A report on the the advantages of using a dual stage method of sanitation
The University of Arizona and a certified independent lab, both recently demonstrated that even 0.10 ppm of chlorine is very effective in treating a pool when there are copper and silver ions present in the pool.1
It is not a question of whether using copper and silver or using chlorine is the better way to keep a swimming pool sanitized and algae free. A good case can be made for either methods. Studies have shown that an ideal method is to use a combination of all three elements.2
G.R. Taylor, at Surrey University, proposed a dual disinfection method after his tests showed that:
"Two different chemicals of metals added together may allow more efficient disinfection kinetics to be achieved. One substance targets the surface of a micro-organism killing and injuring the cells while a second substance targets the nucleic acid of the micro-organism destroying the remaining injured micro-organisms. By using this method of dual disinfection, reduced levels of both substances may be more effective than much higher levels of either individual substance."3
The major advantages of this dual, or two stage disinfection method, are as follows:
Superior sanitation to any single method alone
Reduced testing and maintenance
Conforms with all health department regulations for public pools
A demonstrated cost savings can be achieved
Following is a brief of some important facts and test data on each of the three swimming pool disinfection methods.
The Copper-Silver System
A common and very effective method of purifying swimming pools is to use electronically produced copper and silver ions. It was previously promoted that copper was a more effective algaecide and silver the more effective bactericide. More recent studies have shown each to be highly effective in the control and killing of both bacteria and algae. Together they give superior results. Copper has the ability to pierce the protective outer membrane of a cell and disrupt enzyme balance. Silver is effective because of its capabilities of interfering with DNA production and accelerating the death phase. This method has the advantage over chlorine of remaining very stable in swimming pools. The pool will stay sanitized for days or weeks with the system turned off and no additional copper or silver being added.
Copper and silver are not absorbed through the skin and, therefore, are not carried out of the pool by swimmers. They are also not affected by sunlight and actually become slightly more effective as the water is heated or the pH increases.
Copper and silver are safe. At the normal recommended levels of copper in a swimming pool, a person would have to drink over two gallons of pool water just to get the amount of copper in one vitamin pill. A glass of EPA approved tap water could have five times as much copper in it as a glass of swimming pool water. The tap water could also have five times as much silver as a glass of pool water.
The Environmental Protection Agency completely removed any limits on silver in drinking water in 1989 because they said it presented no hazard to human health.
A multitude of tests have shown the effectiveness of copper and silver in killing E. Coli bacteria. Many other tests have shown that silver also kills viruses and other types of bacteria. Coleman reported that herpes simplex virus (HSV) type I was quite sensitive to silver.4 Richards reported that only 3 ug/1 silver was necessary to prevent the growth of pseudomonas.5 Moroz reported that silver kills salmonella and E. Coli and can kill bacteria highly resistant to antibiotics.6
The Allegheny County Pennsylvania Health Department conducted a test on a 152,000 gallon public pool for an entire season. The average bather load was 200 people per day. The only disinfectant used was 20 ppb of silver. The health department found the water totally free of coliform, pseudomonas and staphylococcus bacteria throughout the season, whereas 65 water samples from 30 other chlorine treated swimming pools in Allegheny County, having a mean concentration of 0.70 ppm of chlorine, did routinely show the presence of bacteria.
The Silver Institute , Washington, D.C., issued a report showing that a 20,000 gallon pool in Lincoln, Nebraska, infused with 50 gallons of sewer effluent was purified to a zero level with only 3.2 ppb of silver in the water as the disinfectant.7
Dr. Charles Gerba at the University of Arizona in Tucson reported recently that legionella pneumophila (which causes the lethal legionnaire's disease and which can be present in swimming pools) was killed approximately 100 times faster when the system was used to add 0.20 ppm of copper and 20 ppb of silver to 0.20 ppm of chlorine as compared to the use of chlorine itself. Legionella is very resistant to even higher levels of chlorine.
Tests performed by Dr. Friede at Villanova University showed that in swimming pool water containing ammonia (a typical swimming pool condition) silver was a much faster and more effective sanitizer than chlorine.
Eighty minutes was required for a virtually complete kill of pseudomonas aeruginosa bacteria using chlorine versus only twenty minutes using silver. Likewise, silver took only one minute for a 70% kill compared to ten minutes for chlorine.
The Conventional Chlorine System
Chlorine is a good disinfectant under certain conditions, but when the pH becomes a little high, a common problem with most pools, chlorine becomes almost totally ineffective. For example, when the pH is 8.0 the chlorine is only 20% effective and at a pH of 8.5 the chlorine is only 8% effective.
