In preliminary treatment, coarse screens can sometimes be omitted if which maceration device is provided to handle large solids in sewage?

Introduction / Context:Coarse screening protects downstream pumps and basins from rags and debris. Where screening and manual raking are undesirable, in-line maceration can be used to reduce solids size so they pass safely through the system.

Given Data / Assumptions:

• Domestic/municipal wastewater with rags and fibrous materials.
• Desire to avoid separate screenings handling and disposal.
• Use of in-line mechanical devices.

Concept / Approach:

Comminutors and shredders grind/coarsely macerate solids to small particles that continue with the flow, reducing the need for coarse bar screens. Plant choice depends on headloss, maintenance, and grit content.

Step-by-Step Solution:

Verification / Alternative check:

Vendor literature and design guides list comminutors/grinders as alternatives to coarse screens in specific layouts.

Why Other Options Are Wrong:

Venturi aerator does not macerate solids; “neither” is incorrect because macerators clearly can replace coarse screens in many designs.

Common Pitfalls:

Ignoring grit abrasion on cutters; placing macerators upstream of grit removal leading to wear; not providing bypass arrangements.

Final Answer:

Both (a) and (b)