Disinfectant, definition

Definitions. Physical and chemical agents that combat pathogenic and nonpathogenic microorganisms are often referred to as disinfectants. Attempts to standardize terminology by health agencies in the United States, such as the CDC, the Pood and Dmg Administration (PDA), and the EPA, have resulted in the following definitions. 

Nearly all ozonation effects and their respective extent and kinetic pattern depend on the amount of ozone consumed in the ozone contactor and subsequent reactors. This requires the search for and definition of optimal operational parameters for an ozonation stage, such as a concentration-time-value (c-f-value) for a given degree of disinfection or the ratio of ozone mass consumed per mass of organic compounds initially present. 

Bolton JR (2000 b) Terms and Definitions in Ultraviolet Disinfection, in Proceedings, Disinfection 2000, Disinfection of Wastes in the New Millennium, 15-18 March 2000, New Orleans, LA, Water Environment Federation, 501 Wythe St., Alexandria, VA, 22314. 

Common definitions of the term disinfection usually aim at its medical aspects related to transmissible diseases and to the killing or irreversible inactivation of the disease-causing organisms by use of chemical agents or physical procedures. This includes the destruction of infectious or other undesirable bacteria, pathogenic fungi or vimses and protozoa on surfaces or any inanimate objects (Block, 1993, Harke, 1987). Thus, disinfection of water, air or surfaces should produce a... 

First, it is to be noted that the reaction is expressed in terms of HOCl. By the eqnivalence of reactions, however, the above reactions can be manipulated if the equivalent amount of the other two species is desired to be known. In monochloramines and dichloramines, therefore, the chlorine is combined in ammonia they are called combined chlorines. As will be shown in subsequent discussions, the concentration of trichloramine is practically zero during disinfection thus, it is not included in the definition of combined chlorine. 

Acid generation. Whether or not acid will be produced depends upon the form of chlorine disinfectant used. Using chlorine gas wiU definitely produce hydrochloric acid. Sodium hypochlorite and calcium hypochlorite will not produce any acid on the contrary, it can result in the production of alkalinity. Superchlorination using HOCI will definitely produce acids. 

The UV radiation disinfects germs in an aqueous system, which can be operated as plug flow, continuous flow, or other modes. The killing efficiency is controlled by many factors, which can be classified into two aspects disinfection kinetics and flow dynamics. Like many other processes in both chemical and environmental engineering, the mathematical modeling of the UV disinfection can be started from simulation of distribution of flow velocity together with definition of suitable kinetic model(s). The disinfection effect in terms of survival of pathogens as a function of operational conditions such as time and dose can then be estimated. Since the mathematical models involve many unknown parameters that must be experimentally determined, they are mainly... 

High concentrations of disinfectants, e.g. chlorhex-idine, phenol or mercury salts, will coagulate the cytoplasm and in fact it was this kind of reaction which gave rise to the epithet general protoplasmic poison , already referred to, providing an uncritical and dismissive definition of the mode of action of disinfectants. There is little doubt, however, that the disinfectants in use in the 1930s had just this effect when applied at high concentrations. 

The % available chlorine from calcium hypochlorite by definition includes CI2, HCIO, and OCl (but not Cl ), is 99.2%, or nearly the same effectiveness on a weight for weight basis as treating with elemental chlorine [9]. As long as the residual chlorine level used with hypochlorite salt disinfections is the same as with chlorine gas, there is no difference in relative effectiveness. 

The application of photodynamic therapy (PDT) in treatment of bacterial infections will definitely continue to attract the attention of scientists. It is considered unlikely that bacteria develop resistance against singlet oxygen therefore, PDT may become a useful weapon to battle infections. For treatment of infections in the oral cavity, a smart toothpaste containing a photosensitizer that is selectively absorbed by bacteria is under development. This can be used in combination with a laser toothbrush designed recently (Moore, 1998). Sensitizers can further be incorporated into bandages for disinfection of wounds or in cellophane films used to wrap food (Moore, 1998). 

A definite schedule should be followed for backwashing and disinfecting the carbon filter. Instructions for this are furnished by the manufacturer of the equipment. 

There are a large number of chemicals which are able to kill micro-organisms in addition to antibiotics. Many of these are used on surfaces or skin and go under a variety of names. Chemicals used in the presence of dirt or dense bacterial populations are known as disinfectants. Antiseptics are used on the skin to reduce the bacterial population and thus the risk of infection. Sterilants are compounds used to sterilise enclosed spaces, whilst preservatives are compounds which stop bacteria attacking organic matter. These definitions form a spectrum and compounds frequently overlap from one group to the next. 

---