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Questions and Answers
What is the primary driving force for ion mobility in electrodialysis?
What is the primary driving force for ion mobility in electrodialysis?
Which of the following is NOT a method of membrane maintenance?
Which of the following is NOT a method of membrane maintenance?
What is the primary objective of backwashing in membrane filtration?
What is the primary objective of backwashing in membrane filtration?
What is the role of air sparging in membrane cleaning?
What is the role of air sparging in membrane cleaning?
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What is the primary mechanism of electrodialysis?
What is the primary mechanism of electrodialysis?
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What is the result of not maintaining membrane modules?
What is the result of not maintaining membrane modules?
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What is the primary goal of chemical cleaning in membrane maintenance?
What is the primary goal of chemical cleaning in membrane maintenance?
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What is the primary benefit of using backwashing in membrane filtration?
What is the primary benefit of using backwashing in membrane filtration?
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What is the primary mechanism of membrane fouling in water treatment?
What is the primary mechanism of membrane fouling in water treatment?
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What is the frequency range for automatic backwash cycles in low-pressure membrane systems?
What is the frequency range for automatic backwash cycles in low-pressure membrane systems?
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Study Notes
Pretreatment in Membrane Processes
- Pretreatment can modify feed water to prevent membrane plugging, fouling, and scaling, and prolong membrane life.
- Various pretreatments include biofiltration, advanced oxidation, pH adjustment, chlorination, and activated carbon.
Household Purification of Water
- Boiling: kills bacteria, spores, cysts, and ova, yielding sterilized water; removes temporary hardness; alters taste but is harmless.
- Chemical disinfection:
- Bleaching powder: contains 33% available chlorine; unstable on exposure to air, light, and moisture.
- Chlorine solution: prepared from bleaching powder; loses chlorine on exposure to light or prolonged storage.
- High-test hypochlorite: more stable than bleaching powder; contains 60-70% available chlorine.
- Chlorine tablets: suitable for small quantities of water but costly.
- Iodine: used for emergency disinfection of water; high costs and physiological activity limit its use.
- Potassium permanganate: no longer recommended due to its oxidizing properties and inability to kill all bacteria.
Membrane Cleaning and Maintenance
- Air sparging: helps scour material off the membrane surface, reducing particles and fouling.
- Chemical cleaning: targets contaminants causing irreversible fouling; frequency depends on membrane characteristics and source water quality.
- Backwashing: removes surface cake during membrane filtration cycle; targets reversible fouling; frequency ranges from 30-90 minutes.
Membrane Processes
- Electrodialysis: flow of ions via an ion exchange membrane, driven by electrical potential; excludes water movement.
- Dialysis: used for desalting, buffer exchange, removal of labeling reagents, drug binding studies, cell growth and feeding, virus purification, and blood treatment.
Importance of Pretreatment in Membrane Processes
- Surface waters require more extensive pretreatment than ground waters due to suspended solids and biological matter.
- Pretreatment coagulation and clarification may be necessary if raw water solids content is high.
- Pretreatment can condition feed water to allow effective membrane treatment.
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Description
This quiz covers various methods of water purification, including pretreatment techniques to prevent membrane fouling and household purification methods such as boiling, chemical disinfection, and filtration.
