Certification Action Line features questions and answers typical of those appearing in Water Quality Association certification examinations. Some answers
may not satisfy everyone or every condition.
| Q. |
When osmotic shock occurs, it does not directly affect the membrane. (True or False)
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| A. |
False. Osmotic shock involves sudden shrinkage or swelling of the membrane.
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| Q. |
Reverse osmosis (RO) requires greater feed pressure than ultrafiltration. (True or False)
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| A. |
True. There are line pressure RO systems, but it is usually true.
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| Q. |
In laboratory use, it is not particularly unusual to find the same water treated by ultrafiltration, RO and deionization (DI). (True or False)
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| A. |
True. Such as pharmaceutical water treatment.
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| Q. |
The advantage of presoftening an RO feedwater containing hardness is the reduction of membrane fouling. ( True or False)
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| A. |
True. Presoftening will help reduce buildup of calcium carbonate and calcium sulfate on the membrane.
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| Q. |
In RO, the membrane is synthetically produced to have specific properties. (True or False)
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| A. |
True. Semipermeable membranes are manufactured from organic substances: cellulose acetate, cellulose triacetate or aromatic polyamide resins.
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| Q. |
The oxygen content of water has an adverse effect on the RO process. (True or False)
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| A. |
False. Oxygen is a dissolved gas and does not in and of itself affect the RO process.
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| Q. |
The rejection percentage is the percent of water going to waste in an RO unit. (True or False)
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| A. |
False. Percent rejection = TDS in feed – TDS in permeate x 100 TDS in feed.
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| Q. |
Since RO does not require regeneration like DI, it is the best method for producing the highest-quality water. (True or False)
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| A. |
False. RO is a physical separation of impurities. DI is more a chemical reaction (ion exchange), which produces a higher-quality product water.
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| Q. |
RO rejects all mineral ions on the same percentage basis. (True or False)
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| A. |
False. RO is selective; different minerals, different percent.
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| Q. |
Higher feedwater temperature improves the refection rate (percent rejection). (True or False)
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| A. |
False. Temperature affects the (permeate flux) product flow rate but does not significantly affect the permeate quality.
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