Wastewater Story - Class 7 Biology - Extra Questions

Name two chemicals used to disinfect water. 

$$\textbf{Solution:}$$


 $$\bullet$$Water disinfection is a commonly utilized procedure in the distribution of water in a certain region.

 $$\bullet$$In this process few chemicals are used to kill microorganisms present in water.

Two chemicals used to disinfect water are Ozone and chlorine.

 $$\bullet$$Ozone: Ozone has great actions against bacteria and virus.

 $$\bullet$$Chlorine: It is a highly effective disinfectant.


Hence, Ozone and chlorine are the two chemicals used to disinfect water. 



What happens when cooking medium is made to flow down the drain. 

If we flow down a cooking medium, it will block the drain pipes and clog the pores of soil.


State reasons for the following:-
The water you drink now-a -days is not safe.

Water pollution is common now-a-days. Water from factories and other sources is let into water bodies without treatment. This water contains harmful chemicals and pathogens that may adversely affect health. Such water is not suitable for human consumption and if consumed may lead to various diseases.


The presence of coliform bacteria beyond the prescribed limit indicates ........................ by disease causing micro-organisms.

Coliform bacteria are rod-shaped gram-negative bacteria which are found in the gut of humans. For example, Escherichia coli. These bacteria are non-spore forming and can ferment lactose  Presence of coliform bacteria in water bodies indicates faecal contamination of water. Contamination of water with faecal matter can cause severe illness as it also indicates the presence of several other disease-causing microorganisms. 
So, the correct answer is 'contamination.


What is sludge? Explain how it is treated.

  • Sludge is a semi-solid slurry that can be produced from a range of industrial processes, from water treatment, wastewater treatment or on-site sanitation systems or Semi-solids such as faeces that settle down during wastewater treatment are called sludge. 
  • This sludge is removed using a scraper and then transferred to a tank where it is decomposed by anaerobic bacteria to produce biogas. This biogas is used as a low-cost fuel for heating, cooking, etc. It is also used to produce electricity. 
  • Dried Sludge is used as manure instead of taking up space in a landfill or other disposal facility to improve and maintain productive soils and stimulate plant growth because it has nutrient-rich organic materials.


Dried ............ is used as manure.

$$\textbf{Correct answer: Sludge}$$

$$\textbf{Solution:}$$

$$\bullet$$Sludge is the solid component of waste water that has accumulated.It's commonly used as manure since it's made of biodegradable elements, primarily food and human waste, and it's an excellent manure for the plants.

Hence, sludge is frequently utilized as a manure.

 

 



Explain the Junction of bar screens in a wastewater treatment plant.

$$\textbf{Solution:}$$
$$\bullet$$ A bar screen is a mechanical filter in a wastewater treatment facility that removes physical pollutants.
$$\bullet$$ Large solid objects, napkins, plastics, cans, and other pollutants in water are examples.
$$\bullet$$ Large solid particles in wastewater, such as rags, napkins, sticks, cans, plastic bags, polyethene, and other materials, are removed by passing the wastewater through a bar screen.
$$\bullet$$ It is a part of the primary filtration flow and is often installed at the influent to a wastewater treatment plant as the first, or preliminary, degree of filtration.




What is the source of water under the ground? 

In ground, rain that seeps from the surface seeps into the ground. Thus, rain water is the major source of water.


Explain the relationship between sanitation and disease.

  • Sanitation refers to public health conditions related to clean drinking water and adequate treatment and disposal of human wastes and sewage. Preventing human contact with faeces is part of sanitation, as is hand washing with soap.
  • RELATIONSHIP BETWEEN SANITATION AND DISEASE:
a) In our country, a large number of people even today do not have sewerage facilities and thus defecate in open fields, railway tracks, etc. The untreated human excreta thus pollute soil and water sources including the underground water. When this contaminated water is used for drinking, it can cause diseases such as cholera, typhoid, hepatitis, dysentery, etc. which may even lead to death. Therefore, the lack of sanitation resulting in the drinking of contaminated water can cause health problems. 
b) If sanitation is there, no disease will occur, but if sanitation is not there various types of disease will occur and spread. So sanitation should be kept to avoid disease.


The terms sewage, sewers and sewerage are interlinked with each other. Can you explain, how?

Sewerage is the system applied in buildings for discharging wastewater known as sewage. It is achieved through a network of pipes, known as sewers, which are connected together. 


Why are open drains a concern? 

Mosquitoes fly mostly breed in dirty water or areas and in open water. Open drains are dirty and have wastes in it, which makes it suitable for mosquitoes and flies to breed in there. 
Open drains are dangerous. Anyone can fall into open drains.


Fill in the blanks in the given passage.
The rainwater and ________________ from other sources such as rivers and ponds seeps through the ______________ and fills the empty spaces and cracks deep below the ground. The process of seeping of water into the ground is called ______________.

The rainwater and water from other sources such as rivers and ponds seeps through the soil and fills the empty spaces and cracks deep below the ground. The process of seeping of water into the ground is called infiltration. 


How are open drains harmful for human health? 

