1. The performance of sludge expansion : Sludge bulking (sludgebulking) Refers to the sludge structure is extremely loose, the volume increases, floating, difficult to sedimentation separation affect the water quality phenomenon. Sludge bulking is generally practiced on all types of activated sludge processes and often takes a long time to adjust in the event of unmanageable conditions.

Sewage treatment technology

The incidence of sludge expansion is quite high. Nearly 50% of urban sewage plants in Europe have different degrees of sludge expansion each year, and the incidence in China is also very high. In view of the sludge expansion, there are many theories in all aspects, but they are not exactly the same. There are even many contradictions which cause great troubles to the water treatment workers.

There are also projects such as bio-pool surface foam, the surface of the second sedimentation tank mud, but the water quality has no effect. Another point of thinking, when swelling occurred 9, the mud settling of deterioration, but a small amount of supernatant is very clear than normal operation pay off! There is such a situation. Some plants, the initial expansion, the water is surprisingly good! Because some swelling occurs, the sludge sticky, the foam to rise high, the more the more the aeration! Affect the appearance and over the ultra-high spill!

When this type of sludge expands, the MLVSS / MLSS ratio of the activated sludge is increased, and the sludge activity is correspondingly increased, which is harmless to the treatment effect. There is no problem as long as it is not serious enough to affect the solid-liquid separation effect. Bio-foam components also have a high biological activity, that is, the composition of the foam after death affects the appearance too much and the leadership does not look good. I commissioned an industrial wastewater plant in 2002 and the plant SVI has been 80-90, but the effluent SS has not had any problems. It seems that this factory SVI has been running high. The key to see how water quality and muddy water separation characteristics. The ideal SVI is 50-100, and the ideal MLVSS / MLSS ratio is 0.65-0.75.

2. Sludge expansion causes:

Activated sludge expansion, according to incentives can be divided into: due to filamentous bacteria caused by abnormal proliferation of filamentous fungi and a large number of viscous material accumulation of non-filamentous bacteria bulking. The former is prone to hair and multiple expansion, resulting in the proliferation of filamentous bacterial sludge bacteria are: bacteria genus, Pseudomonas, Flavobacterium, genus enzymes.

Sewage plants with low concentrations of sewage and sufficient dissolved oxygen do not seem to be prone to sludge expansion. Water quality characteristics, such as high levels of oil or long-chain fatty acids in the water, may also lead to flooding of the MP. Even with the selector sometimes, if the run control is not good or not, the same cause expansion. Water temperature has a great influence on the degree of dissolution and dispersion of oil in water, while the occurrence of oil has a decisive influence on the growth and biological morphology of MP.

021N one reason is the lack of nitrogen, another reason is the high proportion of biodegradable COD; biofilter flow on the sludge does have some impact on the expansion, there is a certain correlation; push flow is not easy to expand, fully mixed easy to expand; Because the oxidation ditch is a completely mixed reaction, the concentration gradient in the ditch is low and the load is not high enough to favor the growth of filamentous fungi, for which DHV is preceded by their own oxidation ditch Anaerobic selector for sludge flow regulation.

From the secondary sedimentation tank operating conditions comparison, seepage flow biochemical pool effluent precipitation was significantly better than completely mixed. In general, the SVI for operations that do not require particularly good A / O processes can reach below 120, while Caruso's SVI should be below 140.

Sewage treatment technology

Changes in water temperature: especially the season of alternating water temperature. Micropropagation of MicrothrixParvicella tends to occur around 12-15 ° C. Reactor Outflow: Carrousel submerged out of stream, which is detrimental to foam skimming. Scum is associated with sludge expansion but not all scum And inflation related.

Early short mud aged activated sludge system, sludge expansion occurs easily in the case of complete mixing, low dissolved oxygen and low dissolved organic biodegradable fast concentration conducive to the growth of filamentous bacteria, the use of flow-pool type, the formation of Concentration gradient can be basically solved; later medium-long mud age system also have similar problems. By disposing selector (completely aerobic, anaerobic, anoxia can eliminate fast biodegradable organic matter) can basically solve the problem. At present, it can not effectively solve the oxidation ditch system with long sludge age. Seasonal (winter and spring) sludge bulking is manifested as low temperature expansion in winter and bio-foam in spring.

3 filamentous bacteria sludge expansion Main types of microorganisms:

Filamentous Gram stain microbial identification. Understanding the characteristics of filamentous fungi from a microscopic microbiological perspective is beneficial both for operation and for research. Know the specific types of filamentous fungi, each has its own characteristics, and then combined with the process can determine the basic reasons, and then choose measures to local conditions.

Filamentous species and suggested control measures. According to Jenkins, M.parvicella control strategy is hypoxic or anaerobic. Type021N is classified as a deficiency caused by nutrients. But the measures are not absolute, relative, difficult to quantify.

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