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November 2009, Vol. 21, No.11
Certification Quiz
Test Your Knowledge of Membranes
True or False Questions:
- Flux is the volume of water that passes through a membrane per unit of time and per unit of surface area of the membrane.
- Microfiltration and ultrafiltration remove impurities via diffusion and electrostatic exclusion.
- Cellulose acetate membranes are well suited to high-pH wastewaters.
- Membrane filtration systems typically function as the limiting hydraulic flow restriction in a wastewater treatment plant.
Multiple Choice Questions:
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Which of the following choices is an advantage of a membrane bioreactor system?
A. Reduced downstream disinfection demand.
B. Availability of extensive long-term data.
C. Decreased potential for system foaming.
D. Ability to treat flows well above design specifications.
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Where are turbidmeters often installed in a system to monitor membrane integrity?
A. In the biological process tank.
B. On the influent side of the membrane.
C. On the effluent side of the membrane.
D. In the effluent discharge flow.
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What is the standard range of operating pressures for an ultrafiltration system?
A. 1–30 lb/in.2.
B. 3–80 lb/in.2.
C. 70–220 lb/in.2.
D. 800–1200 lb/in.2.
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Which of the following choices is not a type of membrane element commonly used on wastewater treatment?
A. Flat sheet.
B. Hollow fiber.
C. Spiral-wound cylinder.
D. Reticulated.
Questions developed by Steve Spicer and reviewed by the Association of Boards of Certification (Ames, Iowa) Validation and Examination Committee.
Answer Key:
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1. True.
2. False. Microfiltration and ultrafiltration remove impurities via sieving — the pores in the membrane are too small to allow suspended solids and some microorganisms to pass. Reserve-osmosis membranes, however, use sieving, diffusion, and electrostatic exclusion to remove suspended and dissolved solids, as well as dissolved salts and metal ions.
3. False. Cellulose acetate membranes are limited to a pH range of 3 to 6.
4. True.
5. a.
6. c. Control systems are often designed to trigger alarms if turbidity exceeds a set point following membrane filtration. Increased turbidity indicates that solids are making their way past the membrane.
7. b.
8. d.
References:
Water Environment Federation (2006). Membrane Systems for Wastewater Treatment, New York: WEF Press/McGraw–Hill.