Which of the following represents the four main stages of water treatment?

The correct choice identifies the four main stages of water treatment: coagulation, sedimentation, filtration, and disinfection.

Coagulation is the initial stage where chemicals, known as coagulants, are added to water to bind and group together small particles, making them easier to remove. This is crucial for clarifying water by reducing turbidity.

Sedimentation follows, where the water is allowed to sit undisturbed. In this stage, the larger coagulated particles, known as floc, settle to the bottom of the treatment tank due to gravity, creating clearer water above.

Filtration is the third stage, where the water passes through various filter media (like sand and gravel) to remove any remaining suspended particles and impurities. This process enhances water quality by ensuring only clean water moves forward.

Finally, disinfection is the last stage, where various methods (such as chlorination, UV light, or ozonation) are employed to kill or inactivate pathogenic microorganisms that can cause disease. This is essential for making the water safe for human consumption.

The other answers propose stages that are not standard in water treatment. Heating and cooling do not generally represent treatment stages, nor do methods like aeration or evaporation that aren't central to the core treatment