They may combine with other components to form cancer-causing compounds. Ozone may be used to disinfect public water supplies, but is rarely used for private supplies. Chlorine is used most often to disinfect private wells. A well may be contaminated when flooded or when the watertight casing is no longer intact. It may be contaminated when opened for maintenance or repair.
Homeowners can chlorinate wells themselves or hire professionals.
If you hire professionals, make sure they are licensed contractors. If you disinfect your well, calculate how much chlorine you need. It is important to disinfect the entire household plumbing system. Chlorine must stay in piping long enough to kill all living organisms. Extension has a publication that helps calculate how much chlorine to add to your system.