Q.1) Describe the treatment process and impurity removal of water
The most and widely used treatment process is as follows:
The object like trees, sticks, vegetation, fish, animal life, boulder, gravel, etc.
- Plain sedimentation
The coarser suspended material can be removed by sedimentation. The process is known as sedimentation.
- Coagulation with sedimentation
The effectiveness of sedimentation increased by mixing certain chemicals with water, so is forms flocculent precipitation and suspended particle settles. The process is known as coagulation with sedimentation.
The finer particle removed the water through the filter. The process is known as filtration.
The filtered water may contain pathogenic bacteria and by adding certain chemicals such as chloride for cleaning the bacteria.
Unpleasant tests and odours may be removed by adding certain chemical compounds such as carbon and ozone etc. The process is called aeration.
It removes the hardness of the water.
It is used to remove iron, manganese and other harmful matter.
Q.2) What is water treatment? Write its objectives.
The raw water which is found in natural sources can’t be directly used by the public for various purposes, before removing the impurities.
For palatability, the water should be free from unpleasant tastes, odors and must have a sparkling appearance. The water must be free from disease-spreading germs.
The amount and type of treatment process will depend on the quality of raw water and the standards of quality to be required after the treatment.
Objectives of water treatment
The following are the objectives of water treatment:
- To make water potable.
- To remove the dissolved gases, murkiness, and color of water
- To kill all the pathogenic germs, which are harmful to human health.
- To remove the turbidity and hardness of the water.
- To remove impurities up to the level recommended in water quality standards.
- To remove suspended impurities such as silt, clay, and sand, etc.
- To eliminate the corrosive nature of water effective pipe.
Q.3) Describe the classification of intakes
Intakes are classified in the following three bases:
A) Bases on intake top under or above water level
1) Submerged intake
If the intake structure is constructed entirely under the water then the intake is called submerged intake.
2) Exposed intake
If the intake structure is constructed near or away from banks of water bodies then the intake is called exposed intake.
B) Based on water retain in the housing structure
1) Dry intakes
If there is no water in the water tower then it is called dry intake. In dry intake, water enters through the entry pot and is directly sent into the conveying pipes but operation valves are used.
2) Wet intakes
If there is water in the water tower of intake then it is called wet intake. In this water level is practical remains as same as the level of the source of supply.
C) Based on types of source
- River intake
- Reservoir intake
- Lake intake
- Spring intake
- Canal intake
- Stream intake
Q.4) Enlist the factors which should be considered while selecting the intake works of water supply
The factors governing the site selection for intakes are as follows:
- As far as possible, the site should be near the treatment plant so that the cost of conveying water will be less.
- Locate intake in the purest zone that helps to reduce the load in the treatment plant.
- Locate intake upstream of sewage disposal point.
- Locate should be such that future expansion is possible.
- The intake should never be located near the navigation channels due to the possibility of pollution caused by the discharge of refuge from ships and boats.
- Intake should be located in such a place where a sufficient quantity of water is available during the dry period also.
- The intake site should be easily accessible during floods and should not get flooded.
- In the case of the meandering river, the intake should not be located on the curves however if the is to be made on curves then it should be made on an outer bank so that water is available all the time.
- Intake site should be well connected by the good approach of road.
Q.5) Define intakes. Write its basic function and components of intakes.
Intakes are structures that help in safely withdrawing water from the source and discharge that water to the intake conduit through which it flows to the supply line.
The main function of the intakes work is to collect water from the water sources and then discharge water so collected, by means of pumps or directly to the treatment plant.
The basic function of intakes
- To ensure the required water.
- To reduce sediment entry.
- To check trash and debris entry along.
- To prevent the entry of ice.
- To secure entry of water with minimum disturbance.
Components of intakes
It consists of:
- An intake conduit( pipe)
Intake conduit conveys the water from the source to the treatment plant or reservoir or intakes well. It consists of the screen at the inlet end to stop large objects from entering into an inlet chamber and also the valve to regulate the flow of water.
- A housing or structure is constructed to support conduit/ pipe, valves, pumps, etc. An intake structure may be a simple block structure to huge concrete towers. It is made up of stone masonry, brick masonry, P.C.C., or R.C.C. The intake structure should be impervious and designed to resist water pressure, forces due to water wind, floating debris, etc.
Q.6) Describe the types of water-related diseases
The disease caused by contaminated water is known as water-related disease. It may be classified as follows:
- Waterborne disease
Water-borne diseases are caused by pathogens carried by water containing sewage contamination. For example; Cholera, dysentery, typhoid, paratyphoid, diarrheas, and other diseases. Improvement of quality of drinking water may check the water-borne disease.
- Water washed disease
The disease caused by unhealthy personal hygiene is called water-washed disease. For example; scabies, trachoma, skin sepsis, fungal infection, etc. Healthy personal hygiene alone with an increased quantity of clean water prevents the disease.
- Water-based disease
The disease is transmitted by aquatic animals and pathogens spending their life in water-based diseases. For example; water snail, guinea worm, lingo flukes, etc.
- Water victor or insect dependent disease
Insects living within the surrounding water sources may carry pathogens and cause disease such insects are called water victor disease. The water-related disease transferred from water by insects is called insect-dependent disease.
Q.7) What are the factors that affect the demand for water?
