What are the types of sewage treatment processes

There are many types of sewage treatment processes, and the following are several common processes:

Physical processing method

Precipitation method: Using gravity to precipitate suspended particles in sewage to the bottom of the tank, thereby separating them from water and achieving the purpose of preliminary purification. For example, in the primary sedimentation tank, larger suspended particles in sewage can be removed through natural sedimentation.

Filtering method: allowing sewage to pass through porous filtering media such as sand filters, activated carbon, etc., to intercept suspended impurities in the sewage and further improve the clarity of water quality. It is commonly used for deep treatment of sewage.

Biological treatment method

Activated sludge method: Air is introduced into sewage to cultivate activated sludge containing a large number of microorganisms. The metabolic process of microorganisms is used to decompose organic matter, nitrogen, phosphorus and other nutrients in sewage, transforming them into harmless substances, thereby achieving the goal of purifying sewage. Common processes include traditional activated sludge process, oxidation ditch, SBR (sequencing batch reactor), etc.

Biofilm method: sewage is brought into contact with biofilm attached to the surface of a solid carrier, and microorganisms on the biofilm adsorb and decompose organic matter in the sewage, achieving sewage treatment. Biological filters such as biofilters, biological turntables, and aerated biofilters all belong to the biofilm process.

Chemical treatment method

Coagulation precipitation method: Adding coagulants such as polyaluminum chloride, ferrous sulfate, etc. to wastewater to condense small suspended particles and colloidal substances into larger particles, and then removing them through precipitation can effectively remove turbidity, color, and some organic matter from wastewater.

Neutralization method: used to treat acidic or alkaline wastewater by adding alkaline or acidic substances to adjust the pH value of the wastewater, making it neutral or close to neutral, in order to meet the requirements of subsequent treatment or meet discharge standards.

Redox method: Using oxidants or reducing agents to convert harmful substances in wastewater into harmless or low toxic substances. For example, using oxidants such as chlorine gas and chlorine dioxide to disinfect and sterilize wastewater, removing bacteria and viruses from the water; Reducing heavy metal ions from a high valence state to a low valence state through a reduction reaction makes them easier to precipitate and remove.

In practical applications, the appropriate combination of sewage treatment processes is usually selected based on factors such as water quality, quantity, treatment requirements, and economic costs to achieve the best treatment effect.