UV radiation penetrates the cell wall of an organism, disrupting its ability to reproduce.

Commonly called UV radiation for short, ultraviolet radiation is one method of water treatment that has been around since the late 1900s. UV disinfection has been used successfully in water and wastewater industries. In the past, water-borne diseases like typhoid and cholera were the major concerns in drinking water. Untreated waste water is allowed to discharge to surface waters. As a result of regulations and advanced wastewater treatment technologies, these diseases are no longer the major issues especially in developed countries because of efficient drainage systems. The focus has shifted to other drinking water problems such as heavy metals (like lead, mercury, arsenic, and aluminum), pesticides, nitrates, cryptosporidium, giardia, and virus. This is just a few of the more than 80 contaminants regulated by the USEPA.

There are two types of treatment systems to remove these contaminants namely point-of-entry (POE) and point-of-use (POU) treatment systems. POE treatment systems treat water to the whole house from the water mains. This treatment device could be large and may require experienced plumber to install. POU treatment systems treat water where the water is dispensed for consumption. POU treatment systems can be undersink filters, counter-top or tabletop filters, pitcher or carafe filters, faucet mounted water filters, showerhead water filters, and portable or camping water filters. Portable or camping water filters can also be tabletop filters, and a bottle with a filter cartridge. The plumbed-in filters may also require an experienced plumber because of extensive installation work.

The presence of cryptosporidium and giardia is unhealthy, and it’s an indication that the water could be contaminated by sewage pollution. Cryptosporidium and giardia symptoms may include diarrhea, abdominal cramps, nausea, and vomiting. Water treatment plants are not capable to effectively remove cryptosporidium and giardia if they are present at higher levels than the treatment plant can tolerate. Similarly, most of the available home water filters are not capable of removing these contaminants from drinking water. To resolve this problem at water treatment plants, a disinfection unit is typically installed at the end of water treatment train – preliminary screening, flocculation, sedimentation, filtration, and disinfection.

This treatment technique is also used in some home water treatment systems to kill the bacteria in the water. Bacteria in the drinking water may have come from inadequate treatment from the water supplies, or from bacteria regrowth within the house plumbing systems. In fact, bacteria regrowth in water is one of many reasons bottled water taste really bad after it has been left for a long time. To resolve the bacteria regrowth phenomena in drinking water, several home water filter systems are designed to include a UV disinfection.

How UV Works
UV radiation is generated by a special light that penetrates the cell wall of an organism. The UV radiation penetrates the cell wall and damage the genetic information of the bacteria and viruses, disrupting their reproduction systems. The ultraviolet radiation system often include activated carbon filter to remove metals and particulates. Effectiveness of an ultraviolet radiation system depends on the intensity of the lamp. The minimum dose of UV light to inactivate bacteria is 38 mWs/cm2 set by the NSF International.

Types of UV Treatment Systems
Similar to water filters, UV systems come as POE and POU. The point-of-entry UV is installed after the whole house water filter. Some point-of-use UV systems are designed with the faucet mounted water filters while some are designed with the counter-top water filters. These systems are usually arranged so that UV assembly is the last stage of treatment after water has passed through the activated carbon, and reverse osmoses filter units. This arrangement will also ensure that suspended particles, tastes and odors are removed prior to UV inactivation of bacteria. High levels of suspended particles will prevent UV lights from reaching the desired targets; tastes and odors cannot be removed by ultraviolet radiation. Some UV systems are designed to remove both the sediments and to kill the bacteria