Better Options I noted your Specifier's Notebook in the July CSE ("There's Something in the Water," p. 66), and feel compelled to address some issues. Back in 1983, after an "incident," I designed and installed a dual filtration wrap-around rechlorination loop for SUNY-HSC in Syracuse, N.Y., which has since been copied in many institutions with a measure of success, to address the focused is...
I noted your Specifier's Notebook in the July CSE ("There's Something in the Water," p. 66), and feel compelled to address some issues. Back in 1983, after an "incident," I designed and installed a dual filtration wrap-around rechlorination loop for SUNY-HSC in Syracuse, N.Y., which has since been copied in many institutions with a measure of success, to address the focused issue of Legionella infiltration, outlined in Legionnaires Disease, Prevention and Control (ISBN 0-912524-79-0, 1993).
Since LD is still with us, one has to wonder why. Australia and the U.K. have excellent codes to cover this illness but still have serious outbreaks with deaths. I suspect that we are not paying close attention to potable water systems and as such, are paying the price for inaction. Let's look at some options you list:
CHLORINE DIOXIDE—Not a serious consideration as the technology is "iffy" at best.
COPPER/SILVER—Ever since inception this has been looked upon with a "jaundiced eye." Consider that potable H/W loops are copper (who designs with galv pipe anymore?), and yet, Legionella bacteria amplify therein. Does one believe that silver is a "sterile medium?" If that were true then all surgical instruments would be silver plated or pure silver. One is told that it is a combination of both, and the ions must be within certain parameters (400/40 ppb), and that to achieve it one needs a contraption that defies logic in its operation. The fact is that there are "newer" models; first it was a 90/10 alloy, then 80/20, and now I believe it is 70/30, with one firm using pure copper and pure silver electrodes. If the objective is to impart a ratio of 400/40 ppb copper/silver ions to the water, one can do a better job with chemical feed pumps, properly designed. Also, lest we be negligent, let us not overlook the metallothionein (MT) issue. Continuous use of heavy metals will result in a population with resistance to both ions. As we bathe in the paradise of a false sense of security, Legionella will awaken us from our sleep with a vengeance!
HEAT TREATMENT—This is effective, but how often does one do it? If you are saying, "down with codes, life is first," then I will carry your banner. It is far less expensive to install thermostatically controlled valves on faucets (to prevent burns) than to defend in a court of law.
SUPER CHLORINATION—Too messy and time consuming, and odds are that it will be done improperly.
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Frank Rosa, Aqua Technical Services, Inc., Liverpool, N.Y.