Temperature disinfectants

Chemical (vapor phase) Ethylene oxide Propylene oxide Formaldehyde (3 - Propiolactone Disinfection temperature Ethylene oxide also used as sterilizing agent Possible carcinogenic activity of p-propiolactone... 

If the third substance dissolves in both liquids (and the solubility in each of the liquids is of the same order), the mutual solubility of the liquids will be increased and an upper C.S.T. will be lowered, as is the case when succinic acid or sodium oleate is added to the phenol - water system. A 0 083 molar solution of sodium oleate lowers the C.S.T. by 56 -7° this large effect has been applied industrially in the preparation of the disinfectant sold under the name of Lysol. Mixtures of tar acids (phenol cresols) do not mix completely with water at the ordinary temperature, but the addition of a small amount of soap ( = sodium oleate) lowers the miscibility temperature so that Lysol exists as a clear liquid at the ordinary temperature. 

Disinfection. Ozone is a more effective broad-spectmm disinfectant than chlorine-based compounds (105). Ozone is very effective against bacteria because even concentrations as low as 0.01 ppm are toxic to bacteria. Whereas disinfection of bacteria by chlorine involves the diffusion of HOGl through the ceU membrane, disinfection by ozone occurs with the lysing (ie, mpture) of the ceU wall. The disinfection rate depends on the type of organism and is affected by ozone concentration, temperature (106), pH, turbidity, clumping of organisms, oxidizable substances, and the type of contactor employed (107). The presence of oxidizable substances in ordinary water can retard disinfection until the initial ozone demand is satisfied, at which point rapid disinfection is observed. 

Antimicrobial agents don t necessarily fall into only one category. For example, a stedlant under various conditions that could affect its action, such as time, temperature, pH, concentration, and presence of organic matter, might become less potent and act only as a disinfectant, a bactericide, or a sanitizer. Likewise, the reverse situation is also possible—a weaker agent under favorable conditions can exert greater activity and move up in category. 

The ampholytes, which must be used in higher concentrations than many other disinfectants when employed at room temperature, are greatiy improved as the temperature is increased. At 20°C, 3250 ppm of Tego 51 killed Pseudomonas aeruginosa in 30 min, at 50°C it required only 100 ppm in the same time (184,185). 

Boiling - This involves bringing the water to its boiling point in a container over heat. The water must be maintained at this temperature 15 to 20 minutes. This will disinfect the water. Boiling water is an effective method of treatment because no important waterborne diseases are caused by heat-resisting organisms. 

In order to ensure the destruction of pathogens, the process of chlorination must achieve certain control of at least one factor and, preferably two, to compensate for fluctuations that occur. For this reason, some authorities on the subject stress the fact that the type and concentration of the chlorine residual must be controlled to ensure adequate disinfection. Only this way, they claim, can chlorination adequately take into account variations in temperature, pH, chlorine demand and types of organisms in the water. While possible to increase minimum contact times, it is difficult to do so. Five to ten minutes is normally all the time available with the type of pressure systems normally used for small water supplies. Many experts feel that satisfactory chlorine residual alone can provide adequate control for disinfection. In their opinion, superchlorination-dechlorination does the best job. Briefly, what is this technique and how does it operate ... 

It has also been demonstrated that the germicidal effectiveness of free and combined chlorine is markedly diminished with decreasing water temperature. In any situation in which the effects of lowered temperature and high pH value are combined, reduced efficiency of free chlorine and chloramines is marked. These factors directly affect the exposure time needed to achieve satisfactory disinfection. Under the most ideal conditions, the contact time needed with free available chlorine may only be on the order of a few minutes combined available chlorine under the same conditions might require hours. 

Table 3 gives recommended ranges of chlorine dosages for disinfection of various wastewaters. Recommended minimum bactericidal chlorine residuals are given in Table 4. Data in Table 4 are based on water temperatures between 20 C to 25 C after a 10-minute contact for free chlorine and a 60 minute contact for combined available chlorine. 

We only briefly mentioned alkaline stabilization, but in reality this is a variation of sludge pasteurization. The basic process uses elevated pH and temperature to produce a stabilized, disinfected product. The two alkaline stabilization systems most common in the U.S. are a lime pasteurization system and a cement kiln dust pasteurization system. The lime pasteurization product has a wet-cake consistency, while the kiln dust pasteurization has a moist solid like consistency. Both products can be transported to agricultural areas for ultimate use. Literature studies show that the kiln dust product can capture a marketable value of 6.60/Mg ( 6.00/ton) to offset hauling costs, while the lime product does not appear to be able to capture financial credits for product revenues at this point in time. The reasons for this are not entirely clear. 

Cooling towers and evaporative condensers release into the atmosphere fine droplets of water, which may carry sources of contamination such as algae and bacteria. Many of these thrive at the temperatures to be expected in water cooling systems and one of them, Legionella pneumophila, has been identified as a particular hazard to health. Cooling apparatus should be cleaned and disinfected frequently to reduce these risks of contamination and should not be located where water droplets can be drawn into ventilation air intakes. 

The effluent from the disinfection step was flowed through a polysulfone spiral wound NF Pilot Plant with 0.7 m of membrane (DSS TEST UNIT M20-0,72-PSO, ALFA-LAVAL) working at room temperature and at 20 bar operation pressure. 

Heat is the most reliable method of virus disinfection. Most human pathogenic viruses are inactivated following exposure at 60°C for 30 minutes. The virus of serum hepatitis can, however, survive this temperature for up to 4 hours. Viruses are stable at low temperatures and are routinely stored at -40 to -70°C. Some viruses are rapidly inactivated by drying, others survive well in a desiccated state. Ultraviolet light inactivates viruses by damaging their nucleic acid and has been used to prepare viral vaccines. These facts must be taken into account in the storage and preparation of viral vaccines (Chapter 15). 

Respirator parts Moist heat (autoclave) Moist heat (low- temperature steam, or hot water at 80°C) Sterilization Disinfection Sterilization by steam where possible Chemicals not recommended may be microbiplogically ineffective, may present hazard to patient safety by compromising the safety devices on the machine... 

Low-temperature steam with formaldehyde is of value in the disinfection/sterilization of some heat-sensitive materials (see also Chapter 20). 

Stainless steel disks are contaminated with a bacterial test suspension and dried. The disinfectant is applied on the dried film on the disk and kept at a specified temperature for a defined time. The disk is than transferred to a previously validated neutralization medium to stop the action of the disinfectant. The cfii of surviving bacteria recovered from the surface is determined quantitatively. 

Please indicate which six of the following issues are the most important when considering the comfort and well-being of users and staff. (Air temperature, bacteria, chloramine levels in the water, chlorinous smells, clear water, fresh air, humidity, pH, residual disinfectant level, trihalomethanes, water temperature, water balance)... 

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