This document provides an overview of environmental engineering as it relates to public water supply systems. It discusses the need for protected water supplies to prevent waterborne diseases. The objective of public water supply systems is to provide safe, wholesome water in adequate quantities. There are various types of water demands, including domestic, industrial, commercial, public, and fire demands. Factors like climate, infrastructure, and cost affect per capita water demand. Population forecasts are needed to design water systems to meet needs over their design periods, typically 20-40 years.

1. ENVIRONMENTAL
ENGINEERING

2. ENVIRONMENTAL ENGINEERING
1) INTRODUCTION
2) NEED FOR PROTECTED WATER SUPPLY
3) OBJECTIVE OF PUBLIC WATER SUPPLY SYSTEM
4) TYPES OF DEMAND
5) PERCAPITA DEMAND
6) FACTORS AFFECTING PERCAPITA DEMAND
7) PREDICTION OF POPULATION

3. INTRODUCTION
• Environmental Engineering - air, water, food,
heat and light.
• Contamination – health effects in human
beings and animals.
• In ancient days – no water supply system.
• People took water from far distance.
• Water is in a contaminated state causing
health problems.

5. INTRODUCTION
• People used lakes, rivers, ponds for their
water supply.
• In the time of less rain rainfall – scarcity of
water.
• During fire breakout – water is needed to put
down fire.
• A good public water supply system supplying
safe and wholesome water is needed.

6. WATER FOR
FIRE FIGHTING
FIRE HYDRANTS

7. NEED FOR PROTECTED WATER SUPPLY
• Water gets contaminated due to animal and
human waste, sewage – causing water borne
diseases – cholera, typhoid, dysentery.
• Public water supply protects the source of
water from impurities like bacteria, chemicals
etc.,(sewage and industrial effluents).
• Public Water Supply also purifies the
contaminated water to make it usable for
drinking and other purpose.

8. RAW WATER TREATMENT PLANT

9. OBJECTIVE OF PUBLIC WATER SUPPLY
1) To supply safe and wholesome water to
consumers. (unpolluted, free from toxic
substances, minerals, organic substances)
2) To supply water in adequate quantity. (providing
the required amount of water to the consumers
with good source and storage facilities)
3) To make water easily available to consumers to
encourage personal and household cleanliness.
(Providing water as near as possible to the
consumer)

10. Water Demands
The amount of water required by the community
for various purpose is called water demand.
Types of Demands:
1. Domestic Demand
2. Industrial and Commercial Demand
3. Public Demand
4. Fire Demand
5. Demand for compensating various losses.

11. DOMESTIC DEMAND
• The water required for actual house hold
activity – Domestic demand.
• Drinking, cooking, bathing, washing, flushing
of water closets etc.,
• In India , as per IS 1172-1983 Domestic water
demand is 135 litres/capita/day.
• In developed countries, this value is about
350 litres/capita/day.

13. DOMESTIC DEMAND
ACTIVITY DEMAND litres/capita/day
Drinking 5
Cooking 5
Bathing 50
Cloth washing 25
Utensils washing 10
House washing 10
Latrine and Urinals 30
Total 135 litres/capita/day

14. INDUSTRIAL AND COMMERCIAL
DEMAND
• Water required in Industries for various
processes is known as Industrial Demand
• Manufacturing process, cooling process,
steam generation, processing and sanitation.
• Water required for private offices, restaurants,
hostels, schools, cinema theatres is known as
Commercial Demand.

15. INDUSTRIAL AND COMMERCIAL
DEMAND
ACTIVITY DEMAND litres/capita/day
Factories 30 - 45
Offices 45
Restaurants / seat 70
Hotels / persons 180
Cinema / seat 15

16. PUBLIC DEMAND
• Water required for public purposes such as
washing of roads, cleaning of public sewers,
watering of parks, public gardens, fountains,
flushing of public water closets and urinals
etc., is known as Public demand.
ACTIVITY DEMAND litres/capita/day
Public gardens 1.5 l/sq.m/day
Street washing 1.0 l/sq.m/day
Sewer cleaning 4.5 l/capita/day

17. FIRE DEMAND
• Water required for the local body to protect
property and human lives from the fury of fire is
known as ‘Fire demand’.
• It can be calculated from population data by
following formulae:
1. Kuchling’s formula
2. Buston’s formula
3. National Board of fire under writers formula
4. Freeman’s formula

18. DEMAND FOR COMPENSATING
VARIOUS LOSSES
• Wastage in pipe line – defective pipe joints,
cracks, faulty valves and fittings.
• Careless and lazy habits of consumers and
inefficient management.
• Thefts and unauthorized water connections.
• Allowance of 15% of the total quantity of
water to compensate for losses, thefts and
wastage of water.