Open drains harmful for human health-
i) Open drains have foul smell and by that they cause air pollution.
ii) Mosquitoes, flies mostly breed in dirty water or areas and in open water.
iii) Humans suffer from water-borne diseases like cholera, typhoid, diarrhoea, as it infects the clean water too. 


Name two alternative arrangements for sewage disposal where there is no sewerage system. 

Two alternative arrangements for sewage disposal where there is no sewerage system-
i. The low cost on-site sanitation systems can be adopted like septic tank.
ii. Composting toilets- It is a dry toilet. In this, excreta, which is without any water or smell is processed by decomposition aerobically. 


Animal waste, oil and urea are some of the organic impurities present in sewage. Name two more organic impurities present in sewage. 

There are both organic and inorganic impurities present in the sewage. Organic impurities present in sewage are-
(I). Vegetable and fruit peel waste, (ii). Pesticides 


Name two inorganic impurities which can be found in sewage. 

There are both organic and inorganic impurities present in the sewage. Inorganic impurities present in sewage are-
i. Nitrate ii. Phosphate 


Match the items of Column I with the items of Column II with reference to sewage. 

  • Inorganic impurities are nitrates and phosphates of different metals.
  • Organic impurities are pesticides and herbicides.
  • Phosphorus and nitrogen are nutrients present in the soil for plants.
  • Cholera and typhoid are water-borne diseases caused by bacteria.


What are the different types of inorganic and organic impurities present in the sewage?

Sewage contains mostly organic and inorganic impurities.
The organic impurities are biodegradable and include human faeces, oil, animal waste, urea (urine), pesticides, herbicides, fruit and vegetable wastes, etc.
The inorganic impurities are non-biodegradable and include metals, phosphates, nitrates, etc.


What is sewage?

Sewage is wastewater released by homes, industries, hospitals, offices, and other users. It also includes rainwater that has run down the street during a storm or heavy rain. The water that washes off roads and rooftops carries harmful substances with it. Sewage is liquid waste. Most of it is water, which has dissolved and suspended impurities.


Complete the following conceptual picture.
1824854_fec3a92f30114a2ea95a25c199a694e0.png

The conceptual picture is completed as
1854564_1824854_ans_004716c5f8f34705ac2e6f56a9127fb2.png


A mixture (x) in water contains suspended solids, organic impurities, inorganic impurities and nutrients (a), (b)disease causing bacteria and other microbes. Give names for (x), (a) and (b)? 

The names are -
$$\to \ x$$ is wastewater or sewage. 
$$\to$$ (a) is nitrogen or phosphorus.
$$\to$$ (b) is Vibrio coma or Salmonella typhi.


Given below is a jumbled sequence of the processes involved in a wastewater treatment plant. Arrange them in their correct sequence. 
(a) Sludge is scraped out and skimmer removes the floating grease.
(b) Water is made to settle in a large tank with a slope in the middle.
(c) Large objects like plastic bags are removed by passing wastewater through bar screens.
(d) Sand, grit and pebbles are made to settle by decreasing the speed of incoming wastewater.
(e) Wastewater enters a grit and sand removal tank. 

The correct sequence is- c,e,d,b,a
(c) Large objects like plastic bags are removed by passing wastewater through bar screens.
(e) Wastewater enters a grit and sand removal tank.
(d) Sand, grit and pebbles are made to settle by decreasing the speed of incoming wastewater.
(b) Water is made to settle in a large tank with a slope in the middle.
(a) Sludge is scraped out and skimmer removes the floating grease. 


What do you mean by composting?

The process of converting plant and animal wastes, kitchen wastes like left-over food, vegetable, and fruit peels, into nutrient-rich manure is called composting. The biodegradable components of garbage are used to make the compost through the process of composting. The waste materials are kept in pits and covered with soil. Microorganisms decompose these waste materials and manure is obtained.
The set of items that are good for making compost are eggshells, vegetable and fruit peels, tea leaves, etc.


Describe various steps of cleaning wastewater in a wastewater treatment plant.

The steps performed for cleaning the wastewater before it is released into the water bodies is known as the wastewater treatment plant. The steps are -
i. A bar screen is placed through which the wastewater is passed to eradicate impurities from it like sticks, rags, cans, plastic packets, etc. 
ii. Then a grit is placed after the bar screen, through which the filtered water is passed for more filtration of sand, grit, and pebble to settle down. 
iii. Now, the water is passed to a large tank which is sloppy towards the middle and impurities like faeces settle down and later are removed with a scraper. The leftover wastewater is known as sludge. 
iv. The sludge is further treated in a bio-gas plant for the production of biogas. The sludge had oils and fats remained it in which are removed by a skimmer. 
v. The treated product is known as clear water, which is treated for the growth of aerobic bacteria by pumping air in it. The air consumes soap. human waste and any unwanted matter. It is kept undisturbed for several hours for the microbes to settle down at the bottom of the tank as activated sludge. The water is removed from the top. 
vi. The completely treated water is discharged into a sea or river or into the ground. 


Class 7 Biology Extra Questions