Class 7 Science Chapter 13 MCQ

The used water should not be wasted. Use water or waste water could be reduced after cleaning it. We must clean the used water by removing various impurities from it, before it is re-used or released into the environment (such as river, lakes sea or ground).

Here, all the statements are correct. Hence, your answer will be option [D].

Biogas and sludge both are the products of wastewater treatment.

Here, all the statements are correct. Hence, your answer will be option [D].

Open drain system is a breeding place for flies, mosquitoes and organisms which cause diseases.

Asthma is not a water-borne disease. It is caused by polluted air.

Here, all the statements are correct. Hence, your answer will be option [D].

The system of a network of pipes used for taking away wastewater from homes or public buildings to the treatment plant is known as “sewerage”.

The full form of WWTP is – Waste Water Treatment Plant. A place where waste water or sewage from houses and other buildings is brought for processing is called waste water treatment plant. The wastewater treatment plant is also called sewage treatment plant.

Phosphate is an inorganic impurity of the sewage.

Here, all the statements are correct. Hence, your answer will be option [D].

In a filtration plant, water is filtered using layers of sand, fine gravel and medium gravel.

Here, all the statements are correct. Hence, your answer will be option [D].

Sewers are not considered as sources of wastewater. Homes, industries and hospitals are considered as a source of waste-water.

It may be necessary to disinfect the treated water with chemicals like chlorine or ozone before releasing it into the distribution system. The ozone layer is a thin part of the Earth’s atmosphere that absorbs almost all of the sun’s harmful ultraviolet light or rays.

Clean water is a basic need of human beings. Unfortunately, clean water that is fit for drinking is not available to all the people. The drinking of contaminated water by the people is responsible for large number of water related disease and even death. By releasing the grave situation created by the extreme shortage of clean and safe drinking water in many parts of the world, the General Assembly of United Nations on the World Water Day on 22nd March 2005 has declared the period 2005 to 2015 as the International Decade for action on “water for life”.

We know that the solid part of sewage is called sludge. The sludge is taken out from the bottom of first sedimentation tank and put into a large, close tank called the digester tank. In the digester tank, many types of “anaerobic bacteria” decompose the organic matter present in the sludge to produce biogas also called sewage gas.

Here, all the statements are correct. Hence, your answer will be option [D].

Sometimes, it may be necessary to disinfect the treated water with chemicals like chlorine or ozone before releasing it into the distribution system. The purpose of disinfection in the treatment of wastewater is to eliminate completely the harmful micro-organisms in the water to be discharged back into the environment.

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

The biogas produced is used as a fuel. The human waste or human excreta can be used in a biogas plant along with cow dung for making biogas. So, in many villages, human excreta from the toilet seats in the homes flows directly into biogas plant through covered drains.

The generation of waste is an essential part of human activities. But we can limit the type of waste and quality of waste produced. We can also help in the proper disposal of waste. It is the responsibility of the Municipality of the area to maintain sanitization at public places but we can also contribute in this effort. All of us have a role to play in keeping our environment clean and healthy. Adopting good sanitization practices should become our way of life. It will keep all of a healthy and happy.

The aeroplanes have a special type of toilet called “vacuum toilets”. So, the human excreta or sewage in an aeroplane is disposed of through vacuum toilets. When we flush the toilet in an aeroplane, then a valve opens in a pipeline which has vacuum inside it. The vacuum in the pipeline sucks the human excreta from the toilet seat with a great force making a loud noise and carries it into a tank on board the aeroplane. When the aeroplane lands at an airport, then the tank containing all the human excreta is emptied into a sewer line into the ground through connecting pipes.

Composting pits are used to provide composting toilets. A composting toilet is a self- contained human waste disposal unit which is not connected to a sewer line or a septic tank. A composting toilet consists of a toilet seat fixed a top a composting chamber which is further connected to a drying chamber. The composting chamber breaks down the human excreta with the help of aerobic microorganisms (such as aerobic bacteria) and converts it into a compost. The composting toilets are used where the water supply is limited or not available at all.