Non-chemical solutions for cooling towers address financial, environmental issues

Facilities around the world that use cooling towers and evaporative condensers are trying to reduce water consumption and sewer charges while maintaining effective cooling water treatment. Many areas of the U.S. are focusing on water conservation, and many others are turning their attention to the health and safety of employees and environmental concerns.
By Abby Harris, VRTX Technologies January 1, 2009

Facilities around the world that use cooling towers and evaporative condensers are trying to reduce water consumption and sewer charges while maintaining effective cooling water treatment. Many areas of the U.S. are focusing on water conservation, and many others are turning their attention to the health and safety of employees and environmental concerns.

About 99% of cooling towers and evaporative condensers are still using chemicals. While effective, these chemicals are designed to kill living organisms, and significant consequences can occur if these substances are mishandled.

In the past year, chemical prices have jumped 50% to 100% for phosphonates and phosphates, the base ingredients used in scale inhibitors. Many chemical manufacturers are doubling the price tag for the corrosion inhibitor sodium hexametaphosphate, and sulfuric acid has doubled in price in the last 12 months. By eliminating the need for chemicals to treat cooling water, facility managers and engineers can erase delivery surcharges and container fees from their monthly water treatment budget.

Non-chemical options

Several alternatives are available that not only save water but eliminate chemical use all together. These systems improve worker safety and eliminate environmental risks. Non-chemical technologies can be grouped into four categories: magnetic/electromagnetic, induced electric field devices, ultrasonic and mechanical.

Magnetic/electromagnetic devices have one or more permanent magnets mounted to the inside or outside of a pipe in which water passes. A strong magnetic field keeps minerals in solution instead of forming on equipment.

Induced electric field devices use pulsed low- and high-frequency electromagnetic fields generated by induction coils wrapped around a pipe. The water is exposed to electric and magnetic fields that keep scale particles in solution. The bacteria in cooling water are controlled by encapsulation and electroporation. Essentially, calcium carbonate powder traps bacteria.

Ultrasonic devices use ultrasonic waves from high-power, high-intensity ultrasonic transducers. As the sound waves pass through the water, it is alternatively compressed and decompressed with potential for cavitation to result.

Mechanical devices most often use pressure pumps to force water into plates, walls or other water streams with intent of producing cavitation. One of these methods is using controlled hydrodynamic cavitation (HDC). The process provides companies with an environmentally friendly alternative to chemicals, while also saving water and improving worker safety.

The technology draws cooling water from the cooling tower or evaporative condenser sump. Precision nozzles create opposing water streams that collide with tremendous kinetic energy and shear. At the point of collision, a near total vacuum is created that degasses the flow. The pressure change causes controlled hydrodynamic cavitation with localized high temperature. The cavitation process creates solid particles, and the rapid change in pressure to a vacuum causes the cell walls of microorganisms to burst, killing the cell. The particles are then filtered out of the system.

Using HCD can increase cycles of concentration to save the average customer approximately 2 million gallons of reusable water annually, while also eliminating the need for chemicals. It also has the potential to help the facility earn LEED credits.

Author Information
Abby Harris is a public relations coordinator for VRTX Technologies.