Lec 4 Water Consumption.pdf

8/14/2019 Lec 4 Water Consumption.pdf

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Environmental Engineering-I

Prof. Dr. Muhammad Zulfiqar Ali Khan

Engr. Muhammad Aboubakar Farooq

Department of Civi l Engineering

The University of Lahore

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Water Demand and Supply

Water Consumption and Water uses.

Types of Variation in Demand

Fire Demand

Population Forecast

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Water Consumption & Water Uses

3



Water Consumption

• It is the total amount of water consumedby a community in one day.

Per Capita Consumption:

• It is the total water consumption divided

by population and number of days in the

year.• It is usual to express Water Consumption

in “l i tres per capita per day ” or lpcd .

4



Formulae:

Water Consumption can be calculated as:

W.C. (lpcd) =

Or

W.C. (lpcd) =

×

• Average Water Consumption = 150 to 600 lpcd

Water Consumption

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Classification of Water Consumed

according to its Ultimate Use

1. DOMESTIC:

Water supplied to Houses, Private Buildings

(Hotels)

Purpose: Sanitary, Drinking, Desert Coolers,

Washing, Bathing, Cooking, Gardening, etc.

Quantity:=30 to 40% of total water supplied.* = 50 to 250 lpcd (Range)

= 135 lpcd (Standard in INDIA)

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1. DOMESTIC: (contd..)

Details of Water Requirement for Domestic Purposes

Sr. No. Description W.C. ( lpcd )

1 Bathing 55

2 Washing of Clothes 20

3 Drinking 5

4 Cooking 5

5 Washing of Utensils 10

6 Washing of House 107 Flushing 30

Grand Total 135 Litres

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2. COMMERCIAL & INDUSTRIAL:



Commercial

Markets, Office Building,Dental Clinics,Workshops, PrivateSchools, Garages

Quantity Range = 10 to 20%

Industrial

Quantity relates to FloorArea = 12.2 m3 / 1000m2

of Floor Area / day

Quantity Range = 20 to 30%

An average of about 20 to 25% may be allowed in design.

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2. COMMERCIAL & INDUSTRIAL: (contd..)

Water Demand for Factories

Sr. No. Factory Products Litres/Kg of Products

1. Sugar 10

2. Oil Refining 12

3. Butter 13

4. Steel 5

5. Glass 75

6. Paper 170

7. Synthetic Fibres 225

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3. PUBLIC USE: for Public buildings i.e. Town

Halls, Jails, Schools, Hospitals, Gardens,

Public Toilets, Street Washing + FIRE

FIGHTING

Quantity:

= 10 to 20% of total Water Supplied



Pipe lines must be capable of giving

discharge of water for FIRE FIGHTING.10



3. PUBLIC USE:

Water Requirements for Public Use:

Water Requirements for Irrigation Purposes inTowns/Cities:

Sr. No. Purpose Water Requirements1. Public Parks 1.5 litres/m2 /day

2. Street Washing 1.0-1.5 litres/m2/day

3. Sewer Cleaning 5 lpcd

Sr. No. Purpose Water Requirements1. Public Parks 17000 litres/hectare /day

2. Private Gardens 17000 litres/hectare/day

3. Roadside Trees 28000 litres/km/day11



Water Supply Requirements for Public Buildings

other than Residences:

12

Sr. No. Type of Building W.C. ( lpcd )

1. Factories (no , with bathrooms) 30, 45

2. Hospitals ( <100 beds, >100 beds) 340, 455

3. Nurses Homes & Medical Quarters 135

4. Hostels 135

5. Restaurants (per seat) 68

6. Hotels (per seat) 180

7. Offices 45

8. Cinemas, theatres 15

9. School ( Day , Boarding) 45, 135



Water Requirements for Live Stock

Sr. No. Live Stock Water Requirements(litre /animal/day)

1. Cows 70

2. Horses 403. Dogs 16

4. Sheep 12

5. Goats 12

6. Chickens 0.1

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4. UNACCOUNTED FOR: Loss of Water through

LEAKS, UNAUTHORIZED Connections.

Remedial Measures:• Proper Maintenance & Universal Metering.

Quantity:

= 10 to 15% of total Water Supplied



• For LAHORE, this loss and wastage is >50%

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Definitions

1. AVERAGE DAILY CONSUMPTION:

It is the average amount of water consumed

by a community in one day divided by the

number of people served.

Av. Daily W.C.=

×

Units: Litre per Capita per Day (or lpcd )

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2. MAXIMUM DAILY CONSUMPTION:

It is the maximum Water Consumption during ANYONE DAY in the year. It is about 150 to 180%

average daily consumption.3. PEAK HOURLY CONSUMPTION:

The peak consumption during ANY HOUR of the

year, EXCLUDING FIRE DEMAND, is called peakhourly consumption. It is around 150% of themaximum daily consumption.

