Do you know the principle of microbial sewage treatment?

1. Introduction to Microorganisms:  

A microorganism is a general term for living things that are not visible or clear to the naked eye.  These include prokaryotes (bacteria, actinomycetes and cyanobacteria), eukaryotes (fungi and microalgae), and acellular organisms (viruses).  Microorganisms have the characteristics of small size, large surface area, amazing fecundity and so on, and can constantly exchange materials with the surrounding environment quickly.  Sewage has conditions for microbial growth and reproduction, so microbes can get nutrients from sewage, and degrade and use harmful substances, so that sewage can be purified.  Therefore, microorganisms can be widely used in sewage purification and treatment for the benefit of mankind.

2. Principle of microbial treatment of wastewater   

The use of microorganisms to treat sewage is actually through the metabolic activities of microorganisms, the organic matter in sewage decomposition, so as to achieve the purpose of sewage purification.  Microorganisms can take up sugars, proteins, fats, starches and other low molecular compounds from sewage.  There are two types of microbial metabolism: aerobic and anaerobic. Therefore, the purification methods are divided into aerobic and anaerobic purification.

①. Aerobic purification

In the presence of oxygen, many aerobic microorganisms find C source, N source, P source, S source and energy in the process of oxidative decomposition of organic matter into CO2 and H2O through catabolism, anabolism and material mineralization. The microbial aerobic purification of sewage is a method that simulates the above principles, aerates and cultivates microorganisms in certain structures, and efficiently purifies sewage.

②.  Anaerobic purification

Under strict anaerobic conditions, most organic matter is decomposed into H2, CO2, H2S, CH4 and other gases during fermentation or digestion of organic matter by microorganisms. The biological anaerobic purification of sewage is based on the principle that sewage can not only be purified after anaerobic fermentation, but also obtain bioenergy CH4. The electron acceptor for energy transfer in micro-matter cells changes from molecular oxygen under aerobic conditions to organic matter under anaerobic conditions. Under anaerobic conditions, macromolecular organic dirt, which is insoluble in water and difficult to decompose, is degraded into soluble substances by extracellular enzymes of microorganisms, and then degraded into low molecular acids and alcohols by methanogenic anaerobic bacteria and hydrogen-producing bacteria, and emits H2 and CO2. Organic acids and compounds are degraded to H2, CO2 and CH4 by methanogens. Methanogens can also use H2 to reduce CO2 and form CH4.

Microbial purification process:

1. The concentration of organic pollutants changes from high to low

2. Heterotrophic bacteria rapidly oxidize and decompose organic pollutants and proliferate, followed by a peak in the number of protozoa fed on bacteria, and then a growth peak of algae due to the mineralization of organic matter, which is conducive to the growth of algae.

3. Dissolved oxygen concentration with organic matter by microbial oxidation decomposition and a large amount of consumption, soon fell to the lowest point, and then, due to the inorganic organic matter and algae photosynthesis and other aerobic microbial number decline, dissolved oxygen returned to the original level.

As a result, the number of microorganisms in the water, the amount of organic matter, the amount of inorganic matter, also drops to its lowest point after a considerable distance from the source. Thus, the water body reverts to its original state.