Environmental Studies ยท Chemistry

Water and Wastewater Treatment

1,423 Questions

This topic deals with water purification, wastewater treatment methods, and industrial effluent management. It includes questions on filtration, disinfection, and water hardness removal. These concepts are tested in environmental science and engineering exams.

Water purificationWastewater treatmentBioremediation strategiesWater hardness removalIndustrial effluent management

Water and Wastewater Treatment Questions

Multiple choice

Permanent hardness of water can be removed by using

  1. Nitrates

  2. Sulphnates

  3. Zeolites

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Zeolites (aluminum silicates) are used to remove permanent hardness of water through ion exchange. They effectively remove calcium and magnesium ions that cause hardness. Nitrates and sulfates are additives, not removers, and zeolite treatment is a proven method.

Multiple choice

The method of destroying harmful bacteria by heat is known as:

  1. distillation

  2. fumigation

  3. sterilisation

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

Sterilisation is the process of destroying or eliminating all forms of microorganisms, especially harmful bacteria, through heat (autoclaving), chemicals, or radiation. Distillation separates liquids by boiling points, fumigation uses chemical gases to kill pests, and culturing involves growing microorganisms in controlled conditions.

Multiple choice

What happens in secondary treatment of sewage water?

  1. Large objects and undissolved impurities are removed.

  2. Water is aerated.

  3. Nitrates and phosphates are removed.

  4. Germs are killed by adding chlorine.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Water is aerated to promote bacterial decomposition in secondary treatment.

Multiple choice

Addition of bleaching powder in small quantities to drinking water is called

  1. convection

  2. chlorination

  3. radiation

  4. electrolysis
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Bleaching powder contains calcium hypochlorite, which releases chlorine when added to water. This process is called chlorination and kills harmful bacteria and microorganisms, making water safe for drinking. Convection is heat transfer, radiation uses electromagnetic waves, and electrolysis splits compounds using electricity.

Multiple choice

Which of the following is added to purify water in big cities?

  1. Calcium carboante

  2. Sodium

  3. Lime

  4. Chlorine
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Chlorine effectively kills bacteria and other pathogens in water supplies. It's the most common disinfectant for municipal water treatment because it provides residual protection throughout the distribution system. Lime is sometimes used for pH adjustment but not as the primary disinfectant.

Multiple choice

Water for civil supplies is commonly purified by

  1. chlorination

  2. distillation

  3. filtration

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

Chlorine is one of the most commonly used disinfectants for water disinfection. Chlorine can be applied for the deactivation of most microorganisms and it is relatively cheap.

Multiple choice

Which of the following water purification methods can be used to inactivate harmful protozoa?

  1. Plumbosolvency reduction

  2. Water fluoridation

  3. Ozone disinfection

  4. Granular Activated Carbon filtering

  5. Desalination
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Ozone is an unstable molecule which readily gives up one atom of oxygen providing a powerful oxidizing agent which is toxic to most waterborne organisms. It is a very strong, broad spectrum disinfectant. It is an effective method to inactivate harmful protozoa that form cysts. It also works well against almost all other pathogens.

Multiple choice

Which of the following statements is not correct regarding the treatment of sewage?

  1. Pretreatment may include a sand or grit channel or chamber, where the velocity of the incoming sewage is adjusted to allow the settlement of sand, grit, stones and broken glass.

  2. Coagulation can be carried out by passing ozone through waste water.

  3. In primary treatment, large sized particles are filtered through screens and residual water is subjected to sedimentation.

  4. Secondary treatment involves aerobic digestion of the organic waste.

  5. In tertiary treatment, the waste water is treated with lime to remove phosphate followed by coagulation.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This option is correct because coagulation can be carried out by adding alum and ferric chloride in waste water.