Water Treatment Distribution and System Design

1
Water Treatment Distribution and System Design

• WQT 121
• Lecture 4
• AWWA. 2006. Chapter 1 Introduction to
  Distribution System Design, 3rd ed

2
Week Objectives
Reading assignment Handouts Transmission and
Distribution Pipelines AWWA. 2006. Ch1 Water
Transmission and Distribution

• Understand Operators Role in Distribution
• 2. Understand types of water systems and water
  system planning.
• 3. Understand main sizing, pressure, velocity,
  and piping materials

3
Water distribution systems consists of pipes,
storage facilities, pumping station, valves, fire
hydrants, meters and other appurtenances?

1. True
2. False

4
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.

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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.

6
Operators Role in Distribution

• Operate system to maintain water quality,
  positive pressures, and control water velocity
  and direction
• Maintain pipes, valves, pumps, to ensure flow
• Operate system to accommodate demand
• Install connection to new users
• Maintain main line and customer water meters.

7
Operators Role in Distribution

• Read meters
• Sample and maintain water quality
• Operate a cross connection control program
• 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

8
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

9
The utilitys annual average day demand is
determined by dividing the?

• 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

10
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

11
The primary role of a water operator is?

1. Avoid boil orders
2. Test the water
3. Treat the water
4. Provide safe clean water that is free of bacteria
   and toxic chemicals

12
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

13
Successful communication requires mutual

1. Agreement
2. Confusion
3. Transmission
4. Understanding

14
The best approach to complaints involving the
operation of a water plant is to

1. Explain the problem and 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

15
If a water supply exceeds the MCL, whose
responsibility is it to notify the consumer?

1. the testing lab.
2. the supplier.
3. the DOH
4. the USEPA

16
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.

17
Case Study Willamette River Water Treatment
PlantWilsonville, OR

• Intake Screens in Willamette River

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Case Study Willamette River Water Treatment
PlantWilsonville, 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.

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Case Study Willamette River Water Treatment
PlantWilsonville, OR
Enhanced Sedimentation Phase
coagulants and fine sand
Clarified water
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Case Study Willamette River Water Treatment
PlantWilsonville, OR
Ozonation
Liquid Oxygen
Converts O2 gas to O3 (ozone)
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Case Study Willamette River Water Treatment
PlantWilsonville, OR
Granular Activated Carbon
6 feet of charcoal w/1ft sand remove residual
turbidity, pathogens, organic chemicals, and
taste/odor compounds
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Case Study Willamette River Water Treatment
PlantWilsonville, 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.
23
Groundwater Systems

• Groundwater extracted for the sole purpose of
  supply.
• May not require treatment
• Space wells so dont need large transmission
  pipes

24
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

25
Rural Water Systems

• Supplies water to remote regions
• Can be groundwater or surface water supply
• Fire protection can be limited

26
Water System Planning Issues

• Water availability
• Source reliability
• Water quality
• Location
• State and Federal requirements

27
The size of water mains, pumping stations, and
storage tanks is primarily determined by?

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

28
Why is excessive water pressure to residential
homes objectionable?

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

29
Policy Considerations

• Current and future growth
• Costs
• Financing Methods
• Zoning and Ordinances
• Regulatory Issues

30
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

31
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?

• 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
  observing signs of water quality deterioration
• D. All of the above

32
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

33
Which of the following is a distribution layout
pattern?

1. Dendritic
2. Grid
3. Parallel
4. Brush

34
Complaints of poor water quality will most likely
occur in which type of main layout?

1. Arterial Loop
2. Tree
3. Grid
4. Nebular

35
An arterial-loop distribution system has flow
from how many directions?

1. 1
2. 2
3. 3
4. 4

36
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.
• 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.

37
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

38
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

39
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 shut-off
  valve should be provided to permit servicing of
  any air relief valve.
• Blowoff valves at low points
• Backflow prevention devices

40
The sudden closure of a check valve will result
in

1. water hammer
2. flow reversal
3. cavitation
4. water aeration

41
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.

42
Pipes of dissimilar metal should not be connected
together because of problems due to

• 1. scale formation
• 2. corrosion
• 3. water hammer
• 4. the venturi effect

43
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
• 1000 gpm for one- and two-family dwellings with
  an area of less than 3600 square feet.
• 1500 gpm or greater for all other buildings.
• 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.

44
When using a fire hydrant, the valve

• 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

45
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

46
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.

47
Which of the following does not affect the
friction loss in a given length of pipe?

• 1. hardness of the water
• 2. number of fittings
• 3. roughness of the interior of the pipe
• 4. velocity of the flow

48
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

49
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

50
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

51
A positive pressure in the distribution system is
desirable to keep toxic substances out of the
system.

1. True
2. False

52
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.

1. True
2. False

53
The size of the water treatment plant as well as
the number of specific processes it uses depend
on which of the following factors?

1. Cost considerations
2. Demand for water by population served and Fire
   protection needs
3. Impurities in raw water
4. Water quality purity standards
5. All of the above

54
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

55
The objectives for this week to become familiar
with basic operator duties and distribution
system layouts has been met

1. Strongly Agree
2. Agree
3. Neutral
4. Disagree
5. Strongly Disagree