Water Supply Systems Lecture 1

Water Supply Systems Lecture notes 1

dr Patryk Wójtowicz

Monday 1 December 14

Contents • Introduction to water distribution systems • History and evolution of water supply systems • Primary function and design criteria of WDS • Anatomy of water supply systems • Layouts of water distribution system • Criteria and classification of water systems

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Water distribution system* • Water distribution system (WDS) is a network of pipelines and structures that distribute water to the consumers

• WDS is designed to adequately satisfy the water requirement for a combination of purposes:

• Domestic • Commercial • Industrial • Firefighting purposes

(*also: Water Supply System - WSS) Monday 1 December 14

History of water distribution systems •

• •

The oldest water distribution systems discovered on the island of Crete are 3500 years old (first usage of pipes). The City of Knossos develops an aqueduct system that uses tubular conduits to convey water. Other ancient civilizations have had surface water canals, but these are probably the first pipes a) Closed/ pressured pipe system. The advanced urban water distribution system of the 250 B.C. - Archimedes principle developed closed type in the Minoan palaces and settlements is very interesting. The evidence

100 A.D. - Roman aqueducts

for it in Minoan Crete comes from the use of terracotta pipes, found at the palace of Knossos and Tylissos, along with several others, albeit in bad condition, at the palace of Phaistos and at Palaikastro, Gournia, Lykastos and Zakro (House B). Among them the best patterns are those of the palace at Knossos, belonging to the earliest middle period and at Tylissos, assigned to the earliest late period although an earlier date has also been proposed for it (Angelakis et al., 2005). 0.72

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0.085

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Figure 1. Minoan water transfer projects: The proposed course (A’- B) of the aqueduct at Knossos with higher spring elevation (Angelakis et al., 2007) (left) and water supply pipes (terracotta pipe sections): cross section and dimensions (upper) and today view (down) (Koutsoyiannis et al., 2008) (right).

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Hellenistic Period (ca. 323-67 B. C.) During the succeeding Hellenistic period, impressive accomplishments were also achieved in

History of water distribution systems

• Early pipelines were made by drilling stones, wood, clay and lead

• 1455 - first cast iron pipe

wooden pipes ceramic pipelines Monday 1 December 14

History of water distribution systems

• 1664 - Palace of Versailles: 35 km long cast iron water main (flanged joints) from Marly-on-Seine to the Palace of Versailles (still in operation). Used for 1400 fountains of “Sun King” Louis XIV

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History of water distribution systems

• • •

1738 — Bernoulli publishes Hydrodynamica.

• • •

1920s — Cement-mortar lining of water mains

1770 — Chezy develops head loss relationship 1845 — Darcy-Weisbach head loss equation developed

1936 — Hardy Cross method developed 1938 — Colebrook-White equation developed

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History of water distribution systems

• 1960s and ’70s — Earliest pipe network digital models created

• 1980 — Personal computers introduced • 2001 — Automated calibration • 2002 — Integration with GIS Section 1.5

A Brief History of Water Distribution Technology

language, researchers at universities begin to develop pipe network models and make them available to practicing engineers. Don Wood at the University of Kentucky, Al Fowler at the University of British Columbia, Roland Jeppson of Utah State University, Chuck Howard and Uri Shamir at MIT, and Simsek Sarikelle at the University of Akron all write pipe network models. Figure

A compu card

A computer punch card

1963 — First U.S. PVC pipe standards. The National Bureau of Standards accepts CS256-63 “Commercial Standard for PVC Plastic Pipes (SDR-PR and Class T),” which is the first U.S. standard for polyvinyl chloride water pipe.

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1963 — URISA is founded. The Urban and Regional Information Systems Associa-

Primary function of WDS •

The purpose of the water distribution system is to deliver water to consumer with appropriate quality, quantity and pressure

•

Distribution systems typically also provide storage, as well as provide flow and pressure adequate for fire protection.

Brewer Secretly Rigs Plumbing in Man's House to Make Beer Flow From Every Tap Monday 1 December 14

System design criteria •

Water quality should not get deteriorated in the main and distribution pipelines on the way from the treatment facility to the customer

•

System should be capable of supplying water to all intended (and planned) places with sufficient pressure head

•

System should be also capable of supplying the required amount of water during fire fighting

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System design criteria contd. •

The layout of the system should be such that no consumer would be without water supply, during the repair or maintenance of any section of the water network

•

All the distribution pipelines should be preferably laid above the sewer lines

•

Pipes should be water-tight to keep water losses due to leakage to the minimum

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System configuration - anatomy of WDS ★rivers, lakes, springs ★man-made reservoirs ★groundwater sources (bores and wells) ★intake structures and pumping stations to extract water from source

