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Q1. Why is water called “our lifeline”?

A Because it is used only for drinking

B Because all living organisms depend on water for survival and it is essential for life processes

C Because it is only used for cleaning

D Because it is available in unlimited quantity

Water is called our lifeline because it is essential for all life processes. Every living organism needs water to survive, grow, and carry out metabolic functions. It is not only for drinking or cleaning, and it is not unlimited.

Q2. What is sewage?

A Clean rainwater collected from rooftops

B The wastewater released from homes, industries, hospitals, and other buildings, containing dissolved and suspended impurities

C Drinking water supplied by the municipality

D Water found in rivers and lakes

Sewage is the wastewater that comes from homes, industries, hospitals, and other buildings. It contains both dissolved and suspended impurities. It is not clean rainwater, drinking water, or natural river/lake water.

Q3. Which of the following is an example of an organic impurity in sewage?

A Nitrates and phosphates from fertilizers

B Human waste (feces and urine), food waste, and vegetable peels

C Heavy metals like lead and mercury

D Plastic bottles and bags

Organic impurities are derived from living organisms. Human waste, food waste, and vegetable peels are organic. Nitrates and phosphates are inorganic chemicals, heavy metals are inorganic, and plastic bottles are non-biodegradable solids.

Q4. Which of the following is an example of an inorganic impurity in sewage?

A Leftover cooked rice

B Nitrates, phosphates, and heavy metals like lead, mercury, and arsenic

C Human feces

D Vegetable peels

Inorganic impurities are mineral-based and not derived from living organisms. Nitrates, phosphates, and heavy metals are inorganic. Leftover rice, human feces, and vegetable peels are organic.

Q5. What are the nutrients commonly found in sewage that can cause water pollution?

A Iron and copper

B Nitrates and phosphates

C Sand and clay

D Oxygen and hydrogen

Nitrates and phosphates are common nutrients found in sewage from human waste, food waste, and detergents. They can cause excessive algae growth (eutrophication) in water bodies. Iron, copper, sand, clay, oxygen, and hydrogen are not the primary nutrient pollutants.

Q6. Which of the following diseases can be caused by drinking water contaminated with sewage?

A Diabetes

B Cholera, typhoid, and hepatitis A

C Cancer

D Asthma

Cholera, typhoid, and hepatitis A are waterborne diseases caused by pathogens present in sewage-contaminated water. Diabetes, cancer, and asthma are not caused by drinking contaminated water.

Q7. What is the main purpose of a Wastewater Treatment Plant (WWTP)?

A To add more pollutants to water

B To remove impurities from sewage and make it safe to release into the environment or reuse

C To store drinking water

D To generate electricity

A WWTP removes impurities from sewage so that the treated water can be safely released into the environment or reused. It does not add pollutants, store drinking water, or generate electricity primarily.

Q8. What is sanitation?

A The process of polluting water

B The provision of facilities and services for the safe disposal of human waste and the maintenance of hygienic conditions

C The construction of large buildings

D The storage of drinking water

Sanitation involves providing facilities for safe waste disposal and maintaining hygienic conditions to prevent disease. It is not polluting water, constructing buildings, or storing drinking water.

Q9. What is a sewer?

A A pipe or underground channel that carries sewage from homes and buildings to a treatment plant or disposal point

B A type of water filter

C A chemical used to clean water

D A disease caused by dirty water

A sewer is a pipe or underground channel that transports sewage. It is not a filter, chemical, or disease.

Q10. What is aeration in the context of wastewater treatment?

A Adding more pollutants to water

B The process of bubbling air (oxygen) through sewage to promote the growth of aerobic bacteria that break down organic matter

C Filtering water through sand

D Adding chlorine to kill bacteria

Aeration is the process of adding air to sewage to support aerobic bacteria that consume organic waste. It is not adding pollutants, filtering, or adding chlorine.

Q11. What is the difference between aerobic and anaerobic bacteria?

A Aerobic bacteria need oxygen to survive; anaerobic bacteria do not need oxygen and are often killed by it

B Aerobic bacteria cause disease; anaerobic bacteria are harmless

C There is no difference between them

D Anaerobic bacteria need oxygen; aerobic bacteria do not

Aerobic bacteria require oxygen for respiration, while anaerobic bacteria survive without oxygen and may even be killed by it. Both types can be beneficial or harmful.

Q12. Which stage of a wastewater treatment plant involves allowing solid particles to settle at the bottom of a tank?

