Unit - 1

Introduction

Q1) What is water supply scheme?

A1)

• Absolutely pure water is never found in nature and which contains only two parts of hydrogen and one part of oxygen by volume. But the water found in nature contains number of impurities in varying amounts. The rainwater which is originally pure, also absorbs various gases, dust and other impurities while filling.
• This water when moves on the ground further carries silt, organic and inorganic impurities. The removal of the turbidity, odour and smell is considered as good and removal of dissolved substances is considered as “chemically pure”. But removal of substances like calcium, magnesium Iron, Zinc etc completely is not good for health. These minerals are required for tissue growth and some act as propylatic in preventing diseases.
• Therefore wholesome water is defined as the water which containing the minerals in small quantities at requisite levels and free from harmful impurities Chemically pure water is also corrosive but not whole some water. The water that is fit for drinking safe and agreeable is called potable water.

Q2) What are the objective of water supply system?

A2)

The objectives of the community water supply system are

1. To provide whole some water to the consumers for drinking purpose.
2. To supply adequate quantity to meet at least the minimum needs of the individuals and to make adequate provisions for emergencies like fire fighting, festivals, meeting etc.
3. To make provision for future demands due to increase in population, increase in standard of living, storage and conveyance
4. To prevent pollution of water at source, storage and conveyance
5. To maintain the treatment units and distribution system in good condition with adequate staff and materials
6. To design and maintain the system that is economical and reliable

Q3) Give importance and necessity of water supply scheme.

A3)

• Water is present in abundant quantities on the Earth’s surface, but not more than 1 percent of the total available water is in the form of liquid fresh water. Most of Earth’s water (1.4 billion cubic km) is in the oceans or frozen in polar ice caps and glaciers. However, ocean water contains about 35 gm/l of dissolved minerals or salts, making it unfit for drinking, industrial or agricultural uses.
• Fresh water, containing less than 3 gm/l of salts, is not uniformly distributed over the globe, resulting in water scarcity. In many locations, the availability of good-quality water is further reduced because of urban development, industrial growth, and environmental pollution.
• In order to ensure the availability of sufficient quantity of good quality water, it is imperative to plan and build suitable water supply schemes, which will provide portable water to the various sections of the society in accordance with their demands and requirements. Hence, each country has developed certain Water Supply Schemes to ensure that good quality potable water is available to its citizens.

Q4) What is water demand?

A4)

• Among all the important needs, water is one of the most important needs of the human beings. So, when any new township is planned along with other amenities, the required water supply for that community, is thought about.
• Water is required for various purposes, drinking water stands first among the all. So the team of town planners have to determine the water demand of that township or the urban settlement.
• Once the demand of water is calculated the next step is to find out the sources of water, which can meet the expected water demand.
• In case of large cities such as Ahmadabad, or Baroda or the industrial complex like Ankaleshwar, one source of lewater supply or one water-works is not enough.
• So in cases of such large populated cities, various water sources are thought about, and more than one water-works for treatment and supply of water, are designed.

Q5) Explain domestic water demand and industrial demand.

A5)

Domestic Water Demand:

• The domestic needs of water include, for drinking, cooking, washing, bathing etc. The domestic water needs generally depend upon the social status, habits, customs of the people.
• The needs also change as the climatic conditions change e.g. In the tropical hot and dry climates more water is consumed than in a settlement, located in the cool climates.
• Under the normal climatic conditions, in India, the per day, per person consumption of water is about 135 litres, while in case of developed, western countries this water consumption is more than 350 litres, per day, per person.
• This higher consumption rate of domestic water is the higher standard of living using air coolers, dishwashers, house laundries etc.
• Out the average total consumption of water, per day, per person, maximum of 55 litres is used for bathing and 20 litres for washing of clothes. Another 30 litres are being used for flushing of latrines. 5 litres each are used for drinking and cooling purposes.

