The proliferation of microorganisms in activated sludge is an inevitable result of the reaction of activated sludge and the degradation of organic matter in the aeration tank, and the proliferation of microorganisms is the growth of activated sludge.
The microbial proliferation of activated sludge is the combined result of microbial proliferation and auto-oxidation (endogenous respiration),
Daily net growth of activated sludge microorganisms in the aeration tank is 33,360
The microorganisms in activated sludge require oxygen supply during metabolic activities. The main functions of oxygen are: ① oxidatively decompose a part of organic matter; ② auto-oxidize a part of the material of its own cells.
In the activated sludge treatment system, the essence of removing organic pollutants from wastewater is the process by which organic substrates are taken up, metabolized and utilized by the activated sludge microorganisms as nutrients. As a result of this process, the sewage is purified. Microbes gain energy to synthesize new cells, and activated sludge grows. Generally, the entire purification reaction process is divided into three stages: ① initial adsorption; ② microbial metabolism; ③ condensation, precipitation and concentration of activated sludge.
The so-called “initial adsorption” refers to: in the activated sludge system, within a short time (10 ~ 30min) after the sewage starts to contact the activated sludge, the activated sludge has a strong adsorption due to its large surface area Capacity, so within a short period of time, a large amount of organic pollutants in suspended and colloidal state can be removed from the wastewater, and the BOD5 value (or COD value) of the wastewater is greatly reduced. However, this is not true degradation. Over time, the BOD5 value of the mixed solution will rise, and after that, the BOD5 value will gradually decrease.
The size of activated sludge adsorption capacity is related to many factors:
① The nature and characteristics of wastewater: it has a good effect on wastewater containing higher concentrations of suspended or colloidal organic pollutants;
② State of activated sludge: After the adsorption is saturated, sufficient regeneration aeration should be given to restore and enhance the adsorption function. Generally, activated sludge microorganisms should enter the endogenous metabolic period.