Water can serve as a reservoir or source for pathogens, which can lead to the transmission of infectious diseases.
Water systems harboring pathogens, such as Legionella and Pseudomonas spp., can also foster the growth of persistent biofilms, presenting a great health risk.
Water can be disinfected with heat, chemicals, or light.
For chemical disinfection of water the following disinfectants can be used: chlorine (Cl2); chlorine dioxide (ClO2); hypochlorite (OCl¯); ozone (O3); halogens: bromine (Br2), iodine (I), bromine chloride (BrCl); metals: copper (Cu2+), silver (Ag+); kalium-permanganate (KMnO4); phenols; alcohols; kwartair ammonium salts; hydrogen peroxide; several acids and bases.
Chlorine also oxidizes iron and manganese so they can be filtered out.
Ozone may be used to disinfect public water supplies, but is rarely used for private supplies (Liukkonen, 2006).
Many antimicrobial agents that are effective against planktonic cells turn out to be ineffective against the same bacteria growing in a biofilm state.
Planktonic and biofilm cells also exhibit different susceptibilities to a certain antimicrobial concentration.
Bacterial adaptive responses play a role in the design of control strategies.
The factors that determine the selection of disinfectants are mainly availability, cost factors, logistics, cost of equipment and safety factor.
Several pathogens causing healthcare-associated infections (HAIs) can be transmitted through a waterborne route.
Legionella, a bacterium that thrives in warm water and can become aerosolized through evaporation of contaminated water and then inhaled, is probably the most recognized.
In hospitalized patients who usually have a concurrent illness, legionellosis can range from a mild pneumonia to a life threatening disseminated disease.
Some pathogens that survive in water systems are opportunistic; they are part of the human microbiome (organisms that normally live harmlessly in or on humans) and cause infection only under certain conditions.
For example, Pseudomonas aeruginosa, bacteria; that can harmlessly live in the human intestinal tract, can cause a wide range of serious diseases including wound infection, pneumonia, and bloodstream infection when it contaminates water used in patient care.
Additional bacteria include Acinetobacter spp., which, although a low virulence organism, frequently causes pneumonia or bloodstream infections in patients residing in the intensive care unit, in part because of its ability to persist in the environment.
Acinetobacter spp. can replicate on environmental surfaces that collect moisture.
Non-tuberculous mycobacteria including Mycobacterium fortuitum can colonize in hydrotherapy pools or can be transmitted as aerosol from showerheads (Squier, Yu, & Stout, 2000).
Molds such as Fusarium are less common causes of infection arising from water sources (Anaissie et al., 2001).
Transmission of pathogens from water sources occurs through contact with contaminated water or through aerosolization of contaminated water.
Disinfectants employed hitherto are harsh, allergens or carcinogenic.