How to run a jar test for polyelectrolyte dosing
A step-by-step jar test to choose a flocculant grade and set a dose, using a water or slurry sample.
A jar test is a small-scale copy of your clarifier. It tells you which polymer works on your water and where to start dosing, before you commit to a drum or a tonne.
What you need
- A set of identical beakers (1 litre) and a stirrer that can hold a fast then a slow speed.
- A fresh, representative sample of your water or slurry.
- Your coagulant (if you use one) and polymer stock solution, for example 0.1%.
- Pipettes or syringes, and a timer.
Steps
- Fill each beaker with the same volume of sample and start the stirrer at a fast speed.
- Add the coagulant first, at your plant dose, and mix for about a minute.
- Add a different polymer dose to each beaker. Keep one beaker with no polymer as a control.
- Drop to a slow stir for several minutes and watch how the flocs form.
- Stop the stirrer and time how fast the flocs settle. Note the clarity of the water above them.
Try it: a jar test you can run here
Set a dose for each jar, then stir and let them settle. This is a teaching model of a typical clarifier sample, not your water; the real numbers come from a jar test on your own sample.
Reading the result
Pick the lowest dose that gives large flocs, fast settling and clear water. Too little polymer leaves fine particles; too much can stabilise the particles again and make the water cloudier. Repeat with the other charge if the first grade does not perform.
We run this test for customers free of charge. Send us a sample.
Not sure which grade suits your water?
Send us a one-litre sample or describe your process. We test it in our lab free of charge and recommend a grade and starting dose.