Commercial and Industrial Water Demand:

• Among the long list of commercial users of water, maximum demand comes from the commercial constructions, Hospitals, Hotels, Cinema houses, Schools Hostels, Sport-Clubs etc.
• The need of the water by any industry depends upon, the process the raw material, seasonality of the industry etc. In case of industrial demand of water also, is measured in terms of per capita, per day demand, so the water needed by any industry also depends upon the number of workers also.
• Sugar mills, paper mills, cotton textile mills, breweries, chemical factories etc. have a very huge demand of water. Generally these industries have their own water supply arrangements.

Q6) What do you mean by water demand for fire fighting and demand of water for public use?

A6)

Water Demand for Fire Fighting:

• The fire in the urban settlement is generally caused by short circuits, explosion, or by the domestic causes or the industrial processes. So, all the large populated cities have to have the fire-fighting arrangements.
• On an average, the need of water for fire-fighting and depends upon the total population of the urban area and on the types of buildings, and also on the basis of the density of population per sq. Unit of land. Generally, for the fire fighting the water requirement can be calculated as:

1. For a city having low buildings-2200 Lit/min.
2. For a city having high building-4500 Lit/min.
3. For market areas, public places 7,650-13,500 Lit/min.
4. For high density of population and for multi-storeyed buildings - 27000 Lit/min.

• The need of water for fire-fighting varies seasonally also i.e. the fire in summer needs more water.

Demand of Water for Public Use:

• The quantity of water needed for the public use such as washing the roads, watering the public parks, cleaning of the sewers etc. covers about 5% of the total consumption of the water by the urban settlement.
• On an average the water required by the public parks is about 16,850 Lits per hec per day.

Q7) Write a short note on demand of water for domestic animals.

A7)

Demand of Water for Domestic Animals:

• For milk, meat, skin, fur etc. the live stock farming is carried around the urban settlements. Each domestic animal has a different need of water for consumption and for cleaning. e.g. Cows need about 68.25 Lits, of water per day per animal.
• While in case of houses it is about 45.50 lits per day per animal. The need of water for chickens is minimum i.e. 0.09 lits. Per day, per bird.
• Per Capita Water Demand
• As we have already seen that in any community, water is used for various purposes by the common man. The demand is measured as litres, per person, per day.

Q8) Give empirical formula.

A8)

The quantity of water required for municipal uses for which the water supply scheme has to be designed requires following data:

1. Water consumption rate (Per Capita Demand in litres per day per head)
2. Population to be served.

Quantity= Per capita demand x Population

Water Consumption Rate

It is very difficult to precisely assess the quantity of water demanded by the public, since there are many variable factors affecting water consumption. The various types of water demands, which a city may have, may be broken into following classes:

Water Consumption for Various Purposes:

Fire Fighting Demand:

The per capita fire demand is very less on an average basis but the rate at which the water is required is very large. The rate of fire demand is sometimes treated as a function of population and is worked out from following empirical formulae:

Q9) What are factors affecting per capita demand?

A9)

Factors affecting per capita demand:

1. Size of the city: Per capita demand for big cities is generally large as compared to that for smaller towns as big cities have sewered houses.
2. Presence of industries.
3. Climatic conditions.
4. Habits of people and their economic status.
5. Quality of water: If water is aesthetically $ medically safe, the consumption will increase as people will not resort to private wells, etc.
6. Pressure in the distribution system.
7. Efficiency of water works administration: Leaks in water mains and services; and unauthorised use of water can be kept to a minimum by surveys.
8. Cost of water.
9. Policy of metering and charging method: Water tax is charged in two different ways: on the basis of meter reading and on the basis of certain fixed monthly rate.

Fluctuations in Rate of Demand

Average Daily Per Capita Demand = Quantity Required in 12 Months/ (365 x Population)

Q10) What are factors affecting per capita demand?

A10)

The following are the main factors affecting for capita demand of the city or town.

