What is the meaning of precoating in a filter?

Precoating in a filter refers to the process of applying a thin layer of filter aid, such as diatomaceous earth or perlite, onto the filter medium before the actual filtration begins. This layer helps to create a uniform surface, improving the filter's efficiency by preventing clogging and enhancing the separation of solids from liquids. Precoating not only extends the life of the filter but also ensures a higher quality of the filtrate by minimizing the risk of filter media contamination.