# Research Status and Development Trend of Wastewater Treatment Technology and Its Low Carbonization
## 3 Low-Carbon Sewage Treatment Technology
### Research Status
#### 3.1.3 Operation Parameter Optimization and Process Improvement  
According to the water quality of different sewage, the treatment process selected by the sewage treatment plant will be different. When facing a specific sewage, the operation parameters of the different treatment process will also change slightly. Only by adjusting the most appropriate operation parameters can the treatment be most effective and require the lowest energy consumption. [PERSON] [80] envisioned the application prospect of energy-saving and low-carbon technology in sewage treatment through the construction of a precise aeration system. [PERSON] [81] et al., based on fuzzy control of three-level inverter frequency conversion speed regulation energy-saving technology, studied the frequency conversion speed regulation system control of a high-powered pump in a sewage treatment plant, and finally realized effective control of a high-powered motor, which can significantly improve the energy-saving effect of a high-power motor in sewage treatment. Through the application of frequency converters in the energy-saving transformation of an aeration fan in a sewage treatment station, [PERSON] [82] adapted the frequency conversion to start slowly, effectively avoiding fan surge, effectively reducing starting current and running current, thus achieving the purpose of energy savings, and at the same time reducing the influence of an overly large or small opening of an intake valve on the load of the rear system. [PERSON] [83] et al. adjusted the sludge layer height of a secondary sedimentation tank to control the sludge return flow of the A/O process, and took the sludge layer height of secondary sedimentation tank as the control variable to establish the sludge return control strategy and controller. An A/O process pilot test device was used to treat real domestic sewage, and the established controller was verified. The results showed that the average effluent ammonia and total nitrogen concentrations were reduced by about 8 and 15%, respectively, compared with the traditional constant sludge reflux ratio control. With an increase in the returned sludge concentration, the sludge discharge and sludge return flow decreased correspondingly. The returned sludge concentration increased by 25.6% on average, and the sludge return flow decreased by 20% on average. The average SSconcentration of effluent was reduced by 35.3%, which could avoid sludge loss and maintain the stable operation of the system. Compared with the traditional constant sludge reflux ratio control, the controller has great advantages in terms of system stability, operation cost and effluent quality by adjusting and improving the high- energy-consumption electrical equipment in the whole sewage treatment plant, especially the high-powered equipment such as the water pump and blower. Appropriate adjustment of operating parameters and process optimization can better realize the low-carbon sustainable development concept of sewage treatment. In the whole water treatment process, different water quality will lead to different treatment intensity of each treatment unit in the process. For example, with different concentrations of nitrogen and phosphorus, COD and BOD in the water, the treatment units are also different, so each unit needs to be adjusted to the most suitable operating parameters, to ensure the best treatment effect under the conditions of the lowest energy consumption and low carbon [84]. Traditional sewage treatment processes use physical or chemical methods to remove colloidal substances in sewage, and biological methods to treat organic pollutants in sewage.