1. Components of Water Supply System

WATER RESOURCES RESOURCES ENGINEER ENGINEERING ING

COMPONENTS OF THE WATER SUPPLY SYSTEM Module 1

DANILO B. PULMA Dean, College of Engineering Eastern Visayas State University U niversity

The

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

Distribution

system is used to describe collectively the facilities used to supply water from its source to the point of usage.

Water

quality should not get deteriorated in the distribution pipes.

It

should be capable of supplying water at all the intended places with sufficient pressure head.

It

should be capable of supplying the requisite amount of water during fire  fighting.

The

layout should be such that no consumer would be without water supply, during the repair of any section of the system.

All

the distribution pipes should be preferably laid one metre away or above the sewer lines.

It

should be fairly water-tight as to keep losses due to leakage to the minimum.



This level provides a protected well or a developed spring with an outlet, but without a distribution system which normally serves 15 to 20 households within a radius of 250 meters;

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

(Communal Faucet System or Stand Posts)

This type of system is composed of a source, a reservoir, a piped distribution network, and communal faucets. Usually, one faucet serves four to six households within a radius of 25 meters.

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Typical Level II System Layout (with Ground Reservoir) Ground Reservoir

Transmission Main Tap Stand

Valve

Distribution Lines

Typical Level II System Layout (with Elevated Storage Tank) Well

Elevated Storage Tank

Pump

Transmission Main

Valve Tap Stand

Distribution Pipes



(Waterworks System or Individual House Connections)

This system includes a source, a reservoir, a piped distribution network, and individual household taps. It is generally suited for densely populated urban areas where the population can afford individual connections.

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Water Reservoir

Well source

13

Spring Box

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 

Springs, Deep Wells, Surface Water (intake, infiltration gallery/infiltration well)



Chlorinator, sand filter, complete water treatment plant



 Raw

water tank, clean water tank

 Pipeline

from source to storage facilities

 Distribution

mains, control valves, individual connections, fire hydrants, booster pumps 15

Sources

Springs

Deep Wells

Sources Surface Water (River)

Rapid sand filters for surface water sources

Iron & manganese removal for groundwater sources

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•

•

•

AERATORS FILTERS CHLORINATION EQUIPMENT pH ADJUSTMENT EQUIPMENT

Facilities Commonly Used for Treatment of Water Wells and Springs •

• •

•

Aerators (for oxidation of iron, and removal of dissolved gases, tastes and odors) Filters (for removal of oxides, lime residue, etc.) Chemical mixers (mainly for addition of lime to adjust acidity) Chlorinators (for disinfection)

Aerators Devices most commonly used for aerating water are: • • • •

Multiple Tray Aerators Cascade Aerators Air Compressor and Diffusor Pipes Spray Nozzle Aerators

Filters -Filtration Cycle Water flows downward through layers of sand and some coarser medium. The material being filtered out accumulates at, or just below, the surface of the filter media and must occasionally be removed by backwashing then to waste, to eliminate clogging effect of removed pre-treatment.

-Backwash Cycle Essential for effective, trouble-free operation of the filter units.

Is the most widely used means of disinfecting public water supplies. It aims to kill any disease-causing micro-organism that might get into the water supply system.

Chlorine Demand –the amount of chlorine that reacts to different compounds of water that combine chemically with chlorine. Chlorine Residual –The amount of chlorine available for disinfection after chlorine demand is satisfied. Contact Time –the time required to kill a micro-organism after chlorine first comes in contact with it. Dosage –refers to the amount of chemical applied to the water. Feed Rate –is the rate at which chlorine solution or gas is injected into the water.





Refers to the injection of a solution of a powdered or a liquid chlorine into the water by the use of a HYPOCHLORINATOR.

“pH” is the scientific shorthand for the concentration of hydrogen ions in the water Value of “pH” in Water  < 7.0 - Acidic 7.0 – Neutral > 7.0 - Alkaline Slightly acidic or slightly alkaline water causes no problems in water, however, strongly acidic water must be treated in order to prevent corrosion of metallic pipe, valves, steel tanks and customer plumbing.

Ground tank

Elevated tank

 Impound  Store

Water

Water

 Equalize

rates of flow

 Equalize

pressure in the distribution system

 Respond

to emergencies



By material (reinforced concrete or steel)



By location/setting (ground or elevated)



By function (fill & draw or floating)

Reservoir 1. Capacity - as a rule of thumb, reservoir capacity = ¼ of daily water demand. 2. In selection of reservoir site, natural elevated areas should be given first priority. In flat areas where elevated reservoir is to be constructed, location is preferably built central to the distribution system or opposite the source to avoid long and/or large diameter pipes. 31

Operation of Reservoir 1. Floating-on-the-Line – water is both pumped into the reservoir and distribution system. Water goes up the reservoir when demand is low, and water is withdrawn from the tank during peak demand. Requires continuous pumping at low capacity. 2. Fill-and-Draw System – Water is pumped directly into the reservoir and from the reservoir, water supply is distributed to the service area through gravity flow. This requires high pumping capacity at shorter duration.

