What is one substance that a sand filter will not effectively remove?

A sand filter is designed to effectively remove larger particles and impurities from water, primarily through physical filtration. It operates by allowing water to flow through a bed of sand, which traps these particles. However, when it comes to dissolved substances, such as dissolved oxygen, the situation is different.

Dissolved oxygen is a gaseous form of oxygen that is mixed in the water, making it invisible and too small to be physically filtered out by sand. Since the primary function of a sand filter is to remove particulate matter, it lacks the capability to separate gases that are dissolved in the water.

In contrast, substances like fine particulate matter, heavy metals, and colloidal silica, despite their small size, can be captured to some extent by the sand due to their particulate nature or interaction with the filter media. Thus, the sand filter effectively addresses these types of impurities, but it cannot affect dissolved gases like oxygen. Understanding the limitations of filtration systems is crucial for effective water treatment and ensuring water quality.