# Environmental Engineering Questions and Answers – Forms of Chlorination

This set of Environmental Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Forms of Chlorination”.

1. The normal dose of chlorine during plain chlorination is ___________
a) 0.5-1ppm
b) 0.1-0.2ppm
c) 0.1-0.5ppm
d) 1-2ppm

Explanation: The normal dose of chlorine during plain chlorination is 0.5-1ppm. It should be applied when the water is clear and its turbidity does not exceed 30 ppm.

2. The normal dose of chlorine during pre chlorination is ___________
a) 0.5-1ppm
b) 0.1-0.2ppm
c) 0.1-0.5ppm
d) 1-2ppm

Explanation: The normal dose of chlorine during pre chlorination is 0.5-1ppm. This results in the oxidization of organic matter and reduce the amount of coagulants required in the water.

3. The normal dose of chlorine during post chlorination is ___________
a) 0.5-1ppm
b) 0.1-0.2ppm
c) 0.1-0.5ppm
d) 1-2ppm

Explanation: The normal dose of chlorine during post chlorination is 0.1-0.2ppm. It is used for protection against contamination.

4. In which form of chlorination, chlorine applies to raw water supply as it enters the distribution system?
a) Plain chlorination
b) Pre chlorination
c) Super chlorination
d) Double chlorination

Explanation: In plain chlorination, chlorine applies to raw water supply as it enters the distribution system. It checks the growth of organic matter, algae and remove taste and odor from water.

5. _________ is the application of chlorine before filtration.
a) Plain chlorination
b) Pre chlorination
c) Super chlorination
d) Double chlorination

Explanation: Pre chlorination is the application of chlorine before filtration. This results in a decrease of coagulant required in the water.

6. __________ is the application of chlorine at two or more points in the purification process.
a) Plain chlorination
b) Pre chlorination
c) Super chlorination
d) Double chlorination

Explanation: Double chlorination is the application of chlorine at two or more points in the purification process. It is applied just before when the water enters the sedimentation tank and after when it leaves the filter plant.

7. The normal dose of chlorine during break point chlorination is ____________
a) 0.5-1ppm
b) 0.1-0.2ppm
c) 3-7ppm
d) 1-2ppm

Explanation: The normal dose of chlorine during post chlorination is 0.1-0.2ppm. It kills bacteria and oxidizes the organic matter present in water.

8. Which of the following regarding break point chlorination is wrong?
a) It will have adequate chlorine residual
b) It will remove manganese
c) It will remove taste and odor
d) It is determined by physical test

Explanation: The break point chlorination is determined by laboratory test. It is represented by instantaneous yellow color if the orthotolidine test when the orthotolidine test is applied.

9. _______ is the application of chlorine beyond the stage of the break point.
a) Plain chlorination
b) Pre chlorination
c) Super chlorination
d) Double chlorination

Explanation: Super chlorination is the application of chlorine beyond the stage of the break point. It is followed by a contact period of 30-60 minutes.

10. The process of removal of excess chlorine from water is ____________
a) Plain chlorination
b) Dechlorination
c) Super chlorination
d) Double chlorination

Explanation: Dechlorination is the process of removal of excess chlorine from water. It can be done aeration or by the use of various chemicals like activated carbon, sodium sulfate in liquid form.

11. Which color is formed when orthotolidine is oxidized by chlorine?
a) Yellow
b) Orange
c) Green
d) Blue

Explanation: Orthotolidine is a colorless organic liquid that is oxidized into a yellow colored compound called Holoquinone.

Sanfoundry Global Education & Learning Series – Environmental Engineering.

To practice all areas of Environmental Engineering, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]