Environmental Studies · 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 evs experiments with water water and its types hard and soft water what floats - what sinks

Permanent hardness of water can be removed by:

  1. permutit process

  2. boiling

  3. ion-exchange

  4. calgon's process
Reveal answer Fill a bubble to check yourself
A,C,D Correct answer
Explanation

Permanent hardness of water can be removed by permutit process. Permutite is an artifical zeolite used for softening of water. Through ion-exchange process, here cation-anion exchange chamber is used to obtain pure water. In calgon's process sodium hexa meta phosphate is used to soften the water.

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Both temporary and permanent hardness in water is removed by:

  1. boiling

  2. filtration

  3. distillation

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

Both temporary and permanent hardness in water is removed by distillation. Temporary hardness can be removed by boiling and filtration. Permenant hardnesscan be removed by: (1) adding washing soda, (2) permutit method (3) by using ion exchange resins.

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks
Both temporary and permanent hardness in water is removed by________.

  1. boiling

  2. filtration

  3. distillation

  4. decantation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Both temporary and permanent hardness in water is removed by distillation. Temporary hardness can be removed by boiling and filtration. permanent hydration can be removed by adding washing soda, permutit method and by using ion exchange resins.
Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Temporary hardness of water can be removed by :

  1. boiling

  2. saponification

  3. clark's method

  4. chlorination
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

The temporary hardness of water can be removed by boiling. $Ca(HCO _3) _2 \xrightarrow {boil} CaCO _3 \downarrow + CO _2 \uparrow + H _2O$.

Clark's method which uses lime (calcium hydroxide), it is also used for removal of temporary hardness of water.
$Ca(HCO _3) _2+Ca(OH) _2 \rightarrow 2CaCO _3+2H _2O$.

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Temporary hardness of water can be removed by:

  1. filtration

  2. boiling

  3. decantation

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

By boiling, the bicarbonates undergo decomposition to form insoluble carbonates of $Ca/Mg$ which can further be removed by filtration.

$Ca{ \left( { HCO } _{ 3 } \right)  } _{ 2 }\left( aq \right) \rightarrow CaC{ O } _{ 3\left( s \right)  }+{ CO } _{ 2\left( g \right)  }+{ H } _{ 2 }O(l)$
$Mg{ \left( HCO \right)  } _{ 3 }(aq)\rightarrow Mg{ CO } _{ 3\left( s \right)  }+{ CO } _{ 2\left( g \right)  }+{ H } _{ 2 }{ O } _{ (l )}$
Then the water obtained will be free from $Ca$ and $Mg$ ions and is soft.

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Hardness of water can be removed by :

  1. adding calcium hydroxide

  2. ion-exchange method

  3. both a and b

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

Hardness of water can be removed by the following two methods:
CLARK'S METHOD 
In Clarks method a calculated amount of calcium hydroxide $Ca (OH) _2$ is added to hard water. Due to reaction, insoluble carbonates are obtained which are separated by filtration.
$Ca(HCO _3) _2 + Ca(OH) _2 2CaCO _3 + 2H _2O$
$Mg(HCO _3) _2 + Ca(OH) _2 CaCO _3 + MgCO _3 + 2H _2O$
ION-EXCHANGE METHOD
In this method sodium zeolite is used as ion-exchanger. Na-zeolite is passed through the pipes containing    hard water. Sodium zeolite is converted into calcium-zeolite or magnesium-zeolite. These are insoluble in water and are separated from water by filtration.
$Ca+2 + Na2-zeolite Ca-zeolite + 2Na+1$
$Mg+2 +Na2-zeolite Mg-zeolite + 2Na+1$

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Hard water is unfit for laundries because:

  1. consumes much soap
  2. leaves dirty strains of '$Ca$' and '$Mg$'

  3. causes irritation on skin

  4. water is very hard to handle
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

Hard water is unfit for laundries because it can not form lather with soap, hence consumption of soap increases and it leaves dirty strains of calcium and magnesium. 

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

Which of the following is not a disadvantage of using hard water?

  1. In production of steam in boilers

  2. Formation of scales in cooking utensils

  3. In cooking,bathing and washing

  4. In ion exchanges
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In an ion exchange using hard water is not a disadvantage since it becomes soft by exchanging anions or cations. $Na^+$, $Ca^{2+}$ and $Mg^{2+}$ ions (from water) are exchanged with $H^+$ ions (from cation exchange resins). $Cl^-$, $SO _4^{2-}$ and $NO _3^{-}$ ions (from water) are exchanged with $OH^-$ ions (from anion exchange resins).

Multiple choice evs experiments with water water and its types hard and soft water what floats - what sinks

What is meant by demineralised water?

  1. Water free from cations and anions

  2. Watrer free from minerals dissolved in it

  3. Wtaer free from impurities
  4. Water free from $Na^{+}$ and $K^{+}$ ions
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Water free from cations $(Ca^{2+}, Mg^{2+}, etc.)$ and anions $(Cl^{-}, SO^{2-} _{4}, HCO^{-} _{3}, etc)  $ is called deionised or demineralised water.