05/16/2022 | Conductivity | 8 MINUTE READ

The Effects of High Conductivity in Cooling Tower Water

cooling tower system

When you measure water, you’ll discover that there are many different measurements and readings you can obtain. These readings can tell you everything from the water’s pH to the amount of dissolved oxygen that’s currently in the water. Another measurement that can be used to asses water quality involves conductivity, which is designed to identify the water’s ability to conduct electricity.

If the conductivity of water is high, this indicates that the water is able to easily pass an electrical current. High concentrations of dissolved salts and minerals in the water usually result in high conductivity readings. A cooling tower is a large heat exchanger that is mainly designed to cool large buildings and make sure that excess heat is removed from industrial processes. Cooling towers work by using the basic water evaporation process to get rid of any waste heat.

Even though cooling towers are effective at removing heat from various industrial processes, these systems are prone to being damaged and becoming less efficient when not properly managed. While there are many methods that can be used to monitor cooling tower water, conductivity is considered to be the most affordable option for maintaining concentration cycles and water quality in a cooling tower.

Even though conductivity readings in cooling towers can be too high or too low, the readings being too high is a much more common scenario. This particular scenario can cause an array of issues. Cooling towers are typically designed with a maximum conductivity level in mind. When conductivity goes above the maximum value on a continual basis, the process and cooling systems can be significantly damaged. This damage can take thousands of dollars to fix, which is why it’s better to identify these issues before they cause ample amounts of damage. This article takes a more detailed look at how high conductivity affects cooling tower water.

How Cooling Towers Systems Work

Cooling towers use water to move waste heat into the atmosphere, which is necessary to ensure that industrial processes don’t cause overheating issues and that large buildings can be properly cooled. Industrial processes generate ample amounts of heat via the formation of hot water. This water must be cooled down to avoid any issues with damaged equipment and similar problems. When properly installed, industrial cooling towers are highly effective at cooling water down by removing excess heat.

When hot water flows directly through a cooling tower, it will be recirculated and exposed to dry and cool air. Heat is able to be separated from the cooling tower by being evaporated. Now that the water has cooled down, it will enter back into the industrial equipment and systems, which allows these systems to cool down to normal temperatures. This cycle is constantly repeated for industrial processes that are being performed on a continual basis.

Another aspect of cooling towers that aids the evaporation process is the use of a warm condenser. This condenser turns water into small droplets that are sprayed out of nozzles and onto a cooling tower fill material. This process results in the water’s surface area increasing, which facilitates enhanced water evaporation and heat loss.

Each cooling tower is also outfitted with a fan, which is positioned at the very top of the tower to bring air in from the lower portion of the tower. The air is pushed in the opposite direction when compared to the condenser water that’s situated along the highest area of the tower. This air carries the heat from evaporating water into the atmosphere.

cooling towers at water treatment plant

Cooling Tower Water Treatment

The water that’s used in a cooling tower must be treated on a regular basis to maintain system efficiency. Since each cooling tower has its own requirements, different treatments can be used to resolve issues and maintain the water quality. Two of the more popular treatments for cooling tower water include filtration and ultrafiltration. The right filters can capture any suspended particles that are present in the water. The types of particles that are removed via filtration and ultrafiltration include sediment, dirt, and sand.

Another option is to perform water softening, which is directly designed to lessen the hardness of water. This issue is brought about by an increased concentration of magnesium and calcium. Water softening and ion exchange processes use a softening resin to trap calcium, magnesium, and iron. Removing these contaminants on a regular basis ensures that scale and rust deposits don’t develop. When these problems occur, the cooling tower’s efficiency becomes worse.

After the water is softened, various chemicals can be added to further improve the quality of the water. For instance, bicarbonates and other corrosion inhibitors improve the water’s pH levels, which means that the water will become less acidic. By making the water less acidic, any metal parts and components should experience less corrosion.

