Disinfection
Authors: Das Tapas K. 
Published: July 2004

This article describes some of the historic use of disinfectants and antiseptics, and disinfection practices, along with most modern and emerging technologies that are proving to be more efficient in disinfecting varieties of microorganisms present in water, air, and solid media.

In rural areas of India, Bangladesh, Brazil, Peru, China, and other underdeveloped and developing nations, waterborne diseases such as typhoid, cholera, hepatitis, and gastroenteritis infect and kill many infants and children each day, according to the World Health Organization (WHO). Wastewaters or water can contain an incredibly large variety of microorganisms, although some are harmless; many, however, are disease causing. These microorganisms must be destroyed before the water is safe to discharge into a receiving body of water or to reclaim and reuse it. With increasing emphasis on promoting a sustainable ecological future and concern over introducing a toxic chemical in the water, the design of the disinfection process is increasingly leaning toward technologies that destroy the pathogens while balancing the effects of this disinfected wastewater on the population of aquatic biota or a drinking water supply.

Disinfection (or pasteurization or sterilization) is a process by which pathogenic microorganisms are killed or inactivated to provide public health protection. Disinfectants and antiseptics are chemicals that kill or inactivate microorganisms such as bacteria, viruses, protozoans, and fungi. The chemicals (and some physical) agents that combat pathogenic and non‐pathogenic microorganisms are known as disinfectants and antiseptics. Therefore, it is important to have background information about these chemical and physical agents, and their role and how they act in the various disinfection processes. Disinfection is most commonly accomplished by the use of (1) chemical agents, (2) physical agents, (3) mechanical means, and (4) radiation.

Chemical agents that have been used as disinfectants include (1) chlorine and its compounds, (2) bromine, (3) iodine, (4) ozone, (5) phenol and phenolic compounds, (6) alcohols, (7) heavy metals and related compounds, (8) dyes, (9) soaps and synthetic detergents, (10) quaternary ammonium compounds, (11) hydrogen peroxide, (12) various alkalis and acids (eg, peracetic acid), and (13) antimicrobial nanoemulsions.

Physical disinfectants that can be used are heat and light. Heating water to the boiling point, eg, will destroy the major disease‐producing nonspore‐forming bacteria. Heat is commonly used in the beverage and dairy industry, but it is not a feasible means of disinfecting large quantities of wastewater because of the high cost. Bacteria and other organisms are also removed by mechanical means during wastewater treatment operations and processes, including coarse screens, fine screens, grit chambers, plain sedimentation, etc.

The major types of radiation that are used for disinfection are ultraviolet (uv), electromagnetic, acoustic, and particle. Gamma rays are emitted from radioisotopes such as Co‐60. Because of their penetration power, uv, gamma rays, and high energy electron‐beam devices have been used to disinfect (sterilize) water, wastewater or sludge, meat, poultry, fish and other foods, and air borne microorganisms or bioaerosols, including anthrax.