Lesson: Wastewater Story

Multiple choice questions

Question: 1

Which of the following is waste water?

(a)            Water trickling from a damaged tap

(b)            Water coming out of a shower

(c)            Water flowing in a river

(d)            Water coming out of a laundry

Solution:

d

Question: 2

Sewage is mainly a ________.

(a)            Liquid waste

(b)            Solid waste

(c)            Gaseous waste

(d)            Mixture of solid and gas

Solution:

a

Question: 3

Which of the following is/are products of wastewater treatment?

(a)            Biogas

(b)            Sludge

(c)            Both biogas and sludge

(d)            Aerator

Solution:

c

Question: 4

Open drain system is a breeding place for which of the following.

(a)            Flies

(b)            Mosquitoes

(c)            Organisms which cause diseases

(d)            All of these

Solution:

d

Question: 5

Water polluted by various human activities, causes a number of water borne diseases. Which of the following is not a water borne disease?

(a)            Cholera

(b)            Typhoid

(c)            Asthma

(d)            Dysentery

Solution:

c

Question: 6

Pick from the following, one chemical used to disinfect water.

(a)            Chlorine

(b)            Washing soda

(c)            Silica

(d)            Coal

Solution:

a

Question: 7

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

(a)            Sewers

(b)            Sewerage

(c)            Transport system

(d)            Treatment plant

Solution:

b

Question: 8

Which of the following is a part of the inorganic impurities of sewage?

(a)               Pesticides

(b)               Urea

(c)               Phosphates

(d)               Vegetable waste

Solution:

c

Question: 9

In a filtration plant water is filtered using layers of

(a)            Sand and clay

(b)            Clay and fine gravel

(c)            Sand and fine gravel

(d)            Sand, fine gravel and medium gravel

Solution:

d

Question: 10

Which of the following is not a source of waste water?

(a)            Sewers

(b)            Homes

(c)            Industries

(d)            Hospitals

Solution:

a

Question: 11

Why are open drains a concern?

Solution:

Open drains are a concern because they create unhygienic and unsanitary conditions. Flies, mosquitoes and other insects that breed in the dirty water are exposed to environment causing many diseases such as malaria, dengue etc.

Question: 12

State whether the following statements are True or False. In case a statement is false, write the correct statement.

(a)               Sewage is a solid waste which causes water pollution and soil pollution.

(b)               Used water is wastewater.

(c)               Wastewater could be reused.

(d)               Where underground sewerage systems and refuse disposal systems are not available, the high cost on-site sanitation system can be adopted.

Solution:

(a)               False, Sewage is a liquid waste which causes water pollution and soil pollution.

(b)               True

(c)               True

(d)               False, where underground sewerage systems and refuse disposal systems are not available, a low cost on-site sanitation system can be adopted.

Question: 13

How are open drains harmful for human health?

Solution:

The sight of open drains is disgusting. The situation worsens in rainy season when the clogged drains start overflowing. Mostly unhygienic and unsanitary conditions prevail due to open drains. Flies, mosquitoes and other insects that breed in open drains are exposed to environment further causing many diseases such as, Malaria, Dengue etc.

Question: 14

Name two inorganic impurities present in sewage.

Solution:

Nitrates and Phosphates

Question: 15

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

Solution:

Human faeces, fruits and vegetable wastes

Question: 16

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

Solution:

(i)                 Septic tanks

(ii)              Composting pits

Question: 17

A man travelling in a train threw an empty packet of food on the platform. Do you think this is a proper waste disposal method? Elaborate.

Solution:

This was not a proper waste disposal method. He should have thrown the waste in a nearby dustbin orcarried it until a proper place was found to dispose it. Waste, not properly disposed, may go into the drains and choke them. Waste strewn here and there also makes public places dirty and unhygienic.

Question: 18

Why should we not throw?

(a)               Used tea leaves into sink?

(b)               Cooking oil and fats down the drain?

Solution:

(a)            Used tea leaves should not be thrown into sink; instead they must be thrown in dustbins, because tea leaves can choke the drains. Tea leaves also do not allow free flow of oxygen, which hampers the degradation process.

(b)            Cooking oils and fats should not be thrown down the drain. They should be thrown in the dustbins because cooking oils and fats can harden and block the pipes.

Question: 19

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

Solution:

Question: 20

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.