★water is carried over long distances through

transmission mains ★pumping main if pressure head is created by pumping ★gravity main if flow maintained by gravitational potential (on account of elevation difference) ★There are no intermediate withdrawals

water sources and intake works

transmission mains

Water distribution system

treatment works and storage

★raw water is transported to treatment plant for

processing ★water after treatment is stored in clear water reservoirs ★water reservoirs provides a buffer for water demand variation (treatment plant is designed for average daily demand) Monday 1 December 14

distribution network

★distribution network delivers water to

consumers through service connections ★water distribution network may have different layout (branched or looped)

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WATER DISTRIBUTION SYSTEM PUMPING STATION

STRUCTURAL

ELECTRICAL

PUMP

DRIVER

DISTRIBUTION STORAGE

PUMPING

PIPING

POWER TRANSMISSION

TANKS

CONTROLS

PIPE

SYSTEM DISTRIBUTION PIPING

VALVE

PIPES

VALVES

COMPONENTS

SUBCOMPONENTS

SUB-SUB COMPONENTS

FIGURE 1.15 Hierarchical relationship of components, subcomponents, and sub-subcomponents for a water distribution system (Cullinane, 1989).

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Distribution System Layout Water distribution mains may IRC_SCWS-book be laid out in 20-11-2002 grids, loops, or branches (much 27 gtb 14:58 Pagina 467 like a tree). Two basic types can be distinguished:

IRC_SCWS-book 27 gtb 20-11-2002 14:58 Pagina 467

Branched (dead-end) network layout

Looped network Chapter 21 layout

Chapter 21

Usually we have a mix of branched and looped layouts - depends heavily on the history and general layout plan of the city roads and streets

✓Grid

or loop systems provide greater ✓Branched layouts result in a number of flow for fire protection and reduce the Fig. 21.1. Types of distribution systems Fig. 21.1. Types of distribution systems dead-end lines that can lead to number ofpossibility dead-end lines • Danger of contamination caused by the possibility that a large part of network will • Danger of contamination caused by the that a large part of network will bacteriological, taste, and odor problems be without water during irregular situations be without water during irregular situations • Accumulation due more to stagnation of the water at the ends theyof sediments, require frequent ✓In addition, • system Accumulation of sediments, due to stagnation of the water at the system ends ends) occasionally resulting in taste and odour problems (“dead” ends) occasionally resulting in taste and odour problems flushing• (“dead” Fluctuating water demand producing rather large pressure variations •

Fluctuating water demand producing rather large pressure variations

Branched and the flow rates Monday 1 December 14 systems are easy to design. The direction of the water flow Branched systems are easy to design. The direction of the water flow and the flow rates

Layout of network • Urban water networks have mostly looped configurations

• Rural water networks have branched (dead-end) configurations

• The cost of a WDS depends upon proper

selection of the geometry of the network. The selection of street layout adopted in the city planning is important to provide a minimum-cost water supply system

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Advantages of the branched pattern

• The design calculation is simple and easy • A smaller number of cut-off valves are required and the operation and maintenance cost is low

• Pipe-laying is simple

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Disadvantages of the branched pattern •

The system is less successful in maintaining satisfactory pressure in the remote areas and is therefore not favoured in modern waterworks practice

•

One main pipeline provides the entire city, which is quite risky. Any defect, damage or breakage at one point of this line will disrupt the supply of water beyond that point, cutting off service to the whole area. This could be dangerous, especially if there is a fire

•

The head loss is relatively high, requiring larger pipe diameter, and/or larger capacities for pumping units. Water hammer could also cause burst of lines

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Dead ends at line terminals might affect the quality of water by allowing sedimentation and encouraging bacterial growth due to stagnation

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A large number of scour valves are required at the dead ends, which need to be opened periodically for the removal of stale water and sediment

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The discharge available for fire fighting in the streets will be limited due to high head loss in areas with weak pressure

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Looped network configurations patterns

• The most common water supply configurations of looped water supply systems are:

• gridiron pattern • circular or ring pattern • radial pattern

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Gridiron pattern •

In the gridiron system the main supply line runs through the center of the area and sub- mains takeoff from this in perpendicular directions

• •

The branch lines interconnect the sub-mains

• •

All of the pipelines are interconnected and there are no dead ends

This system is ideal for cities laid out in a rectangular plan (e.g. New York, most city centres)

Water can reach a given point of withdrawal from several directions

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Advantages of gridiron pattern •

The free circulation of water, without any stagnation or sediment deposit, minimizes the the chances of pollution due to stagnation