The various factors affecting the demand for water are as follows;
- Climate conditions
The quality of water required in hotter and dry places is more due to the use of air coolers, air conditioners, a sprinkling of water in lawns, gardens, washing of rooms, etc.
- Size and type of community
Bigger the size, the higher the demand due to a lot of public places of utility and recreation such as parks, lawns, ponds of foundations, etc.
- The living standard of people
The higher the living standard, the higher will be the demand.
- Quality of water
If the quality of water is good then demand will be higher and vice-versa.
- Pressure in the supply
Higher in the pressure, loss of water is more and higher will be the demand.
- System of supply
There are two types of systems of supply either throughout the day or limited period. Water demand is less in the intermittent system due to many problems faced in this system like limited water, storage requirement, etc.
- Cost of water
If the cost of water is higher, demand will be lower.
- Method of charging
To sustain a water supply system charging is essential. The various traffic system may be adopted in water supply for charging such as monthly basis or metering system, which affects the demand for water.
- Sewerage system
If a sewerage system is provided in the community, water required for flushing and cleaning increases the demand.
- Education and awareness of the people
- Age of the community
- Availability of local resources.
Q.8) Describe the selection criteria of a good source for a drinking water supply project.
The following factors are generally considered while selecting a source of water supply for a particular town or city.
- Quantity of water
There should be a sufficient quantity of water to meet all the demand throughout the year. City extension and design period must have been cared in this content.
- Quality of water
The source should have safe wholesome, free from pollution of any kind and other undesirable impurities. The impurities present in the water should be less as possible and there should be removed easily and cheaply.
It should be near to the consumer’s area or town as far as possible. There may be either surface or ground surfaces and the selection of the source depends upon their factors.
- Cost of water supply project
It should be able to supply water of good quality and quantity at less cost. The cost depends upon the location, ground level of the city and source distance between source and distribution area, etc. The gravity flow system is generally cheaper than pumping.
Q.9) What are the sources of underground water?
The water that is found below the surface of the earth is known as underground water or groundwater and the source ( device) containing the groundwater is known as underground water or ground sources of water.
The quality of groundwater is generally good due to natural filtration as it percolates then infiltrate deeper strata.
The various forms of ground sources are as follows:
- Gravity (depression, surface, artesian)
- Infiltration galleries
- Infiltration wells
- Wells and tube wells
- Open/ dug/ draw well (shallow and dip)
- Tube well (shallow and deep) Strainer, cavity pipe, slotted, perforated
- Artesian well
Q.10) What are the sources of surface water?
The water which is found on the surface of the earth is known as surface water and the source containing (device) the surface water is surface sources. River, stream, ponds, etc are surface sources of water.
- It starts from the run-off and ends at the ocean/reservoir.
- It is formed by the combination of the stream and springs, etc.
- It may be snow-fed, rain-fed, or both.
- It starts from run-off and ends in the river.
- Discharge is more in rainy seasons and either zero or less discharge in the dry season.
- Water from the stream is good in quality.
- A natural basin with an impervious bed in the mountain region is known as a lake.
- It collects water from springs, rain, stream, etc.
- The quality of water mainly depends upon the characteristics of the catchment.
- A naturally depressed land or artificially excavated land filled with water is called a pond.
- It is found in mountains, hills,s and plain areas of Nepal.
- It is constructed for swimming, fish farming, and irrigation purposes.
Q.11) Write the objectives of the water supply system.
An organized water supply system has the following objectives:
- To provide safe wholesome water to the consumers in adequate quantity efficiency at low cost.
- To make adequate provisions for emergencies like fire fighting, festivals, meeting, etc.
- To make water available within easy reach of consumers.
- To supply water rich in reliability, quality, quantity in an effective and efficient way.
- To reduce environmental pollution and unemployment.
- To improve the economic condition of the locality and maintain better sanitation.
- To protect from waterborne disease.
Q.12) What are the different types of water?
The definitions of the different types of water are explained below.
- Pure and impure water
Pure water is pure H2o while impure water is H2o with other chemicals. Pure and impure water have different boiling points. Impure water is that water that has impurities such as salts, hardness, metal ions, and so on. Actually, pure water is never found in nature.
- Portable and wholesome water
The water which is clear and free from suspended matter and smell should not contain an excess of dissolved impurities, which is known as portable water. It should also be testy, safe, and suitable for drinking and domestic purposes.
The water which contains impurities up to a certain limit such that it may not be harmful to human health is known as wholesome water. In other words, wholesome water is that water that is not chemically pure but does not contain anything harmful to human health.
- Polluted and contaminated water
Water containing excess amounts of impurities such as minerals salts, gases, micro-organisms, etc is called polluted water.
The water which contains pathogenic bacteria is known as contaminated water. It is always polluted and unfit for use.
Q.13) Write the importance of water.
Two-third of the earth’s surface is covered by water and the human body consists 75% of it, from it is clear that water is one of the prime elements responsible for life on earth.
Without water we can’t survive everywhere water is needed for various purposes as follows:
- For cooking and drinking
- For heating and air cooling
- For growing crops
- For bathing and washing
- For watering lawns and gardens
- For street washing
- For fire fighting
- For recreation in swimming pool, foundations and cascades
- For power generation and various industrial processes, etc.
Ancient civilizations developed along the river banks due to the availability of water for domestic and irrigation purposes.