CWS Water Treatment Equipment & Technologies 2 — Questions and Answers
Question 1: What is the primary purpose of a brine tank in a water softener system?
- To filter sediment from incoming water
- To store salt used for resin regeneration (Correct answer)
- To hold treated softened water for distribution
- To neutralize acidic water before softening
Correct answer: To store salt used for resin regeneration
The brine tank stores salt (sodium chloride or potassium chloride) which is dissolved into a brine solution used to regenerate the ion exchange resin.
Question 2: Which membrane process operates at the lowest operating pressure among the four main pressure-driven membrane technologies?
- Reverse osmosis
- Nanofiltration
- Ultrafiltration
- Microfiltration (Correct answer)
Correct answer: Microfiltration
Microfiltration operates at the lowest pressures (typically 5–45 psi) because it targets the largest particles — bacteria, sediment, and protozoa — requiring less driving force.
Question 3: In an ultraviolet (UV) disinfection system, what component must be monitored regularly to ensure effective microbial inactivation?
- Inlet pressure gauge
- UV intensity sensor (or UV transmittance) (Correct answer)
- Flow control valve position
- Drain valve actuator
Correct answer: UV intensity sensor (or UV transmittance)
UV intensity sensors monitor the actual UV dose delivered; reduced transmittance from fouling or lamp aging directly lowers germicidal effectiveness.
Question 4: A carbon block filter is superior to a granular activated carbon (GAC) filter for removing chloramines primarily because:
- Carbon blocks use a different carbon source (coconut shell) than GAC
- The compressed block provides longer contact time with denser carbon (Correct answer)
- Carbon blocks also remove hardness minerals unlike GAC
- Carbon blocks operate at higher flow rates than GAC filters
Correct answer: The compressed block provides longer contact time with denser carbon
The compressed structure of carbon block filters forces water into closer, longer contact with the carbon media, improving chloramine reduction efficiency compared to the channeling that can occur in GAC beds.
Question 5: What is 'bypass hardness' in the context of residential water softening?
- Hardness minerals that pass through the softener during normal service
- Hard water intentionally blended with softened water to raise final hardness slightly (Correct answer)
- Residual hardness left on resin beads after incomplete regeneration
- The hardness level of water entering the brine tank
Correct answer: Hard water intentionally blended with softened water to raise final hardness slightly
Bypass hardness refers to a controlled blending of a small fraction of hard water into the softened water stream to achieve a target finished hardness above zero, often preferred for taste.
Question 6: Which type of RO membrane configuration is most commonly used in residential point-of-use systems?
- Hollow fiber
- Plate-and-frame
- Spiral-wound (Correct answer)
- Tubular
Correct answer: Spiral-wound
Spiral-wound membranes are the dominant configuration for residential RO because they pack a large membrane surface area into a compact cylindrical housing at low cost.
Question 7: What does a 'salt efficiency' rating express for an ion exchange water softener?
- The percentage of salt that dissolves completely in the brine tank
- The amount of hardness removed per pound of salt used during regeneration (Correct answer)
- The ratio of salt weight to resin weight in the system
- The number of regeneration cycles possible before salt refill is needed
Correct answer: The amount of hardness removed per pound of salt used during regeneration
Salt efficiency is expressed in grains of hardness removed per pound of salt consumed, with higher values indicating more economical use of regenerant.
CWS Water Treatment Equipment & Technologies 2
What is the primary purpose of a brine tank in a water softener system?