Well Water Disinfection: Chlorine, Ozone or UV?
For all practical purposes, well disinfection systems fall into two broad categories: Those that are chlorine-based and those that aren’t. Both categories and each specific methodology offer advantages and disadvantages, so let’s look at some particulars.
Chlorine disinfection methods have been used since the 1920s. While chemical disinfection poses some concerns, its long track record, effectiveness against bacteria and relative safety explain why it remains one of the most widely used approaches.
Continuous chlorination systems use a feed pump to deposit controlled amounts of chlorine into the well or inline tank. Chlorine levels must be tailored to well size, water temperature and pH. Continuous systems provide ongoing protection against normal bacteria loads and may retard the growth of iron bacteria associated with biofouling. There are two basic approaches:
Simple chlorination systems are designed to deliver low concentrations of chlorine (0.2 to 0.5 ppm) in a small processing tank that ensures water (and bacteria) remain in contact with the chlorine for at least 30 minutes.
Super chlorination systems apply more chlorine (3 to 5 ppm) for a shorter length of time, usually about 5 minutes, and may incorporate a carbon filtering system to remove the chlorine smell and taste.
At present, there are two accepted technologies that provide an alternative to chlorine:
Ozone is an effective way to disinfect water. It’s more powerful than chlorine, requires no chemicals, and kills bacteria, mold and viruses. It also oxidizes iron, manganese and sulfur, so these particulates can more readily be filtered from your water supply. Ozone is produced using special equipment called an ozonator. There are various full-sized inline ozonators on the market along with smaller units that can be adapted for use in cisterns or storage tanks.
Ultraviolet (UV) radiation systems utilize UV light to kill bacteria. A sensor determines the appropriate dosage level and adjusts the UV exposure time to respond to changes in water quality. Water that contains high levels of sediment or dissolved minerals can reduce the effectiveness, but in general UV systems are effective against bacteria, somewhat effective against viruses and have no impact on cysts or worms.
In each instance above, the systems are primarily designed to reduce bacteria levels to make water safe for consumption, although ozone and UV radiation have some effect on viruses as well. Additional water processing and filtration equipment is required to address other water quality issues such as odors, high levels of sedimentation, pH, salinity or hardness.