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Water is available at every point, with minimum loss of head, because of the pipeline interconnections

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Enough water is available at streets fire hydrants, as the hydrant will draw water from the various branches of water lines

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During repairs, only a small area of distribution is affected

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Disadvantages of gridiron pattern

• A large number of cut-off valves are required • The system requires longer pipe lengths with larger diameters

• The hydraulic calculations of discharge,

pressure and velocities in the pipes is difficult and inconvenient

• The cost of pipe-laying is higher

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Circular (ring) pattern WATER SUPPLY SYSTEMS • VOL. I: SYSTEM CONCEPTS

CHAPTER 4: WATER DISTRIBUTION SYSTEM DESIGN CONCEPTS

•

In circular (also ring) pattern the supply main forms a ring around the distribution area

•

The branches are connected cross-wise to the mains and also to each other

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Circular pattern is most reliable for a town with well planned streets and roads Figure 4-7: Layout of a Typical Looped Water Distribution System

It is important to note that many older water systems have been updated. By laying a primary feeder around the perimeter of the community to tie in all of the dead-end mains to improve both flow distribution and water pressures through the community. A simple example of this concept is presented in Figure 4-8.

Figure 4-8: Typical Small City Distribution System Monday 1 December 14

Advantages and disadvantages of circular pattern

• The advantages and disadvantages of circular system are the same as those of the gridiron system

• Only in case of fire, a larger quantity of water is available, because the available length of the distribution main is much larger

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Radial pattern •

In a radial system, the whole area is divided into a number of distribution districts

•

Each district has a centrally located distribution reservoir (elevated) from where distribution pipes run radially towards the periphery of the distribution district

• •

This system provides swift service, without much loss of head The design calculations are much simpler

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Water systems classifications - water pressure criterion

•

There are two basic types of water supply systems to create water pressure within the distribution system:

• •

Gravity feed systems Pumping pressure systems tertiary pumping station (or booster station) primary pumping station

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secondary pumping station

Gravity water distribution •

Gravity distribution is possible when the treated water source is located at some needed elevation above the supplied community

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In this type of system, sufficient pressure is available due to gravity to maintain water pressure in the mains for domestic consumption and fire service demand.

•

This is the most reliable and economical method of distribution

•

Higher pressures for firefighting, however, requires the use of mobile fire department pumpers and, in some cases, stationary booster pumps on the water system to provide needed fire flows at representative fire hydrants with a required residual pressure

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Pumps and elevated storage •

Through the use of pumps and elevated storage, the excess water pumped during periods of low consumption is stored in elevated tanks or reservoirs

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During periods of high consumption, the stored water supplements the water that is being pumped

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This method allows fairly uniform flow rates and pressures throughout the water system

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Since the stored water supplements the supply used for fires and system breakdowns, this method of operation is fairly reliable

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Pumps without storage •

When stationary pumps are used to distribute water, and no storage is provided on the distribution system, the pumps force water at the required volume and pressure directly into the mains

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This is the least desirable type of distribution system because a power failure could interrupt the water supply

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As water consumption varies, the pressure in the water mains is most likely to fluctuate

•

To conform to varying rates, several pumps are made available to add water output when needed, a procedure requiring reliable and tested automated control at the water plant

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Another disadvantage is the fact that the peak power demand of the water plant is likely to occur during periods of high electric power consumption, thus increasing power costs to operate the water system

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Classification of water distribution systems - water source criterion

•

Community water systems can be divided into four basic classifications according to the water source:

• •

High or low reservoirs that hold water for gravity feed

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Pumps at well sites that pump water to the treatment facility. Based on the difference in elevation between the treatment facility and the community to be served, the water may flow by gravity through the distribution systems, or there may be the need for another pumping station

•

A combination of gravity flow and one or more pumping stations to transport the water from the source point to all of the water demand points on the distribution system

Pumping station systems where the raw water is pumped from the source point to the treatment plant and then either pumped directly into the distribution system or into storage to be used on demand by the community

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High-level reservoir system •

In a high-level reservoir system a water source must be at proper elevation above the treatment facility in order to provide sufficient head pressure so that no pumping station is required (usually at least 30 meters)

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If there is sufficient elevation difference between the treatment facility and the distribution piping in the community, it is possible to design a water system that does not require pumping stations

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The head pressure for supplying water to the distribution system must be sufficient to meet both consumer demand and needed fire flows at any conditions

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Gravity feed systems are highly reliable under all weather conditions that may cause disruption to the pumped systems. There is no mechanical component to break down or fail when the power source goes down.

