# Research Status and Development Trend of Wastewater Treatment Technology and Its Low Carbonization
## 3 Low-Carbon Sewage Treatment Technology  
As one of the major sources of greenhouse gas emissions, the current sewage pollution removal technology mainly relies on energy dissipation and pollution transfer. The treatment process has high energy consumption and emits a large amount of greenhouse gases such as CO2, CH4 and N2O. To effectively control the greenhouse gas emissions from sewage treatment plants and achieve the emission reduction requirements under the dual-carbon target, the traditional concept of sewage treatment must be challenged. It is required that the process of sewage treatment should be as low-carbon as possible, to realize self-sufficiency in energy and full utilization of resources in the process of sewage treatment, and make up for energy consumption and recycle resources by relying on the energy and resources contained in sewage treatment plants or the sewage itself [53]. The removal process of activated sludge in conventional municipal sewage treatment technology still has serious problems of high energy consumption. The removal rate of nutrients and pollutants in sewage can reach more than 95%, but the consumption of aeration energy and waste sludge cannot be ignored. In a hypothetical calculation, a municipal sewage treatment plant with a treatment capacity of 15,000 m\({}^{3}\)/d consumes 2582.68 Kw\(\cdot\)h of electricity in the biochemical treatment unit and sludge disposal alone, not including air pollution and greenhouse gas emissions produced in the treatment process. Thus it can be seen that the application of low-carbon wastewater treatment technology is very important. The most serious problem of the push-flow activated sludge method is that the sludge at the head and tail of the tank receives the aeration time unevenly, which leads to a large amount of wasted aeration, resulting in unnecessary energy consumption. The characteristic problem of the push-flow reaction tank is that the BOD concentration is high where the water flows in, and low where the water flows out, so the number of aerators should decrease along the long direction of the tank, that is, to increase the spacing between aerators. In this way, the BOD concentration of the effluent can be met, one-time input can be reduced, and unnecessary aeration can be reduced [54]. The author believes that an intelligent aeration management system can be designed, through which the aeration capacity and aeration time of the push-flow gallery can be intelligently regulated, to make the oxygen demand of the sludge just enough to achieve the purpose of low carbonization and energy savings [55; 56]. The completely mixed activated sludge method is a unified operation mode after the sludge and wastewater are completely mixed. Compared with the push-flow activated sludge method, it has no major problems in aeration energy consumption, but because it is a completely mixed operation, it is prone to sludge expansion and the production of excessive residual sludge, which affects effluent quality. In the face of the problems of the process system, it is necessary to monitor the process operation management in detail and continuously observe the water quality changes to prevent sludge buildup. In case of emergency, drugs can be added to enhance sludge settlement performance or directly kill filamentous bacteria through emergency measures [57]. Both the pure-oxygen-aerated activated sludge method and the SBR process are relatively mature. The biggest common problem is that the equipment is more complex and the requirements for management personnel are higher. In addition, these four process systems have two common problems that most need to be solved: aeration energy loss and sludge disposal energy loss. The essence of the activated sludge method is the adsorption and metabolism of activated sludge microorganisms to remove pollutants, and the metabolism needs to absorb oxygen, and the energy consumption of aeration is difficult to avoid.