A Aeration

B Sedimentation (primary treatment)

C Disinfection

D Filtration

Sedimentation is the process where solid particles settle at the bottom of a tank due to gravity. This is a physical treatment step. Aeration adds air, disinfection kills pathogens, and filtration removes particles.

Q13. What is the purpose of adding chlorine or using UV light in wastewater treatment?

A To add colour to the water

B To disinfect the water by killing harmful bacteria, viruses, and other pathogens

C To make the water taste better

D To remove solid particles

Chlorine and UV light are used to kill pathogens in treated water, making it safe for release or reuse. They do not add colour, improve taste, or remove solids.

Q14. What happens if untreated sewage is released directly into a river?

A The river becomes cleaner

B The oxygen level in the river decreases, fish die, and waterborne diseases spread

C The river water becomes safe to drink

D Nothing happens

Untreated sewage pollutes rivers, depleting oxygen, killing aquatic life, and spreading diseases. It does not clean the river or make it safe.

Q15. Which of the following is a common disease caused by bacteria present in contaminated water?

A Malaria

B Cholera

C Dengue

D Cancer

Cholera is caused by the bacterium Vibrio cholerae, which is spread through contaminated water. Malaria and dengue are mosquito-borne, and cancer is not waterborne.

Q16. What is the role of aerobic bacteria in a wastewater treatment plant?

A To produce methane gas

B To break down organic impurities in the presence of oxygen

C To settle at the bottom of tanks

D To disinfect the water

Aerobic bacteria consume organic waste in the presence of oxygen during aeration. They help remove organic impurities. Anaerobic bacteria produce methane, and disinfection kills pathogens.

Q17. Why is proper sanitation important for preventing disease?

A Because it makes the city look beautiful

B Because it prevents human waste from contaminating drinking water sources and living areas, stopping the spread of pathogens

C Because it increases the amount of waste

D Because it has no effect on health

Sanitation prevents disease by safely disposing of human waste, keeping drinking water sources and living areas free from contamination. It is not about appearance, increasing waste, or having no effect.

Q18. What is the first step in a typical wastewater treatment plant?

A Aeration

B Sedimentation

C Screening to remove large objects like sticks, rags, and plastic bottles

D Chlorination

The first step is screening to remove large debris that could damage equipment. Aeration, sedimentation, and chlorination come later in the treatment process.

Q19. What happens to the sludge removed from sedimentation tanks in a WWTP?

A It is dumped directly into rivers

B It is sent to a sludge digester where anaerobic bacteria break it down, producing biogas (methane) that can be used as fuel

C It is burned immediately

D It is buried in people’s gardens

Sludge is treated in a sludge digester by anaerobic bacteria, producing biogas that can be used as fuel. It is not dumped, burned, or buried directly.

Q20. Which of the following is a virus that can be spread through contaminated water?

A Vibrio cholerae (bacteria)

B Salmonella typhi (bacteria)

C Hepatitis A virus

D Plasmodium (parasite)

Hepatitis A is a viral disease spread through contaminated water. Vibrio cholerae and Salmonella typhi are bacteria, and Plasmodium is a parasite.

Q21. What is the meaning of “potable water”?

A Water that is polluted and unsafe to drink

B Water that is safe enough to drink without causing health problems

C Water that is only used for washing clothes

D Water that has been used in factories

Potable water is safe for drinking and does not pose health risks. It is not polluted, only for washing, or factory water.

Q22. Why is it dangerous to swim in a river that receives untreated sewage?

A The water is too cold

B The water contains disease-causing microorganisms (pathogens) that can cause infections if swallowed or enter through cuts

C The water is too hot

D The water is too deep

Untreated sewage contains pathogens that can cause infections if a person comes into contact with the water. It is not about temperature or depth.

Q23. What is a septic tank?

A A tank that stores drinking water

B An underground tank used for on-site sewage treatment in areas without connection to a central sewer system

C A tank used for fish farming

D A type of water filter

A septic tank is an underground system for treating sewage on-site, typically in rural or unsewered areas. It is not a water storage tank, fish tank, or filter.

Q24. What is the purpose of the grit chamber in a wastewater treatment plant?

A To add chemicals to the water

B To remove heavy inorganic particles like sand, gravel, and small stones that could wear down equipment

C To kill bacteria with chlorine

D To add oxygen to the water

The grit chamber removes heavy inorganic particles to protect equipment from wear. It does not add chemicals, kill bacteria, or add oxygen.

Q25. How do anaerobic bacteria help in wastewater treatment?

