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Q1. Wastewater generated in hospitals primarily consists of

• Radioactive substances
• Acids and bases
• Plastic
• Dead debris

Solution

Wastewater from hospitals contains several types of disease-causing germs and radioactive substances used in the treatment of diseases.

Q2. The dissolved and suspended impurities in sewage are called

• Scum
• Contaminants
• Sludge
• Biofilms

Solution

Several dissolved and suspended impurities in the sewage are called contaminants. When disposed in water bodies, sewage causes health hazards for humans and animals.

Q3. Which chemical substance is used to kill bacteria in drinking water?

• Fluorine
• Bromine
• Chlorine
• Iodine

Solution

Chlorine acts as a disinfectant as it kills the bacteria present in water and makes water safe for drinking.

Q4. Anaerobic decomposition of sewage takes place in

• Aeration tank
• Sewage tank
• Septic tank
• Digestion tank

Solution

A septic tank is an alternative method for sewage disposal in which anaerobic bacteria decompose waste.

Q5. Which one of the following processes does not occur in a sewage treatment plant?

• Screening
• Sedimentation
• Clarification
• Humification

Solution

Sewage treatment involves screening, sedimentation and clarification of wastes present in sewage.

Q6. Marine and coastal environmental pollution is caused by 

• Salts
• Oil-based products
• Detergents
• Fertilisers

Solution

Marine and coastal environmental pollution is caused mainly by oil-based products.

Q7. Which among the following is a light metal which pollutes water?

• Mercury
• Selenium
• Lead
• Cadmium

Solution

Once in the aquatic environment, selenium can rapidly bioaccumulate and reach levels that are toxic to fish and wildlife. 

Q8. Which of the following kill microbes which help clean water? (A) Paints (B) Medicines (C) Insecticides

• (A) and (B)
• (B) and (C)
• (A) and (C)
• (A), (B) and (C)

Solution

Chemicals such as paints, medicines and insecticides kill microbes which help clean water.

Q9. Chemical pollutants in water include

• Viruses
• Bacteria
• Algae
• Detergents

Solution

Detergents change the chemical structure of water and cause water pollution.

Q10. The tank in which aerobic bacteria grow and decompose organic waste is called

• Septic tank
• Aeration tank
• Sewage tank
• Digestion tank

Solution

Air is pumped through the clarified water in an aeration tank which allows aerobic bacteria to grow and consume organic contaminants.

Q11. Which of the following wastes do not clog drains?

• Tea leaves
• Sanitary napkins
• Food remains
• Water used for cleaning utensils

Solution

Tea leaves, sanitary napkins and food remains should not be disposed of in the kitchen sink as these clog drains. Water used for cleaning utensils flows easily and does not clog drains.

Q12. What is used to remove oil and grease from wastewater?

• Clarifier
• Skimmer
• Scrubber
• Scraper

Solution

Floating materials such as oil and grease in sludge are removed with a skimmer to clear the water.

Q13. Increase in the concentration of toxic waste per trophic level is called

• Biological magnification
• Eutrophication
• Biological oxygen demand
• Chemical oxygen demand

Solution

Increase in the concentration of toxic waste per trophic level is called biological magnification.

Q14. In a biogas plant, cow dung and water are mixed in equal proportion to make

• Slurry
• Sludge
• Scum
• Biofilm

Solution

In a biogas plant, cow dung and water are mixed in equal proportions to make slurry which undergoes anaerobic degradation in the presence of water.

Q15. Which water is suitable for drinking?

• Potable water
• Wastewater
• Distilled water
• Sewage water

Solution

Potable water is suitable for drinking as it is free from microorganisms and dissolved impurities.

Q16. Which substance helps dirt particles in water to form lumps?

• Alum
• Charcoal
• Sand
• Chlorine

Solution

Alum helps to precipitate the impurities present in water and settle them down.

Q17. Clarified water in a wastewater treatment plant emerges from which tank?

• Sedimentation tank
• Sewage tank
• Septic tank
• Digestion tank

Solution

Clarified water emerges from the sedimentation tank.

Q18. Which of the following is not a part of a wastewater treatment plant?

• Clarifier
• Vertical bars
• Aeration tank
• Settling chamber

Solution

Vertical bars, aeration tank and clarifier are all parts of a wastewater treatment plant. Wastewater is first passed through vertical bars and then through a clarifier. The aeration tank allows aerobic decomposition of organic waste and produces activated sludge. Settling chamber is not a part of the wastewater treatment plant.

Q19. In a wastewater treatment plant, the sewage is passed through

• Horizontal bars
• Vertical bars
• Transverse bars
• Diagonal bars

Solution

In a wastewater treatment plant, the sewage is passed through a screen of vertical bars which remove large solid materials such as plastic bags, cans and sticks.

Q20. Which of the following is an alternative safe method for sewage disposal?

• Biogas production
• Dumping wastes in open areas
• Burning wastes
• Burying wastes

Solution

Excreta is allowed to flow into a biogas plant through covered drains, and the biogas thus produced can be used as fuel.