Climatic conditions:

The quantity of water required in hotter and dry places is more than cold countries because of the use of air coolers, air conditioners, sprinkling of water in lawns, gardens, courtyards, washing of rooms, more washing of clothes and bathing etc. But in very cold countries sometimes the quantity of water required may be more due to wastage, because at such places the people often keep their taps open and water continuously flows for fear of freezing of water in the taps and use of hot water for keeping the rooms warm.

Size of community:

Water demand is more with increase of size of town because more water is required in street washing, running of sewers, maintenance of parks and gardens.

Living standard of the people:

The per capita demand of the town increases with the standard of living of the people because of the use of air conditioners, room coolers, maintenance of lawns, use of flush, latrines and automatic home appliances etc.

Industrial and commercial activities:

As the quantity of water required in certain industries is much more than domestic demand, their presence in the town will enormously increase per capita demand of the town. As a matter of the fact the water required by the industries has no direct link with the population of the town.

Pressure in the distribution system:

The rate of water consumption increase in the pressure of the building and even with the required pressure at the farthest point, the consumption of water will automatically increase. This increase in the quantity is firstly due to use of water freely by the people as compared when they get it scarcely and more water loss due to leakage, wastage and thefts etc.

System of sanitation:

Per capita demand of the towns having water carriage system will be more than the town where this system is not being used.

Cost of water:

The cost of water directly affects its demand. If the cost of water is more, less quantity of water will be used by the people as compared when the cost is low.

Types of variation in water Demand

        Seasonal variations

        Monthly variations

        Daily variations

        Hourly variations

Q11) What are variation in demand?

A11)

1. Seasonal variations: - The demand peaks during summer. Firebreak outs are generally more in summer, increasing demand. So, there is seasonal variation.
2. Daily variations: - More construction on Sunday and holiday and during storm and dust.
3. Hourly variations -During active household working hours i.e. from six to ten in the morning and four to eight in the evening, the bulk of the daily requirement is taken. During other hours the requirement is negligible. Moreover, if a fire breaks out, a huge quantity of water is required to be supplied during short duration, necessitating the need for a maximum rate of hourly supply.                

• This normal variation in demand should generally be assessed and known in order to design supply pipes, service reservoirs, distributaries pipes etc.

Assessment of Normal variations

1. Maximum daily consumption is generally taken as 180% of the average daily consumption.

Maximum Daily Demand = 1.8 X Average Daily Demand = 1.8q

2.     Maximum hourly consumption is generally taken as one 150% of its average hourly consumption.

Peak Demand = 1.5 X Average Hourly consumption of the maximum day

= 2.7 X Annual Average Hourly Demand

Goodrich formula for finding ratio of steel demand rates to their corresponding means:

P = 180 X t0.10

Where,                           

P = % of annual average draft for the time ‘t’ in days.

t = time in days from 1/24 to 365.

When,                           

t = 1 day for daily variations

P = 180 X (1)0.10 = 180

Maximum daily demand = 180%                

Q12) What is design period?

A12)

The future period or the number of years for which a provision is made in designing the capacities of the various components of the water supply scheme is known as design period 30 years.

Factor governing the design period

a) Useful life of component structure and the chances of their becoming old and obsolete.

b) Is and difficulty in expansion, if undertaken at future dates. Difficult extension then high design period.

c) Amount and availability of additional investment likely to be incurred for additional provisions.

d) Rate of interest on borrowings and the additional money invested. Less interest rate than high design period.

e) Anticipated rate of population growth including possible shifts in communities, industries and commercial establishments.

Design period for different components of water supply scheme

Q13) What is population forecasting?

A13)

When the design period is fixed the next step is to determine the population of a town or city population of a town depends upon the factors like births, deaths, migration and annexation. The future development of the town mostly depends upon trade expansion, development industries, and surrounding country, discoveries of mines, construction of railway stations etc may produce sharp rises, slow growth, stationary conditions or even decrease the population. For the prediction of population, it is better to study the development of other similar towns, which have developed under the same circumstances, because the development of the predicted town will be more or less on the same lines.

