CWS Water Treatment Equipment & Technologies 3 — Questions and Answers
Question 1: What is the function of the 'freeboard' space in a water softener mineral tank?
- It stores excess brine above the resin bed
- It allows resin to expand and tumble freely during backwash (Correct answer)
- It provides space for air pockets that assist regeneration
- It holds a layer of gravel underbed separate from the resin
Correct answer: It allows resin to expand and tumble freely during backwash
Freeboard is the empty space above the resin bed that allows the resin beads to expand and agitate during the backwash cycle, releasing trapped sediment.
Question 2: Which chemical is most commonly used in a chemical feed pump to raise the pH of acidic well water?
- Sodium hypochlorite
- Polyphosphate
- Soda ash (sodium carbonate) (Correct answer)
- Potassium permanganate
Correct answer: Soda ash (sodium carbonate)
Soda ash (sodium carbonate) is widely injected ahead of the pressure tank to neutralize acidic water and raise pH, protecting plumbing from corrosion.
Question 3: A 5-micron absolute-rated filter cartridge differs from a 5-micron nominal-rated cartridge in that the absolute-rated filter:
- Has a lower pressure drop under the same flow conditions
- Guarantees removal of virtually all particles at or above 5 microns (Correct answer)
- Is constructed from activated carbon rather than spun polypropylene
- Requires lower inlet pressure to function properly
Correct answer: Guarantees removal of virtually all particles at or above 5 microns
An absolute rating means the filter is tested to remove 99.9% (or greater) of particles at the stated size, whereas nominal ratings are loosely defined efficiency approximations.
Question 4: In a greensand filtration system for iron removal, what chemical is used to continuously regenerate (or backwash-regenerate) the greensand media?
- Citric acid
- Potassium permanganate (Correct answer)
- Sodium thiosulfate
- Hydrogen peroxide
Correct answer: Potassium permanganate
Potassium permanganate (KMnO₄) oxidizes ferrous iron to ferric iron on the greensand surface and regenerates the manganese dioxide coating of the media.
Question 5: What term describes the volume of water an RO system produces daily under standard test conditions?
- Flux rate
- Gallons per day (GPD) rating (Correct answer)
- Recovery percentage
- Concentration factor
Correct answer: Gallons per day (GPD) rating
The GPD (gallons per day) rating specifies how much permeate (product water) an RO membrane produces in 24 hours under standardized pressure, temperature, and TDS conditions.
Question 6: Which type of water treatment system is specifically designed to reduce total dissolved solids (TDS) by forcing water through a semi-permeable membrane under pressure?
- Distillation unit
- Reverse osmosis system (Correct answer)
- Deionization system
- Electrodialysis reversal system
Correct answer: Reverse osmosis system
Reverse osmosis applies hydraulic pressure to overcome osmotic pressure and push water through a semi-permeable membrane, rejecting dissolved salts and other TDS.
Question 7: What is the primary advantage of a demand-initiated regeneration (DIR) controller on a water softener versus a time-clock controller?
- It eliminates the need for a brine tank entirely
- It triggers regeneration based on actual water usage rather than a fixed schedule (Correct answer)
- It uses less salt per regeneration cycle by heating the brine
- It measures water pH to determine when regeneration is needed
Correct answer: It triggers regeneration based on actual water usage rather than a fixed schedule
A DIR controller tracks gallons used and triggers regeneration only when the resin capacity is nearly exhausted, saving salt and water compared to time-clock regeneration on a fixed schedule.
CWS Water Treatment Equipment & Technologies 3
What is the function of the 'freeboard' space in a water softener mineral tank?