Definitions

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Where Max. Daily Consumption and Peak

Hourly Consumption and Monthly Average

Consumption is used????

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Maximum Daily Demand is used to design Service

Reservoirs (Overhead Tanks etc).

Peak Hourly Demand is used to design WaterDistribution System (Pumps etc).

Monthly Average Demand is used for main Reservoirs

(Dams etc).



Ratios used in Lahore (WASA)

Maximum Daily

Consumption:

Average Daily

Consumption1.5 : 1

Peak Hourly

Consumption:

Maximum Daily

Consumption1.5 : 1

Peak Hourly

Consumption :Average Daily

Consumption 2.25 : 1

For Design of WATER DISTRIBUTION SYSTEM,

Consider:• PEAK HOUR FLOW WHICH EVER

• MAX. DAY+FIRE DEMAND IS GREATER..

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Factors affecting Water Consumption

1. CLIMATE

2. STANDARD OF LIVING

3. COMMERCIAL/INDUSTRIAL ACTIVITY

4. EXTENT OF SEWERAGE

5. METERING/COST OF WATER

6. QUALITY OF WATER

7. DISTRIBUTION SYSTEM PRESSURE

8. SIZE OF CITY

9. EFFICIENCY OF THE SYSTEM10. TYPE OF SUPPLY (CONTINUOUS, INTERMITTANT)

11. LEVEL OF SERVICE (Stand post, Yard Connection, Full Plumbing)

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1. Climate:

When temperature is high then waterconsumption will be high. In domestic use, there

is more water consumption for bathing duringsummer and in public places more water will beused for lawn and street sprinkling. Duringsummer everybody takes bath twice or thriceand washes clothes, more water is used fordrinking purpose and more water is consumedin running desert coolers for air conditioning .


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2. Standard of Living:

People having better standards of living and high

economic status would consume more water as

compared to low standard of living.

3. Commercial and Industrial Activity:

Water consumption is usually higher toaccommodate commercial and industrial

activities.


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4. Extent of Sewerage:

When there is large sewerage system, thenmore water is required by the community forsanitary utilizations and for efficient drainage

through pipes, drains and sewers.5. Metering/Cost of Water:

A metered and costly supply ensures minimumwastage of water as the consumer knows thathe has to pay money for water used by him andthus he is more careful in use. Meters also helpin reducing/eliminating the losses through leaks

and illegal connections.


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6. Quality of Water:

When quality of water is wholesome then

people will use more water as compared tothat of unhygienic quality.

7. Distribution Pressure of the system:

This factor is of great importance in case ofmultistorey buildings. Adequate Pressure mean

an continuous and constant supply of water.


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8. Size of City:

With the increase in size of city, populationincreases and thus per capita waterconsumption is found to be increased. In small

town and the private resources may remain inuse even after the introduction of public watersupply. But in large cities, public water supply isa necessity so more per capita water

consumption is there. Also in large cities a lot ofwater is required to maintain clean and healthyenvironments while in small town it is notrequired.


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8. Size of City: (contd…)

Effect of Population on Rate of Consumption


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Population W.C. (LPCD)

Upto 5000 905000 - 20000 110

20000 - 50000 135

50000 - 200000 180Over 200000 200



9. Efficiency of the System:*

If a water supply system is efficient means noleakage is there then water losses will be low andconsequently less water consumption.

10. Type of Supply: ( Continuous, Intermittent) • Continuous Supply: Water is supplied

continuously throughout 24 hours a day. Thus

more water consumption.• Intermittent Supply: Water is supplied for specific

or fixed hours during the day only, resulting inreduction of Water Consumption.


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11.Level of Service:*

• Stand Post: One water tab in a town (usually

in backward areas).

• Yard Connection: One Water point at a home

(in under-developed Areas).

•

Full Plumbing: Whole plumbing in the houses,buildings is fabricated and based on public

water supply (in developed Area).


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Wh E ti ti f W t C ti i



Why Estimation of Water Consumption is

Necessary???• One of the important parameters required in

the design of Water Supply System is to set anestimate giving the total quantity of waterthat will be required after the completion ofsupply works. This estimation helps in

determination of sizes and capacities of theconstituents (pipes, pumps etc.) of watersupply system. Estimation is based onfollowing aspects:

I. Design Population (Population at the end ofdesign period)

II. Rate of per Capita per day Water supply.

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Design Period

• This is the period into the future for which

estimation is to be made.

• The Design period should neither be too long

so that overall cost of project should be

appropriate and financial burden is notthrown on the present population, nor too

short so as to avoid the design becoming

uneconomical.• Practically, the design period is kept from 20

to 30 years and considered as sufficient for

design purposes 29

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