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Talking about the common problems of the second settling pond

Time : 2020-08-27

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Talking about the common problems of the second settling pond



In the daily operation of the sewage system, the abnormality of the secondary sedimentation tank is the most common phenomenon. For example, the increase of suspended solids in the effluent of the second settling tank and the floating mud in the second settling tank have been experienced by everyone.


Today we will talk about the analysis and solutions of two common anomalies in the Second Shenchi.

1. Increased suspended solids in the effluent of the secondary sedimentation tank
(1) The expansion of activated sludge makes the sludge settling performance worse, the mud-water interface is close to the water surface, and some sludge fragments overflow through the outlet weir. The countermeasure is to analyze the causes of sludge expansion and eliminate them one by one.

(2) The concentration of activated sludge in the aeration tank is too high, the mud-water interface of the secondary settling tank is close to the water surface, and some sludge fragments overflow through the outlet weir. The countermeasure is to increase the amount of surplus sludge discharge.

(3) The disintegration of activated sludge causes the flocculation of the sludge to decrease or disappear, and the sludge fragments flow out with water. The countermeasure is to find the reasons for the disintegration of sludge, eliminate and solve them one by one.

(4) Activated sludge stays in the secondary settling tank for too long, and the sludge overflows with water flow after decomposing due to hypoxia. The countermeasure is to increase the amount of return sludge and shorten the residence time in the secondary settling tank.

(5) When the water temperature is high and the nitrate content in the water is high, the sludge denitrification and denitrification phenomenon occurs in the secondary settling tank, and the nitrogen-coated large sludge floats to the water surface and overflows with the water flow. The countermeasure is to increase the amount of return sludge and shorten the residence time of sludge in the secondary settling tank.
  
2. Sludge floating in the secondary settling tank
Sludge floating in the secondary sedimentation tank refers to the phenomenon that the sludge is acidified or denitrified in the secondary sedimentation tank, causing the sludge to float to the surface of the secondary sedimentation tank. The floating sludge itself has no quality problems, and its biological activity and sedimentation performance are normal.

The main reason for the floating is that the normal sludge stays in the secondary settling tank for too long, and the dissolved oxygen is gradually consumed and acidified, producing H2S and other gases attached to the sludge flocs, causing the sludge to float up. When the mixed solution entering the secondary sedimentation tank contains a large amount of nitrate, the sludge is denitrified in the secondary sedimentation tank due to the lack of sufficient dissolved oxygen (DO<0.5mg/L), and the nitrogen generated by denitrification will also adhere to the sewage. On the sludge floc, its density is reduced, causing the sludge to float.

The measures to control the floating of sludge are to discharge the remaining sludge in time and increase the return sludge to prevent the sludge from staying too long in the secondary settling tank; the second is to strengthen the oxygenation at the end of the aeration tank to increase the inlet The dissolved oxygen content in the mixed liquid of the secondary sedimentation tank ensures that the sludge in the secondary sedimentation tank is not in an anaerobic or anoxic state. For the floating of sludge caused by denitrification, it can also increase the discharge of surplus sludge, reduce the age of sludge, and achieve the purpose of controlling denitrification by controlling the degree of nitrification.
   
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Benefits: 
Bio Target Floc can:
Improve SV30;
Improve system shock resistance;
Does not affect microbial activity;
Increase COD and total phosphorus removal.