The sludge settles extremely poorly
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In the oxidation ditch process, the sludge has extremely poor sedimentability; almost no sedimentation occurs within the SV30 period, at around 98%. The DO level is around 3, while the MLSS value is approximately 4000. The direct reason is the rectification work at the plant; sludge removal was suspended for 5 days, and it has been 2 months now with no change in this situation. Microscopic examination revealed filamentous fungi, finely fragmented sludge, and moderate activity. The incoming water has a COD of 450 and a TN level of 55, and the water treatment performance has been fairly good. It’s just the settlement difference. I tried using PAC as well as PAM, but with no effect – the sludge wouldn’t settle, the secondary sedimentation tank kept filling with sludge, and it was impossible to remove the sludge. Solve!
How is the dissolved oxygen? The preliminary judgment is: 1. Low load, low COD in the influent or low inflow volume ； 2. The F/M ratio is too low, resulting in sludge aging ； 3. Excess DO leads to excessive oxidation, causing the sludge to disintegrate. The impact on the effluent is minimal in the short term; however, if it is delayed for a few more days, an increase in SS and COD levels in the effluent will occur. Countermeasures: 1. Reduce dissolved oxygen ； 2. Reduce MLSS and increase sludge discharge ； 3. Increase external return flow ； 4. Supplement some nutrients if possible.
We plan to add some nutrients now and observe the effects.