Almost every wastewater plant runs the SV30 test. Running the test is great and coupled with MLSS/MLVSS numbers gives the Sludge Volume Index (SVI) which converts settled volume to a more standardized number based on MLSS in grams. The test can also give you other valuable information. Make a few observations over 30 minutes and you can see:
- Information of where you are on the growth curve
Look at how fast the MLSS settles. Is the supernatant turbid? Are there "fines" floating on top? This can be related to biomass growth curve . - If allowed to sit over 12 - 20 hours - denitrification potential
When allowed to sit after the 30 minute test. If the sample has nitrate present and denitrifying cultures, you will see small bubbles and floating sludge. If you see the same action in the secondary clarifiers, you may want to lower bed depth or solids residence time in the clarifier.
Bulking - filamentous vs non-filamentous - SV30 shows bulking but it can also give you an idea of what type. Filaments make for a rough water/MLSS layer. Non-filamentous bulking has a more "gel" appearance when settling.
- Toxic shock loadings
Acute toxicity hits settling tests earlier than most other indicator tests. If you see turbidity caused by deflocculation, you need to start looking for spills that upset the EPS production and create conditions where cells enter lag/log phase growth. - Hints on adjusting wasting rates
Sludge that settles too fast or leaves turbid supernatant can benefit from adjusting wasting rates. Confirm hints from SV30 with other tests and always remember to waste sludge. It does cost $ to keep solids in the wastewater system.
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