CWS Filtration Media & Technologies 3

Question 1

What is the recommended maximum service flow rate for a greensand filter treating iron-bearing water?

Accepted Answer

3–5 gpm/ft²

Answer

Greensand filters are typically rated for 3–5 gpm per square foot of bed area to allow adequate contact time for iron oxidation and filtration.

Question 2

In a pressure vessel filter, the term 'differential pressure' refers to:

Accepted Answer

The pressure drop across the filter media from inlet to outlet

Answer

Differential pressure (ΔP) is the pressure drop across the filter bed from influent to effluent, and rising ΔP indicates media loading and signals backwash need.

Question 3

Manganese greensand regeneration in the continuous regeneration (CR) mode uses which oxidant?

Accepted Answer

Potassium permanganate

Answer

In continuous regeneration mode, potassium permanganate (KMnO₄) is added to the influent to continuously re-oxidize the greensand coating as it removes manganese.

Question 4

Which media type would be MOST appropriate for a filter designed to target arsenic removal?

Accepted Answer

Iron-based adsorptive media (GFH or similar)

Answer

Granular ferric hydroxide (GFH) and similar iron-based adsorptive media are highly effective for arsenic adsorption, particularly As(V), due to strong ligand exchange with iron hydroxide sites.

Question 5

What is the purpose of a support gravel bed beneath filter media in a pressure filter?

Accepted Answer

To provide even distribution and prevent media from entering the underdrain

Answer

Graded gravel underbedding supports the filter media, prevents fines from escaping into the underdrain, and promotes even backwash flow distribution across the entire bed.

(CWS) Certified Water Specialist Practice Test

(CWS) Certified Water Specialist Practice Test

CWS Filtration Media & Technologies 3