Waste Water Engineering Questions and Answers – Total Dissolved Solids – 2

This set of Basic Waste Water Engineering Questions and Answers focuses on “Total Dissolved Solids – 2”.

1. What is the process by which Total dissolved solids are removed?
a) Reverse Osmosis
b) Ultrafiltration
d) Clarification

Explanation: The total dissolved solids are removed by reverse osmosis. Water passing through a semi permeable membrane is subjected to pressure greater than osmotic pressure. In this process, the ions are removed.

2. What is the limit of total dissolved solids in treated water which is to be used for the gardening purpose?
a) 1200 mg/L
b) 1100 mg/L
c) 1000 mg/L
d) 500 mg/L

Explanation: The limit of total dissolved solids in treated water is 1200 mg/L. This holds good for surface water. According to the applications, the limit of total dissolved solids is fixed.

3. What is the percentage of TDS removed by the reverse osmosis membrane?
a) 97-99%
b) 50-60%
c) 60-70%
d) 70-90%

Explanation: The amount of TDS removed is around 97-99%. This depends on the membrane used. This depends on the salt rejection of the membrane.

4. What is the flux assumed while designing the reverse osmosis system to treat surface water?
a) 3-10 LMH
b) 14-28 LMH
c) 28-32 LMH
d) 32-40 LMH

Explanation: The flux assumed while designing the reverse osmosis system to treat surface water is 14-28 LMH. This depends on the influent TDS. Also, this also depends on the required TDS in the treated effluent.

5. What is the flux assumed while designing the reverse osmosis system to treat well water?
a) 3-10 LMH
b) 13-23 LMH
c) 24-30 LMH
d) 30-35 LMH

Explanation: The flux assumed while designing the reverse osmosis system to treat well water is 24-30 LMH. This depends on the influent TDS. Also, this also depends on the required TDS in the treated effluent.
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6. What is the flux assumed while designing the reverse osmosis system to treat RO permeate?
a) 3-10 LMH
b) 13-20 LMH
c) 23-30 LMH
d) 34-50 LMH

Explanation: The flux assumed while designing the reverse osmosis system to treat RO permeate is 34-50 LMH. This depends on the influent TDS. Also, this also depends on the required TDS in the treated effluent.

7. What is the % flux decline per year assumed while designing the reverse osmosis system for treating surface water?
a) 7.3-9.9
b) 9.9-11.2
c) 11.2-14
d) 14-16

Explanation: The % flux decline per year assumed while designing the reverse osmosis system for treating surface water is 7.3-9.9. The SDI considered is between 2-4. This is a very important factor while designing a reverse osmosis system.

8. What is the % flux decline per year assumed while designing the reverse osmosis system for treating well water?
a) 4.4-7.3
b) 8.5-11.5
c) 12-15
d) 15-18

Explanation: The % flux decline per year assumed while designing the reverse osmosis system for treating surface water is 4.4-7.3. The SDI considered is between 2-4. This is a very important factor while designing a reverse osmosis system.

9. What is the % flux decline per year assumed while designing the reverse osmosis system for treating RO permeate water?
a) 2.3-4.4
b) 4.4-7.3
c) 7.3-9.9
d) 12-16

Explanation: The % flux decline per year assumed while designing the reverse osmosis system for treating surface water is 2.3-4.4. The SDI considered is between <2. This is a very important factor while designing a reverse osmosis system.

10. What is the limit of LSI assumed while designing the reverse osmosis system without a scale inhibitor?
a) <0.2
b) 0.5-1
c) 1-2
d) 2-4

Explanation: The LSI is <0.2 assumed without scale inhibitor while designing the reverse osmosis system. With organic scale inhibitor, the value assumed is different. It is assumed <1.8.

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