Coagulants are chemicals that facilitate the aggregation of suspended particles in wastewater, allowing them to form larger particles or flocs. Common coagulants include aluminum sulfate (alum) and ferric chloride, which neutralize the negative charges on particles, promoting their aggregation. Following coagulation, flocculants — such as polyacrylamide — enhance the formation and settling of these flocs in the sedimentation process. This step is crucial in removing solids and turbidity from sewage, making it a fundamental part of primary treatment.