Water treatment — in flocculation, which property of flocculated particles does not change?

Introduction / Context:
Flocculation is the gentle mixing stage after coagulation where destabilized colloids agglomerate into larger, settleable flocs. Understanding which particle characteristics evolve (and which remain effectively unchanged) helps operators interpret jar tests and optimize mixing energy and coagulant aids.

Given Data / Assumptions:

• We consider individual primary particles combining into aggregates (flocs).
• Water chemistry (pH, alkalinity) and coagulant dose are appropriate for aggregation.
• “Weight” here is interpreted as the intrinsic material density/weight per unit solid content of the constituent particles (not the growing mass of an aggregate as it captures more solids).

Concept / Approach:

During flocculation, particles collide and stick, forming irregular aggregates. The aggregate’s size increases and its shape becomes more irregular (higher porosity/floc factor). However, the intrinsic material density of the constituent solids does not change; what changes is bulk (apparent) density due to entrapped water and porosity. Classical teaching phrases this as: size and shape change, but the basic particle material property (often described in questions as “weight”/“specific gravity”) does not.

Step-by-Step Solution:

Verification / Alternative check (if short method exists):

Jar tests show rising floc size without chemical change in mineral composition; density of solid phase remains the same, although aggregate apparent density can differ.

Why Other Options Are Wrong:

Size and shape clearly change during flocculation; “none of these” ignores evident aggregation effects.

Common Pitfalls (misconceptions, mistakes):

Confusing intrinsic solid density with aggregate bulk density; assuming flocculation alters chemistry of the solid phase.

Final Answer:

weight