The IWP-A2O type domestic sewage treatment integrated device mainly relies on the AO+ filtration treatment process in the equipment to remove organic pollutants and ammonia nitrogen. The working principle is that in the A-level, due to the high concentration of organic matter in the sewage, the microorganisms are in a gas-deficient state. At this time, the microorganisms are facultative microorganisms. They convert and decompose the organic nitrogen in the sewage into NH3-N, and use the organic matter as an electron donor at the same time. , converts NO-N.NO-N into N. In addition, some organic carbon sources and NH-N are used to synthesize new cellular substances, so the A-level pool not only has a certain function of removing organic matter, reducing the organic load of the subsequent aerobic pools to facilitate digestion, but also depends on the presence of raw water. The higher concentration of organic matter can complete the reverse digestion, and finally eliminate the eutrophication of nitrogen pollution. At the O level, the concentration of organic matter has been greatly reduced, but there is still a certain amount of organic matter and high NH-N. In order to further oxidatively decompose the organic matter, and at the same time, the digestion can proceed smoothly when the carbonization is completed, a good biological contact oxidation tank with low organic load is set up in the O-level tank. In the O-level tank, there are mainly aerobic microorganisms and auto-oxygen Type bacteria (digestive bacteria), in which aerobic microorganisms decompose organic matter into CO2 and H2O, and self-aerobic bacteria (digestive bacteria) use the inorganic carbon produced by the decomposition of organic matter or CO2 in the air as a nutrient source to convert NH3- N is converted to NO-N.NO-N. The effluent part of the O-class pool is returned to the A-class pool to provide electron acceptors for the A-class tank.