Regarding the sudden drop in settlement ratio
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I’m currently conducting pilot tests with 4 different bacterial strains; after 24 hours, the sedimentation ratio increased to 75+. Microscopic examination showed a significant presence of filamentous bacteria. However, after 48 hours, the sedimentation ratio of two of these strains dropped suddenly to 30-40. I need help.
This post was last edited by zhaolijun on 2015-9-2 at 17:53. Bacteria multiply in large numbers during the initial stage, and with the abundant nutrients supplied, cell secretions and excess hydrocarbons lead to sludge bulking. It isn’t filamentous bacteria that cause this bulking; some bacterial strains secrete polysaccharides that accelerate sedimentation. Based on technical analysis, it is estimated that the bacteria responsible for rapid sedimentation are of this type.
Under microscopic examination, it is checked whether the amount of filaments has decreased and whether the properties of the sludge have improved. Generally, it is normal for SV to decline as the sludge matures due to changes in its settling properties, and this is also a sign of improvement. It’s easier to judge when combined with MLSS.
As the sludge matures, free bacteria gradually decrease, and swimming ciliates are replaced by more advanced sessile and creeping ciliates. The flocculation property of the activated sludge improves continuously, SV30 decreases, and SVI keeps dropping until it reaches the recommended value, allowing the operation to return to normal.
It could also be that there is less substrate, the dissolved oxygen level is low, and as a result more organisms die.