•

W S S • V . I: S C 4: W D S D C This is a very economical system since there is noC substantial power requirement to run the water system

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ATER

UPPLY

YSTEMS

OL

YSTEM

ONCEPTS

HAPTER

Figure 4-2

ATER

ISTRIBUTION

YSTEM

ESIGN

ONCEPTS

Low level reservoir systems •

A low level reservoir systems typically require a pumping station to transport water to the treatment plant

•

If the land area is relatively flat, a second pumping station to pump treated water directly to the distribution system or to elevated storage to provide the required pressure and volume to meet instantaneous flow demand

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The elevated storage can be designed to minimize the direct pumping W S S • V . I: S C C 4: W D S D C requirements

Monday 1 December 14

ATER

UPPLY

YSTEMS

OL

YSTEM

ONCEPTS

HAPTER

ATER

ISTRIBUTION

YSTEM

ESIGN

ONCEPTS

Direct pumping systems • •

Direct pumping systems feeds water to the treatment plant and then a second pumping system transports water to a storage holding area (clear well, Figure 4-3 standpipe storage tank) 3) Direct pumping systems: Figure 4-4 illustrates how a direct pumping station feeds water to the treatment plant and then a second pumping system transports water to a storage holding area, such as a clear well, to a standpipe storage tank that is maintained full as domestic consumption varies throughout a single day. This minimizes the time the pump or pumps actually have to run. The pumps also may be designed and arranged to pump the treated water directly into the distribution system when there is a high demand on the water system. This could occur when there is a major fire in the community.

This combination of pipe and tank minimizes the time the pump or pumps actually have to run FILTRATION PLANT

PUMP STATION

WELL CASING Monday 1 December 14

PUMP STATION

DISTRIBUTION SYSTEM

Pumping station at well sites + gravity storage WATER SUPPLY SYSTEMS • VOL. I: SYSTEM CONCEPTS

CHAPTER 4: WATER DISTRIBUTION SYSTEM DESIGN CONCEPTS

4) Pumping station at well sites and gravity storage: In this type of supply system, one drilled well, or a field of wells, feed water to a ground-level pumping station. This concept is presented in Figure 4-5. Chapter 3 indicates that the water treatment for ground water supplies may be less rigorous than for surface water supplies. The quality of the ground water in many areas of the country is so good that the only treatment necessary is chlorination through an injection method in the pipes that carry the non-potable water. In most cases, any other required water treatment generally is handled in a similar manner. The treated water either flows by gravity to the distribution system or is pumped to one or more elevated storage tanks. Potable water flows by gravity from the storage tank to the distribution system. Small communities that essentially operate off individual wells might want to consider this type of system. This is a more efficient way to provide water that is reliable year round, and is a system that can meet both consumer demands and needed fire flow requirements. This concept should be investigated with reference to the reduction in fire insurance premiums as the result of having a recognized water delivery system.

•

In pumping station from well sites to a gravity storage, one or a field of drilled well, feed water to a ground-level pumping station

•

The treated water either flows by gravity to the distribution system or is pumped to one or more elevated storage tanks

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Elevated tanks may be located at the beginning, centre or end of water network

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Composite water supply systems •

In some specific conditions of areas served by the water system, especially topography may require using a composite system (mixed type) that uses components from more than one of the typical water systems

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Examples of mixed water supply systems:

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Adding pumping stations to a gravity reservoir system to increase pressure and volume during peak demand periods (esp. for a fire flow requirement)

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Booster pumping stations may be installed where there is a need for more than one service level based on pressure demand

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Direct pumping into the distribution system may be supplemented by gravity tanks that "float" on the system to maintain pressure and flow characteristics during different demand periods through the day and night

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Gravity tanks are especially useful for improving the reliability of any water system, care must be taken to allow for proper mixing of water stored

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Systemy strefowe

Monday 1 December 14

Supplementary reading • Larry Mays (2000) Water Distribution System

Handbook, Chapter 1, McGraw-Hill, New York.

• Assignment:

Prepare short paper (4 A4 pages) summarizing all important information from supplementary reading. Paper should include introduction and several subchapters.

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Literature •

Mays et al. (2000) Water distribution systems handbook, McGraw-Hill, New York.

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Savic et al. (2011) Water distribution systems, ICE Publishing, Thomas Telford Ltd, London.

•

Swamee and Sharma (2008) Design of water supply pipe networks, Wiley.

•

Computer Modeling of Water Distribution Systems - Manual of Water Supply Practices, M32 (3rd Edition). American Water Works Association (AWWA). Online version available at: http://app.knovel.com/hotlink/ toc/id:kpCMWDSM0G/computer-modeling-water/computermodeling-water

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