The following are the standard methods by which the forecasting population is done.

1. Arithmetical increase method
2. Geometrical increase method
3. Incremental increase method
4. Simple graph method
5. Decrease rate of growth method
6. Comparative graph method and The master plan method

VARIATIONS IN DEMAND

The per capita demand of town is the average consumption of water for a year. In practice it has been seen that this demand does not remain uniform throughout the year but it various from season to season, even hour to hour.

SEASONAL VARIATIONS

The water demand varies from season to season. In summer the water demand is maximum, because the people will use more water in bathing, cooling, lawn watering and street sprinkling. This demand will becomes minimum in winter because less water will be used in bathing and there will be no lawn watering. The variations may be upto 15% of the average demand of the year.

DAILY VARIATIONS 

This variation depends on the general habits of people, climatic conditions and character of city as industrial, commercial or residential. More water demand will be on Sundays and holidays due to more comfortable bathing, washing etc as compared to other working days. The maximum daily consumption is usually taken as 180% of the average consumption.

HOURLY VARIATIONS

On Sundays and other holidays the peak hours may be about 8 A.M. Due to late awakening where as it may be 6 A.M. To 10 A.M. And 4 P.M. To 8 P.M. And minimum flow may be between 12P.M. To 4P.M. When most of the people are sleeping. But in highly industrial city where both day and night shifts are working, the consumption in night may be more. The maximum consumption may be rise upto 200% that of average daily demand. The determination of this hourly variations is most necessary, because on its basis the rate of pumping will be adjusted to meet up the demand in all hours.

As per IS: 1172-1963, under normal conditions, the domestic consumption of water in India is about 135 litres/day/capita. But in developed countries this figure may be 350 litres/day/capita because of use of air coolers, air conditioners, maintenance of lawns, automatic household appliances.

The details of the domestic consumption are

a)      Drinking------ 5 litres

b)     Cooking------ 5 litres

c)      Bathing------ 55 litres

d)     Clothes washing------ 20 litres

e)      Utensils washing------ 10 litres

f)       House washing------ 10 litres per 135 litres/day/capital

Q14) What are the sources of water?

A14)

Ground Water

Ground water refers to any supply of water that lies below the soil layer. Ground water can exist withinside the soil itself or among rocks and different materials. Most groups attain their water from underground aquifers, or rock formations able to conserving big quantities of freshwater. Only three percentage of the water on the earth is taken into consideration freshwater, with a trifling 30 percentage of that small quantity being determined as groundwater. Pollution, seawater infection and overuse threaten this precious resource.

Surface Water

Sources of floor water can consist of any above-floor series of water including rivers, lakes, ponds and oceans. Some reassets of floor water also are fed via way of means of underground aquifers. Surface water money owed for eighty percentage of the water people use.

Ocean Water

Although ocean water makes up almost ninety seven percentage of all water on earth, it isn't always a feasible supply of potable water except salt and different impurities are eliminated. Desalination, the system through which salt is eliminated from water, is a unexpectedly developing practice. While salt and different microscopic debris may be eliminated from water in a number of ways, the maximum promising approach is through opposite osmosis. This system forces saltwater through filters with microscopic pores that get rid of salt and different microbes. Reverse osmosis calls for huge quantities of energy, making it a totally highly-priced system.

Ice Caps and Glacial Melting

Of the three percentage of earth's water taken into consideration freshwater, 70 percentage of that small quantity is presently locked in glaciers and ice caps. In theory, frozen glacial and ice cap water will be melted and used, however the quantity of strength had to soften and delivery considerable portions of ice make it economically impractical. Glaciers and ice caps additionally play vitally crucial roles withinside the law of earth's climates and international temperatures, making their protection very crucial.

Q15) What do you mean by rain water?

