# Environmental Engineering Questions and Answers – Physical characteristic of Water

This set of Environmental Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Physical characteristic of Water”.

1. The size of suspended solids lies in the range of ________
a) 10-3 – 10-6 mm
b) 103 – 106 mm
c) 10-1 – 10-3 mm
d) 101 – 103 mm

Explanation: Size of suspended solids – 10-1 – 10-3 mm, size of colloidal solids – 10-3 – 10-6 mm, size of dissolved solids < 10-6 mm.

2. Suspended solids are measured by which of the following?
a) Turbidity rod
b) Gravimetric test
c) Chromatography
d) Jackson’s turbidity meter

Explanation: Turbidity rod and Jackson’s turbidity meter is used to find turbidity whereas chromatography is used to detect odour. Hence b is the correct answer.

3. The maximum permissible limit for suspended solids is ____________
a) 10 mg/l
b) 20 mg/l
c) 30 mg/l
d) 40 mg/l

Explanation: The maximum permissible limit for suspended solids is 30mg/l for testing waste water which is set by the Environmental Protection Agency (EPA).

4. Identify the correct relation between the following?
a) Dissolved solid = Total solid + Suspended solid
b) Dissolved solid = Total solid – Suspended solid
c) Total solid = Dissolved solid / Suspended solid
d) Dissolved solid = Suspended solid – Total solid

Explanation: Dissolved solid is the difference between total solid and suspended solid. Suspended solid is non-filterable solid whereas dissolved solid is filterable solid.

5. Which method is used to measure the color of water?
a) Gravimetric analysis
b) Chromatography
c) Tintometer method
d) Hydrometer analysis

Explanation: The colors in water are measured by Tintometer method. It is measured on Burgess scale or cobalt scale by Nessler’s tube.

6. 1 TCU (True Color Unit) is equivalent to _____
a) The color produced by 1 g of platinum cobalt
b) The color produced by 1 mg of platinum cobalt
c) The color produced by 1 mg of platinum cobalt in 1L of distilled water
d) The color produced by 1 mg of platinum cobalt in 1mL of distilled water

Explanation: 1 TCU (True Color Unit) is equivalent to color produced by 1 mg of platinum cobalt in 1L of distilled water. The true color unit is also called a Hazen unit.

7. The range for threshold odour number is __________
a) 0-3
b) 1-5
c) 1-3
d) 0-5

Explanation: The maximum value of Threshold odour number is 3 and its range is 1-3. The threshold odour number is used to measure the intensity of taste and odour.

8. Threshold odour number testing is preferred in hot water.
a) True
b) False

Explanation: TON testing is preferred in cold water as in hot water due to increase in temperature, taste and odour can change.

9. One JTU is equivalent to turbidity produced by __________
a) 1mg of fine silica dissolved in 1L of distilled water
b) 1g of fine silica dissolved in 1L of distilled water
c) 1g of fine silica dissolved in 1ml of distilled water
d) 1mg of fine silica dissolved in 1ml of distilled water

Explanation: 1 JTU is equivalent to turbidity produced by 1mg of fine silica dissolved in 1L of distilled water. It is called as Jackson’s turbidity unit and is based on the absorption principle.

10. If the PO value is 6, what does it imply?
a) No perceptible odour
b) Very faint odour
c) Very distinct odour
d) Extremely strong odour

Explanation: The PO value indicates the odour intensity. 6 is the maximum PO value and it indicates extremely strong odour.

11. The range of temperature of water that is required to do the temperature test is __________
a) 10-250C
b) 0-250C
c) 10-300C
d) 20-300C

Explanation: To do the temperature test of water, its temperature should be between 100C and 250C and the temperature higher than 250C is considered objectionable.

12. Which of the following statement is wrong regarding turbidity?
a) It is an extent to which light is absorbed by particles in the water
b) It is expressed in ppm
c) It depends on the fineness of particle present in the water
d) Turbidity rod is a laboratory method to measure turbidity

Explanation: Turbidity rod is a field method not a laboratory method to measure turbidity.

13. The permissible limit of turbidity of domestic water is ____ ppm.
a) 5-10
b) 1-5
c) 10-50
d) 10-30

Explanation: According to WHO, the permissible limit for drinking water is 5NTU.

14. What is the full form of NTU in context with turbidity?
a) Number of transfer unit
b) Neurological turbidity unit
c) Nephelometric turbidity unit
d) Network terminal unit

Explanation: The value of turbidity measured by nephelometer is expressed in terms of NTU. Sometimes, it is referred as FTU or Formazin turbidity unit.

15. When depth of insertion of turbidity rod increases, the reading in the turbidity rod ___
a) Decreases
b) Increases
c) First decrease, then increase
d) Remains constant

Explanation: Turbidity rod is inserted inside the water and the reading at which needle becomes invisible gives the turbidity.

Sanfoundry Global Education & Learning Series – Environmental Engineering.

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