The secondary anoxic supernatant level is 986, but the effluent from the sedimentation tank is only a little over 580. Why?
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The secondary anoxic supernatant level is 986, but the effluent from the sedimentation tank is only a little over 580. Why? Then, the COD of the water exiting the secondary sedimentation tank remained unchanged compared to that in the primary sedimentation tank. A two-stage AO process is used to treat pig farming wastewater, with an SV30 value of 25% in all 4 biological treatment tanks
It is theoretically impossible for the COD level of the effluent to be high, but this phenomenon occurs frequently in actual operation. Why is that? 1. The issue of residence time is that, due to the effect of residence time, the relationship between the effluent and the influent cannot be reflected; in other words, the current effluent is the result of the influent from that same period plus the residence time. If the residence time is 1 day, then it is the influent from 1 day ago that has the greatest impact on the current effluent ； 2. The impact of biochemical processes is generally due to undissolved microorganisms, i.e., SS; when the effluent contains mud or colloids, COD levels will inevitably rise ； 3. Failures in the secondary sedimentation tank affect the quality of the effluent; issues such as surface load exceeding design values, short-circuiting, heavy-phase flow, anaerobic or partial anaerobic conditions, and denitrification can all result in the effluent containing sediment ； 4. There is short-circuiting occurring, with water flowing directly from the inlet to the outlet ； 5. The sampling is unrepresentative or incorrect.