Regarding the issue of low sludge concentration in the aerobic tank
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We deal with chemical wastewater; the volume of wastewater is around 100 tons per day, and when diluted water is added, it amounts to about 300 tons, for a total of roughly 400 tons per day. We generate around 50 tons of highly acidic wastewater per day, which must first go through iron-carbon microelectrolysis before entering a collection tank. Water is added to this tank for dilution, after which the wastewater proceeds to the primary aerobic stage, followed by the secondary aerobic stage, before being discharged. However, recently the sludge concentration in both the primary and secondary aerobic stages has been decreasing, with values around 2500. The sedimentation ratios are 50 for the primary stage and 70 for the secondary stage. The DO level is quite high, at 6 to 7 (with the air flow already adjusted to its minimum). There is not much foam in either the primary or secondary aerobic stages. It seems that the sludge concentration is too low at the moment; how can it be increased (without adding more sludge)? I checked under a microscope and found that the sludge was loose, with no worms! Could any expert please help me think of a solution!
Maintaining the sludge concentration is directly related to the BOD of the influent water; firstly, without sufficient BOD, it is not possible to maintain a high MLSS level. Reducing the discharge of excess sludge at low load levels will instead accelerate the aging process of the sludge. Based on your question, it seems that the BOD of the incoming water is low. Additionally, the low concentration of organic matter results in low aerobic activity, which in turn leads to high dissolved oxygen levels. These high dissolved oxygen levels accelerate the aging process of the sludge, causing its amount to decrease over time. Suggestions: 1. Increase the outflow rate to reduce the sludge age ； 2. When it is not possible to reduce the aeration volume, the SBR method with intermittent aeration can be used ； 3. Determine whether there is a deficiency in nutrients, and replenish them promptly ； 4. Increase the carbon source, enhance sludge discharge, and restore sludge activity as soon as possible ； 5. It is estimated that normal function can be gradually restored within 3–5 days at the first level.