Coagulation in water treatment involves a reaction between the coagulant and what substance present in the water?

Coagulation in water treatment is a critical process used to remove suspended particles and contaminants from water. The primary reaction involves a coagulant, typically a chemical such as alum (aluminum sulfate), that interacts with certain substances present in the water to form larger particles, or flocs, which can be subsequently removed through sedimentation and filtration.

The correct answer focuses on alkalinity, which plays an essential role in coagulation processes. Alkalinity refers to the water's capacity to neutralize acids and is primarily a measure of the bicarbonates, carbonates, and hydroxides in the water. When a coagulant is added, it reacts with the alkalinity present, facilitating the formation of flocs. This reaction helps optimize the pH levels, ensuring that the coagulation process is effective. Adequate alkalinity is necessary for the charged particles to form stable aggregates, which are crucial for efficient sedimentation and removal.

Other choices, while related to the overall water quality, do not play the same direct role in the coagulation reaction. Minerals and contaminants encompass a wide range of substances that could be present in water but do not specifically react with coagulants in the coagulation process. Organic matter can also be part of the water