Disinfectants, reduced power

Mercuric chloride has a concentration exponent of 1 thus, the activity will be reduced by the power of 1 on dilution, and a threefold dilution means the disinfectant activity will be reduced by the value 3 or 3, that is to a third. Put another way the disinfection time will be three times as long. In the case of phenol, however, with a concentration exponent of 6, a threefold dilution will mean a decrease in activity of 3 = 729, a figure 243 times the value for mercuric chloride. This explains why phenols may be rapidly inactivated by dilution and should sound a warning bell regarding claims for diluted phenol solutions based on data obtained at high concentrations. 

The preozonation of the water by means of excess ozone from the ozonation chamber has been introduced chiefly to utilize all the ozone injected into the ozonation chamber water. In eliminating ozone losses, the first concern was to reduce the operating and installation costs appreciably. But it was also desired to see if, by satisfying part of the ozone demand of the water before the actual disinfection operation by means of the recovered ozone, it would be possible to obtain a subsequently more powerful bactericidal action with smaller ozone dosages. The object has been attained. 

The principal adverse effect of hypochlorite is its corrosive action on metallic surfaces, because of its high oxidizing power. This limits its use for disinfection of stainless steel manufacturing equipment. However, when strong disinfection is needed on surfaces contaminated by biofilms, hypochlorite is recommended because of its high activity, together with the addition of metasilicate to help reduce the corrosive activity of the bleach. 

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