Filtration is a process used in water treatment to remove solid particles and other impurities from water. During filtration, the clear water passes through filters that have different pore sizes and are made of different materials such as sand, gravel, and charcoal. These filters remove dissolved particles and germs such as dust, chemicals, parasites, bacteria, and viruses. Filtration is one of the core stages of water and wastewater treatment and is often used in combination with other processes such as coagulation, sedimentation, and disinfection.

There are different types of filtration processes, including:

• Gravity filtration: This method of filtering impurities uses gravity to pull liquid through a filter. This form of filtering occurs through beds of granular media and consists of interception, straining, flocculation, and sedimentation.

• Membrane filtration: This type of filtration utilizes microfiltration and ultrafiltration. The water goes through a filter membrane with very small pores that only let through water and other small molecules such as salts and tiny, charged molecules. Reverse osmosis is another filtration method that removes additional particles from water.

• Precoat filtration: This version of filtration involves a porous support surface that is given a sacrificial coating of diatomaceous earth or other suitable material each time the filter has been cleaned. A small amount of the diatomaceous earth is applied continuously during filtration.

Filtration is an important step in ensuring the quality of drinking water. It removes particles and impurities that can cause health problems and affect the taste and odor of water. However, filtration alone may not be sufficient to keep water safe for use, especially in water that may become aerosolized or is on its way to human consumption. Water treatment, on the other hand, can tackle the trace chemicals and minute organisms that live in water. Water treatment adds options such as chlorine or iodine to the water to kill bacteria, viruses, and other living, biological components that could make humans sick and foul equipment.