Unit – 3

1. Explain sources of water supply?

To supply the required amount of water demand the planners of the scheme must go in to the search of nearby water sources. The various sources of water can be classified into two categories

1. Surface Sources 
   • Ponds and lakes
   • Stream and rivers
   • Storage reservoir
   • Ocean, (generally not used for water supplies at present technologies are available)

2.     Sub Surface

• Water Sources or Underground Sources  Springs
• Infiltration wells
• Wells and tube wells
• Infiltration galleries

Lakes and streams

• A natural lake represents a large body of water within land with impervious bed.  Hence, it may be used as source of water supply scheme for nearby localities.  The quantity of runoff that goes to the lake should be accurately determined and it should be seen that it is at least equal to the expected demand of locality.  Similar is the case with streams which are formed by the surface runoff. It is found that the flow of water in streams is quite ample in rainy season.  But it becomes less and less in hot season and sometimes the stream may even become absolutely dry.
• The catchment area of lakes and streams is very small and hence, the quantity of water available from them is also very low.  Hence, lakes and streams are not considered as principal sources of water supply schemes for the large cities.  But they can be adopted as sources of water supply schemes for hilly areas and small towns.
• The water which is available from lakes and streams is generally free from undesirable impurities and can therefore be safely used for drinking purposes.

Ponds

• A pond is a man-made body of standing water smaller than a lake.  Thus ponds are formed due to excessive digging of ground for the construction of roads, houses, etc and they are filled up with water in rainy season.  The quantity of water in pond is very small and it contains many impurities.
• A pond cannot be adopted as a source of water supply and its water can only be used for washing of clothes or animals only.

Rivers

• Since the dawn of civilization, the ancient man settled on the banks of river, drank river water and ate fish caught from river water and sailed down rivers to find out unknown lands. 
• Large rivers constitute the principal source of water supply schemes for many cities.  Some rivers are perennial while others are non-perennial.  The former rivers are snow fed and hence, water flows in such rivers for all the seasons.  The latter type of rivers dries in summer either wholly or partly and in monsoon, heavy flood visits them.  For such types of rivers, it is desirable to store the excess water of flood in monsoons by constructing dams across such rivers.  This stored water may then be used in summer.

Storage reservoirs

An artificial lake formed by the construction of dam across a valley is termed as a storage reservoir.  It essentially consists of the following three parts

• A dam to hold water
• A spillway to allow the excess water to flow and
• A gate chamber containing necessary valves for regulating the flow of water

At present, this is rather the chief source of water supply schemes for very big cities.  The multipurpose reservoirs also make provisions for other uses in addition to water supply such as irrigation and power generation. 

2.    Explain Impurities in water and their effects?

8 main types of water contaminants, and how they can be prevented.

1.Microorganisms

Bacteria, algae and fungi all regularly interfere with sterile research applications. Bacteria can adversely influence cell and tissue culture by competing at enzyme-active sites on substrates.

If free-floating bacteria form biofilms on surfaces, they can be extremely difficult to remove. These biofilms can grow for several years, spontaneously releasing bursts of bacteria, along with their associated endotoxins and nucleases.

These nucleases then break down DNA and RNA in samples, and the endotoxins will have a negative effect on the growth and function of cells.

2.Viruses

Viruses – referred to as non-living nucleic acids – adversely affect tissue and cell growth. They’re extremely small, with most of them falling between 0.01 – 0.3 microns, and they can survive for long periods of time. Once they’ve been spotted in water, they should be removed as soon as possible.

3.Pyrogens

For mammalian cell cultures, and the preparation of solutions or devices that will later have contact with humans and other mammals, it’s crucial that the water used is pyrogen-free.

The most significant component of pyrogens – a form of endotoxin – is lipopolysaccharides (LPS), which is derived from Gram-negative bacteria walls. If LPS gets into the blood or spinal fluid, it can be toxic and cause a fever.

4.Dissolved Inorganic Ions

Silicates, chlorides, calcium, fluorides, magnesium, phosphates, bicarbonates, sulphates, nitrates and ferrous compounds are all forms of dissolved inorganic ions.

