Water polishing

A water filter removes impurities from water by means of a fine physical barrier, a chemical process or a biological process. Filters cleanse water to different extents for purposes such as providing agricultural irrigation, accessible drinking water, public and private aquaria, and the safe use of ponds and swimming pools.

Filters use sieving, adsorption, ion exchanges, biological metabolite transfer, and other processes to remove unwanted substances from a quantity of water. And unlike a sieve or screen, a filter can potentially remove particles much smaller than the holes through which its water passes.

Types of water filters include media filters, screen filters, disk filters, slow sand filter beds, rapid sand filters, cloth filters, and biological filters such as algae scrubbers.

Point-of-use filters for home use include granular-activated carbon filters (GAC) used for carbon filtering, depth filter, metallic alloy filters, microporous ceramic filters, carbon block resin (CBR), microfiltration and ultrafiltration membranes. Some filters use more than one filtration method. An example of this is a multi-barrier system. Jug filters can be used for small quantities of drinking water. Some kettles have built-in filters, primarily to reduce limescale buildup.

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Wikipedia