Settling behavior: In sedimentation, discrete (granular) particles exhibit what change while settling under quiescent conditions?

Introduction / Context:
Sedimentation theory distinguishes between discrete (Type I) settling and flocculent (Type II) settling. Understanding the difference is vital for selecting and designing clarification processes and for correctly interpreting jar tests and settling column data.

Given Data / Assumptions:

• Discrete (granular) particles are non-flocculent.
• Chemistry and surface conditions remain constant during settling.
• No coalescence or breakage is assumed.

Concept / Approach:
Discrete settling implies each particle settles independently without changing its physical characteristics. The drag force and terminal velocity are functions of particle size, shape factor, and density difference, but these parameters are treated as constant during the observation period for Type I settling.

Step-by-Step Explanation:
Consider Type I (discrete) regime: particles do not coalesce or flocculate.Size, shape, and specific gravity remain constant for each particle.Therefore, there is no change in size, shape, or weight while settling.

Verification / Alternative check:
Textbook definitions of Type I settling explicitly state that particles settle as individual entities with invariant properties, in contrast to flocculent settling where agglomeration changes effective size and settling velocity.

Why Other Options Are Wrong:
Options a–c: contradict the definition of discrete settling.Option e: describes flocculent settling, not discrete settling.

Common Pitfalls:

• Assuming all suspended solids flocculate; many mineral particles behave discretely in plain sedimentation.
• Confusing biological flocs with inert granular particles.

Final Answer:
None of these