The instability in water caused by these ions will negatively influence chemical and biological reactions. Results include the formation of protein-protein and protein-lipid interaction, altering enzymatic activity, and delaying the growth of cells and tissue.

5.Dissolved Organic Compounds

These are derived from animal and plant decay, in addition to any human activities that involve the introduction of alcohol, protein, pesticides, chloramine, herbicides or detergents into the environment.

Dissolved organic compounds interfere with high performance liquid chromatography (HPLC), gas chromatography and fluoroscopy.

6.Dissolved Gases

Water contains naturally dissolved carbon dioxide, nitrogen and oxygen, but these gases can alter the pH of lab water, which upsets the ionic balance. Concentrations of oxygen and nitrogen can affect the rate of biochemical reactions; and high concentration of dissolved gases can cause a bubble formation, which obstructs the flow through chromatography columns and micro-channels.

Dissolved carbon dioxide raises water acidity, reducing the capacity of ion exchange resins in DI systems.

7.Suspended Particles

When large suspended particles of clay, sand, silt or vegetation between 1 – 10µm are found in water, they cause turbidity and settle at the bottom.

Suspended particles can foul reverse osmosis membranes, filters and chromatography columns, especially if the system stems from a reservoir or tank within the building.

8.Colloidal Particles

Colloidal particles are much smaller than suspended particles, at just 0.01 – 1.0µm, and they don’t settle.

Colloidal particles regularly interfere with analytical techniques, and bypass ion exchange resins, which result in lower resistivity in DI water.

How to Prevent Contaminants

The main way to prevent and remove contaminants are through water purification systems. Different technologies have been created, each specialising in the removal of specific contaminants.

For example, whilst the process of distillation won’t remove ionised gases, inorganic ions or dissolved non-ionised gases, they will filter out bacteria and pyrogens.

Reverse osmosis (RO) is hailed as one of the most effective ways of removing contaminants, as this process removes up to 99% of impurities in water. Dissolved organics and ionics, suspended impurities, bacteria and pyrogens are all removed from water when RO is used.

To conclude, contaminants can be very damaging to water. Once found, they should be removed as soon as possible, using the most effective form of water purification technology.

3.    Explain Purification of water?

Water purification, process by which undesired chemical compounds, organic and inorganic materials, and biological contaminants are removed from water. That process also includes distillation (the conversion of a liquid into vapour to condense it back to liquid form) and deionization (ion removal through the extraction of dissolved salts). One major purpose of water purification is to provide clean drinking water. Water purification also meets the needs of medical, pharmacological, chemical, and industrial applications for clean and potable water. The purification procedure reduces the concentration of contaminants such as suspended particles, parasites, bacteria, algae, viruses, and fungi. Water purification takes place on scales from the large (e.g., for an entire city) to the small (e.g., for individual households).

4.     Explain Modern purification processes?

7 Methods Of Water Purification Process 

The water purification process or access to pure and healthy water for drinking purposes can protect millions of lives every year. This can be achieved by the following methods which are given below-

1. Boiling

Boiling water is one of the cheapest and best ways to purify water. Water is one of the natural solvents which can dissolve almost everything. This property of water makes its natural habitats for various kinds of pathogens which can’t be seen by the naked eye. The boiling of water removes these kinds of pathogenic germs and bacteria.

2. Coagulation & flocculation

This is the first step of the water purification in which some chemicals are added into the water for the removal of the suspended particle from the water. These added particles can be organic such as bacteria, viruses, fungi, algae and any other natural organic compound and inorganic in nature such as clay and silt.

The addition of inorganic coagulants such as aluminum sulfate or iron salt such as iron chloride induces several chemical and physical interactions among the particles. The negative charge on the particles gets neutralized by the inorganic coagulants and starts forming a metal hydroxide of aluminum ions and iron.

