Headworks unit operations: In a wastewater treatment plant, which type of material is primarily removed in a grit chamber?

Introduction / Context:
Grit chambers are among the first unit operations in a wastewater treatment facility. They are designed to protect downstream equipment by removing abrasive and settleable materials. Understanding what these units target helps in proper sizing and operation.

Given Data / Assumptions:

• Flow is raw sewage entering headworks after coarse screening.
• Velocity control maintains a zone where heavy particles settle while organics stay in suspension.
• Common grit includes sand, silt, eggshells, and similar materials.

Concept / Approach:
Grit chambers exploit gravity settling at controlled velocities (often around 0.3–0.6 m/s) to capture dense, inorganic particles while minimizing capture of biodegradable organics. Removing inorganics reduces pump wear and prevents deposition in channels and aeration systems. Organics are later handled in primary clarifiers and biological units; dissolved pollutants require different processes such as biological oxidation or advanced treatment.

Step-by-Step Solution:
Recall the purpose: protect equipment by removing abrasive solids.Identify target materials: inorganic grit like sand and silt.Choose “Inorganic.”

Verification / Alternative check:
Operation manuals describe grit washing to minimize organic carryover and disposal of separated inorganics, confirming the intended removal class.

Why Other Options Are Wrong:
Organic/Fatty: Typically float or remain in suspension at grit-chamber conditions; removed later by skimming or biological treatment.Dissolved: Not removed by physical settling; requires chemical/biological processes.

Common Pitfalls:

• Running velocities too low, which traps organics and creates odour.
• Neglecting grit washing, leading to putrescible content in grit.

Final Answer:
Inorganic