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

Pumps are operated at constant head



Pumps need not be operated continuously

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Short-time power outages do not affect water pressure and supply



Pressures in the distribution system may be equalized by strategic location of the tank

Advantages of Ground Reservoir 

Lower first cost



Lower maintenance cost



Easy observation of stored-water quality

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Greater safety

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Avoidance of unsightliness and other objectionable features of elevated storage

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Operating Storage (15 % to 30 % of ADD)

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Emergency Storage (2 hrs of Peak Hour Demand)

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Fire Storage

TRANSMISSION LINE

Intake Box

Pressure Breaker 

Hydraulic Grade Line Isolation Valve

 Air Release Valve Reservoir 

Blow Off Valve

Isolation Valve

Service Area

DISTANCE = 4,500 meters

EL. 54.00

 Assuming a PVC pipe, C = 140, what diameter is required to transmit 30 lps from the spring to the reservoir ?

Max OWL = 36.60 Max OWL = 33.50 38

Pipelines where customers tap

Layouts of Distribution Network The

distribution pipes are generally laid below the road pavements, and as such their layouts generally follow the layouts of roads.

There

are, in general, four different types of pipe networks; any one of which either singly or in combinations, can be used for a particular place.

They are: Dead

End System

Radial

System

Grid

Iron System

Ring

System

Dead End System... It

is suitable for old towns and cities having no definite pattern of roads.

Advantages Relatively

cheap.

Determination

of discharges and pressure easier due to less number of valves.

Disadvantages Due

to many dead ends, stagnation of water occurs in pipes.

Radial System... The

area is divided into different zones.

The

water is pumped into the distribution reservoir kept in the middle of each zone.

 The

supply pipes are laid radially ending towards the periphery.

Advantages: It

gives quick service.

Calculation

of pipe sizes is easy.

Grid Iron System... It

is suitable for cities with rectangular layout, where the water mains and branches are laid in rectangles.

Advantages Water

is kept in good circulation due to the absence of dead ends.

In

the cases of a breakdown in some section, water is available from some other direction.

Disadvantages Exact

calculation of sizes of pipes is not possible due to provision of valves on all branches.

Ring System...  The

supply main is laid all along the peripheral roads and sub mains branch out  from the mains.

  This

system also follows the grid iron system with the flow pattern similar in character to that of dead end system.

 So,

determination of the size of pipes is easy.

Advantages Water

can be supplied to any point  from at least two directions.

Hydraulic Considerations: 

Friction loss in pipe (Hazen Williams C)



Hydraulic grade line

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Pumping Equipment

Most pumps used in waterworks, including both well pumps and booster, are of the centrifugal turbine or submersible type.

Pumping Facilities

Pump selection

Static water level Pumping water level

Pump size should be determined by : i) Well yield ii) No. of operating hours Base (sustained flow) Peak hour flow Scheduled delivery iii) “Fill-and-draw” or “Float” system iv) Hydraulic zones v) Delivery pressures • • •

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Pump selection - Centrifugal pumps for total dynamic head (TDH) of 6 m or less - Jet pumps or submersible pump for 6 to 20 m TDH - Submersible pumps or a vertical line shaft turbine pump for TDH >20 m

Power  (Kw) = 9.81 x (1/eff) x Q X TDH Q = discharge (CMS) TDH = total dynamic head (m) eff = 60% to 80% Power (HP) = Kw/0.746 54

Terminology of Pump Performance 





Head and Pressure Head Loss  –  Pressure that is lost due to friction between water and the walls of the  pipe or between individual drops of water. Efficiency  –  is the total energy supplied to the water by the pump expressed as a percentage of the total electrical or mechanical energy supplied to the driver.

Pump Efficiency  –  Usable work produced by the  pump. Motor Efficiency  –  actual power delivered by the motor



Horse Power (HP)  –  basic unit of mechanical energy to lift a given amount through a given distance in a given time.

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Total Dynamic Head (TDH)  –  the total TDH the  pump must deliver includes lift and pipeline head losses.

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Lift  –  the total vertical distance the water is raised.

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Capacity  –  is the rate of flow of water being  pumped.

  Shut-Off

Head  –  the head pumped against the which there is no discharge.

PALMA PEREZ DEEPWELL MLANG, NORTH COTABATO