These metal hydroxide i.e. Aluminum and iron hydroxide precipitate combine together and form a large compound under a natural process called Brownian motion or under induced mixing called flocculation. These metal hydroxides start absorbing the suspended particle in the water and induce removal of those suspended particles by a subsequent process of sedimentation & filtration.

Organic coagulants are a man-made organic polymer. This polymer contains the high molecular size and when it added into the water it starts absorbing the suspended particle present in the water and forms flock.  

3. Sedimentation

Sedimentation is a physical process that removes suspended particles from the water using gravity. The particle which settles out from the water is called sediment or sludge. The thick layer of sediment is known as consolidation.

Water containing flocculation basin enters into the sedimentation basin, The sedimentation basin is a large tank that has low water velocities which allow the suspended particle to settle at the bottom. The flocculation basin and sedimentation basin are closed to each other that is why this process does not allow the floc to break up.

Before the coagulation process in the water treatment process, sedimentation could be used to decrease the suspended particle present in the water. But after the coagulation process sedimentation is used to reduce the solid particle from the water so that the filtration process can function effectively.

4. Filtration

Any mechanical, physical or biological operation which is used to separate solids from the fluids (i.e. Liquid or gas) by adding a medium which only allows the fluids to pass through it but doesn't allow the solids to pass. The fluids which pass through it is called the filtrate. There are various methods of filtration such as hot filter, cold filter, and vacuum filter and all these filters aim to separate the substance.

Filtration is one of the active water purification processes among all the methods used for purification. It is mainly based on physical and chemical processes. Filtration ensures that your drinking water is safe for consumption purposes because it removes all kinds of water contamination from the water.

When you compare the water filtration process with reverse osmosis (RO) that filtration is most effective as it removes much smaller molecules like chlorine and pesticides. Distillation is not only effective but also economical as it doesn’t require more energy as compared to reverse osmosis. During the filtration process, little loss of water takes place.

5. Disinfection

The process of cleaning something to destroy microbes is regarded as disinfection. It could be done by removing harmful micro-organisms or by adding disinfectant chemicals. Disinfection can be achieved by chlorine, chlorine dioxide, chloramine, ozone, and ultra-violate (UV) rays.

Chlorine and its compounds such as chlorine dioxide and chloramine is a strong oxidant which efficiently kills the micro-organism whereas ozone is unstable molecules which produce natation oxygen which acts as a powerful oxidizing agent. Ultra-violate rays are very effective at reducing contamination.

6. Distillation

The process of separation of any substance from a liquid mixture through selective boiling and condensation. It could be done to achieve complete or partial separation which results in a higher concentration of the selective compound.

Distillation is one of the water purification methods which utilize heat to collect pure water in the form of vapor. According to the scientific fact, distillation is one of the best water purification methods because the boiling point of water is less as compared to the other water pollutant and disease-causing agent.

In the distillation process to achieve water purification, water is subjected to heat until it reaches its boiling point. After that, water is allowed to vaporize and directed into the condenser to cool. After cooling vapors reverse into water that is clean and pure. Another substance that has a higher boiling point remains in the container.

This method of water purification has its advantage and disadvantages. The advantage of distillation is that it affects water purification methods in terms of eliminating bacteria, germs, salts, and other heavy metals like leads, Arsenic. The notable disadvantage of distillation is that it is a slow process and requires a heat source for the water purification process. This process has one significant disadvantage that it is only effective for the smaller quantity not for the large scale.

7. Chlorination

Chlorine is one of the powerful water purification methods which kills germs, parasites, and other disease-causing agents present in your regularly used water. Chlorine is one of the cost-effective water purification methods among all the know water purification methods. It is mostly used in municipal water to deliver pure and safe water for home consumption.

A hydraulic structure is a structure submerged or partially submerged in any body of water, which disrupts the natural flow of water. They can be used to divert, disrupt or completely stop the flow. An example of a hydraulic structure would be a dam, which slows the normal flow rate of river in order to power turbines. A hydraulic structure can be built in rivers, a sea, or any body of water where there is a need for a change in the natural flow of water.

