Flocculation is crucial in drinking water treatment, yet conventional techniques like jar tests may lack precision in capturing particle heterogeneity. To overcome this, a non-intrusive image-based system was employed to directly assess flocculation using aggregate size distribution (ASD). Integrating ASD into a kinetic model with a single parameter (β) allowed for tracking ASD during flocculation. Bench and pilot-plant scale experiments validated our approach. Sensitivity analysis confirmed β's responsiveness to ASD variations (r > 0.92), with modelling indicating errors averaging around 5%, underscoring its efficacy in assessing flocculation efficiency. Linking ASD coefficients from bench to pilot-scale models facilitates predicting flocculation performance.