. Given this
information, what is the approximate
horse power of the pump?
a. 2.0 HP
b. 8.6 HP
c. 15 HP
d. 30 HP
3.
Calculate the solids recovery rate of
a vacuum filter using the following
data:
Filter area - 425 ft2
Sludge filtered – 72,000 gal
Sludge solids – 4%
Sludge volatile solids - 62%
Cake solids – 18%
Cake produced – 54 wet tons
Operation hours - 8
a. 64%
b. 75%
c. 81%
d. 90%
A system’s sewer billing rate is
twice the water rate. What is the
total bill for a customer who used 3,500
gallons of water if the billing rate is a
base rate of $30.00 for the first 1,000
gallon and then $0.25/1,000 gallons for
additional gallons used?
a. $30.62
b. $61.25
c. $91.88
6.
Determine the detention time in
hours for a basin that is 12 feet
wide, 15 feet and 20 feet deep and
receives a flow of 120 gpm?
a. 2.6 hrs
b. 3.7 hrs
c. 4.0 hrs
Find the removal efficiency of a
primary clarifier that received an
influent BOD of 250 mg/L and reduced
the BOD to 130 mg/L before reaching
the RBC?
a. 5.2%
b. 52%
c. 60%
15.0 hp is provided to a motor that
is only 92% efficient. What is the
available water horsepower (whp) if the
pump is 85% efficient?
a. 1.2 whp
b. 7.4 whp
c. 10.2 whp
d. 11.7 whp
9.
Find the average flow per day in
MGD for the following flow rates:
120 gpm, 235 gpm, 175 gpm and 152
gpm.
a. 0.682 MGD
b. 170.5 MGD
c. 0.246 MGD
d. 1440 MGD
10.
The pressure reading at the
bottom of a water tank is 85 psi,
what is the level of water in the tank?
a. 36.8 ft
b. 115 ft
c. 196.4 ft
d. 200 ft
Answers on page 42
www.vrwa.org
41

http://www.vrwa.org
# Table of Contents for the Digital Edition of Streamline - Spring 2013

From the President
From the Executive Director
What If?
Stormwater Management
Soapbox Farewell
Water and Wastewater Certifi cation Exam Test Taking Tips
Past 25 Years of VRWA
Proactive vs. Reactive
Asset Management and Drought Management
Is the Tank Contaminating the Water?
Committed to the Future of Rural Communities
Standard Operating Procedure For Leak Detection Using the Pressure Hold Method
The Virginia RATES Program is at Your Service
Ergs, Joules and Other Stuff
Employee Introductions
VRWA 25th Annual Exposition Agenda
Wastewater Math
eLearning Benefits
Do You Know What Your VRWA Benefi ts Are?
Membership Application
Throwing My Loop
VRWA Mailbag
Welcoming New Members
Training Calendar
Board Of Directors
VRWA Committees
Index To Advertisers/Ad.com
# Streamline - Spring 2013

http://www.nxtbook.com/naylor/VRWQ/VRWQ0119
http://www.nxtbook.com/naylor/VRWQ/VRWQ0418
http://www.nxtbook.com/naylor/VRWQ/VRWQ0318
http://www.nxtbook.com/naylor/VRWQ/VRWQ0218
http://www.nxtbook.com/naylor/VRWQ/VRWQ0118
http://www.nxtbook.com/naylor/VRWQ/VRWQ0417
http://www.nxtbook.com/naylor/VRWQ/VRWQ0317
http://www.nxtbook.com/naylor/VRWQ/VRWQ0217
http://www.nxtbook.com/naylor/VRWQ/VRWQ0117
http://www.nxtbook.com/naylor/VRWQ/VRWQ0416
http://www.nxtbook.com/naylor/VRWQ/VRWQ0316
http://www.nxtbook.com/naylor/VRWQ/VRWQ0216
http://www.nxtbook.com/naylor/VRWQ/VRWQ0116
http://www.nxtbook.com/naylor/VRWQ/VRWQ0415
http://www.nxtbook.com/naylor/VRWQ/VRWQ0315
http://www.nxtbook.com/naylor/VRWQ/VRWQ0215
http://www.nxtbook.com/naylor/VRWQ/VRWQ0115
http://www.nxtbook.com/naylor/VRWQ/VRWQ0414
http://www.nxtbook.com/naylor/VRWQ/VRWQ0314
http://www.nxtbook.com/naylor/VRWQ/VRWQ0214
http://www.nxtbook.com/naylor/VRWQ/VRWQ0114
http://www.nxtbook.com/naylor/VRWQ/VRWQ0413
http://www.nxtbook.com/naylor/VRWQ/VRWQ0313
http://www.nxtbook.com/naylor/VRWQ/VRWQ0213
http://www.nxtbook.com/nxtbooks/naylor/VRWQ0113
http://www.nxtbook.com/nxtbooks/naylor/VRWQ0412
http://www.nxtbook.com/nxtbooks/naylor/VRWQ0312
http://www.nxtbook.com/nxtbooks/naylor/VRWQ0212
http://www.nxtbook.com/nxtbooks/naylor/VRWQ0112
http://www.nxtbook.com/nxtbooks/naylor/VRWQ0411
http://www.nxtbook.com/nxtbooks/naylor/VRWQ0311
http://www.nxtbook.com/nxtbooks/naylor/VRWQ0211
http://www.nxtbookMEDIA.com