A/O process: This process consists of an anoxic section (A section) and an aerobic section (O section). In the anoxic stage, denitrifying bacteria use organic matter in wastewater as a carbon source to reduce nitrate nitrogen in wastewater to nitrogen gas, achieving the goal of denitrification. In the aerobic stage, aerobic microorganisms completely oxidize and decompose organic matter in wastewater into carbon dioxide and water in an environment with sufficient oxygen, while converting ammonia nitrogen into nitrate nitrogen. The A/O process is relatively simple and does not require additional carbon sources. Organic matter in the original wastewater can be used as the carbon source, greatly reducing construction and operating costs. In addition, denitrification is carried out before nitrification, and internal circulation is set up to effectively improve denitrification efficiency. The aeration tank is located at the back end, which can further remove residual pollutants during denitrification and ensure the quality of treated water.

SBR process: also known as sequencing batch activated sludge process, its main feature is to carry out water inlet, aeration reaction, sedimentation, drainage and other processes in the same reaction tank in chronological order. This process does not require specialized secondary sedimentation tanks and reflux sludge equipment, greatly simplifying the treatment process. During operation, the SBR process can flexibly adjust the operating cycle and time allocation of each stage according to changes in water quality and quantity, and has strong adaptability. Moreover, the SVI value (sludge volume index) of this process is low, the sludge sedimentation performance is good, and it is not easy to cause sludge swelling. At the same time, it also has good nitrogen and phosphorus removal effects, can achieve automated control, and is flexible and convenient to operate.

MBR process: also known as membrane bioreactor process, which combines membrane separation technology with biological treatment technology. In MBR systems, microorganisms decompose and metabolize organic matter in wastewater within the bioreactor, while membrane modules are used to achieve solid-liquid separation. Compared with traditional sedimentation separation methods, membrane separation can more efficiently intercept microorganisms and suspended solids, significantly improving the effluent quality. The effluent suspended solids and turbidity are almost zero, and the removal rate of bacteria and viruses is extremely high. The effluent quality can reach or even approach the standard of medium water, and can be directly reused. It has great application advantages in areas with water scarcity.