The operating principles of the Dolphin Series are based on four essential methods of action: electromagnetic signal; interaction of the induced electric field with colloidal particles; control of microbial populations; and corrosion control. These methods of action as discussed as follows.

A. Electromagnetic Signal

The Dolphin's pulsed-power system (PPS) works by changing how calcium carbonate and other dissolved minerals precipitate from solution. Pulsed-power fields activate colloidal nucleation sites in the bulk solution. These activated sites become the preferential nucleation sites for precipitation.

Calcium carbonate is the mineral commonly present in water with the lowest solubility, i.e., it is the first precipitate to form in a cooling tower. Precipitation of calcium carbonate and other dissolved minerals occurs when the minerals in solution reach supersaturation levels. Supersaturation is primarily reached by the evaporation of water. The evaporated water contains no minerals, and the decreased volume of fluid increases the concentration of minerals.

The precipitation of calcium carbonate can occur as either a surface-nucleating scale or a colloidal-nucleating powder in the bulk solution. Growth on existing solids is thermodynamically favored. The unique spectrum of electromagnetic fields produced by pulsed power shifts the CaCO3 equilibrium chemistry to favor formation of stable crystal nuclei in the bulk solution. Thus crystal growth and precipitation will occur in solution and accumulate as a loose powder instead of on a surface as a scale.

Photomicrographs of the two minerals are shown on the following magnifications:

The morphology of these two photos displays the typical layered structure of adherent, surface-nucleating scale, and the amorphous, almost spherical, appearance of the pulsed-power induced, bulk-solution precipitate. These samples were collected from cooling towers receiving chemical or pulsed-power treatment, respectively.

The amorphous precipitate does not adhere to the pipe wall but remains with the bulk solution and is removed via blowdown and/or side-stream filtration. The Dolphin uses colloidal science instead of inorganic chemistry to control scaling.

C. Control of Microbial Populations

The Dolphin System™ is a bacteriostatic product rather than a true bactericide. Although the bacteria are not killed, they are controlled. A chemically controlled tower trying to balance the cost of biocide chemicals and the cost of corrosion inhibitors that are needed to protect the tower from the biocides will usually aim for a Total Bacteria Count as measured in a standard 48-hour, 35º C heterotrophic plate count (method SMEWW 9215) of about 20,000 to 50,000 CFU/ml. In addition, many of the bactericides are species-specific, and they must be periodically changed to prevent a different species from flourishing. Mutation of species such that previously effective biocides become ineffective on the mutated species is a problem for chemically controlled towers.

With a Dolphin , although the bacteria are not immediately killed, they are controlled. Total Bacteria Count using the standard 48-hour test will typically show 1,000 to 2,000 CFU/ml in a cooling tower being operated under a normal blowdown regime. The following figure shows typical results achieved with pulsed-power. Tower #1 and Tower #2 are located at a manufacturing facility in Connecticut. They are 175-ton towers being run at 8 cycles of concentration. As shown below, each tower is plotted as a separate line. Tower #1 had been under PPS control for nearly one year before the data were taken. The results show levels ranging between 102 and 104 counts, with 103 being a typical value. There is no discernible pattern in the values.

Tower #2 presents the bacterial counts while under chemical treatment (until 3/22/00) and then during PPS treatment. The bacterial concentrations under chemical control are high and erratic, ranging from 103 to 106 CFU/ml, with 105 being a typical value. The large drops in counts correspond to high levels of free chlorine in the system. The quick recovery of the biological counts is indicative of a viable biofilm in the system and a variable odor was present.

PPS installed on Tower #2 on 3/22/00

There are two separate mechanisms that cause these low levels of biological activity. The first relates to the well-established effect in water treatment that coagulation and calcium carbonate precipitation will result in a microbial reduction. Operating a tower with coagulation and precipitation occurring in the bulk solution, as it happens in water treatment plants, will incorporate microbes in the water into the growing crystal precipitates. This effect is not as pronounced in scale formation, since only the bacteria close to surfaces can be incorporated into the precipitate. The encased bacteria can be revived, but they are physically constrained in the precipitate and unable to reproduce. With microorganisms controlled by physical incorporation, changes in the make-up of the microbe population over time will have no effect on the efficacy of the system. Mutation or resistant strains of bacteria do not flourish in a pulsed-power controlled tower.

The second mechanism involves sub-lethal injury that controls bacteria even when there is no precipitation occurring. This mechanism is based on the interaction of the low frequency radiation generated by the pulsing with the bacteria.

Since the frequency of the Dolphin cooling-tower products are the same as the Maxwell products, the energy of each individual photon is the same with both devices. The flux with the Maxwell device is 100 times higher than the flux with Dolphin devices; therefore, the number of photons per pulse is 10,000 times higher. A cooling-tower Dolphin device thus uses a fraction of the energy that the Maxwell devices use on a per pulse basis. However, because cooling towers involve recirculating water, a Dolphin device on a cooling tower will "see" each bacterium many times before the bacterium exits the system. In a typical cooling tower setup, each bacterium will see over 5000 pulses, exposing the bacteria to over 50% of the total amount of radiation as with the Maxwell device.

Spreading this exposure over a few hours does not have the same biological effect as a single dose; however, there is damage to the microorganisms. This damage is sufficient to inhibit reproduction but not sterilize the system. The bacteria can recover in a few days, but while they are recirculating through the Dolphins they are inactive.

D. Corrosion Control

Corrosion inhibition with the Dolphin System ™ is accomplished indirectly by maintaining sufficient cycles of concentration to force the system into the alkaline mode at the saturation point of calcium carbonate, which is a cathodic corrosion inhibitor. In this type of water system, the expected corrosion rate on mild steel is 2 to 5 mils per year. The Cooling Technology Institute Guideline WTP-130 lists corrosion rates in cooling towers on mild steel of 2 to 5 mpy as "good" and 0 to 2 mpy as "excellent". In many municipal water systems phosphates or silicates are as corrosion inhibitors to meet EPA's copper/lead requirements. In these systems when cycled up, the corrosion rate on mild steel is typically less than 2.0 mpy.

Pulsed power technology offers significant advantage in corrosion control over chemical treatment with respect to copper. While copper is very resistant to most domestic waters, it is subject to pitting attack by either microbial growth or high levels of oxidizing biocides (chlorine, bromine). Typical chemical regimes use a triazole as a copper corrosion inhibitor to protect the copper from the oxidizing biocide. Triazoles form a protective film on the copper surface and protect the underlying metal. However, triazoles are attacked by oxidizing biocides and, if they are at too low a level, can actually acerbate localized galvanic attack by only partially covering the metal. A pulsed-power system eliminates these sources of corrosion, while maintaining its excellent biological control without oxidizing biocides.

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