Bacteriological plate counts. Notice the dramatic difference between the chemically treated tower (left side of photo) and the VEM treated tower (right side).

VEM technology is the basis for cold pasteurization -- a FDA approved technique used in the food industry to pasteurize fluids such as fruit juices. Microorganisms contained in the juices are eliminated through exposure to high levels of electromagnetic radiation. However, the energy flux levels used in this process are at least 100 times higher than the levels for cooling tower water treatment.

VEM systems used for cooling tower water treatment are not true bactericides. Instead, they control microbe populations by limiting their ability to reproduce. This is accomplished through two mechanisms:

Encapsulation: when calcium carbonate precipitates into a bulk solution, it encapsulates (surrounds) the bacteria. Although the bacteria constrained within the powder is still alive, it is unable to reproduce.
Electroporation: since cooling tower water is re-circulated within the system, the bacteria are repeatedly exposed to low levels of electromagnetic energy. This causes damage to the cell walls. Although the damage is not enough to kill the bacteria, it inhibits their ability to reproduce. The amount of bacteria in water is measured using standardized tests. The goal for most chemically treated towers is a Total Bacteria Count of between 20,000 and 50,000 CFU/ml.

When chemicals are used for biological control, bacteria population levels often vary considerably and may ‘spike’ (shown on the left). This is especially true if the biocides are manually applied in batches (instead of using automated feed pumps). Finally, bacteria can become resistant to the chemicals being used. For this reason, the type of biocide used must periodically be changed.