STUDIES IN IONIZATION DISINFECTION

Abstract

PURPOSE OF STUDY:
Viruses tend to be more resistant than bacteria to disinfection regimes. Although chlorination is widely used to control viral contamination, high levels of chlorine promote the formation of organic compounds in water that may be hazardous to human health. An alternative method, copper and silver ion treatment, is known to be effective against bacteria and algae. The authors tested electrolytically generated copper and silver ions, alone and in the presence of reduced levels of free chlorine, in treating water sample to which either bacteriophage MS-2 or poliovirus had been added to test effectiveness against viral contamination.

MATERIALS AND METHODS:
Purified bacteriophage MS-2 and poliovirus type I were prepared by standard methods in pellet form. The viral pellets were placed in samples of filtered well water. The virus-containing samples were then exposed to one of the following treatment regimens: (1) no added disinfectant, i.e. untreated control; (2) low levels of free chlorine; (3) a combination of copper: silver with free chlorine; (4) copper: silver ions without chlorine; or (5) either copper or silver without chlorine. Experiments were performed in duplicate at room temperature. Linear regression analysis was performed to calculate the viral inactivation rates for each treatment regimen.

RESULTS:
The bacteriophage MS-2 inactivation rate for copper alone was significantly higher when the concentration reached 400 ug/liter. The MS-2 inactivation rate for electrolytically generated copper and silver ions together was greater than for either metal alone, suggesting an additive effect. Although not significant for very low levels of chlorine, the addition of 0.3 mg/liter of free chlorine to a 400/40 ug/liter copper/silver regimen significantly enhanced MS-2 inactivation rates.

Similarly for poliovirus, the activation rates achieved with the 400/40 copper/silver regimen were significantly greater as compared with untreated controls. The number of poliovirus were reduced approximately 2.5 log 10 within 72 hours. The addition of 0.3 mg/liter of free chlorine again improved the inactivation rates achieved, although in this case the improvement did not reach statistical significance. Poliovirus showed greater resistance to inactivation by any means tested than did bacteriophage MS-2.

CONCLUSIONS:
Electrolytically generated copper and silver ions demonstrate efficacy against bacteriophage MS-2; further improvement occurs with the addition of reduced levels of free chlorine. The same regimen is capable of inactivating an enteric virus such as poliovirus in the presence or absence of free chlorine. The same regimen is capable of inactivating an enteric virus such as poliovirus in the presence or absence of free chlorine. Therefore, a regimen in which copper: silver ion treatment is combined with low levels of chlorine should prove useful as a method of disinfecting water against viral contamination.

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