Another problem with chlorine is the difficulty of maintaining a residual in the generally accepted range of 1.0 to 3.0 ppm. Chlorine is dissipated rapidly by sunlight. It is also absorbed through the skin. The effective chlorine in a pool can be almost totally depleted in a few hours. This can happen even when a automatic chlorinating system is used.
Dr. Peter Gaffney, Professor of Microbiology at Georgia State University, in a study "Microbiological Evaluation of Swimming Pools in Fulton County Georgia (Atlanta)" reported that out of 282 pools tested, 55% had a chlorine level of less than 0.5 ppm. He also reported that over 50% of the pools which had a chlorine level above 2.0 ppm still had both E. Coli and Pseudomonas bacteria present.
This indicates that a large percentage of pools do not always maintain a sufficient level of chlorine and even in those that do, a large percentage are still not safe for swimming.
The results of an independent test of commercial spas being treated with chlorine in Portland, Oregon, were reported in "Swimming Pool Age &Spa Magazine" in November 1985. The report showed that 28 out of 30 (93%) of the spas tested did not meet health department standards.
In 1985, USA Today reported " Swimmers had significantly more eye, ear and skin infections than non-swimmers, largely because of high bacteria and virus levels in pools, according to Illinois Public Health Researcher, Linda Berrafato." If the conventional chlorine method was working, swimmers would not have significantly more infections than non swimmers. What all of these tests are showing is that chlorine by itself is not doing a satisfactory job of protecting the health of swimmers.
Dual Disinfection Method
The new dual or two stage disinfection method is an answer to the deficiency associated with chlorine. The dual method provides excellent results without relying on the sometimes unattainable, near perfect water conditions required for satisfactory results.
By using the dual disinfection method of Taylor, at Surrey University, Thurman and Gerba at the University of Arizona have demonstrated that copper and chlorine do function as dual disinfectants as shown in the graph.
This graph shows that even in a minute, 0.10 ppm of chlorine plus copper was very effective whereas this amount of chlorine by itself as totally ineffective. In another test conducted by The George Washington University Medical School, the combination of silver and chlorine showed an even faster kill rate than copper and chlorine did. Their results on E. Coli bacteria showed that even 0.05 ppm of chlorine and 40 ppb of silver killed 100% of E. Coli bacteria in only 15 seconds. Chlorine by itself will not do this even at much higher levels.
The test data from several independent sources clearly demonstrates that using a combination of copper, silver, and chlorine as a disinfectant and algaecide in swimming pools will do a better job of insuring the health of swimmers with no increased risk because of the following:
A residual level of chlorine is still maintained in the pool and this in itself does provide some level of protection (good, but not always adequate).
The copper and silver is a disinfectant that would be very effective even without chlorine. They are not adversely affected by sunlight, high pH or high temperatures the way chlorine is.
The dual disinfectant benefits will be available as long as there is even a trace of chlorine left in the pool, as shown previously. This allows a considerable margin of error in maintaining a pool. Any system that does not allow for this margin of error is not going to produce satisfactory results.
Conclusions
Numerous tests conducted by many certified independent labs and universities demonstrate that a combination of copper, silver, and chlorine is much more effective than chlorine alone.
The scientific facts available conclude that a combination of chlorine plus the copper and silver system is a proven, safe and economical approach to purifying water in swimming pools and spas. The new dual disinfection method is also easy to implement in public and commercial pools because there are usually no laws or regulations that need to be changed
REFERENCES
1.Thurman, R. and Gerba, C., The Molecular Mechanisms of Copper and Silver Ion Disinfection of Bacteria and Viruses, University of Arizona, Tucson, 1988.
2.Gerba, C. and Kutz, S., Microbiological Evaluation of Free Chlorine and Copper: Silver Ions against Pseudomonas Aeruginosa and Legionella Pneumophila, Department of Microbiology and Immunology, University of Arizona, Tucson, 1988.
3.Taylor, G.R., The Effect of Disinfectants on Picornavirus Structure and Ineffectivity, in Viruses and Disinfection of Water and Wastewater,
4.University Surrey, Guilford, Surrey, 1982.
Coleman, V.R., Wilkie, J., Levinson, W.E. Stevens, T., and Jawetz, E., Inactivation of Herpes Virus hominis Types 1 and 2 by Silver Nitrate in vitro and vivo, Antimicrobial Agents and Chemother., 4, 259, 1973.
5.Richards, R.M.E., Antimicrobial Action of Silver Nitrate, Microbios, 31, 83, 1981.
6.Moroz, O.G., Kulskii, L.A., Prokuryakova, N.B., Rudenko, A.V., and Florensova, K.M., Susceptibility of Organisms which cause Intestinal Infections to Removal by Silver, Khimiya; Tecknologiya Vody., 2, 275, 1980.
7.The Silver Institute, Washington, D.C.
--------------------------------------------------------------------------------