Monitoring particle aggregation processes.

A wide range of test methods for monitoring particle aggregation processes is reviewed. These include techniques for measuring aggregation rates in fundamental studies and those which are useful in the monitoring and control of practical coagulation/flocculation processes. Most emphasis is on optical methods, including light transmission (turbidity) and light scattering measurements and the fundamentals of these phenomena are briefly introduced. It is shown that in some cases, absolute aggregation rates can be derived. However, even when only relative rates can be obtained, these can still be very useful, for instance in defining optimum flocculation conditions. Some of the methods available for investigating properties of aggregates (flocs), such as size, strength and fractal dimension are also discussed, along with some related properties such as sedimentation rate and filterability of flocculated suspensions.