How to judge the aging of sludge in aeration tank?

1. Judgment points of activated sludge aging (ie appearance)

(1) When the sedimentation ratio is done in the initial stage, the supernatant becomes turbid, and there are finely divided sludge suspended, which is difficult to settle. Slowly, there will be scum and floating sludge in the secondary sedimentation tank.

(2) The sludge aging will lead to an increase in the oxygen consumption of the sludge in the aeration tank. (Watch for signs of a sudden drop in dissolved oxygen)

(3) Microscopic examination showed that the sludge structure was loose, with few filamentous bacteria, many rotifers, and few protozoa. The color of the sludge turned light and yellow, or appeared very dark, gray and black, and did not have a fresh luster.

(4) The foam produced by the returning secondary sedimentation tank sludge is between the surfactant and the biological foam, and it feels a little sticky.

(5) If the organic load rate (F/M) is too low, the probability of activated sludge aging is high.

Organic load rate (F/M), also called sludge load. F refers to organic matter, M refers to microorganisms, which refers to the amount of organic matter that a unit weight of activated sludge withstands in a unit time, or the amount of organic matter removed by the effective volume of the biochemical tank in a unit time. When activated sludge aging usually occurs or may occur, F/M is at a low level or for a long time, especially when F/M is lower than 0.05, there is a high probability of activated sludge aging.

2. Analysis of the causes of activated sludge aging

(1) The sludge is not discharged in time, and the sludge age is too long

(2) The influent water is in a low load state for a long time, and the activated sludge is aging

(3) Activated sludge caused by excessive aeration

The direct result of over-aeration is the disintegration and auto-oxidation of activated sludge. The reason for the disintegration is that the frequent shearing action leads to the disintegration of the activated sludge. The understanding of auto-oxidation is that oxygen itself is an oxidant, and excessive aeration will naturally oxidize the activated sludge.

(4) Activated sludge concentration control is too high

If the concentration of activated sludge is controlled too high and there is not enough influent substrate concentration to support, it will eventually lead to the aging of activated sludge.

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