The removal of organic pollutants and ammonia nitrogen primarily relies on the AO biological process within the equipment. The principle involves the anaerobic state of microorganisms in Stage A, due to the high concentration of organic matter in the wastewater. These microorganisms are facultative, converting organic nitrogen in the wastewater into NH3-N, while utilizing organic carbon as an electron donor to convert NO2-N and NO3-N into N2. Additionally, they use part of the organic carbon source and NH3-N to synthesize new cellular material. Therefore, Stage A does not possess specific organic matter removal capabilities, but it reduces the organic load for subsequent aerobic ponds, facilitating nitrification. It also relies on the higher concentration of organic matter in the raw water to complete denitrification, ultimately eliminating eutrophication pollution. In Stage O, although the organic matter concentration has significantly decreased, there is still a certain amount of organic matter and a high NH3-N level. To further oxidize and decompose organic matter, and to ensure smooth nitrification while carbonization is complete, an aerobic biological contact oxidation pond with a lower organic load is set up in Stage O. In the Stage O pond, aerobic microorganisms and autotrophic bacteria (nitrifying bacteria) utilize inorganic carbon produced from organic matter decomposition or atmospheric CO2 as a nutrient source to convert NH3-N in the wastewater into NO2-N and NO3-N. A portion of the effluent from Stage O is recycled back to Stage A, providing an electron acceptor and ultimately eliminating nitrogen pollution through denitrification.

Comprised of an A-grade anaerobic digestion tank, two O-grade aerobic digestion tanks, a sludge concentration tank, a clear water discharge tank, and manholes (observation holes), this manufacturer-direct supply of buried integrated sewage treatment equipment is both economical and practical. It offers savings in equipment investment and operational costs, boasts mature technology, a simple structural design, and is user-friendly.