July 8, 2024 Longchang Chemical

Responding to the government’s environmental protection requirements, the five situations and countermeasures of the secondary sedimentation tank effluent with mud

Existence of shock load

Judgment point: The effluent is accompanied by turbidity.

Analysis: Activated sludge load caused by the discharge of water entrained particulate matter is mostly activated sludge particles are not settled, by the impact of the activated sludge activity to enhance the activity of the activated sludge, due to the high activity between the particles makes the activated sludge particles flocculation between the poor. Both appear a lot of fine unflocculated activated sludge particles.

Process control index performance:

1.SV: slow settling, diffuse turbidity of supernatant.

2.DO: the same aeration DO is obviously low, about 30% lower.

3. Sludge growth: sludge growth is rapid about 20% growth per day.

4. F/M: F/M exceeds 0.5.

5. Countermeasures: Reducing the shock load can be achieved by homogenizing the water quality and quantity in the materialization area. Also increase the MLSS to counteract the load.

Aging of activated sludge

Points for judgment: The supernatant has fine unsettled flocs but the interstitial water is clear.

Analysis: causes of aging of activated sludge:

① untimely mud discharge; ② too low concentration of feed water; ③ too high MLSS control.

Process control index performance:

1.SV30: settlement speed up (90% of the process in 3min); activated sludge compressibility increase (SV30 less than 8%); settlement color is too dark (dark brown).

2. DO: aeration reduced DO is still high.

3. Sludge growth: reduced from before.

4. Countermeasures: Grasp the F/M value Avoid long-term low load operation Increase the concentration of influent substrate and reduce MLSS.

Activated sludge poisoning

Points for judgment: If the protozoa disappear obviously, accompanied by discharge water with suspended particles, the COD of the effluent water rises obviously.

Analysis: The normal metabolism of activated sludge is affected by the impact and inhibition of toxic substances, resulting in the death of part of the peripheral activated sludge, which is then disintegrated and partially dissolved into the mixture, leading to a significant increase in COD effluent.

Process control index performance:

1.SV: supernatant turbidity, sludge color dark, supernatant is always in a turbid state and settling time has no relationship.

2.DO: the same aeration strength DO is higher than usual.

3. Sludge growth: new sludge is not visible, MLSS is decreasing. During the period of decreasing activated sludge concentration, the formal activated sludge disintegration continues, and the particles entrapped in the drainage water are most obvious, and it usually returns to normal in a week after eliminating the toxic or inert materials. However, during the recovery period, because of the strong activity of sludge growth, the drainage water is still entrained with particles.

4. Countermeasures: Increase sludge discharge and replace the inhibited activated sludge.

Denitrification phenomenon in the process of sedimentation

Point of judgment: the gas generated in the denitrification process entraps the sludge to float.

Analysis: activated sludge mixture concentration is high and aeration is seriously insufficient, coupled with the mixture contains ammonia nitrogen organic nitrogen and other denitrification reaction leads to the activated sludge will have been settled on the float.

Process control index performance:

1.SV: activated sludge first settles and then floats up the activated sludge will sink again after mixing.

2.DO: anoxic condition.

3. Countermeasures: improve aeration; improve substrate concentration; reduce the nitrogen content of feed water to avoid imbalance due to C/N.

Excessive aeration

Judgment points: flocculation ability to weaken, serious flocs do not have the ability to flocculate.

Analysis: excessive aeration is not conducive to the normal growth and reproduction of activated sludge, activated sludge flocs rupture under the action of air bubbles.

Process control index performance:

1.SV: throughout the settling process, more fine particles in the supernatant, both sinking and slowly floating and the water between the particles is a hazy feeling.

2.DO: long-term high aeration (low load).

3. Countermeasures: reduce aeration; reduce sludge discharge.

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