Article Dewatering of barite clay wastewater by inorganic coagulants...

You can get it from plot of "Height of interface vs time" by drawing a tangent.

You can use following paper. This paper review different methods for thickener design. Flocculation experiments is the key factor in thickener design:

Article Sedimentation and suspension flows: Historical perspective a...

Hakim Lounici Sina Ghassa Abhishek Kumar Thank you very much for your response. I read many articles in this area. My question is that when should I read the height of water interface to calculate settling rate in order to draw settling rate to flocculant dosage graph?

It's a question of exercise At the beginning, the interface seems unclear and difficult to read but after a few tests especially if we work at high concentrations of bentonite or clay, our eyes will get used to demarcate the interface For me if my memories are good it is from the third test that I began to distinguish the interface good luck

Hakim Lounici I really appreciate your response.

send me your émail or skype anything to help you

Hakim Lounici As soon as we see the water interface, we should measure the settling rate at that moment?

Of course

The key is to take exactly the same reference in this way, the error made would be the same for all the points

Hakim Lounici That's right. Thank you very much.