Water Treatment Distribution
and System Design
WQT 121
Lecture 4
AWWA. 2006. Chapter 1: Introduction to Distribution System
Design, 3rd ed
Week Objectives
Reading assignment:
Handouts: Transmission and Distribution Pipelines
AWWA. 2006. Ch1 Water Transmission and Distribution
1. Understand Operators Role in Distribution
2. Understand types of water systems and water
system planning.
3. Understand main sizing, pressure, velocity, and
piping materials
Water distribution systems
consists of pipes, storage
facilities, pumping station,
valves, fire hydrants, meters and
other appurtenances?
1. True
2. False
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Key Words
• Surface Water Systems: Treatment and use of surface
water to supply industries and domestic residences.
• Groundwater Systems: Groundwater extracted for the sole
purpose of supply.
• Purchased Water Systems: A water utility that purchases
water from another entity (may be contaminated or cant
meet demand).
• Rural Water Systems: Located in rural areas and may be
many miles away from customers. They can use surface or
groundwater for supply.
Key Words
• Dead ends Single main that is difficult to repair and
maintain proper flow (should be avoided in water supply)
• Shut Off Valves Necessary for easy access to repair and
maintain a water system.
• Main Sizes – Must be sized to meet the peak domestic,
commercial, and industrial demands in the area to be
served.
• Water Distribution System – made up of pipes, valves, and
pumps which treated water is moved from treatment plant
to consumers. A system includes water treatment facilities,
water meters, water storage and fire protection.
*** Want sufficient volume at adequate pressure.***
Operators Role in Distribution
1. Operate system to maintain water quality,
positive pressures, and control water velocity
and direction
2. Maintain pipes, valves, pumps, to ensure flow
3. Operate system to accommodate demand
4. Install connection to new users
5. Maintain main line and customer water meters.
Operators Role in Distribution
6. Read meters
7. Sample and maintain water quality
8. Operate a cross connection control program
9. Maintain maps and records
10.Keep up to date on new technologies
11.Recommend repairs, replacements, or
improvements.
12. Provide good safe clean drinking water
The average amount of water
used per person per day is:
a. 25-30 gpd
b. 50-60 gpd
c. 75-100 gpd
d. 100-150 gpd
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The utility’s annual average day
demand is determined by
dividing the?
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a.
a. Water use per month by the
number of days in that
month
b. Total water use for a year by
365 days
c. Water use per week by seven
days
d. Average day demand by the
number of residents
Public relations are important
because we:
1. Want to finish our work
in a hurry
2. Don't want to be late for
lunch
3. Hate listening to
whiners
4. Must deal with the
public
5. Want to keep our jobs
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The primary role of a water
operator is?
Avoid boil orders
Test the water
Treat the water
Provide safe clean
water that is free of
bacteria and toxic
chemicals
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2.
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4.
Operators of water distribution
systems are responsible for?
1. Safe drinking water to
everyone
2. Keeping prepared for
the future
3. Operating and
maintaining systems
4. All of the above
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Successful communication
requires mutual:
Agreement
Confusion
Transmission
Understanding
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3.
4.
proposed solution and offer
to conduct a tour of the
plant for those complaining
2. Keep all persons except for
operating personnel out
3. Never admit there is a
problem or cause for the
complaint
4. Publicize the problem as
much as possible
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The best approach to complaints
involving the operation of a
water
plant
is
to:
Explain the problem and
If a water supply exceeds the
MCL, whose responsibility is it to
notify the consumer?
the testing lab.
the supplier.
the DOH
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Surface Water Systems
• Surface water sources are open to contamination
from human and animal waste and other pollution.
•Must comply with the federal Surface Water
Treatment Rule (SWTR) and include filtration,
disinfection, operating, monitoring, and reporting
requirements.
•Water is always treated prior to distribution
•Treatment for Microorganisms, turbidity, and
must have a minimum disinfectant residual.
Case Study: Willamette River Water
Treatment Plant
Wilsonville, OR
•Intake Screens in
Willamette River
Case Study: Willamette River Water
Treatment Plant
Wilsonville, OR
• Opened April 2002
•Can process 15 million gallons per day (mgd).
•Low of approximately 2 mgd in the winter to nearly 6 mgd in
the peak of the summer.
•City's water system includes storage tanks throughout town
with a total combined capacity of nearly 11 million gallons.
•Wilsonville's former water supply (a system of 8 local wells)
is also available for use in emergencies.
