What is a typical pre-treatment process for surface water before it is used as drinking supply?

Coagulation is a critical pre-treatment process for surface water before it is utilized as a drinking water supply. During coagulation, chemicals known as coagulants are added to the water to promote the clumping of suspended particles and impurities, such as silt, organic matter, and microorganisms. This process is essential because it helps to make the subsequent filtration process more effective by aggregating these small particles into larger flocs that can be more easily removed from the water.

This method is particularly important in treating surface water, as it often contains high levels of turbidity due to natural sediments and contaminants. By using coagulation, water treatment plants can greatly enhance water quality and ensure that the water meets safety standards for consumption.

While filtration, chlorination, and ozonation are also important steps in water treatment, they typically follow the coagulation process. Filtration, for instance, will remove the larger floc particles that result from coagulation, while chlorination and ozonation are primarily used for disinfection to eliminate pathogens after the majority of physical impurities have already been addressed. Each of these processes plays a unique role in the overall treatment of drinking water, but coagulation specifically targets the initial step of removing suspended solids from surface water.