Diluted SV30 test - for systems with very high MLSS

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.