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).

Sewage is mainly a liquid waste. The waste water and faeces from homes and other buildings which is carried away in sewers, called sewage.

Biogas and sludge both are the products of wastewater treatment.

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

Sewage is a liquid waste which causes water pollution as well as soil pollution.

Chlorine is the chemical used as water disinfectant.

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 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.

In the vermi processing toilet, the human excreta is treated by earthworms in a pit.

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

In the that processing toilet, the human excreta is treated by earthworms in a pit not by cockroaches and round worms. The earthworms gradually eat up all the organic matter present in human excreta, decompose it and pass out from their body in the form of worm casting also called vermi-cakes.

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.

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 sewage is a complex mixture containing suspended solids, organic and inorganic impurities, nutrients, saprotrophic and disease-causing bacteria and other microbes. a)Inorganic impurities – Nitrates, Phosphates, metals. b)Organic impurities –Human faeces, animal waste, oil, urea (urine).

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 drinking of water contaminated with untreated human excreta becomes the most common route for the spreading of water-borne diseases. Some of the water borne diseases spread in this way are, Cholera, Typhoid, Polio, Meningitis, Hepatitis and Dysentery. Many common infections can spread by airborne transmission are tuberculosis, influenza, small pox etc.

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

It has been suggested that we should plant “eucalyptus trees” all along the sewage ponds. This is because eucalyptus trees absorb all the surplus waste water from the sewage ponds rapidly and release pure water vapor into the atmosphere through transpiration. In this way, eucalyptus tree help in purifying wastewater quite rapidly.

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

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.

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