Environmental Studies · General Awareness

Water Quality and Pollution

1,263 Questions

Water Quality and Pollution examines the sources, mechanisms, and impacts of contaminants in aquatic ecosystems. It covers crucial environmental concepts like eutrophication, biochemical oxygen demand, and thermal pollution. This subject frequently appears in general science and environmental studies sections of various examinations.

Eutrophication CausesThermal Pollution EffectsBiochemical Oxygen DemandSynthetic Fertilizer ImpactsWastewater SourcesAquatic Ecosystem Toxicity

Water Quality and Pollution Questions

Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

High biological oxygen demand indicates:  

  1. the absence of microbial pollution

  2. moderate microbial pollution

  3. the intense level of microbial pollution

  4. all of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Biological Oxygen Demand (BOD) refers to the amount of dissolved oxygen that aerobic organisms need in order to break down organic material in water over time. Its high value indicates the intense level of microbial pollution.

Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

Water pollution can be classified into chemical and thermal pollution.

Is the above statement correct?

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Water pollution caused due to the chemicals such as the chemical waste from the industries, chemicals used in agriculture such as pesticides, herbicides, etc. All these results in chemical water pollution.

Thermal water pollution is caused by the radioactive wastes that are emitted to the water which results in degradation of the water quality.

Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

Water pollution can be defined as:

  1. Physical change in the properties of water

  2. Chemical change in the properties of water

  3. Biological change in the properties of water

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

There are various chemical pollutants which on mixing changes the colour, taste or other physical quality; changes the natural state of odourless, colourless form by bringing chemical changes and biological changes include an addition of pathogenic bacteria to the water by untreated sewage waste.

Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

If BOD value is greater than 17 ppm, then water belongs which of the following to category?

  1. Normal water

  2. Highly polluted water

  3. Usable water

  4. Slightly polluted water
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Clean water would have BOD value of less than 5 ppm whereas highly polluted water could have BOD value 17ppm or more.

Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

Which of the following water pollutants encourage the formation of algae?

  1. Insecticides

  2. Heavy metals

  3. Plant nutrients

  4. Sediments
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Explosive growth of plants and algae is a response to the addition of excess nutrients, mainly phosphates, which induces, the decaying of which consumes oxygen from the water causing water pollution. Phosphates are among the major nutrients that is required by plants for growth. 

Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

Measurement of rate of oxygen utilisation by the unit volume of polluted water over a period of time is referred to as:

  1. fermentation

  2. chemical oxygen demand

  3. oxidation potential

  4. biological oxygen demand
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Biochemical oxygen demand is the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period. The BOD value is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days of incubation at $20^{\circ}C$ and is often used as a surrogate of the degree of organic pollution of water.

BOD is similar in function to chemical oxygen demand (COD), in that both measure the amount of organic compounds in water. However, COD is less specific, since it measures everything that can be chemically oxidized, rather than just levels of biodegradable organic matter

Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

Sewage water is purified by

  1. microorganisms

  2. light

  3. fish

  4. aquatic plant
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In general, all common methods of sewage purification use sedimentation processes by which solids (sludge) sink to the bottom – in some cases this primary sludge is removed for further treatment.

After this comes the secondary or biological treatment of sewage purification, this involves biological processes and the use of microorganisms that “eats” away a lot of the hazardous contaminants. Use of oxygen by various implementation techniques is very important.

After the secondary stage of sewage purification comes final settlement of biological solids and then a tertiary treatment that removes even better the rest of the biological and organic materials in the water. 

Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

Which of the following is a measurement of water pollution ?

  1. PSC

  2. PCB

  3. BOD

  4. COD
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

  1. Polar stratospheric clouds (PSCs) are the medium on which reservoir chlorine compounds are converted into ozone-destroying chlorine radicals, they are essentially two types of  PSC known as type 1 and type 2.
  2. Polychlorinated biphenyl (PCBs) is a group of organic compounds used in the manufacture of plastics, as lubricants, in transformers, adhesives and so forth. They are highly toxic to aquatic life and persist in the environment for long periods of time. They can accumulate in food chains and may produce harmful side-effects at high concentrations.
  3. Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed (i.e demanded ) by aerobic biological organisms to break down organic material present in a given water sample at a certain temperature over a specific time period.
  4. Chemical oxygen demand (COD) is defined as a  measure of the oxygen equivalent of the organic matter content of a sample that is susceptible to oxidation by a strong chemical oxidant. Therefore, BOD is a measurement of water pollution.

