The main pollutant of urban sewage is organic matter,so most of the biological methods are used at home and abroad.There are also chemical methods,such as the use of chemically enhanced primary treatment.

Oxidation ditch is a variant of the activated sludge method.It differs from the traditional activated sludge method in hydraulic flow pattern.It is a circulating flow connected end to end,usually using delayed aeration.stable.It does not have an initial settling tank and sludge digestion tank,and the treatment facilities are greatly simplified.Oxidation ditch has the advantages of traditional activated sludge method,the efficiency of removing organic matter is very high,and also has the function of denitrification.If an anaerobic tank is added in front of the ditch,phosphorus can also be removed at the same time.The high efficiency and simplicity of the oxidation ditch make it widely used in small and medium-sized urban sewage treatment plants.

Sequential batch activated sludge method,its basic feature is to complete the biochemical reaction of sewage,precipitation,drainage and sludge in a reaction tank,not only eliminating the primary settling tank and sludge digestion tank,but also eliminating the secondary settling The treatment facilities of the pond and return sludge pump room are simpler than the oxidation ditch,and the treatment effect is good.Some processes also have strong nitrogen and phosphorus removal functions.The process has high requirements for automatic control.In the past,the automatic control equipment was not enough.This process cannot be promoted.In recent years,the application of automatic control technology and instruments in sewage treatment has passed the test.Therefore,the process has been vigorously promoted and has become a process that is very concerned by the industry.