Activated carbon filters are used to remove unwanted tastes, odors, radon, and some man-made volatile organic contaminants from drinking water. The efficiency of the unit depends on the type of activated carbon installed, the filter bed depth, the type of contaminants in the water and their concentration, and the contact time between the water and the carbon filter. Activated carbon filters do not adsorb every type of contaminant equally well. Carbon filters are easy to install and maintain, and operating costs are usually limited to filter replacement. Depending on the type and concentration of the contaminant being removed, some carbon filters may require special hazardous waste handling and disposal, which can be costly. Other filter types are available including charcoal and ceramic materials that treat the water similarly, through adsorption of the contaminant onto the filter.polyacrylamide pam
The solid material used in an activated carbon filter is a specialized carbon manufactured for this purpose. Contaminants adhere to the surface of these carbon granules or become trapped in the small pores of the activated carbon. Generally, an activated carbon filter is used with a pre-treatment filter to remove sediment or iron particles that may be present and can clog the carbon filter.
Granular activated carbon (GAC) treatment is most common for private water systems. Granular activated carbon is an effective filter for removing organic chemicals that may be in drinking water. Many other small devices use carbon that has been pressed into a solid block. Use of block carbon may result in a significant drop in home water pressure. These devices also clog easily if the water is cloudy or turbid.
A synthetic resin may be a substitute for carbon. Although activated carbon is efficient in removing a variety of organic chemicals, a specially formulated synthetic resin may be a better absorber for a specific contaminant.
The effectiveness of an activated carbon unit depends on the extent of contact between the carbon and the untreated water. During regular operation of any device, channels form within the carbon filter, allowing some water to bypass the filtering material, short-circuiting treatment. Since treatment depends on the carbon granules adsorbing the chemical contaminants, these channels decrease the contact time and the effectiveness of the carbon filter unit. A disadvantage of block carbon is that if it is unevenly compressed when manufactured, irregular flow patterns may affect the effectiveness of contaminant removal.
There are two main procedures to determine how much a carbon filter can adsorb: the iodine test and the phenol test. The iodine number is defined as the amount of iodine (in milligrams) adsorbed by one gram of carbon under a certain set of conditions. The larger the number, the more the carbon filter can adsorb. Phenol is another measure of effectiveness. The lower the phenol number, the better the carbon is at removing organics. When comparing home carbon devices, pay attention to these values.
Please keep in mind that manufacturers tend to report the best removal rate for their product. The values are frequently the amount the unit will remove at the beginning of use for a single contaminant at moderate concentrations. Units having a larger bed volume of carbon usually remove a greater quantity of contaminants. Some types of activated carbon will remove specific contaminants better than others. Buyers need to examine as many products as possible, and know exactly what contaminant they want the unit to remove. You will also need to know how much water is used in the home on an average day to adequately size the treatment system. Additionally, have both the raw water (prior to treatment) and the treated water retested after a unit is installed to ensure it is functioning properly.anionic polyacrylamide polymer