What are the types of sewage treatment methods?

Sewage treatment refers to the waste water generated in cities, industries, rural areas and other places, after treatment, to achieve discharge standards or reuse standards of a series of processes. Sewage treatment is mainly divided into three stages: primary treatment, intermediate treatment and advanced treatment. Primary treatment refers to the process of removing large debris and suspended matter in sewage, intermediate treatment refers to the process of removing dissolved matter and colloidal matter in sewage, and advanced treatment refers to the process of removing organic matter, inorganic matter and microorganisms in sewage.

According to the different treatment methods, sewage treatment technology can be divided into physical treatment, chemical treatment, biological treatment and other types. Physical treatment is mainly the use of the principles of physics, such as gravity, filtration, precipitation, adsorption and other ways to treat sewage; Chemical treatment is mainly the use of chemical agents to treat sewage; Biological treatment is the use of microorganisms to decompose, transform and adsorb organic matter in sewage. Biological treatment technology is the most widely used and most mature sewage treatment technology at present, which has the advantages of economy, high efficiency and environmental protection, and is the mainstream method of sewage treatment.

In sewage treatment technology, the simplest and most common method is anaerobic aerobic (A/O) biological treatment. This method uses anaerobic reactor and aerobic reactor to treat, which is a mixed biological treatment method. The specific operation is to first enter the wastewater into the anaerobic reactor, use anaerobic bacteria to convert the organic matter in the wastewater into methane, carbon dioxide and other substances, and then enter the treated wastewater into the aerobic reactor, and use aerobic bacteria to further oxidize and decompose the methane, carbon dioxide and other substances in the wastewater, so as to meet the discharge standards or reuse standards. A/O biological treatment has the advantages of simple operation and low maintenance cost, so it has been widely used. In this method, the proportion of anaerobic and aerobic reactors is also a factor to be considered. According to different processing requirements, different proportions can be used for processing. For example, in the treatment of high-concentration organic wastewater, a larger proportion of anaerobic reactors are used, and for low-concentration organic wastewater, a larger proportion of aerobic reactors are used. In addition, for some simple sewage treatment requirements, such as the sewage treatment of communities, schools, etc., can also be treated by artificial wetland methods similar to natural wetlands. Constructed wetland is a kind of artificial treatment facility built to imitate the ecosystem of natural wetland. It has the advantages of simple design, low maintenance cost, and can combine sewage treatment and landscape benefits to achieve good ecological results. In general, the A/O biological treatment method and the constructed wetland treatment method are very simple and economical sewage treatment methods, and they have good applicability for some simple sewage treatment requirements. However, for the treatment of some complex industrial wastewater or high-concentration organic wastewater, more advanced sewage treatment technology needs to be used.

The following are some cases of the actual application of A/O biological treatment method and constructed wetland treatment method: The application of A/O biological treatment method in industrial sewage treatment: The pH value of the production wastewater of a chemical company is low, the content of organic matter is high, and the traditional biochemical treatment is difficult to meet the discharge standard purification requirements. Through the modification of the treatment process, the A/O biological treatment method was adopted, and the original treatment system was changed into anaerobic-aerobic bioreactor. The treatment effect was significantly improved, and the average COD (chemical oxygen demand) of the daily effluent was reduced to about 500mg/L, stably meeting the discharge standard requirements. The application of constructed wetland treatment method in urban sewage treatment: The rural sewage treatment project of Jiaonan Town, Longwan District, Wenzhou City, Zhejiang Province, adopts the treatment process of constructed wetland. The project uses the low-lying natural environment to collect and divert a large amount of sewage to the constructed wetland for treatment, and removes organic matter, nitrogen, phosphorus and other pollutants in the sewage through the joint action of plants and microorganisms. The treated sewage can be used to irrigate farmland and achieve the purpose of resource reuse. These cases prove that A/O biological treatment method and constructed wetland treatment method have a wide application prospect and good treatment effect in the actual sewage treatment. At the same time, it also shows that different treatment methods should be selected according to the specific situation in the sewage treatment process to achieve the best treatment effect and economic benefits.