A ____ is operating properly if the rotation is correct, no solid break through and the head loss is zero.

• A. Micro screen
• B. Belt filter press
• C. Clarifier
• D. Sand filter

Answer: (A)

The situation tests how a solids-separation device is judged by its motion, its ability to stop solids from passing through, and its pressure drop. A micro screen is a rotating screening device that continually turns to prevent clogging and to keep solids from breaking through the screen. When the rotation is at the correct speed and the screen is clean, solids are retained and there is no blockage building up, so the flow experiences essentially no pressure drop across the screen. That combination—proper rotation, no solids breakthrough, and zero head loss—fits a rotating screening unit best.

The other options don’t align with these indicators. A belt filter press is a dewatering unit that inherently has pressure loss as it compresses and removes water, not a zero head loss scenario. A clarifier works by gravity settling, not rotation, and it develops head loss due to the liquid passing through the settling basin. A sand filter also relies on a fixed bed and backwashing; it isn’t a rotating device and head loss changes with bed loading.