Laboratory practice in wastewater analysis: Which apparatus is used for evaporation and measurement of settlable solids in sewage?

Introduction / Context:

Settlable solids testing helps assess grit and heavier particulate fractions in wastewater primary treatment. The Imhoff cone is a standardized device for measuring the volume of settleable solids after a defined settling period.

Given Data / Assumptions:

• Objective: identify the correct apparatus for settlable solids measurement.
• Standard settling interval (typically 60 minutes) applies to Imhoff cone tests.

Concept / Approach:

The Imhoff cone is a clear, conical vessel graduated at the tip to read settled solids volume directly (e.g., mL/L). It is specifically designed for wastewater settleability tests.

Step-by-Step Solution:

Verification / Alternative check:

Wastewater lab manuals list the Imhoff cone method for primary settling performance checks.

Why Other Options Are Wrong:

• Jar / test tube / generic beaker (breaker): Not standardized for direct volume reading of settled solids in mL/L.
• Graduated cylinder only: Lacks the conical tip and standardized graduation for this test.

Common Pitfalls:

• Confusing jar tests for coagulation with settlable solids measurement.

Final Answer:

an Imhoff cone