Water and Wastewater.com Help Forum - Centrifuge (spin) test

Water and Wastewater.com Help Forum - Centrifuge (spin) test

Question
Anyone remember the spin test for solids management? I remember how to do the test.....just can't recall what the numbers meant. I know it was not a true representation of the % Solids. Any help? Using the 12.5 mL graduated vials.

We are down on staffing and some of the concessions are losing a couple days of non-DMR lab data...we are looking to get at least an idea of what is going on with our MLSS in an extended aeration process.

I realize we could probably do the analyses along with the lab and establish some sort of reference chart.....

Answer
as you already noticed the volume of the sediment after spinning cannot be a true representation of % solids.
Consider the following
# depending on the properties of the suspended solids and centrifugal acceleration time to reach equilibrium will vary.
# the relation of equilibrium sediment volume to suspended solids depends on properties of suspended solids, but also markedly on solids concentration. The higher the concentration the higher the excess pressure acting on the sediment.

From this you can see that a spin test can be a method for fast characterization of properties of suspended solids, when total solids are determined in parallel (Our company is offering a multisample analytical centrifuge, which is also applicable for this purpose).
For the intended purpose of measuring suspended solids the method will only be reliable if properties of suspended solids are fairly constant.