If only the drinking and cooking water supply must be treated, a by-pass unit saves money, but if bath and wash water must also be treated, a whole house stationary filter would be chosen. Since contaminant removal is a function of carbon volume and contact time if the same filter cartridge is used for either stationary or line by- pass systems, a lower removal would be expected in the stationary system. Contaminant removal is further discussed in the following sections. Almost any carbon source can be used but coal has been the most common. The process results in a granular product that may be used in the granular form or ground into a powder which is formed into blocks or embedded into pads.
Activated carbon is an adsorption medium.
Substances become bonded to the carbon and are tightly held there. Activated carbons differ in how readily they adsorb various contaminants and how rapidly they become filled with a particular contaminant or group of contaminants. The activity of an activated carbon is a function of the type of carbon used, the contaminant being adsorbed and the size of the carbon particles. The effectiveness of removal, however, is primarily a function of the amount of activated carbon present and the duration of contact with the water being treated. Contaminants also vary in how readily they will bond with activated carbon.