Case Study: Willamette River Water
Treatment Plant
Wilsonville, OR
Enhanced Sedimentation Phase
coagulants and fine sand
Clarified water
Case Study: Willamette River Water
Treatment Plant
Wilsonville, OR
Ozonation
Liquid Oxygen
Converts O2 gas to O3 (ozone)
Case Study: Willamette River Water
Treatment Plant
Wilsonville, OR
Granular Activated Carbon
6 feet of charcoal w/1ft sand remove residual turbidity,
pathogens, organic chemicals, and taste/odor
compounds
Case Study: Willamette River Water
Treatment Plant
Wilsonville, OR
Chlorine Disinfection
maintain disinfection as the water is pumped through pipes to
customers at the far ends of the City's water distribution system.
Groundwater Systems
• Groundwater extracted for the sole purpose of
supply.
•May not require treatment
• Space wells so don’t need large transmission
pipes
Purchased Water Systems
• Groundwater or surface water supply becomes
inadequate (West Linn & Lake Oswego)
• Contamination
• Operator may not need to treat
• Good quality water
• Must be good accountants
Rural Water Systems
• Supplies water to remote regions
• Can be groundwater or surface water supply
• Fire protection can be limited
Water System Planning Issues
• Water availability
• Source reliability
• Water quality
• Location
• State and Federal requirements
The size of water mains,
pumping stations, and storage
tanks is primarily determined
by?
67%
1. Maximum day demand during any 24
hour period during the previous year
2. Population served
3. Per-capita water use
4. Fire protection requirements
33%
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Why is excessive water pressure
to residential homes
objectionable?
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1. Increases particulate matter reaching
customer
2. Causes erosion of copper plumbing
due to the high velocities, giving the
water a metallic taste
3. Decreases the life of water heaters and
other water bearing appliances
4. Causes foaming of faucets
64%
Policy Considerations
• Current and future growth
• Costs
• Financing Methods
• Zoning and Ordinances
• Regulatory Issues
Which of the following are
important for system layout
A. planning the system,
B. configuring a system,
C. mapping a system,
D. choosing a valve
arrangement
E. All of the above
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What are some of the programs and
operational procedures that can be
implemented by water utilities to help
ensure the delivery of the best water
quality to the consumers?
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A. Establish a cross connection control
program and maintain system pressure
over 30 PSI,
B. Flush the system periodically and maintain
the highest possible disinfectant residual at
all times
C. Monitor water quality throughout the
distribution system, and take actions when
0%
observing signs of water quality
deterioration
D. All of the above
System Layout
• Plan and Configure
•Arterial-large mains surround system
•Grid-All mains interconnected, water from
several locations
•Tree-water starts with transmission main and
branches off
• Map and Size
Which of the following is a
distribution layout pattern?
Dendritic
Grid
Parallel
Brush
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2.
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4.
Complaints of poor water quality
will most likely occur in which
type of main layout?
100%
Arterial Loop
Tree
Grid
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An arterial-loop distribution
system has flow from how many
directions?
1
2
3
4
67%
17%
11%
4
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2
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1
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2.
3.
4.
Dead Ends
• Dead End Mains
• Restricted flow because of one main
• Water can become stagnant or degrade
• All customers beyond repair point lose water
access when main is fixed.
(a) In order to provide increased reliability of service and reduce head loss, dead
ends shall be minimized by making appropriate tie-ins whenever practical.
(b) Where dead-end mains occur, they shall be provided with a fire hydrant if flow
and pressure are sufficient, or with an approved flushing hydrant or blow-off for
flushing purposes. Flushing devices shall be sized to provide flows which will
give a velocity of at least 2.5 fps in the water main being flushed. No flushing
device shall be directly connected to any sewer.
What water quality problem is
most likely to occur at dead-end
mains?
1. Dirty water
2. Taste and odor
3. Milky water due to air
bubbles
4. Dirty clothes due to
manganese
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Mapping
• Existing System
• Existing and planned streets
• Expansion areas
• All topographic and subsurface features
• Population densities and predictions
• Normal water consumptions
• Proposed additions or changes
Valving
• Need shutoff valves (repair and maintenance)
•Valves shall be located at not more than 500 foot intervals in commercial districts and
at not more than one block or 800 foot intervals in other districts. Where systems serve
widely scattered customers and where future development is not expected, the valve
spacing shall not exceed one mile.
• Air and vacuum at high points
• The air relief valve should be placed so as to prevent problems due to freezing. A shutoff valve should be provided to permit servicing of any air relief valve.
• Blowoff valves at low points
• Backflow prevention devices
The sudden closure of a check
valve will result in
water hammer
flow reversal
cavitation
water aeration
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Mains
• Must supply for fire flow requirements (Fire
insurance code) and domestic use
• High value districts (8-12”), Residential (6-8”)
Sized to meet peak demands
For water mains not connected to fire hydrants, the minimum line size shall be 4-inch
diameter. Minimum water main size serving a fire hydrant lateral shall be 8-inch diameter
unless a hydraulic analysis indicates that required flow and pressures can be
maintained by smaller lines.
