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NEWS
NCD's Showed No Effectiveness
April 16, 2010

New research supported by The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) indicates that non-chemical devices (NCD) marketed to control the growth of biological agents, such as Legionella in cooling towers, may not materially reduce biological growth.

Research project No. 1361, Biological Control in Cooling Towers Using Non-Chemical Water Treatment Devices, a two-year project recently completed by Dr. Radisav Vidic at the University of Pittsburgh, evaluated five non-chemical devices using different technologies to control biological activity in a model cooling-tower system. The devices studied included a hydrodynamic cavitation device, pulsed and static electric field devices, an ultra-sonic device and a magnetic device.

In Dr. Vidic’s research, none of the non-chemical devices measurably reduced planktonic or sessile microbial populations in comparison to no-treatment tests and to a conventional chemical microbial control treatment protocol. The findings appear to be inconsistent with previous research by non-chemical device manufacturers and some independent researchers on some of the same devices tested in the ASHRAE study. Those other studies reported measurable degrees of biological control within the parameters of testing conducted.

The study results are still subject to final approval by the sponsoring technical committee, TC 3.6 — Water Treatment. ASHRAE anticipates formal approval and the release of the final report for this project at its 2010 Annual Meeting Conference in June.


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