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WATER AND WASTEWATER ENGINEERINGModule I: Water quantities Requirement
DOMESTIC WATER DEMAND It depends upon the habits, social status,
climatic conditions and customs of people. In India, Average consumption per capita is
135litres/day as per IS 1172-1171.
In developed countries 350 litres/capita/dayis due to use of air coolers, air conditioners, maintenance of lawns, automatic household appliances such as home laundries, dishwaters etc.
Drinking 5 litres
Cooking 5 litres
Bathing 55 litres
Clothes washing
20 litres
Utensils washing
10 litres
House washing
10 litres
135 litres
INTRODUCTION
Types of Demand Domestic water Demand Commercial and Industrial demand Fire-demand Demand for public uses Compensate losses
WATER FOR DOMESTIC AND NON-DOMESTIC NEEDS( ACCORDING TO MANUAL ON WATER SUPPLY AND TREATMENT BY MINISTRY OF URBAN DEVELOPMENT (MUD), NEW DELHI
Description Amount of water(lpcd)
1.For communities with population upto 20,000(a)Water supply through stand
post (b)Water supply through
house service connections
40 (min.)
70 to 100
2. For communities with population 20,000 to 1,00,000
100 to 150
3. For communities with population above 1,00,000
150 to 200
COMMERCIAL AND INDUSTRIAL DEMAND(WATER SUPPLY REQUIREMENTS FOR PUBLIC BUILDINGS OTHER THAN RESIDENCE AS PER IS 1172-1963
Type of building Consumption per capita per day (Litres)
(a) Factories where bathrooms are required to be provided
45
(b) Factories where no bathrooms are required to be provided
30
Hospitals including laundry per bed
(a) No of beds not exceeding 100 340
(b) No of beds exceeding 100 450
Nurses’ homes and medical quarters 135
Hostels 135
offices 45
Restaurants (per seat) 70
Hotel (per bed) 180
Cinema concert halls and theatres (per seat) schools(a) Day schools(b) Boarding Schools 45
135
Garden, Sports grounds 3.5 per sq.m.
Animals/ vehicles 45
FIRE DEMAND ACCORDING TO NATIONAL BOARD OF FIRE
Q = 4640√P (1-0.01√P)Where Q- Quantity of water required in litres/minP- population of the town in thousands It is used when population of town is upto 2
lakhs If the population is > 2 lakhs , the provision
of 54,600 litres/min is made with extra provision of 9100 to 34,600 litres/min for a second fire.
FIRE DEMAND ACCORDING TO FREEMAN FORMULA
Q= 1135.5 (P/10) +10 F= 2.8 √P
F- period of occurrence of fire in years
FIRE DEMAND ACCORDING TO KUICHLONG’S FORMULA (FOR INDIA)
Q = 3182 √P For residential cities following fire demand is
used: For town having low building – 2200
litres/min For town having higher building – 4500
litres/min For costly colonies or valuable market and
public places – 7650 to 13,500 litres/min For 3 –storied densely populated colonies –
upto 27,000 litres /min
FIRE DEMAND ACCORDING TO BUSTON’S FORMULA
Q= 5663 √P Limitation It does not considered type of locality,
buildings, public places or industrial area It gives same result for residential and
industrial area.
FIRE DEMAND ACCORDING TO ACCORDING TO MANUAL ON WATER SUPPLY AND TREATMENT BY MINISTRY OF URBAN DEVELOPMENT (MUD), NEW DELHI
Q = 100 √P
DEMAND FOR PUBLIC USE
Water requirements for public purpose
Purpose Water requirements(litres/m2/day)
Public parks 1.4
Street washing 1.0-1.5
Sewer clearing 4.5
DEMAND FOR PUBLIC USE
Water requirements for Live stock
Live stock Water requirements (litres/m2/day)
Cows 68.25
Hog 18.20
Chickens 0.09
Goats 13.60
Horses 45.50
Sheep 13.60
DEMAND FOR PUBLIC USE
Water requirements for Irrigation Purpose
Purpose Water requirements (litres/m2/day)
Public parks 16850
Private Gardens 16850
Roadside trees 28150
COMPENSATE LOSSES DEMAND
Water lost due to defective pipe –joints, cracked and broken pipes, faulty valves and fittings
Water lost due to unauthorized and illegal connections
15% allowance of the total quantity of water is made to compensate for losses, thefts and wastage of water.
PER CAPITA DEMAND
Per capita demand = Q/(P *365)
Domestic use 135 litres/capita/day
Industrial Use 40 litres/capita/day
Public use 25 litres/capita/day
Fire demand 15 litres/capita/day
Losses, wastage and thefts
55 litres/capita/day
270litres/capita/day
FACTORS AFFECTING RATE OF DEMAND
Size and type of community Standard of living Climatic conditions Quality of water Pressure in the supply System of supply Sewerage Metering Water rates Age of community Lawn sprinkling
VARIATIONS IN RATE OF DEMAND
Maximum seasonal consumption: 130% of annual average daily rate of demand
Maximum monthly consumption: 140% of annual average daily rate of demand
Maximum daily consumption: 180% of annual average daily rate of demand
Maximum hourly consumption: 150% of average for the day
R.O.Goodrich formula p- 180t-0.1
EFFECT OF VARIATION IN CONSUMPTION ON DESIGN
Filters and pumps It is designed for 1.50 times the average daily
demand. Distribution mains
It is designed for the maximum hourly demand of the maximum day.
Multiplying factor – 1.8*1.5 Sedimentation tanks and water reservoirs
It is designed for the average daily rate of consumption.
DESIGN PERIOD
The number of years for which the designs of water works have been done is known as design period.
The design period is between 22-30 yrs. Following factors should be kept in mind for
design period: Funds available for the completion of the project. If
more funds available the design period shall be less Life of pipe and other structural materials used in
water supply scheme. As far as possible the design period should be nearly
equal to the materials used in water supply works. Rate of interest on loans taken to complete the
project. Anticipated expansion rate of the town.
DESIGN PERIOD FOR PROJECT COMPONENTS
Component Design Period (years)
Storage by dams 50
Infiltration works 30
Pump sets(i) All prime movers except
electric motors(ii) Electric motors and pumps
30
15
Water treatment units 15
Pipe connections to the several treatment units and other smallappurtenances
30
Raw water and clear water conveying mains
15
Clear water reservoirs at the head works, balancing tanks and service reservoirs ( over head or ground level)
15
Distribution system 30