A They break down organic matter in the absence of oxygen, reducing sludge volume and producing methane gas

B They add oxygen to the water

C They remove heavy metals

D They kill all viruses

Anaerobic bacteria break down organic matter without oxygen, reducing sludge and producing methane gas (biogas). They do not add oxygen, remove heavy metals, or kill viruses.

Q26. What is eutrophication?

A The process of cleaning water with chlorine

B The excessive growth of algae in water bodies due to excess nutrients (nitrates and phosphates) from sewage and fertilizers

C The removal of solid particles from water

D The addition of oxygen to water

Eutrophication is the overgrowth of algae caused by excess nutrients, leading to oxygen depletion and harm to aquatic life. It is not cleaning, removing solids, or adding oxygen.

Q27. Which of the following is a sign that a water body is polluted with sewage?

A Clear, clean-smelling water

B Foul odour (bad smell), cloudy or dark colour, and presence of floating solids

C Many fish and aquatic plants

D High oxygen levels

Sewage pollution causes bad odour, cloudiness, and floating solids. Clear, clean-smelling water with many fish and high oxygen indicates clean water.

Q28. What is the role of chlorine in making drinking water safe?

A It removes solid particles

B It kills bacteria, viruses, and other pathogens that cause waterborne diseases

C It adds a pleasant taste to water

D It removes dissolved minerals

Chlorine disinfects water by killing pathogens. It does not remove solids, add taste, or remove minerals.

Q29. What is biochemical oxygen demand (BOD)?

A The amount of oxygen needed by bacteria to break down organic matter in a water sample

B The amount of chlorine needed to disinfect water

C The temperature of the water

D The number of fish in the water

BOD measures the oxygen required by bacteria to decompose organic matter. High BOD indicates high organic pollution. It is not chlorine, temperature, or fish count.

Q30. Why should you never drink water directly from a river or lake without treatment?

A Because it is too cold

B Because it may contain disease-causing microorganisms (pathogens) from sewage or animal waste

C Because it contains too much oxygen

D Because it is always salty

Natural water bodies may contain pathogens from sewage or animal waste, making them unsafe to drink without treatment. It is not about temperature, oxygen, or salt.

Q31. What is the purpose of the “bar screen” in a wastewater treatment plant?

A To remove large floating objects like rags, sticks, plastic bottles, and other debris

B To add oxygen to the water

C To settle out sand and gravel

D To kill bacteria with chemicals

Bar screens remove large debris to protect equipment. They do not add oxygen, settle sand, or kill bacteria.

Q32. What is the difference between a sewer and a drain?

A There is no difference; they are the same thing

B A sewer carries sewage (wastewater from toilets, bathrooms, kitchens); a drain usually carries stormwater (rainwater) or surface runoff

C A drain carries sewage; a sewer carries stormwater

D A sewer is above ground; a drain is underground

Sewers carry wastewater from buildings, while drains carry rainwater or surface runoff. They are not the same, and their functions differ.

Q33. Which of the following is a parasite that can be spread through contaminated water?

A Vibrio cholerae (bacteria)

B Giardia lamblia (protozoan parasite)

C Influenza virus

D Streptococcus (bacteria)

Giardia lamblia is a protozoan parasite spread through contaminated water. Vibrio cholerae and Streptococcus are bacteria, and influenza is a virus.

Q34. What happens during the aeration step of wastewater treatment?

A Sewage is allowed to sit undisturbed so solids settle

B Air is pumped into the sewage, promoting the growth of aerobic bacteria that consume organic waste

C Chlorine is added to kill bacteria

D Large objects are removed by screens

Aeration adds oxygen to support aerobic bacteria in breaking down organic matter. It is not sedimentation, chlorination, or screening.

Q35. What is the final step before treated water is released into a river from a WWTP?

A Screening

B Sedimentation

C Disinfection (usually with chlorine or UV light)

D Aeration

Disinfection is the final step to kill remaining pathogens before water is released. Screening, sedimentation, and aeration are earlier steps.

Q36. Why is it important to treat sewage before releasing it into a river?

A To add nutrients to the river

B To prevent oxygen depletion, fish kills, and the spread of waterborne diseases

C To make the river flow faster

D To increase the temperature of the river

Treating sewage prevents pollution, protects aquatic life, and stops the spread of diseases. It does not add nutrients, speed flow, or increase temperature.

Q37. What is a “combined sewer system”?

A A system where sewage and stormwater (rainwater) flow in the same pipes

B A system where each house has its own septic tank

C A system with no pipes at all

D A system where sewage is treated in each building

A combined sewer system carries both sewage and stormwater in the same pipes. It is not individual septic tanks, no pipes, or on-site treatment.

