Gravity Thickening

Static Cylinder Tests

These tests make use of a two liter graduated cylinder in which feed solids concentration, flocculant dosage, pH and temperature can be varied to determine the rise rate and unite area of the material tested as well as underflow density.

Dynamic Thickening Tests

This test utilizes a continuous bench scale unit equipped with a motorized rake mechanism and pumps for continuous feed and flocculant delivery. An underflow pump is used to withdraw solids from the bottom of the unit to measure the solids content at various hydraulic loading rates. This test is used to design high rate, high density and paste type thickeners.


Static and dynamic thickening test data can be collected to determine thickener sizing and operating parameters.  The type of testing to be conducted will be determined by both the type of thickener desired (conventional, high-rate, high-density, etc.) and by the amount of sample available for testing.

Static Thickening Testing

Static thickening tests will be conducted on each distinct sample.  The effect of feed solids concentration, flocculant dosage, underflow density and other controllable physical parameters (within flowsheet constraints) will be examined.

Compression zone data, important in high rate thickener sizing, is also gleaned from static tests.

Static thickening tests examine flocculation requirement, hydraulic loading rate, unit area requirements, feed solids concentration sensitivity, and to predict underflow solids concentration for conventional thickeners.

Dynamic Thickening Testing

Continuous tests will be conducted on each distinct sample in a bench-scale dynamic thickener.  Again, feed solids concentration, flocculant dosage, system hydraulics and so forth will be examined to define parameters important for sizing and operating a high rate thickener.

Continuous high rate thickening tests to examine feed rate (hydraulic stress) versus flocculant dosage and feed solids sensitivity at known pH.

Static extension tests to predict underflow solids concentration with time in the dynamic test unit at higher rake speeds, as compared to results produced from standard conventional thickening test methods with a lower rake speed.

High Density Thickening Testing

For deep-bed, and/or paste thickening test work, feed is pumped continuously into deep bed columns and underflow density measurements are taken over an extended period of time to determine the effect of bed depth on underflow compaction.