CE 6001, Unit 1 Sources, Demand and Quality of water

 

1.1 Water Supply Schemes

1.1.1 Objectives:

The main objectives of a water supply scheme are:

• To provide clean and safe drinking water to the population.

• To supply adequate water for domestic, industrial, and firefighting needs.

• To ensure continuous water supply with proper pressure.

• To promote public health by reducing water-borne diseases.

1.1.2 Components:

The key components of a water supply system include:

1. Source of Water – river, lake, groundwater, etc.

2. Intake Structures – for drawing water from the source.

3. Pumping Station – to lift water to higher elevations.

4. Water Treatment Plant – to purify the water.

5. Storage Reservoirs – to store clean water.

6. Distribution System – pipes, valves, etc., to deliver water to users.

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1.2 Sources of Water

1.2.1 Surface and Subsurface Sources of Water:

Surface sources:

• Rivers, lakes, ponds, and reservoirs.

• Easily accessible but prone to pollution.

Subsurface sources:

• Wells, springs, and boreholes.

• Usually cleaner and less polluted.

1.2.2 Intake Structures:

These are structures built to draw water from sources like rivers or lakes. They include screens to prevent debris from entering the supply.

1.2.3 Definition and Types of Intake Structures:

Definition:
An intake structure is a device or structure through which water is collected from a source for further treatment and distribution.

Types:

• Submerged intake

• Exposed intake

• Canal intake

• Reservoir intake

1.2.4 Factors Governing the Location of an Intake Structure:

• Quality of water

• Availability of water throughout the year

• Minimum pollution and silt

• Ease of access for maintenance

• Proximity to treatment plant

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1.3 Demand of Water

1.3.1 Factors Affecting Rate of Demand:

• Population size and growth

• Living standards

• Climate (hot regions need more water)

• Type of buildings (multi-storey, industrial, etc.)

• Fire demand

1.3.2 Variations of Water Demand:

• Seasonal variation: More water in summer.

• Daily variation: Peak in the morning and evening.

• Hourly variation: Hour-to-hour changes depending on usage.

1.3.3 Forecasting of Population:

This is necessary to plan future water supply systems.

1.3.4 Methods of Forecasting of Population:

1. Arithmetic Increase Method

2. Geometric Increase Method

3. Incremental Increase Method

4. Graphical Method

1.3.5 Simple Problems on Forecasting of Population:

(You can include numerical examples like using the arithmetic increase method to predict population in the next 10 years.)

1.3.6 Design Period:

The number of years for which a water supply project is planned. Usually ranges from 15 to 30 years depending on the component.

1.3.7 Estimating Quantity of Water Supply:

This is done by multiplying the population with per capita demand (litres per person per day) and considering losses and future growth.

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1.4 Quality of Water

1.4.1 Need for Analysis of Water:

• To check if water is safe for drinking.

• To ensure it meets health standards.

• To identify impurities or harmful substances.

1.4.2 Characteristics of Water

1.4.2.1 Physical, Chemical and Biological Characteristics (only introduction):

• Physical: Colour, taste, odour, turbidity.

• Chemical: Presence of salts, metals, pH, hardness.

• Biological: Presence of bacteria, viruses, and algae.

1.4.2.2 Testing of Water:

Important tests include:

• Total Solids – measure of all dissolved and suspended matter.

• Hardness – caused by calcium and magnesium salts.

• Chlorides – excess can affect taste and cause corrosion.

• Dissolved Oxygen (DO) – necessary for aquatic life.

• pH – ideal range is 6.5 to 8.5.

• Fluoride – should be within permissible limit to avoid dental issues.

• Nitrogen Compounds – high levels indicate contamination by waste.

• Bacteriological Tests:

  • E. coli, B. coli Index, MPN (Most Probable Number): These show the presence of disease-causing bacteria.

1.4.2.3 Sampling of Water:

• Water samples should be taken properly from different points and stored in clean, sterilized containers for testing.

1.4.2.4 Water Quality Standards as per IS 10500:

• Indian Standard (IS 10500) gives permissible and desirable limits for drinking water.

• Ensures water is safe for human consumption.