With the acceleration of society, industrialization and urbanization, environmental problems are becoming more and more serious, especially water pollution has become one of the major obstacles restricting sustainable development. As an important part of environmental protection, the development and application of sewage treatment technology is of great significance for promoting the construction of ecological civilization and ensuring people's health. This paper will discuss several key nodes in the process of sewage treatment, and analyze their value in realizing water resources recycling and ecological environment protection.

A, sewage collection system

Efficient and reasonable sewage collection is the first and crucial step of sewage treatment. By establishing a perfect underground pipe network system, domestic sewage and industrial wastewater can be effectively collected in the treatment plant for centralized purification. In addition, different pretreatment measures should be taken for sewage from different sources, such as removing large particles of impurities and adjusting pH value, so as to reduce the burden of subsequent processes and improve the overall efficiency.

Second, the primary treatment (physical method)

After entering the sewage treatment plant, the sewage will first pass through a series of facilities, such as grille and grit chamber, and separate suspended solids and some organic substances by gravity. The main purpose of this stage is to reduce the pollutant load and lay the foundation for further chemical or biological treatment.

Third, secondary treatment (biochemical method)

After the initial filtration, the remaining dissolved organic matter needs to be further degraded by microorganisms. Activated sludge process is one of the most common secondary treatment methods, which consumes the residual harmful components in water by cultivating specific flora. In recent years, with the progress of science and technology, new technologies such as MBR membrane bioreactor and SBR sequencing batch reactor are gradually applied in practice, which greatly improves the removal rate and stability.

IV. Advanced Treatment (Advanced Oxidation/Reverse Osmosis)

In order to achieve stricter discharge standards or direct reuse, it is often necessary to further purify the secondary treated water. Ozone oxidation and ultraviolet disinfection can effectively kill pathogens; Membrane separation methods such as nanofiltration, ultrafiltration and even reverse osmosis can accurately intercept trace pollutants and ensure that the effluent quality meets the requirements of relevant national laws and regulations.

V. Recycling of renewable resources

Finally, after all the above processes are completed, clean and safe water can be re-injected into natural waters or supplied to industrial and agricultural production and daily life of residents. At the same time, valuable by-products extracted from wastewater, such as fertilizer raw materials and energy gas, can also be rationally developed and reused, thus forming a virtuous circle.

In a word, sewage treatment is not only an effective way to eliminate environmental pollution, but also an indispensable part to promote comprehensive, coordinated and sustainable economic and social development. Facing the challenges brought by global climate change, we should continue to increase investment, constantly innovate and improve various key technologies, and strive to create a clean and beautiful new world.