Tricky Waste Water Engineering Questions and Answers

This set of Tricky Waste Water Engineering Questions and Answers focuses on “Reverse Osmosis Membrane Properties – 2”.

1. What is the permeate flux of UTC series?
a) 0.5
b) 0.8
c) 1
d) 3.3
View Answer

Answer: b
Explanation: The permeate flux of the RO membrane UTC series is 0.8, BARC-TFC1 is 0.45, BARC-TFC2 is 0.55, NS-100 is 0.7, NS-200 is 0.8, NS-300 is 3.3, PA-300/RC-100 is 1 and CP is 0.06.

2. What is the percentage salt rejection of PES-1000?
a) 98 %
b) 99 %
c) 99.8 %
d) 99.9 %
View Answer

Answer: d
Explanation: The percentage of salt rejection for RO membrane NS-100 is 99 %, NS-200 is 99.8 %, NS-300 is 68 %, PES-1000 is 99.9 %, PA-300/RC-100 is 99.4 % and FT-30 is 99%.

3. Which of these is true about reverse osmosis membranes?
a) They get hydrolysed at extreme low/ high pH conditions
b) They get hydrolysed at extreme high pH conditions
c) They get hydrolysed at extremely low pH conditions
d) They don’t get hydrolysed at extreme low/ high pH conditions
View Answer

Answer: a
Explanation: The cellulose acetate membranes get hydrolysed at extreme low/ high pH conditions. Cellulose acetate membranes are 100 microns thick. Modern membranes are blend acetate cellulose membranes.

4. Which of these materials can be made into thin film composite?
a) Polyamide
b) Cellulose acetate
c) Cellulose triacetate
d) Polyethylene sulphate
View Answer

Answer: a
Explanation: Polyamide membranes are used to make thin film composite membranes. These are available in hollow fibre sheets. These are also available in flat sheets.

5. Which of these pollutants cannot be tolerated by the hollow fibre sheets?
a) Free chlorine
b) BOD
c) COD
d) Free magnesium
View Answer

Answer: a
Explanation: The pollutants which a hollow fibre sheet cannot handle is free chlorine. It causes irreversible damage to the fibre sheet. It affects the salt rejecting capacity.

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6. What is the concentration of chlorine upto which these spiral wound membranes can withstand?
a) 2.0 ppm
b) 1.0 ppm
c) 1.5 ppm
d) 2.5 ppm
View Answer

Answer: b
Explanation: The concentration upto which these membranes withstand chlorine concentration is 1 ppm. These membranes do not require pretreatment. They are less expensive as maintenance is less.

7. What is the diameter assumed for hollow fine membranes for treating sea water?
a) 90 microns
b) 95 microns
c) 100 microns
d) 105 microns
View Answer

Answer: b
Explanation: The diameter assumed for hollow fine membranes for treating sea water is 95 microns. Du pont made the first hollow fine fibre. These membranes are self-supporting types.

8. What is the diameter assumed for hollow fine membranes for treating brackish water?
a) 90 microns
b) 95 microns
c) 85 microns
d) 80 microns
View Answer

Answer: c
Explanation: The diameter assumed for hollow fine membranes for treating brackish water is 85 microns. Du pont made the first hollow fine fibre. These membranes are self -supporting types.

9. Which type of membrane exhibit low flux?
a) Isotropic
b) Anisotropic
c) Asymmetric
d) Tubular
View Answer

Answer: a
Explanation: The membrane which exhibits very low flux is isotropic. These membranes exhibit high resistance to flow. Hence they have low flux.

10. Which type of membrane exhibit high flux?
a) Isotropic
b) Anisotropic
c) Symmetric
d) Tubular
View Answer

Answer: b
Explanation: The membrane which exhibits very high flux is anisotropic. These membranes exhibit high salt rejection. These membranes have a very thin rejecting skin.

11. Which of these can be operated by turbulent flow?
a) Tubular
b) Spiral wound
c) Plate and frame
d) Hollow fibre
View Answer

Answer: a
Explanation: The membrane which can be operated by turbulent flow is tubular type membrane. This reduces scaling and fouling. Thus this reduces the operation and maintenance cost.

12. What type of structure does the hollow fibre have?
a) Symmetric
b) Asymmetric
c) Isotropic
d) Anisotropic
View Answer

Answer: b
Explanation: The hollow fibre membranes have asymmetric structure. These are produced as long capillary tubes. These do not require additional physical support.

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