Figure 1. Processing of GAC (Granular Activated Carbon) from coconut shells: traditional open pit method (A) ; barrel method (B) and “green” production using gasification systems reactor (C). Photos courtesy of Filtrex Holdings Group.

anister filters and tanks. Both methods are limited by the type of carbon used. One method uses in-line canisters (typically 4”x20”) containing carbon block filters that are changed annually. These filters are created by compressing very finely pulverized activated carbon in a binding medium and fusing it into a solid block. Carbon block filters can remove particles down to 1 micron and also remove Giardia and Cryptosoridium if present and eliminate the problems of channeling of the carbon. These filters are so dense that they minimize the potential for bacterial growth.

Other whole house, chlorine-removal devices are stand-alone carbon tanks used in complex treatment sequences, or in tanks that may be combined with embedded electromagnetic devices. These latter systems are frequently backwashed and may waste as much water as a conventional softener. Carbon block filters are effective in removing chlorine and VOCs (Volatile Organic Compounds), but they do not protect you from other harmful contaminants that might be present in water. GAC, the media found in most household (faucet and pitcher) filters, are also very limited in their contaminant removal capabilities. Because of the potential for bacterial growth and its inability to remove metals and radionuclides in water, carbon filtration is a poor choice for most well water except where chlorine is used for specific oxidation applications (such as for iron, manganese or arsenic III) and then removed by dedicated carbon block filters that are changed on a scheduled basis.

Anti-scalant Systems / Salt-free Systems
Anti-scalant systems are designed to reduce or eliminate lime scale accumulation, but water softening, or ion exchange, is the only proven method for softening water. Salt-free systems are not a substitute for softeners and are poor choices for consumers accustomed to softened water; but they are ideal for customers who want to conserve water, avoid the hassles of salt use and the discharge of chlorides into the environment. Some systems that are touted as salt-free are actually wasteful backwashing systems. The key is the presence of an electronic control head, which is used to time and control backwashing. Magnets and other catalytic systems are not generally accepted methods for mitigating hardness, but they do work in some cases and may offer the consumer a more cost-effective solution to lime scaling (but not contaminant removal).

Dissolved Oxygen Generators
By creating high levels of dissolved oxygen in the water, these oxygen-generating devices are effective in oxidizing iron and manganese minerals, thus enabling easy removal by filtration, while eliminating unpleasant iron, manganese and hydrogen sulfide odors. An electrical current is passed between an anode and cathode positioned some distance apart in the water solution. The electrical current pulls the positive and negative charges of the water molecule apart, causing it to split into hydrogen and oxygen, efficiently producing extremely small oxygen micro-bubbles, which are unable to break the surface tension of the water. As a result, virtually all the released oxygen remains dissolved in solution and available for oxidizing contaminants. Test case experiments are in progress to confirm that this process will also oxidize Arsenic III, which will allow it to be removed, along with Arsenic V, by reverse osmosis.

Ozonation
Ozone (O3) is a relatively unstable molecular “free radical” of oxygen, which readily gives up one atom of oxygen and becomes a powerful oxidizing agent that is toxic to most waterborne organisms. Ozone oxidizes by attaching the extra oxygen atom to anything that can be oxidized. The only by-product of ozone is pure oxygen. The high oxygen content of ozonated water provides numerous benefits including disinfecting viruses, algae spores, fungus, mold, and yeast spores on contact. Ozone also oxidizes and precipitates iron, sulfur, and manganese so they can be filtered out of solution. Ozonation is commonly applied by installing an ozone generator in an atmospheric surface tank or cistern.

Ultraviolet (UV) Treatment
UV light works by attacking the genetic core (DNA) of bacteria and viruses, destroying their ability to function and reproduce. The process is simple but effective and destroys 99.99 percent of harmful microorganisms within microseconds without adding chemicals or changing the taste or color of the water. (See Figure 2) UV is more effective than chlorine in disinfection against organisms such as Cryptosporidium, which is resistant to chlorine.