Q21. In many villages, where sewers are not available, human excreta from the toilet seats flows through the drains into

• Biogas plant
• Incinerator
• Kiln
• Landfill

Solution

In many villages, where sewers are not available, human excreta from the toilet seats flows through the drains into a biogas plant. The biogas produced is used as a fuel.

Q22. Which of the following is an inorganic contaminant present in water?

• Decayed food
• Faeces
• Rotten vegetables
• Salts and minerals

Solution

Decayed food, faeces and rotten vegetables are the organic contaminants present in water which aerobic bacteria act and decompose.

Q23. Organic matter discharged into water bodies substantially utilises

• Oxygen
• Nitrogen
• Carbon
• Sulphur

Solution

Organic matter discharged with sewage into water bodies utilises oxygen and thereby disturbs the ecological balance.

Q24. Organic matter which settles into a clarifier in a wastewater treatment plant is called

• Sludge
• Slurry
• Biofilm
• Scum

Solution

Organic matter which settles into the clarifier of a wastewater treatment plant is called sludge.

Q25. Which of the following is not obtained after the digestion of sludge during wastewater treatment?

• Methane
• Carbon dioxide
• Humus-like material
• Oxygen

Solution

Sludge is used to obtain methane, carbon dioxide and humus-like material by a process called digestion.

Q26. Which bacteria decompose waste in the presence of oxygen?

• Anaerobic bacteria
• Cyanobacteria
• Aerobic bacteria
• Lactobacilli

Solution

Aerobic bacteria decompose waste in the presence of oxygen and produce activated sludge.

Q27. Which of the following are used for the safe disposal of human excreta in those areas where sewerage system does not exist and water supply is limited or not available at all?

• Chemical toilets
• Vacuum toilets
• Composting toilets
• Septic tank toilets

Solution

A composting toilet is a self-contained human waste disposal unit which is not connected to a sewer line. It breaks down and dehydrates human waste to a compost which can be added to soil to make it fertile. 

Q28. Water contaminated by which of the following wastes contains mostly poisonous chemicals?

• Agricultural
• Domestic
• Industrial
• Electronic

Solution

Poisonous chemicals are mostly present in industrial wastewater.

Q29. During chlorination, chlorine is added in carefully controlled amounts to

• Allow floating particles to settle
• Remove unpleasant taste and smell
• Remove fine particles of impurities
• Kill bacteria

Solution

During chlorination, chlorine is added in carefully controlled amounts to kill bacteria. This disinfects water.

Q30. Which of the following diseases is not caused by improper disposal of sewage?

• Cholera
• Heart attack
• Jaundice
• Typhoid

Solution

Heart attack is not caused by the improper disposal of sewage. All the other diseases are caused by the improper disposal of sewage as the germs of these diseases breed in stagnant water.

Q31. What is used to remove organic waste from sludge?

• Clarifier
• Skimmer
• Scrubber
• Scraper

Solution

A scraper is used to remove organic waste from sludge.

Q32. Which of the following is a water-borne disease?

• Influenza
• Tuberculosis
• Typhoid
• AIDS

Solution

Typhoid is a water-borne disease. Influenza and tuberculosis are air-borne diseases. AIDS spreads through sexual contact.

Q33. Besides distillation, the other way of desalination of wastewater is

• Chlorination
• Filtration
• Sedimentation
• Reverse osmosis

Solution

Reverse osmosis is a technique used to remove a large majority of contaminants from water by pushing the water under pressure through a semi-permeable membrane. When salt water is passed through reverse osmosis membrane, majority of the dissolved salts are removed and pure water is left behind.

Q34. Settling tanks through which wastewater is passed are called

• Grit chambers
• Digestion tanks
• Clarifiers
• Aeration tanks

Solution

Settling tanks through which wastewater is passed and solid wastes are removed are called grit chambers.

Q35. In a wastewater treatment plant, activated sludge is produced in

• Aeration tank
• Sewage tank
• Septic tank
• Digestion tank

Solution

In an aeration tank, aerobic bacteria decompose the organic waste and produce activated sludge.

Q36. Which epidemic is very common after floods?

• Cholera
• Smallpox
• Plague
• Influenza

Solution

Flood water contaminates drinking water and excreta flows onto the surface which causes cholera.

Q37. Which of the following does not act as a source of wastewater?

• Open drains
• Stagnant water
• Leaking pipes
• Water stored in water vending machines

Solution

Open drains, stagnant water and leaking pipes cause water pollution and are thus a source of wastewater.

Q38. Which chemical is added during the sedimentation step to allow settling of floating particles in water?

• Alum
• Charcoal
• Potash
• Lime

Solution

During sedimentation, chemicals such as alum are added to the water. This allows the particles floating in the water to stick together and form lumps which settle to the bottom of the tank.

Q39. Low cost onsite sewage disposal systems includes (A) Septic tanks (B) Composting pits (C) Chemical toilets

• (A) and (B)
• (B) and (C)
• (A) and (C)
• (A), (B) and (C)

Solution

Low cost onsite sewage disposal systems such as septic tanks, composting pits and chemical toilets are being encouraged to improve sanitation and prevent water-borne diseases.

Q40. Which of the following is used to decompose human excreta?

• Redworms
• Flatworms
• Roundworms
• Tapeworms

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