Q38. Which of the following bacteria is commonly used as an indicator of fecal contamination in drinking water?

A Lactobacillus

B E. coli (Escherichia coli)

C Streptococcus

D Bacillus subtilis

E. coli is used as an indicator of fecal contamination because it is commonly found in human and animal waste. It is not Lactobacillus, Streptococcus, or Bacillus subtilis.

Q39. What is the purpose of a “clarifier” or “secondary sedimentation tank” in a WWTP?

A To add oxygen to the water

B To allow the bacterial flocs (clumps of microbes) to settle out after aeration

C To remove large objects with screens

D To disinfect the water with chlorine

The clarifier allows bacterial flocs to settle after aeration, separating treated water from sludge. It does not add oxygen, remove large objects, or disinfect.

Q40. What is the main source of nitrates and phosphates in sewage?

A Industrial chemicals only

B Human waste, food waste, and detergents (from washing clothes and dishes)

C Rainwater

D Sand and gravel

Nitrates and phosphates come from human waste, food, and detergents. They are not only from industrial chemicals, rainwater, or sand.

Q41. What is the role of the “skimmer” in a sedimentation tank?

A To add air to the water

B To remove floating materials like grease, oil, and scum from the surface

C To settle sand to the bottom

D To add chlorine

Skimmers remove floating materials like grease and oil from the surface of sedimentation tanks. They do not add air, settle sand, or add chlorine.

Q42. Why do people in some rural areas still practice open defecation despite health risks?

A Because it is healthier than using a toilet

B Because of lack of toilets, lack of awareness, or cultural practices

C Because it is cleaner

D Because it saves water

Open defecation persists due to lack of facilities, awareness, or cultural habits. It is not healthier, cleaner, or water-saving.

Q43. What is the difference between primary treatment and secondary treatment in a WWTP?

A Primary treatment is biological; secondary treatment is physical

B Primary treatment removes solids by physical processes (screening, sedimentation); secondary treatment removes organic matter using biological processes (aeration, bacterial digestion)

C There is no difference

D Primary treatment adds chlorine; secondary treatment removes chlorine

Primary treatment is physical, removing solids. Secondary treatment is biological, removing organic matter. They are not the same.

Q44. Which of the following is a waterborne disease caused by a virus?

A Cholera

B Typhoid

C Hepatitis A

D Dysentery

Hepatitis A is a viral waterborne disease. Cholera, typhoid, and dysentery are caused by bacteria.

Q45. What is the purpose of a “manhole” in a sewer system?

A To allow sewage to flow faster

B To provide access for inspection, cleaning, and maintenance of underground sewers

C To add chemicals to the sewage

D To store sewage during heavy rain

Manholes provide access for maintenance and inspection. They do not speed flow, add chemicals, or store sewage.

Q46. Why do aerobic bacteria need oxygen to break down organic waste?

A They use oxygen to breathe (cellular respiration) just like humans and animals do

B They use oxygen to build their cell walls

C Oxygen is their food

D They do not actually need oxygen

Aerobic bacteria use oxygen for cellular respiration to break down organic matter. Oxygen is not their food, and they do need it.

Q47. What is “sludge” in the context of wastewater treatment?

A The clear, treated water that is released from the plant

B The semi-solid mixture of settled solids removed from sedimentation tanks

C The foam created by aeration

D The large objects removed by bar screens

Sludge is the semi-solid waste from sedimentation. It is not treated water, foam, or large debris.

Q48. How does boiling water make it safe to drink?

A It removes solid particles

B It kills most bacteria, viruses, and parasites that cause disease

C It adds minerals to the water

D It makes the water taste better

Boiling kills pathogens, making water safe to drink. It does not remove solids, add minerals, or improve taste significantly.

Q49. What is the function of the “return activated sludge” (RAS) process in a WWTP?

A To add chlorine to the water

B To recycle some of the settled bacteria from the secondary clarifier back to the aeration tank to maintain a healthy population of decomposers

C To remove large objects

D To add oxygen to the water

RAS recycles bacteria to maintain the population of decomposers. It does not add chlorine, remove large objects, or add oxygen directly.

Q50. Why is water considered a “lifeline” for sanitation as well as for drinking?

A Because water is only used for drinking

B Because water is essential for carrying away waste through sewers and for cleaning, which prevents disease

C Because water is only used for agriculture

D Because water has no role in sanitation

Water is essential for sanitation, as it carries waste away and enables cleaning, preventing disease. It is not only for drinking or agriculture, and it does have a role in sanitation.