What is the flocculant added before sewage treatment?

The addition of flocculants is a crucial step in modern wastewater treatment processes, and the quality of wastewater treatment is directly related to the effectiveness of this step. So, what are flocculants? What impact do they have on wastewater treatment? This article provides a detailed discussion of the definition, classification, working principles of flocculants, and their applications in wastewater treatment, aiming to deepen our understanding of this process.

In conclusion, flocculant addition in wastewater treatment is a critical chemical process that promotes the rapid aggregation of suspended particles and colloidal particles in water, making them easy to settle or filter, thereby enhancing the efficiency of wastewater treatment.

Common coagulants include inorganic flocculants, organic flocculants, and natural flocculants. Inorganic flocculants like ferric chloride and aluminum sulfate generate highly polar and adsorbent iron and aluminum ions in water, which combine with organic and inorganic impurities in water to form flocs. This significantly reduces the residence time of pollutants in water. For example, adding aluminum sulfate to urban wastewater treatment plants effectively removes suspended solids and some soluble organic substances, improving water quality.

Organic flocculants like polyaluminum salts and polyaluminum silicates can form non-electric high polymers. In addition to their adsorption and chelation effects, they can efficiently adsorb and purify organic pollutants such as oil and colloids in wastewater. Using polymerized aluminum salts for industrial wastewater treatment can effectively remove heavy metals and colored impurities from water, ensuring compliance with discharge standards.

Natural flocculants like starch and chitosan can effectively prevent the collision and movement of fine suspended particles. Due to their natural, renewable, safe, and environmentally friendly characteristics, they are becoming increasingly popular. For example, using chitosan for the treatment of certain agricultural wastewater not only effectively removes suspended solids from water but also reduces heavy metal content. Moreover, it has biodegradable advantages, thereby reducing environmental pressure.

Therefore, inorganic, organic, and natural flocculants play irreplaceable roles in wastewater treatment processes, each with its own mechanism and characteristics. This is of great significance for improving water environmental quality and protecting the ecological environment.

Effects of coagulants in wastewater

• Preliminary treatment phase: In the initial stage of wastewater treatment, there are generally many suspended solids and fine particles. In this step, coagulants play a role in aggregating these suspended substances and particles into larger particles, making it easier for them to settle or be filtered. This helps purify wastewater and reduces subsequent processing loads.
• Sedimentation phase: Coagulants also play a certain role in the wastewater treatment process. They adsorb suspended particles and force them to settle, achieving the goal of clean water quality. This method is widely used in the treatment of sludge and wastewater.
• Filtration phase: During the filtration process, coagulants can help capture tiny particles remaining in the water, improving water clarity. This is particularly important in drinking water treatment.

Therefore, the addition of flocculants in wastewater treatment can effectively remove suspended solids and particles from wastewater, playing a significant role. Their use not only improves water quality but also has positive effects on the environment and human health. Understanding and applyingflocculants rationally is essential for wastewater treatment processes. This article aims to deepen our understanding of this crucial step and provide a scientific basis for clean water supply.