What type of pretreatment must be cleaned manually when the amount of debris is relatively small?

• A. bar screen
• B. sand trap
• C. wire-mesh screen
• D. cyclone degritter

Answer: (B)

When debris is light, the pretreatment that fits best is one designed for simple, manual cleaning of settled grit. A sand trap (grit chamber) works by letting heavier particles settle to the bottom, where they can be removed during routine maintenance with a manual cleanout or drain. This keeps maintenance straightforward and inexpensive when debris isn’t abundant, without relying on automatic scrapers or rinsing mechanisms. In contrast, bar screens and wire-m mesh screens are typically cleaned more continuously to prevent clogging from even small amounts of solids, and a cyclone degritter operates as an automatic unit that handles grit removal without requiring manual cleaning. So for a small debris load, a sand trap is the most appropriate choice because it aligns with simple, manual cleanup.