CWS Iron, Manganese & Hydrogen Sulfide Removal 3

Question 1

What is the primary difference between 'clear-water' iron and 'red-water' iron?

Accepted Answer

Clear-water iron is ferrous (dissolved); red-water iron is ferric (oxidized particulate)

Answer

Clear-water iron is dissolved ferrous iron that appears colorless when first drawn but turns red-brown upon exposure to air; red-water iron is already oxidized ferric iron visible as particles.

Question 2

Hydrogen sulfide in well water is most effectively removed by which treatment approach?

Accepted Answer

Aeration or chlorination followed by filtration

Answer

Hydrogen sulfide is a dissolved gas that must first be oxidized or stripped from solution via aeration or chlorination before filtration removes residual solids.

Question 3

Which water condition is most likely to keep iron in dissolved ferrous form and prevent natural oxidation?

Accepted Answer

Low pH and low dissolved oxygen

Answer

Low pH and low dissolved oxygen create reducing conditions that favor soluble ferrous iron and prevent it from oxidizing to insoluble ferric iron.

Question 4

A water sample tests at 0.6 mg/L iron and 0.08 mg/L manganese. Which statement correctly describes these results against EPA secondary standards?

Accepted Answer

Both exceed EPA secondary standards

Answer

Both readings exceed their respective SMCLs: iron SMCL is 0.3 mg/L (0.6 exceeds it) and manganese SMCL is 0.05 mg/L (0.08 exceeds it).

Question 5

Which aeration system design is most effective for removing high concentrations of hydrogen sulfide gas from water?

Accepted Answer

Packed tower aeration or spray aeration open to atmosphere

Answer

Packed tower or spray aeration maximizes air-to-water contact in an open atmosphere, allowing hydrogen sulfide gas to escape efficiently.

(CWS) Certified Water Specialist Practice Test

(CWS) Certified Water Specialist Practice Test

CWS Iron, Manganese & Hydrogen Sulfide Removal 3