6.    Explain Water conveyance systems?

Water Conveyance System

1.Open channel flow

Open Channel Open channel: The most common type of water conveyance system is the open channel. In the open channel, water flows with a free water surface i.e a surface on which pressure is equal to local atmospheric pressure.

2.Pipe flow

Pipe flow, a branch of hydraulics and fluid mechanics, is a type of liquid flow within a closed conduit (conduit in the sense of a means of containment). The other type of flow within a conduit is open channel flow. These two types of flow are similar in many ways, but differ in one important aspect. Pipe flow does not have a free surface which is found in open-channel flow. Pipe flow, being confined within closed conduit, does not exert direct atmospheric pressure, but does exert hydraulic pressure on the conduit.

7.    Define Watershed management

Watershed management is a term used to describe the process of implementing land use practices and water management practices to protect and improve the quality of the water and other natural resources within a watershed by managing the use of those land and water resources in a comprehensive manner.

8.    Explain the importance of Watershed management ?

Runoff from rainwater or snowmelt can contribute significant amounts of pollution into the lake or river. Watershed management helps to control pollution of the water and other natural resources in the watershed by identifying the different kinds of pollution present in the watershed and how those pollutants are transported, and recommending ways to reduce or eliminate those pollution sources.

All activities that occur within a watershed will somehow affect that watershed’s natural resources and water quality. New land development, runoff from already-developed areas, agricultural activities, and household activities such as gardening/lawn care, septic system use/maintenance, water diversion and car maintenance all can affect the quality of the resources within a watershed. Watershed management planning comprehensively identifies those activities that affect the health of the watershed and makes recommendations to properly address them so that adverse impacts from pollution are reduced.

Watershed management is also important because the planning process results in a partnership among all affected parties in the watershed. That partnership is essential to the successful management of the land and water resources in the watershed since all partners have a stake in the health of the watershed. It is also an efficient way to prioritize the implementation of watershed management plans in times when resources may be limited.

Because watershed boundaries do not coincide with political boundaries, the actions of adjacent municipalities upstream can have as much of an impact on the downstream municipality’s land and water resources as those actions carried out locally. Impacts from upstream sources can sometimes undermine the efforts of downstream municipalities to control pollution. Comprehensive planning for the resources within the entire watershed, with participation and commitment from all municipalities in the watershed, is critical to protecting the health of the watershed’s resources.

9.    Methods for water shed management?

1. To improve the groundwater level, several civil structures are constructed in the watershed area, pits and trenches.
2. The pits or trenches are dogged at equal intervals on the skipping surface to cut the surface – flow and to allow it to percolate through these trenches to enrich the ground level.
3. Stone embankment or earthen dams.
4. They are constructed to check the surface – runoff in the catchment areas, to enrich the groundwater.
5. The farm pond.
6. They are constructed near the agriculture field in the catchment area to provide enough surface water to the filed and also to enrich the groundwater.
7. Dykes or underground barriers.
8. These structures are constructed in the small surface streams e.g. The nallahs, to prevent the free groundwater flow and allow the water-table to come up, to help to improve the irrigation through the dug – wells.

9.    Explain Roof top rain water harvesting and its need for it ?

Rooftop Rain Water Harvesting is the technique through which rain water is captured from the roof catchments and stored in reservoirs. Harvested rain water can be stored in sub-surface ground water reservoir by adopting artificial recharge techniques to meet the household needs through storage in tanks. The Main Objective of rooftop rain water harvesting is to make water available for future use. Capturing and storing rain water for use is particularly important in dryland, hilly, urban and coastal areas. In alluvial areas energy saving for 1m. Rise in ground water level is around 0.40 kilo watt per hour.

Need for Rooftop Rain Water Harvesting

1. To meet the ever increasing demand for water  

2. To reduce the runoff which chokes storm drains

3. To avoid flooding of roads

4. To augment the ground water storage and control decline of water levels

5. To reduce ground water pollution

6. To improve the quality of ground water

7. To reduce the soil erosion

8. To supplement domestic water requirement during summer, drought etc