1. Toxic substances
The sudden increase in the content of toxic substances or organic matter in the influent can damage or even lose the metabolic function of microorganisms, and the activated sludge loses its purification and flocculation activity. This situation often occurs in industrial wastewater treatment plants, usually due to excessive discharge of factory accident wastewater, causing the sewage treatment system to operate under overload.
2. Low load
If the treated water volume or sewage concentration remains low for a long time and the aeration rate remains at a normal value, excessive aeration will occur, causing excessive self oxidation of the sludge, a decrease in the flocculation performance of the bacterial flocs, and ultimately leading to sludge disintegration. Over time, it may also cause the sludge to lose some or all of its activity, and lose its purification function when the organic load of the influent increases, resulting in a sharp deterioration of the effluent quality.
3. High load
Excessive carbon sources enter the system, and under high substrate conditions, the carbon sources adsorbed by bacteria cannot be metabolized, and hydrophilic polysaccharides are secreted on the surface of the bacteria, making it difficult to precipitate and compress. The bacteria are also in the logarithmic phase, at which point they have strong activity, leading to the disintegration of bacterial micelles.
4. CN ratio imbalance
When nitrogen is severely lacking, expansion may also occur. Because if nitrogen is lacking, microorganisms cannot fully utilize carbon sources to synthesize cellular substances due to their work, and excess carbon sources will be converted into extracellular storage of polysaccharides. Sludge is difficult to settle and compress, leading to disintegration.
5. Excessive aeration
Excessive aeration can cause frequent shear action, leading to the disintegration of activated sludge. In addition, excessive aeration can exacerbate the oxidation of sludge itself, resulting in sludge disintegration for various reasons.
6. Aging of sludge
Sludge aging is caused by excessive sludge age. In systems with no or less sludge discharge for a long time, the composition of sludge changes, the active ingredients decrease, and the inorganic content increases, leading to the phenomenon of sludge disintegration.
7. Temperature
As is well known, temperature can affect the activity of microorganisms, so temperature is an important condition that affects bacteria. If the temperature is too low, the transportation of nutrients will be hindered, and microorganisms will not receive nutrients. The speed of metabolism will be greatly reduced, leading to a large amount of high viscosity sugars gathering together, causing sludge to disintegrate; If the temperature is too high, bacteria cannot withstand the high temperature and will die in large numbers.
8. Expansion and disintegration of filamentous bacteria
A normal activated sludge has a dense structure and good growth of microbial communities. Under a microscope, the outer edge of the microbial communities is neat and clear, and ciliated protozoa can be found. The sludge is in the shape of alum flowers, with good flocculation, sedimentation, and concentration performance. The sludge volume index (SVI) is around 100. For normal activated sludge, there is an appropriate proportional relationship between the two. If filamentous bacteria grow and reproduce too much, The growth and reproduction of bacterial clusters will be inhibited, and many filamentous bacteria will extend beyond the surface of the sludge, causing the flocs to loosen and disintegrate.