Guidance: Generally, velocity in a water main should not exceed 5 fps. Mains should be
designed with sufficient excess capacity to provide for anticipated future connections.
Pipes of dissimilar metal should
not be connected together
because of problems due to
100%
1. scale formation
2. corrosion
3. water hammer
4. the venturi effect
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Fire Hydrants
The design of the distribution system shall be consistent with Appendix B of the 2003
International Fire Code. As specified in this code, minimum fire-flow requirements are:
1. 1000 gpm for one- and two-family dwellings with an area of less than 3600 square feet.
2. 1500 gpm or greater for all other buildings.
3. Average spacing between hydrants must be no greater than 500 ft.
Guidance: Generally, individual hydrant spacing may range from 350 to 500 feet depending
on the area being served. Hydrants should be provided at each street intersection and at
intermediate points between intersection. The planning of hydrant locations should be a
cooperative effort between the water utility and local fire officials.
4. Exceptions can be granted
5. Water mains not designed to carry fire flows shall not have fire hydrants connected to
them.
6. The design engineer shall verify that the pipe network design permits fire-flows to be
met at representative locations while minimum pressures as required by R309-105-9 are
maintained at all times and at all points in the distribution system.
Guidance: For guidance on conducting this analysis, refer to AWWA Manual M31,
Distribution System Requirements for Fire Protection.
7. As a minimum, the flows to be assumed during a fire-flow analysis shall be the "peak day
demand" plus the fire flow requirement.
When using a fire hydrant, the
valve:
1. should never be
opened completely
2. be opened only during
the hours of 8 AM to 5
PM
3. be opened to the
desired amount of flow
4. be opened all of the way
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The primary reason for dry barrel
fire hydrants is to:
1. allow easy maintenance
2. prevent water hammer
3. keep the hydrant from
freezing
4. keep the barrel from
rusting
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Main Pressure
•Minimum static pressure 35 psi (High
fire flow)
• During use not drop below 20 psi
•Residential water pressure 50-75 psi
• The distribution system shall be designed to maintain minimum pressures as required in
R309-105-9 (at ground level) at all points of connection, under all conditions of flow, but
especially during peak day flow conditions, including fire flows.
•Guidance: The normal working pressure in the distribution system should be between 40
and 60 psi. When static pressure exceed 80 psi, pressure reducing devices should be
provided on mains in the distribution system, or individual home pressure reducing
valves should be installed per the Utah Plumbing Code.
Which of the following does not
affect the friction loss in a given
length of pipe?
58%
1. hardness of the water
2. number of fittings
3. roughness of the
interior of the pipe
4. velocity of the flow
21%
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From a sanitary standpoint, the
pressure in a distribution system
should never be allowed to fall to
zero because
1. low pressure allows
bacteria to multiply
2. ground water may enter
and back siphonage
may occur
3. the chlorine residual will
drop faster
4. the main may collapse
76%
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Main Velocity and Materials
• Minimum 5 ft/sec
• What are a materials strength, pressure
rating, durability, corrosion resistance,
smoothness of inner surface, ease of tapping
and repair, maintenance?
•External load- pressure on pipe from ground after burial
•Internal load -hydrostatic pressure of water within pipe
• Pipes should be rated at 2.5-4 times pressure
rating of system)
•PVC, Iron, Steel, Concrete
Polyethylene pipe material will reduce water loss, is
economical, and is capable of handling a variety of
environmental conditions from extreme cold,
earthquakes and corrosive materials.
1. True
2. False
92%
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A positive pressure in the
distribution system is desirable
to keep toxic substances out of
the system.
100%
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1. True
2. False
In general, if a water utility produces 40 to 60 pounds
per square inch (psi) of water in its water mains,
individual service pressure should be sufficient to
provide adequate pressure when
measured on the customer's side of the meter.
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1. True
2. False
The size of the water treatment plant as
well as the number of specific processes
it uses depend on which of the following
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factors?
a. Cost considerations
b. Demand for water by
population served and
Fire protection needs
c. Impurities in raw
water
d. Water quality purity
standards
e. All of the above
Two fundamental treatment
requirements for public water
systems using surface water
sources are:
1. Coagulation and
sedimentation
2. Lime softening and
disinfection
3. Filtration and aeration
4. Disinfection and filtration
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The objectives for this week to become
familiar with basic operator duties and
distribution system layouts has been met
43%
38%
Strongly Agree
Agree
Neutral
Disagree
Strongly Disagree
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5.