Filtration Media & Technologies Flashcards

Which of the following best describes the 'empty bed contact time' (EBCT) parameter used in carbon filtration design?

Answer: The time water spends in contact with carbon media as it flows through the bed

EBCT is calculated as bed volume divided by flow rate and represents the theoretical contact time water has with activated carbon media, influencing contaminant removal efficiency.

A customer reports their calcite neutralizer filter is consuming media faster than expected. The most likely cause is:

Answer: Very low pH and high CO₂ in the source water

Calcite dissolves at a rate proportional to influent acidity; very low pH combined with high CO₂ aggressively dissolves calcite, requiring more frequent media replenishment.

Iron bacteria in a well can cause a filter to foul rapidly. Which treatment strategy is most effective before the filter?

Answer: Shock chlorination of the well and continuous chlorine injection

Shock chlorination disinfects the well to reduce iron bacteria populations, and continuous chlorine injection upstream of the filter kills bacteria and oxidizes iron before it reaches the media.

What is the primary advantage of catalytic carbon over standard granular activated carbon for treating chloramine-containing water?

Answer: Catalytic carbon has enhanced surface catalysis that decomposes chloramines more rapidly

Catalytic carbon's modified surface chemistry greatly accelerates the decomposition of chloramines, whereas standard GAC removes chloramines slowly through a combination of adsorption and reaction.

In membrane filtration, which process operates at the highest transmembrane pressure and removes the smallest particles?

Answer: Reverse osmosis

Reverse osmosis operates at the highest pressure (100–1000 psi) and removes dissolved salts, viruses, and ionic contaminants at the sub-nanometer scale.

A filter media's 'bed depth to grain diameter ratio' (L/d) is important because:

Answer: Insufficient L/d results in poor particle capture and early breakthrough

An adequate L/d ratio (typically ≥1000 for sand) ensures enough contact opportunities for particles to be captured; too shallow a bed relative to grain size allows particles to pass through without removal.

Which of the following is a key indicator that a carbon filter has reached the end of its effective service life?

Answer: Breakthrough of target contaminants in the effluent

Contaminant breakthrough — the appearance of target substances (e.g., chlorine, VOCs) in the effluent at unacceptable levels — is the definitive indicator that carbon adsorption capacity is exhausted.