Media Filtration and Water Softening
Water is a very complex fluid. It contains a little bit of practically everything that it contacts; the air while falling as rain, the earth as it percolates into the ground, the piping as it is transported, and all kinds of organic and inorganic matter it may contact in its series of uses. Dissolved minerals in the water that contain an electric charge are called ions. These ions can be either positive or negatively charged with electrons. The positive ions are called cations and the negative ions are called anions. It is these positive cations in the form of calcium, magnesium, iron, and manganese that causes the hardness that is associated with water. Removal of these hardness ions via ion exchange is the process used for softening water.
The idea behind a water softener is simple. The calcium and magnesium ions in the water are replaced with sodium ions. Since sodium does not precipitate out in pipes or react badly with soap, both of the problems of hard water are eliminated. To do the ion replacement, the water in the house runs through a bed of small plastic beads or through a chemical matrix called zeolite. The beads or zeolite are covered with sodium ions. As the water flows past the sodium ions, they swap places with the calcium and magnesium ions. Eventually, the beads or zeolite contain nothing but calcium and magnesium and no sodium, and at this point, they stop softening the water. It is then time to regenerate the softener with the brine sodium solution from the brine tank.
Carbon filtering is a method of filtering that uses a piece of activated carbon to remove contaminants and impurities, utilizing chemical adsorption. Each piece of carbon is designed to provide a large section of surface area, to allow contaminants the most possible exposure to the filter media. One pound (454g) of activated carbon contains a surface area of approximately 100 acres. This carbon is generally activated with a positive charge and is designed to attract negatively charged water contaminants. Carbon filtering is commonly used for water purification but is also used in air purifiers.
Carbon filters are most effective at removing chlorine, sediment, and volatile organic compounds (VOCs) from water. They are not effective at removing minerals, salts, and dissolved inorganic compounds. Typical particle sizes that can be removed by carbon filters range from 0.5 to 50 micrometers. The particle size will be used as part of the filter description. The efficacy of a carbon filter is also based upon the flow rate regulation. When the water is allowed to flow through the filter at a slower rate, the contaminants are exposed to the filter media for a longer amount of time.
Filters are manufactured with a variety of different components. Depending on the application the filter tanks can be made of polyglass, FRP, carbon steel, or stainless steel. The polyglass is the most economical and can be used in a broad range of applications. High temperature, high-pressure applications usually require carbon steel tanks, or in the case of high purity or food processing, stainless steel may be required.