Filtration Media & Technologies Flashcards
7 cards from real CWS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Filtration Media & Technologies flashcards as text
Which filter media would be MOST appropriate for a whole-house system where the source water contains both high iron and significant hydrogen sulfide (H₂S)?
Answer: Catalytic carbon with continuous air injection
Catalytic carbon paired with air injection oxidizes both iron and hydrogen sulfide effectively before they are filtered, addressing both contaminants in a single vessel system.
What does the term 'turbidity' measure, and which unit is used to report it?
Answer: Cloudiness caused by suspended particles, reported in NTU
Turbidity measures the light-scattering cloudiness of water caused by suspended particles and is expressed in Nephelometric Turbidity Units (NTU).
In a point-of-use ultrafiltration system, which contaminant class CANNOT be reliably removed?
Answer: Dissolved lead ions
UF membranes (0.01–0.1 µm pores) effectively remove bacteria, protozoa, and most viruses, but dissolved ionic contaminants such as lead require reverse osmosis or ion exchange for removal.
A properly sized sediment pre-filter upstream of an RO membrane serves primarily to:
Answer: Remove suspended particles that would foul or damage the RO membrane
Sediment pre-filtration removes suspended solids that would physically plug RO membrane channels, extending membrane life and maintaining system flux.
What is 'channeling' in a filter bed, and what is the most common cause?
Answer: Flow bypassing media through cracks caused by improper backwash or media compaction
Channeling occurs when water finds preferential flow paths through voids or cracks in the media, bypassing proper filtration; it is most often caused by inadequate or infrequent backwashing that allows media to compact unevenly.
Coagulation-assisted filtration improves filter performance primarily by:
Answer: Destabilizing colloidal particles so they form larger, filterable flocs
Coagulants such as alum or ferric chloride neutralize the negative charge on colloids, allowing them to aggregate into flocs large enough to be captured within the filter media.
Which operational parameter most directly controls the service run length (time between backwashes) of a sediment filter?
Answer: Turbidity and suspended solids load in the influent
The higher the influent turbidity and suspended solids concentration, the faster the media bed loads and the more frequently backwashing is required to restore filter performance.