Effective disinfection time

Rincdn, A.G. and Pulgarin, C. (2004b) Bactericidal action of illuminated Ti02 on pure Escherichia coli and natural bacterial consortia Post irradiation events in the dark and assessment of the effective disinfection time. Appl. Catal. B Environ. 49, 99-112. 

When the water is too alkaline, swimmers experience similar physical discomfort—burning eyes and nose and itchy, dry skin. The effect on the pool, however, is different. When water is alkaline, calcium dissolved in the pool water can precipitate (fall) out of solution. A precipitate is a solid that forms from a solution due to a chemical reaction. This solid creates unsightly scales on the sides of the pool. Like water that is too acidic, alkaline water also affects the efficiency of the chlorine. More chlorine needs to be added to alkaline water to effectively disinfect the pool. Over time, a swimming pool that is not kept at a neutral pH can become very expensive to maintain. 

Chlorine is still a time-tested effective disinfectant. In many parts of the world, it is indispensable in drinking water. 

For wastewater treatment, the recommended chlorine dosage for disinfection purposes should produce a chlorine residual of 0.5-1 mg/L after a specified contact time. Effective contact time of not less than 15 min at peak flow is recommended. Practical chlorine dosages recommended for wastewater disinfection and odor control are presented in below ... 

The quality of water is important to human health. Water-borne diseases cause about 80% of the world s sickness. Because humans drink about 2 L of water per day, even small amounts of toxic compounds in drinking water have significant effects over time. But, what is pure water What is polluted water With numerous terms such as pure, purified, distilled, and disinfected to describe our drinking water, how do we know what we are getting ... 

Specify the optimum chlorine dosage, contact time and pH range for effective disinfection. 

Tetrasilver tetroxide is a powerful oxidizer for sanitizing swimming pools, hot tubs, and industrial cooling system waters (see Water, treatment of SWIMMINGPOOLS, SPAS, AND HOT tubs). This oxide is slightly soluble and its dissociation into silver ions is enhanced by the addition of the oxidizer KgSgOg. Bivalent and trivalent silver disinfectants have been shown to be from 50 to 200 times more effective as sanitizers than monovalent silver compounds. 

The effectiveness of disinfection increases with the amount of contact time available. 

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. 

The reason for this confusing situation is that all efficacy data are depending from the test method used to find the effective time - concentration ratio of the disinfectant. 

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