Solution:

(c), (e), (d), (b), (a)

Question: 21

Three statements are provided here which define the terms $–$ (a) sludge (b) sewage and (c) wastewater. Pick out the correct definition for each of these terms.

(a)               The settled solids that are removed in wastewater treatment with a scraper.

(b)               Water from kitchen used for washing dishes.

(c)               Wastewater released from homes, industries, hospitals and other public buildings.

Solution:

(a)               Sludge

(b)               Wastewater

(c)               Sewage

Question: 22

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

Solution:

(x) $\stackrel{}{\to }$ Sewage

(a) $\stackrel{}{\to }$ Nitrates, phosphates, and metals

(b) $\stackrel{}{\to }$ Phosphorus and nitrogen

Question: 23

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

Solution:

Sewage is liquid waste consisting of dissolved and suspended impurities called contaminants.

Organic impurities- human faeces, animal waste, oil, urea (urine), pesticides, herbicides, fruit, and vegetable waste, etc.

Inorganic impurities- nitrates, phosphates, and metals

Question: 24

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

Solution:

Sewage is a liquid waste which is produced during wastewater treatment and causes water and soil pollution. Generally, in our homes or public buildings, one set of pipes is used for bringing clean water and another set of pipes for taking away wastewater. The pipes that take away waste waters are called sewers. Sewers create a network of big and small pipes, and are collectively known as sewerage. Sewerage is like a transport system that carries sewage from the point of being produced to the point of disposal, i.e. treatment plant.

Question: 25

Fill in the blanks in the following statements using words given in the box.

air, hand pumps, cholera, water, large, ground

A very _________ number of our people defecate in the open. It may cause _________ pollution and soil pollution. Both the surface water and _________ water get polluted. _________ water is the source for wells, tubewells and _________. Thus it becomes the most common route for _________ borne diseases like _________, dysentery, etc.

Solution:

(i)                 Large

(ii)              Water

(iii)            Ground

(iv)             Ground

(v)               Handpumps

(vi)             Water

(vii)          Cholera

Question: 26

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

Solution:

Treatment of wastewater involves physical, chemical, and biological processes that remove the substances, which contaminate the wastewater.

(a)            The first step of wastewater treatment is the physical removal of large objects such as plastics, cans, sticks, rags etc. These objects are passed through the bar screens or metal rods which separate the objects from the water.

(b)            After the objects are removed from the water by the bar screens the liquid enters a large sand removal tank called a grit chamber. The incoming wastewater is kept still, so that if there are any heavy solids like sand or gravel present in it, they will settle down at the bottom.

(c)            From the grit chamber, the water enters another large tank called a Clarifier. It is a circular sedimentation basin which separates the remaining solid objects, such as faeces, from the water. The solid objects which settle down at the bottom is called sludge. The sludge is removed with a scraper and transferred to a separate tank it is decomposed by anaerobic bacteria.

(d)            After the physical impurities are removed from the wastewater, the liquid enters an aeration basin. Air is pumped into the clarified water which allows microorganisms to grow. Bacteria consume human waste, food waste, soaps and other unwanted matter still remaining in the clarified water.

(e)            The microorganisms consume human waste, food waste and other unwanted matter and settle down at the bottom of the tank as activated sludge. Activated sludge is actually dark mud which is rich in bacteria and protozoa.

(f)             From the aerated basin, the water enters the secondary clarifier for further removal of any impurities. The activated sludge is sent to the digester where the bacteria further breaks down the material.

(g)            The material which is removed from the digester and sand drying beds or machines is processed into a product called bio solids. Bio solid is used as manure, returning organic matter and nutrients to the soil.

(h)            The final step in the treatment of wastewater is the use of a disinfectant such as chlorine to kill harmful bacteria still in the treated water. Sometimes ultraviolet light is used instead of chemicals. The treated water is then discharged into the sea, a river or into the ground.

Question: 27

Think and suggest some ways to minimise waste and pollutants at their source, taking your home as an example.

Solution:

(a)            Cooking oil and fats should not be thrown down the drain and instead should be thrown in dustbins.

(b)            Chemicals like paints, solvents, insecticides, motor oil, and medicines may kill microbes that help purify water. So, these should not be thrown down the drain.

(c)            Used tealeaves, solid food remains, soft toys, cotton, sanitary towels, etc. should also be thrown in the dustbin.

(d)            We should not defecate in the open.