Related Experiment Video
Updated: Jul 16, 2026

Capturing Flow-weighted Water and Suspended Particulates from Agricultural Canals During Drainage Events
Published on: November 7, 2017
First flush and natural aggregation of particles in highway runoff
1Dept. of Civil and Environmental Engineering, Univ. of California, Los Angeles, CA 90095-1593, USA.
Abstract:
Particle Size Distribution (PSD) in highway runoff was monitored in the 2004-2005 rainy season at three highway sites in west Los Angeles, California. PSD was measured for 200 grab samples for 18 storm events. Particles and especially larger particles showed a strong first flush. On average, the initial 20% runoff volume transported approximately 28% total number of particles between 0.5 and 2 microm in diameter, more than 30% of particles between 2 and 30 microm and more than 40% of particles larger than 30 microm. A naturally occurring aggregation was observed with smaller particles and mixing experiments were performed to determine the possible benefits for sedimentation and filtration. Samples composited from grab samples manually collected over the first hour of runoff were gently mixed (G = 38) and small particle concentration decreased by more than 50%. After 24 hours the number of particles with diameter between 0.5 and 7 microm decreased by 51% with gentle mixing and the same size particles decreased by only 14% without mixing. Number of particles with diameter larger than 20 microm increased by 6 and 4.5 times with and without mixing, respectively. Slow mixing can improve sedimentation efficiency by more than 40% for particles less than 20 microm in diameter.
Related Concept Videos
Coagulation
Precipitate Formation and Particle Size Control
The obtained precipitate should be either a pure substance of known composition or easily converted to one by a simple process, such as ignition or drying. In addition, the precipitate should be insoluble and easily filterable. In general, filterability...
Colloidal precipitates
Aggregates Classification
Petrographic classification groups aggregates based on common mineralogical characteristics. Some of the common mineral groups found in aggregates are...
Types of Coprecipitation
Sometimes, ions in a crystal lattice can undergo isomorphous replacement by inclusions of similar charge and size. For...
Precipitation Processes