Other chemicals that can be used during the treatment of cooling tower water include algaecides and scale inhibitors. The final aspect of treating cooling tower water involves blowdown treatment, which removes solid waste and similar contaminants from any blowdown. The treated water can then be reused in the cooling tower.

Common Cooling Tower Water Treatment Problems

Cooling tower water must be kept at a certain quality and conductivity level to ensure that the cooling tower processes can be performed efficiently. These units depend on water to transfer heat from industrial processes and equipment into the atmosphere, which is the only way to ensure that this equipment cools down to appropriate levels. In the event that the water isn’t properly transferring heat, the cooling tower is no longer able to function correctly, which can create serious problems depending on what the cooling tower is being used for.

Likely the most common issue affecting cooling tower water involves biological contamination. Fungi, bacteria, algae, and viruses all invariably enter the water supply because of the hot and humid environment within the cooling tower. Along with worsening cooling tower efficiency and damaging equipment, any evaporated water that carries bacteria can cause various illnesses and diseases if inhaled.

As mentioned previously, high conductivity is another common problem. If you obtain high conductivity readings when measuring the water with a conductivity sensor, these readings indicate that the water is contaminated and likely contains high levels of pollutants. Like any water system, corrosion is possible in cooling towers as well. Whenever water comes into direct contact with metal, corrosion may occur. Keep in mind that water corrosion can cause conductivity levels to increase. The many issues that are brought about by corrosion include damaged equipment, debris in the water supply, and leaks.

Some of the additional problems that are common in cooling tower water include:

  • High amounts of water blowdown – High concentrations of minerals and chemicals can accumulate when the water in the system evaporates. The blowdown process gets rid of these contaminants by replacing some of the cooling tower water with fresh makeup water. At the same time, treatment chemicals and circulation water are removed, which can waste water and increase costs.
  • Scaling – If the water in a cooling tower consists of high levels of calcium and magnesium, these minerals can create deposits, which form on many surfaces in the cooling tower environment. When too much scale develops, the cooling tower itself can become damaged and worsen in efficiency.
  • Water waste – Cooling towers invariably use a high amount of water, which is problematic since water is a scarce resource. Any inefficiencies in the system lead to water waste.
AC voltage source in conductivity applications

What Causes High Conductivity in Cooling Tower Water?

While there are several reasons why the conductivity in cooling tower water can increase, the main reason is that the water could contain high levels of contaminants. The contaminants that contribute to an increase in conductivity include iron, calcium, and magnesium. Iron may seep into the water when corrosion occurs.

Another common cause of high conductivity in cooling tower water is an issue with the blowdown valve. In the event that this valve is clogged or too small, not enough water is being bled, which leads to high conductivity. If contaminated water gets into the system in some manner, a well-functioning blowdown valve would still be unable to reduce the conductivity to optimal levels.

Cooling tower smoke

Best Practices for Cooling Tower Management

If you manage a cooling tower or are in charge of treating cooling tower water, there are some best practices that you should keep in mind. Since high conductivity is a serious problem with cooling tower water, it’s highly recommended that you install conductivity sensors in your industrial facility to maintain system efficiencies and prevent any further damage.

These sensors will provide continuous monitoring, which means that any instance of conductivity levels becoming too high or too low will be detected. Make sure that you select a conductivity sensor that’s designed to be used in industrial settings as opposed to laboratory settings. By knowing when conductivity levels expand past the normal range, you’ll be able to resolve these problems before they worsen. Preventing scale buildup, corrosion, and high conductivity makes it more likely that your cooling tower will continue to operate at high efficiency.

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Posted by Dominic O'Donnell on May 16, 2022

Sensorex is a global leader in the design and manufacture of quality sensors for water quality and process applications. The company offers more than 2000 sensor packages for pH, ORP, conductivity, dissolved oxygen, free chlorine, chlorine dioxide, UV transmittance and other specialty measurements, as well as a full line of sensor accessories and transmitters. Its expert technical support engineers solve analytical sensor challenges with custom designs and off the shelf products.

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