What is the primary function of the underdrain in a pressure filter system?

The primary function of the underdrain in a pressure filter system is to collect and remove the filtered water. In these systems, water is forced through a filter medium, such as sand or anthracite, which captures particulates and impurities. Once the water has passed through the filter media, it collects in the underdrain system, which is designed to efficiently gather and transport the clean water to the next phase of filtration or to distribution.

The underdrain not only serves to remove the filtered water but is engineered to maintain even distribution and prevent clogging of the filter medium during the filtration process. This aspect allows for consistent flow rates and ensures that the filtration system operates effectively.

Other functions, such as facilitating water entry or managing chemical concentrations, are not the primary roles of the underdrain, and while they play important roles in filtration processes, they do not define the specific purpose of this critical component.