NCERT 7th Class (CBSE) Science: Wastewater Management

Question: How can you control the generation of sewage at homes?

Answer: The generation of sewage at homes can be controlled-

1. By monitoring what is thrown in the drain.
2. The disposal of cooking oil and fats down the drain leads to blockage. The fats and oils harden and block the pipes which is hazardous. Oils and fats must always be disposed off in dustbins.
3. Chemicals like paints, solvents, insecticides, motor oil and medicines may kill decomposer microbes that help purify water. So, these must never be thrown down the drain.
4. Used tea leaves, solid food remains, soft toys, cotton, napkins etc. should also be thrown into the dustbin. These wastes choke the drains. They do not allow the free flow of oxygen. This hampers the degradation process of the garbage by microorganisms.

Question: Explain the importance of sanitation.

Answer: Sanitation is an hygienic practice of ensuring cleanliness of our surroundings for maintain good health. Sanitation can be maintained by the proper disposal of refuse or the waste produced due to human activities. This can be done by proper wage of toilets, sewer systems, treatment of wastewater, safe disposal of garbage and implementing practices of personal hygiene.

A few steps that can be taken for better sanitation are:

1. People in rural and urban areas should be educated about sanitation.
2. The government should provide monetary aid for the construction of proper sewerage.
3. Sufficient toilets should be constructed in public places. If sanitation in such places is poor, diseases can spread fast as people travelling from one place to another can act as carriers of diseases.
4. Washbasins with clean water supply and soap should be provided.
5. Proper dustbins should be provided for the disposal of refuse.
6. Surroundings must be kept clean by not allowing water to stagnate because stagnated water can be a breeding place for mosquitoes and other insects.
7. All the open drains should be covered.
8. Garbage cans and public dustbins must be cleared every day in order to prevent diseases.

Question: What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.

Answer: Waste water from houses, industries, hospitals etc. and rain water that runs over land containing waste matter such as excreta.

Sewage water contains harmful substances with it which washes off roads and rooftops. It is a complex mixture containing suspended solids, organic and inorganic impurities, nutrients, saprotrophic and disease causing bacteria and other microbes. So, when sewage discharge untreated into rivers or seas, it will be dangerous for aquatic plants and animals.

Question: Why is it necessary to treat sewage before disposing it off in a water body.

Answer: It is necessary to treat sewage as sewage treatment consists of remaining solid materials from sewage. It is necessary because if we put the same water in water bodies, it can cause harm to human and aquatic life.

Question: Name four diseases that can be caused by improper drainage system.

Answer: Yellow fever, malaria, dengue and cholera.

Question: Define the following: Scum, sludge, Industrial effluents, Clarified water, Contaminants, Manhole.

Answer: Scum: The waste material which floats in the settling tank is called scum.

Sludge: The waste material that settles down at the bottom of the settling tank is called sludge.

Industrial effluents: The waste water from the industries may contain lubricant oil, paints, dye, chemicals and metals. These are called industrial effluents.

Clarified water: The water that is left after the removal of sludge and scum.

Contaminants: Sewage water contains detergents, toxic chemicals, food wastes, blood, human animal tissues etc. These kinds of materials present in the waste water is called contaminants.

Manhole: The junction of the sewerage from different homes of the street or lane has an opening, which can be used for maintenance of the sewerage by the personnel from the city corporation. This opening is called a manhole.