Option (C) is correct.

Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

Which of the following statement is false?

  1. Lower the concentration of D.O., the more polluted is the water sample
  2. The tolerable limit of lead in drinking water is $50\ ppm$
  3. Water is considered pure if it has BOD less than $5\ ppm$
  4. In COD determination, the pollutants resistant to microbial oxidation are not oxidized by an oxidizing agent like $K _{2}Cr _{2}O _{7}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In COD, the degradation is affected by an oxidizing agent, $K _2 Cr _2 O _7.$ COD  is a measure of amount of oxygen , required to degrade or breakdown the organic matter. 

Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

Biochemical Oxygen Demand (BOD) is a measure of organic material present in water. BOD value less than 5 ppm indicates a water to be ________.

  1. rich in dissolved oxygen

  2. poor in dissolved oxygen

  3. highly polluted

  4. not suitable for aquatic life
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Clean water has BOD which is less than 5 ppm. If it is equal to or more than 12 ppm, then the water is considered as polluted. So this indicates water be rich in dissolved oxygen, that helps the microorganisms to oxidize inorganic and organic materials. 

Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

Pollution of lakes and rivers affects aquatic life. Fish cannot live in water that has oxygen less than $4$ milligrams per liter. Other freshwater aquatic life (including anaerobic bacteria) also cannot survive without adequate oxygen. 'BOD' stands for:

  1. Biological oxygen demand

  2. Bacterial oxygen deficit

  3. Basic oxygen demand

  4. Building oxygen deposits
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
BOD stands for Biological Oxygen Demand is the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample at a certain temperature over a specific time period.
Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

Clean water would have Biochemical oxygen demand (BOD) value of less than:

  1. 17 ppm

  2. 5 ppm

  3. 200,000 ppm

  4. 10 ppm
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
A water supply with a BOD level of 3-5 ppm is considered moderately clean. In water with a BOD level of 6-9 ppm, the water is considered somewhat polluted because there is usually organic matter present and bacteria are decomposing this waste.
Hence, clean water would have a BOD value of less than 5.

Hence, the correct option is $\text{B}$
Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

Biological Oxygen Demand (BOD) can be defined as:

  1. the amount of oxygen required by bacteria to break down the organic matter of a sample of water

  2. the amount of chemicals required to break down the organic matter of a sample of water

  3. the amount of phosphate required to oxidise the organic matter of a sample of water

  4. the amount of organic matter present in the given sample of water
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

BOD refers to the dissolved oxygen that the microorganisms like bacteria need to oxidize, means to break down inorganic and organic matter in water. It is a measure of water quality. 

Multiple choice chemistry water too little to waste pollution of water water pollution planet earth

What does $BO{D} _{5}$ represent?

  1. Biological oxygen demand in five days

  2. Dissolved oxygem left after five days

  3. Dissolved oxygen consumed in five days

  4. Microorganisms killed by ozone in sewage treatment plants in five hours
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$BO{ D } _{ 5 }$ stands for 5-day Biochemical Oxygen Demand. The BOD test measures, oxygen is used as microbes breathe as they eat the contaminants  in wastewater.

Multiple choice evs sources of water the lithosphere and the hydrosphere first aid safety and first aid

Life is sustainable with water only because 

  1. It makes 90% of the protoplasm

  2. Translocation of nutrients inside the body occurs wiith the help of water

  3. Water loss in form of sweating helps to maintain body temperature

  4. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Protoplasm is the material comprising the living contents of a cell. It consists of 70- 90% water along with the minerals, sugars, amino acids, proteins, enzymes, etc. The translocation of nutrients inside the body occurs viz. blood which also major consists of water. In an environment with excessive heat, water loss in the form of sweating keeps the body cool. Thus, water maintains body temperature. 

So, the correct answer is 'All of the above'.