The SV30 test uses a dedicated settleometer or 2L graduated cylinder to measure settling velocity and compaction in wastewater treatment biomass. (Note - always use the same size cylinder or settleometer to run the tests). To account for changes in MLSS concentration, the SVI takes the SV30 number and divides by MLSS in grams (some facilities use MLVSS in grams) - just use the same divisor each time.
Now for the SVI or SV30 being too low. Usually compact sludge is a good thing - it means no bulking and clarifiers with not solids carryover. However, if sludge settles too quickly or compacts too much there can be problems including turbidity, recycle (RAS) system troubles, and occasionally floating fines causing effluent TSS problems. Usually the problem is "Old Sludge" where lower F/M conditions over the long term result in bacteria consuming the extracellular polymer substances (EPS). Once the EPS percentage drops:
How do you investigate and fix the problem
Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.
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