Contaminated, dirty or otherwise impure water can be cleaned and purified by using various filtration and chemical treatment methods. In cases of true emergency, dirty water can be cleaned out, although not necessarily disinfected, using evaporation techniques.
The best method one should use in the process of treating or purifying water varies depending on the situation. In cases where disinfected water simply needs to have particles removed, it can be filtered through a thin material like a coffee filter, which will remove the sediment. However, if water is both dirty and potentially contaminated, disinfecting methods should be used in addition to basic purifying filtration. When used in proper amounts and according to directions, chemicals like iodine tincture, iodine tablets, chlorine bleach and granular calcium hypochlorite can be used to disinfect water. Prolonged boiling is also an effective way to kill microorganisms and other harmful materials in dirty water.
Most municipal water systems use a combination of physical filtration and chemical treatment to purify and clean water before delivering it to people's homes and businesses. The water is first screened to remove large particles and even animals like fish if they live in the water source. After this is accomplished, a process of settling, chemical purification, and filtration through fine sand or gravel helps get the water pure and clean.