Diluted SV30 test - for systems with very high MLSS - BIOLOGICAL WASTE TREATMENT EXPERT

Diluted SV30 test - for systems with very high MLSS

2/18/2020

Photo of SV30 test from http://web.deu.edu.tr/

When you have MLSS above 5,000 mg/L, SV30 tests often have solids with a very narrow band of supernatant. This can make it difficult to diagnose problems with pin floc, settling velocity, and compaction. If you see the water phase of less than 20% of the settleometer, the diluted SV30 test may prove useful. Here is how to run a diluted SV30:

Fill your settleometer with 25 - 50% MLSS taken from the aeration basin. Make sure you mix the sample first to ensure you have solids all suspended.
Use effluent or tap water to fill the settleometer. Again mix the MLSS/Water blend to suspend the solids.
Start 30 minute timer. Note sludge level at time 5, 10, 15, 20, 25, & 30. Adjust dilution to have SV30 settled solids reading between 150 - 300 ml on the settleometer. After settling, note floating solids and pin-floc in the supernatant. You should also let the solids continue to compact for 2 - 4 hours. Evaluating the compacting solids gives information about how concentrated the RAS solids will become in the secondary clarifier.
For reporting purposes and SVI calculations, remember to multiply by your dilution factor.

Frederik Wynants

2/21/2020 12:04:52 am

When i run al diluted SV30 i get straggler flocs in the supernatant. The more i dillute the more stragglers. What does that mean ? Initial MLSS concentration is around 3700 mg/L. By straggler flocs i mean relative big but fluffy, light macroflocs.

Grace Wright

5/10/2021 10:44:34 am

The short answer is, It depends.

What is your MLSS?
What is your SV30 without dilution?

If you are not over 5000 mg/L and 750-800 on your MLSS / SV30
it probably does not mean much.

Have you run a side by side?
One not diluted and the other diluted?
If they were not pretty close after adjusting for the dilution factor there isn't much point in doing them.

Generally young sludge settles pretty quick leaving straggler flock behind. Sludge should be tan to brown. Increase augmentation (waste less).

Generally old sludge settles very fast, leaves a lot of particles behind, is very dark to black in color and the supernatant is dark and ashy. Decrease augmentation (waste more).

Are you using a real settlometer or a cylinder?
We have seen higher numbers on the same sample when using the tall form over a using a true settlometer.

5/13/2021 10:23:22 am

Thank You for you answer Grace. I use a 1 liter glass cylinder. I am aware of the fact that the type of recipient can influence the SV30 value. But what fascinates me are the effluent suspended solids in the supernatant. Obviously the initial concentration of the MLSS has to do with it. Probably some kind of flocculation phenonemon i think.

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Diluted SV30 test - for systems with very high MLSS

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