Coagulation is a chemical process in water treatment aimed at aggregating small suspended particles into larger particles, making it easier to separate and remove them from the water. After coagulation treatment, the particles in the water form something called “flocs,” which become increasingly heavy and large, aiding in sedimentation or filtration. Coagulation is a widely used purification process in drinking water, industrial water, and swimming pool water treatment.
I. Different Types of Coagulation in Water Treatment
A. Water Pollution Issues In the field of water treatment, common water pollutants include suspended particles, organic matter, microorganisms, and other impurities. Sediments, silt, dust, algae, and other solid particles are all suspended solid particles that can cause water turbidity and a decline in water quality. By adding appropriate coagulants to the water, these particles can be coagulated into flocs, effectively improving water quality and reducing water pollution.
B. Water Clarification Process Coagulation is a commonly used water purification process designed to collect and remove solid particles from water, resulting in clear and transparent water quality. This method is widely applied in maintaining water quality standards in swimming pools, water tanks, and industrial water treatment.
C. Coagulation in Drinking Water Treatment Pretreatment of raw water is a crucial step in ensuring water environmental quality, and coagulation is a key process in achieving this goal. Coagulation treatment of fine particles, bacteria, organic matter, and impurities in water is essential to ensure the clarity and safety of treated water. Selecting appropriate coagulants and dosages is critical in drinking water treatment.
D. Coagulation in Industrial and Wastewater Treatment In industrial and wastewater treatment processes, a large amount of solid particles, oils, heavy metals, chemicals, and pollutants are often generated. In these fields, the use of coagulants is common, aimed at assisting in the removal and purification of wastewater, allowing for legal discharge or recycling.
II. Common Coagulants
A. Aluminum-Based Coagulants Common aluminum-based coagulants include aluminum sulfate and aluminum chloride. These coagulants work by adding aluminum ions to water, allowing them to react chemically with negatively charged particles. Aluminum coagulants can aggregate negatively charged particles into larger flocs, making them easier to settle or filter. This series of coagulants finds extensive applications in water purification, drinking water treatment, and wastewater treatment.
B. Iron-Based Coagulants Iron-based coagulants mainly include ferric chloride and ferrous sulfate. Similar to aluminum-based coagulants, iron coagulants work by adding iron ions to water to neutralize negatively charged particles. These ions combine with particles, forming flocs that can be easily settled or removed. Iron-based coagulants play a crucial role in wastewater treatment, industrial water treatment, and wastewater treatment.
C. Organic Coagulants Organic coagulants are generally high-molecular-weight compounds such as polyaluminum, polyferric, and polyaluminum chloride. Their molecular structures enable excellent adsorption of suspended particles and organic matter in water. Organic coagulants are widely used in water treatment for water sources with high turbidity, complex water quality, and containing substances such as oil, dyes, and organic matter.
Coagulation is an essential step in water treatment and purification processes, contributing to the improvement of water quality, sustainable water resource development, reduction of pollutant emissions, assurance of drinking water safety, and protection of the ecological environment. To apply coagulation effectively in different water treatment scenarios, understanding its fundamental principles and common types is essential.