Treatment processes for different sewage

The choice of sewage treatment process depends on many factors such as the source, composition, type and concentration of pollutants. Different sewage has different characteristics, so different treatment processes or combined processes are needed to achieve the corresponding treatment effect.

Common sewage types and treatment processes

1. Domestic sewage

Characteristics: Mainly derived from residents' lives, containing organic matter, suspended solids, pathogens, etc.

Treatment process:

Primary treatment: Mainly remove large suspended particles and some grease, commonly used screens, grit chambers, etc.

Secondary treatment: Mainly remove organic matter, commonly used activated sludge method, biofilm method, etc.

Third-level treatment: Mainly remove nutrients (nitrogen, phosphorus), disinfection, commonly used chemical precipitation, filtration, disinfection, etc.

2. Industrial wastewater

Characteristics: Wide sources, complex composition, and pollutant types and concentrations vary greatly.

Treatment process:

Pretreatment: According to the nature of the wastewater, pretreatment such as neutralization, oxidation-reduction, and precipitation is carried out.

Biochemical treatment: For biodegradable organic matter, a treatment process similar to that of domestic sewage is used.

Physical and chemical treatment: For organic matter and heavy metals that are difficult to degrade, methods such as adsorption, ion exchange, and membrane separation are used.
Special treatment: For some wastewaters with special properties (such as cyanide-containing wastewater and oil-containing wastewater), special treatment processes are required.
3. Agricultural wastewater
Features: Mainly from farms, farmland drainage, etc., containing organic matter, nutrients, pathogens, etc.
Treatment process:
Physical treatment: Screening, sedimentation, etc.
Biological treatment: Aerobic or anaerobic biological treatment to remove organic matter and nutrients.
Land treatment: Use the treated sewage for irrigation, and further remove pollutants through the purification effect of the soil.

Main factors affecting the selection of sewage treatment processes

Sewage composition: Organic matter concentration, suspended solids content, pH value, temperature, toxic substances, etc.
Emission standards: Different regions and industries have different requirements for sewage discharge standards.
Treatment scale: The size of the treatment scale will affect the choice of process.
Economic factors: Investment and operating costs of the process.
Site conditions: Land area, topography, etc.
Commonly used sewage treatment processes
Activated sludge method: Through aeration, microorganisms are multiplied in water to form activated sludge, which adsorbs and oxidizes organic matter in sewage.
Biofilm method: Use microorganisms to form biofilms on the surface of fillers to treat sewage.
Physicochemical method: Including coagulation sedimentation, filtration, adsorption, ion exchange, etc.
Membrane separation method: Use the selective permeability of the membrane to separate pollutants in sewage.
Advanced oxidation technology: Use strong oxidants such as ozone and hydrogen peroxide to oxidize and degrade difficult-to-degrade organic matter.

Optimization of sewage treatment process

With the continuous development of sewage treatment technology, people's requirements for sewage treatment are getting higher and higher. In order to improve sewage treatment efficiency and reduce treatment costs, it is necessary to optimize sewage treatment processes, such as:

Process combination: Combine different treatment processes to give full play to their respective advantages and improve treatment effects.
Process parameter optimization: Optimize process operation by adjusting parameters such as aeration volume, sludge age, and reflow ratio.
Application of new materials and technologies: Introduce new fillers, membrane materials, etc. to improve treatment efficiency.