Environmental Studies · Chemistry

Water and Wastewater Treatment

1,345 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

Primary treatment of sewage involves

  1. Production of biogas

  2. Physical removal of particles by filtration and sedimentation

  3. Formation of floc

  4. Digestion of floc by anaerobic microbes
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Primary treatment of sewage is a physical process that involves the removal of large and small particles through filtration and sedimentation. Biological processes like floc formation occur during secondary treatment.

Multiple choice

Activated sludge has the ability to settle quickly this enables it to

  1. be rapidly pumped back from sedimentation to aeration tank.

  2. absorb pathogenic bacteria while sinking to the bottom of the settling-tank

  3. anaerobically digested and be discarded.

  4. absorb colloidal organic matter.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Activated sludge consists of a mass of bacteria and fungi that settle quickly. This allows a portion of it to be recycled back into the aeration tank as an inoculum for further treatment.

Multiple choice

Passage of effluents into oxidation tank is for

  1. Primary treatment

  2. Secondary treatment

  3. Tertiary treatment

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

Primary treatment involves physical removal of particles. Secondary treatment is a biological process where microorganisms in an oxidation tank or aeration tank break down organic matter in the effluent.

Multiple choice

In a water treatment plant what is removed in secondary treatment?

  1. all solids

  2. sediment

  3. mostly nitrogen

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

Secondary treatment in a wastewater plant is a biological process that uses microorganisms to break down organic matter, which includes nitrogen and phosphorus compounds, rather than just physical solids.

Multiple choice chemistry metals chemical properties and uses of metals and non-metals introduction to metals physical properties of non-metals

Which of the following non-metal is commonly used for purifying water?

  1. Sulphur

  2. Oxygen

  3. Chlorine

  4. Xenon
Reveal answer Fill a bubble to check yourself
C 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. Although several methods eliminate disease-causing microorganisms in water, chlorination is the most commonly used. Chlorination is effective against many pathogenic bacteria, but at normal dosage rates it does not kill all viruses, cysts, or worms. When combined with filtration, chlorination is an excellent way to disinfect drinking water supplies.

Multiple choice biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

Primary treatment reduces BOD, ranges from;

  1. 30-60%

  2. 0-70%

  3. 30-35%

  4. 20-80%
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Primary treatment in wastewater treatment typically reduces BOD by about 30-35% through physical processes like screening and sedimentation. This level of reduction is consistent with standard wastewater treatment engineering data. Higher reductions (like 30-60% or more) usually require secondary treatment with biological processes.

Multiple choice biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

Which is the correct ascending arrangement of BOD of sewage(S) distillery effluent(DE), paper mill effluent(PE) and sugar mill effluent(SE)?

  1. SE$<$PE$<$S$<$DE
  2. PE$<$S$<$SE$<$DE
  3. S$<$DE$<$PE$<$SE
  4. SE$<$S<$PE$<$DE
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • BOD is the Biological Oxygen Demand that is created when there is an excessive quantity of the organic matter in the water body and its decomposition is initiated by the decomposing bacteria. More the amount of organic waste, the higher will be the BOD and so more will be pollution in the water body. 
  • This causes an extreme reduction in the dissolved oxygen and suffocates the aquatic animals. 
  • Distillery effluent is rich in organic waste left from alcoholic fermentation and it has the highest BOD. 
Sugar mill effluent follows the distillery effluent in the concentration of organic content. The sewage water contains the excreta and detergents mixed with it. 
  • Papermill effluent has the lowest concentration of the organic mass.

Hence, the correct answer is 'PE< S< SE< DE'.