19. WATER LOSSES

20. Calculation of fire demand
• Calculation of fire demand:
1. Kuichling’s formula 𝑄 = 3182 √𝑃
2. Buston’s formula 𝑄 = 5663 √𝑃
3. National Board of fire under writers formula
𝑄 = 4637 √P(1-0.10√𝑃)
4. Freeman’s formula 𝑄 = 1136
𝑃
5
+ 10
and 𝐹 = 2.8√𝑃

21. PROBLEM ON FIRE DEMAND
Where,
Q= Quantity of water in litres per minutes.
P=Population in thousands.
F=Number of simultaneous fire streams.
Example:
Compute the fire demand for a city having
population of 1,70,000 using various formulae

22. PROBLEM ON FIRE DEMAND
Given data:
Population = 1,70,000 ,𝑃 = 170 𝑖𝑛 𝑡ℎ𝑜𝑠𝑎𝑛𝑑𝑠
Solution:
1. Kuichling’s formula:
𝑄 = 3182 𝑃 = 3182 170 = 41488
𝑙
𝑚𝑖𝑛
𝑄 =
41488
1000𝑥60
= 0.6915 𝑐𝑢𝑚𝑒𝑐𝑠

23. PROBLEM ON FIRE DEMAND
2. Buston’s formula
𝑄 = 5663 𝑃 = 5663 170 = 73836.49
𝑙
𝑚𝑖𝑛
𝑄 =
73836.49
1000𝑥60
= 1.231 𝑐𝑢𝑚𝑒𝑐𝑠

24. PROBLEM ON FIRE DEMAND
3. National board of fire under writers formula
𝑄 = 4637 𝑃 1 − 0.1 𝑃
𝑄 = 4637 170 1 − 0.1 170 = 52576
𝑙
𝑚𝑖𝑛
𝑄 =
52576
1000𝑥60
= 0.876 𝑐𝑢𝑚𝑒𝑐𝑠

25. PROBLEM ON FIRE DEMAND
4. Freeman’s formula
𝑄 = 1136
𝑃
5
+ 10 = 1136
170
5
+ 10
𝑄 = 49984
𝑙
𝑚𝑖𝑛
𝑄 =
49984
1000𝑥60
= 0.833 𝑐𝑢𝑚𝑒𝑐𝑠
No. of fire streams,
𝐹 = 2.8 170 =36 nos.

26. PERCAPITA DEMAND
• The consumption of water for one person in
one day is known as percapita demand. If ‘Q’
is the total quantity of water required by a
town per year in litres for the population P
then,
Percapita Demand =
𝑄
𝑃𝑥365
l/day

27. FACTORS AFFECTING PER CAPITA
DEMAND
i) People’s habits
ii) Industrialisation
iii) Public Services
iv) Climate
v) Systems of supply
vi) Metering of water supply
vii) System of drainage
viii)Availability of
supplementary sources
ix) Distribution
pressure
x) Cost of water
xi)Quality of
water
WATER METER

28. FACTORS AFFECTING PER CAPITA
DEMAND (cont.)
i) People’s habit:
People with high standard of living require
more water than those belonging to middle
class and low income groups.
ii) Industrialisation:
The requirements varies from industries to
industry. Wet processing industries requires a
huge quantity of water for cooling purpose.

29. FACTORS AFFECTING PER CAPITA
DEMAND (cont.)
iii) Public Services:
Developed cities, towns and township
require more water for watering of parks,
gardens and roads.
iv) Climate:
People living in hot climate areas requires
more water.

30. FACTORS AFFECTING PER CAPITA
DEMAND (cont.)
v) Systems of supply:
Water requirement in continuous supply will be more
compared to intermittent supply. In continuous supply
wastage will be more.
vi) Metering:
If meters are used and consumer are charged
consumption of water will reduce.
vii) Systems of drainage:
The existence of sewerage system consumes more
water for cleaning, flushing of toilets and urinals.

31. FACTORS AFFECTING PER CAPITA
DEMAND (cont.)
viii) Availability of supplementary sources:
If supplementary sources like wells are used,
demand over municipal water supply will reduce.
ix) Distribution Pressure:
The consumption of water is more in high
drainage pressure due to more wastage in taps.
x) Cost of water:
If the cost of water is high, consumption is less.

32. FACTORS AFFECTING PER CAPITA
DEMAND (cont.)
xi) Quality of water:
If the quality of water is good and the
people will not use the other sources available
like wells and pumps hence the demand will be
more.

33. PREDICTION OF POPULATION
(FORECAST)
• Water supply project is designed to cater the
needs of community upto the end of the
design period. Design period – 20yrs to 40yrs
• It is forecast the population at the end of
design period.
Following are the important methods to forecast
population:
1. Arithmatical increase method
2. Geometrical increase method

34. PREDICTION OF POPULATION
(FORECAST)
3. Incremental increase method
4. Decreased rate of growth of method
5. Graphical comparison method
6. Graphical extension method
7. Zoning method
8. Ratio and correlation method
9. Growth composition analysis method.

35. THANK YOU