Regarding the problem of blackening in the sludge of the aerobic tank
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I work with chemical wastewater; recently, the level of pollutants in the effluent has been quite high, around 1000. The sludge in the aerobic tank has turned black; it seems to have lost its vitality. How can we restore the color of the sludge? We have already increased the aeration level, but after 10 days the sludge remains black. May I ask how experts would address this processing process, which involves going from the equalization tank to the primary sedimentation tank, then to the adjustment tank, followed by the anaerobic tank and the aerobic tank, and finally the secondary sedimentation tank? The COD level of the incoming water is 4000, and the concentration in the aerobic tank is around 2000; meanwhile, the SV30 value remains at 95. The secondary sedimentation tank discharges very little sludge; only a small amount is removed when the sludge on its surface is about to float to the top. 250 tons of water are introduced daily.
Why isn’t sludge discharged from the secondary sedimentation tank? With such a high SV30 value, and a settling ratio remaining above 85% for an extended period, it represents a serious malfunction.
1. Drain the sludge as soon as possible; keeping the MLSS at 3–4 g/L is sufficient. If conditions permit, it can also be adjusted based on the F/M ratio； 2. Stop feeding water to allow a period of anaerobic conditions, and monitor DO regularly; resume water feeding only once DO exceeds 2 ； 3. Reduce the backflow volume or temporarily stop backflow to extend the residence time ； 4. Reduce the flow at other gas-consuming points, and increase the aeration in the aerobic tank to the maximum level ； 5. Lower the water level in the aerobic tank by siphoning it off or pumping out a portion of it.
The common cause of blackening in aerobic sludge is insufficient dissolved oxygen; find ways to increase it. SV30 is too high; is continuous aeration better, or should an aerobic process such as SBR with intermittent operation be used?
The sludge in my papermaking wastewater treatment plant has also turned black; the DO level is too low, always below 1. The water temperature is high, above 39 degrees, and the concentration of the incoming water is too high, resulting in excessive load. Now, fresh water is added to the biochemical tank to dilute the concentration.