A15)

• Rainwater is a fantastically smooth water supply and with essential warning it could be even used for potable consumptions. Importantly, it's far a loose supply and may be accumulated in a huge amount from roof catchments and different pavement regions which may be used for numerous purposes (e.g., lawn watering, bathroom flushing, laundry, cooling and heating, hygienic use and drinking).
• Therefore, rainwater harvesting can play an vital position in water sustainability via way of means of decreasing the strain on mains water deliver. Many research said a very good quantity of water financial savings in a constructing via way of means of the use of rainwater harvesting gadget (Hajani and Rahman, 2014). For example, Muthukumaran et al. (2011) proven that approximately of 40% potable water may be stored via way of means of the use of rainwater in a residential constructing in local Victoria in Australia. Ward et al. (2012) observed that an office-primarily based totally rainwater harvesting gadget may want to keep round 87% water (amount of mains water stored) in a nondomestic constructing.
• A rainwater harvesting gadget collects runoff from a catchment place (e.g., roof place and paved place) and normally includes a garage tank, deliver and distribution networks, and an overflow unit. Among the additives of a rainwater harvesting gadget, the garage tank is generally the biggest aspect of the entire set up value.
• Therefore, a right financial evaluation and layout are essential earlier than enforcing the rainwater harvesting structures in constructing for you to enhance their overall performance and benefits, and to achieve quick payback length. In order to assess the monetary feasibility of rainwater harvesting gadget, lifestyles cycle value assessment (LCCA) want to be integrated in the course of the making plans of a constructing production. LCCA is a way of comparing the value of a product over its lifestyles span wherein all of the past, present, and destiny coins flows are transformed to offer values. Several research have said LCCA of a rainwater harvesting gadget and commented high-quality outcomes at the monetary feasibility of these structures, which can play a vital aspect in enhancing water sustainability in homes.
• Zhang et al. (2009) evaluated the monetary feasibility of rainwater harvesting gadget in high-upward thrust homes in 4 capital towns in Australia (e.g., Sydney, Perth, Darwin, and Melbourne) and proven that each one the towns had the capability to provide true monetary go back the use of rainwater harvesting gadget. They observed shortest payback length (approximately 10 years) of rainwater harvesting gadget (approximately 10 years) in Sydney. Domenech and Sauri (2010) observed the payback length in among 33 and forty three years withinside the metropolitan place of Barcelona in Spain for a single-own circle of relatives family relying at the rainwater tank size.
• Imteaz et al. (2011) said that production value of a industrial rainwater tanks linked to huge roofs in Melbourne may be recovered with 15–21-12 months time relying at the tank size, climatic conditions, and destiny water price.

Q16) What is ground water spring?

A16)

• Springs are fashioned whilst groundwater flows onto the floor. This commonly takes place whilst the groundwater desk reaches above the floor level. Springs can also be fashioned due to karst topography, aquifers, or volcanic activity. Springs additionally were discovered on the sea floor, spewing warm water at once into the sea.
• Springs fashioned due to karst topography create karst springs, wherein floor water travels via a community of cracks and fissures—openings starting from intergranular areas to big caves, later rising in a spring. A herbal spring on Mackinac Island in Michigan The forcing of the spring to the floor may be the end result of a constrained aquifer wherein the recharge region of the spring water desk rests at a better elevation than that of the opening. Spring water pressured to the floor via way of means of increased reassets are artesian wells.
• This is viable although the opening is withinside the shape of a 300-foot-deep (ninety one m) cave. In this example the cave is used like a hose via way of means of the better increased recharge region of groundwater to go out via the decrease elevation opening.
• Non-artesian springs may also truly float from a better elevation via the earth to a decrease elevation and go out withinside the shape of a spring, the usage of the floor like a drainage pipe. Still different springs are the end result of stress from an underground supply withinside the earth, withinside the shape of volcanic activity. The end result may be water at increased temperature which includes a warm spring. Sunrise at Middle Spring, Fish Springs National Wildlife Refuge, Utah The movement of the groundwater usually dissolves permeable bedrock which includes limestone and dolomite, growing massive cave systems