The water filtration process entails allowing water to pass through a filter material or, in some cases, forcing the water through it with pressure. Filtration can remove particulate matter, metals, and microbial pathogens, depending on the filtering medium used. Filters come in a variety of sizes, ranging from small models that attach to household faucets to those used in municipal water treatment systems, but they all work on the same principles.
The main components of any water filtration process are filter media, which are the materials that capture contaminants from the water. Sand is frequently used in large water treatment systems, and it is occasionally mixed with anthracite coal. Granular activated carbon is a popular choice for small household filters because it has been processed to have a higher surface area, allowing it to absorb more contaminants. Manganese greensand is a type of sand that has been treated to remove iron and manganese from water. Diatomaceous earth filters are commonly used in swimming pools.
Small filters usually only have one material, whereas larger filters have multiple layers of filter media. Sand filters, for example, have a layer of gravel on top of which is a layer of sand. If anthracite coal or another fine-grained filter material is included in the filter, it is layered on top. The water moves slowly through the small particles in the upper layers of the filter, then faster through the gravel layer, and finally collects in the underdrain until it is ready to move on to its next destination.
The water flowing through, or being forced through, the filter is the only visible action in the water filtration process, but several processes are taking place to remove contaminants from the water. Because larger contaminants cannot pass through the filter material, they are sieved out. Filter material particles adsorb contaminants like gases and particulates such as metals and minerals. Contaminants adhere to the filter material’s surfaces, which is referred to as adsorption.
Biological breakdown is another part of the water filtration process that removes contaminants for a particular type of filter called a slow sand filter. The schmutzdecke, or layer of microorganisms that forms on top of the sand in slow sand filters, is a layer of microorganisms that forms on top of the sand in the filter. The microorganisms in the schmutzdecke break down organic contaminants and can eat harmful bacteria in the water.