Top 10 viva/interview questions on salphates present in water

Presence of Sulphates in water/wastewater

Sulphates is widely distributed in nature and may also be present in natural waters in concentration ranging from few hundred to several thousand ppm. Sulphates occur naturally in a number of minerals, like barite, epsomite and gypsum. These dissolved minerals contribute to the mineral content of drinking-waters. Sulfate is the second most abundant anion in seawater. Its high concentration owes to the high to moderate solubility of the salts that it forms with the major cations in seawater, namely, Na, Mg2+, and Ca2+.

The amount of sulphates in wastewater is a factor of concern in determining the magnitude of problems that can arise from reduction of sulphates to hydrogen sulphide. For example knowledge of the sulphates content of the sludge or waste fed to digestion units provides a means of estimating the hydrogen sulphide content of the gas produced. From this information, the design engineer can determine whether scrubbing facilities will be needed to remove hydrogen sulphide and size of the units required.

Here are some viva or interview question-answers based on determination of sulphate content in given water sample.

1. In this method, the sulphates present are estimated in the form of
a) Barium Sulphate
b) Calcium Sulphate
c) Sodium Sulphate
d) Magnesium Sulphate

2. The turbidity is measured using UV-visible spectrometer at
a) 410 nm
b) 420 nm
c) 430 nm
d) 440 nm

3. For plotting a standard graph, the minimum requirement is
a) 3 standards
b) 2 standards
c) 1 standards
d) 4 standards

4. The conditioning reagent, contains _______
a) Glycerol
b) Phenol
c) Sodium sulphate
d) Sodium Hydroxide

5. The minimum detectable concentration by turbidimetric method is
a) 10 ppm
b) 5 ppm
c) 1 ppm
d) No limitations

6. A calibration curve is the plot of
a) absorbance against concentration of solutions
b) absorbance of solutions against time
c) time against concentration of solutions
d) concentration of solutions against time

7. As per Beer - Lambert’s Law the amount of light absorbed is _______ the concentration of the solution.
a) inversely proportional
b) directly proportional
c) greater than
d) smaller than

8. Transmittance is the ratio of the intensity of transmitted light to that of incident light.
a) True
b) False

9. The optical density is _______ to concentration of the substance.
a) directly proportional
b) inversely proportional

10. Blank solution is used in colorimetric estimation to
a) nullify the absorbance caused due to the colouring impurities present in the reagents
b) check the instrument
c) nullify the error caused by the instrument
d) nullify the error caused by colour

ANSWER KEY:
1) a
2) b
3) b
4) a
5) c
6) a
7) b
8) True
9) a
10) a

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