Cooling Tower Water Testing

Cooling towers are the most efficient way to remove heat from a system. Commercial buildings, industrial processes, refrigeration equipment and manufacturing tools use water cooled by the towers. Cooling towers make our indoor environments more comfortable, hospitals safer, facilitate manufacturing, and make food storage and processing possible. While these systems perform an essential function, they come with risks like corrosion, scale and microbiological activity. With so many operations relying on cooling towers, cooling tower water testing is essential.

What Does a Cooling Tower Do?

Cooling towers remove heat from water by latent heat of evaporation. As water cascades over the surfaces in the tower fill, the warmer air draft causes the water give up heat thru evaporation. Delta T, the difference in water temperature from the incoming water and the basin of the tower measured cooling tower efficiencies.

The single largest user of cooling towers is comfort cooling. Commercial buildings, schools, hospitals, factories and other large buildings use water-cooled equipment to create a more pleasant internal environment. After comfort cooling, tower water is widely used in a lot of manufacturing processes — some examples are metal extrusion, welding, plastic forming, drink bottling, refrigeration and food processing. Cooling water is a very efficient way to remove heat from a process and dissipate it into the atmosphere!

The Need for Cooling Tower Testing

When evaporation occurs, the impurities dissolved in the water remain and do not go off with the vapor. As a result, the ion concentration increases as water cycles through the cooling tower. If your total dissolved solids is 200 ppm when the tower is filled, the solids concentration can quickly reach 1000 ppm as the tower water cycles up!

The biggest problem with the solids concentrating is scale. The TDS (Total Dissolved Solids), Alkalinity, ph and Calcium all rise as the tower cycles go up. Corrosion can be caused by high levels of Chlorides, life sustaining microbiological nutrient levels rise too, providing optimum conditions for slime forming bacteria and Legionella. On top of performance and safety problems, water cooling tower standards require regular testing to protect the public.

A water treatment professional can develop a cooling water treatment program to control scaling, corrosion and microbiological activity. The water treater can provide equipment like metering pumps and chemical tanks to feed and monitor the chemical levels and tower conditions. A well-planned controller system will maintain your systems perfectly.

Cooling Tower Water Testing

With all the potential risks that come with cooling tower water, regular testing is paramount. Water treatment professionals often rely on ongoing water monitoring, a complete cooling water test kit and a defined treatment plan to manage risks. The very first things the water treatment professional needs to test in the tower water are:

• Conductivity/TDS
• Alkalinity
• Calcium
• System temperature (the hottest surface in the system)
• pH
• Chlorides

These parameters are used to calculate the Langelier and or Ryznar stability index. Interpretation of these indexes will help the water treater to create and monitor a treatment plan. The Langelier index formula is pH – pH sub s which Is calculated using TDS, Total Alkalinity, Calcium and temperature.

The Langelier index is used to calculate maximum cycles of concentration. Based on your program’s ability to control scale formation, you can multiply each test for Ca, TDS and Alkalinity by 2,3,4, 5 etc and increase the pH by increments of .5 pH units to calculate Langeliers at different cycles and find the optimal cycles of concentration.

Once the optimum cycles of concentration are reached, bleed-off is used to maintain the levels of contaminants.

Chlorides are the ideal test for cycling. The technician measures tower Chlorides and make-up Chlorides. Tower Cl Divided by Make-up Cl = Cycles of concentration. Chlorides need to be monitored because they are corrosive and the tower concentration needs to be kept under control.

Conductivity is important as automated control equipment uses conductivity to control bleed. The tester needs to be sure his meter reading and the controller reading are in sync.

pH is a factor in both scale and corrosion and should be tested daily. If your scale control program uses acid, pH monitoring is mandatory. Any glitch in the automated equipment can cause rapid scaling or heavy corrosion very quickly!

In some areas, softeners are used to eliminate scale potential and support corrosion inhibition. When using softeners, Total Hardness, Chlorides, Alkalinity and pH need to be monitored daily. The softened water should be tested every shift for hardness and if the resin is exhausted and hard water is entering the system, regenerate the softener at once.

If you select a Phosphonate program, daily testing is recommended. Polyphosphates may be used for threshold scale and corrosion inhibition. Daily testing will help ensure good results.

Microbiological Testing & Control in Cooling Towers

When monitoring your water cooling tower, noting microbiological activity is critical to human safety and system performance. With the possibility of Legionella and sludge formation, testing procedures include a range of methods.

Legionella pneumophila serogroup 1 poses a threat for everyone. This bacterium proliferates in the lungs and can cause death if not properly treated. New York City and the State of New York require a dipslide bacteria count weekly to monitor the microflora population. The incubation period is 48 hours.

ATP (Adenosine Triphosphate) can be measured using a luminometer and the living population can be enumerated by subtracting the Free ATP (Dead cells) from the Total ATP = the living biomass.

Other noxious organisms like SRBs, Slime formers, Nitrogen using bacteria and Iron related bacteria can be cultured using Biological Activity Reactions Tests (BART).
Sulfate Reducing bacteria can cause a lot of harm to metal systems. Their waste product is H2S which hydrolyzes to form sulfurous and sulfuric acids.

Slime formers and IRBs are all filamentous bacteria that form layers of slime. The slime matrix can plug water lines, corrode surfaces and breed Legionella. A secondary effect from IRBs is an anaerobic environment under the slime that allows the SRBs to proliferate. Waste from the SRBs frees Iron from steel surfaces that feeds the IRBs, a perfect ecology until the structure bursts!

Monitoring Cooling Tower Systems With Tracers

Typically, inhibitors are added to cooling water at a specific proportion to prevent corrosion, scale and other occurrences. If the conductivity of the water changes, the inhibitor levels may shift and fail to work as they should. Using standard bypass or glycol feeders alone to inject these chemicals may not be the most reliable method.

Tracers are compounds that can be accurately tested and help the water treater assess their level of treatment. Molybdates are used by a lot of manufacturers to trace their products. A known aliquot of Molybdate is added to the product formula, and since the compound is inert the level translates to ppm of product.

PTSA fluorescent dye is widely used in feeders now to trace cooling water products. A sample of the tower water is added to a meter cell, then the tester pushes the button and the meter provides a reading. The PTSA level directly corresponds to the treatment level. Pyxis and Turner Design offer superb PTSA testing meters, and the method is very fast and very accurate.

AquaPhoenix: Your Single Source for Cooling Tower Water Test Kits

If you need reliable test kits for cooling tower water at your facility, AquaPhoenix can help. We’ll work with you to create a custom kit containing all the supplies essential for completing the process. With AquaPhoenix, you won’t have to meet any minimum order requirements. We also provide same-day or next-day shipping for all in-stock items.

Please reach out to us to learn more about our cooling tower water test kits. We can provide hardness test kits, alkalinity test kits, chloride test kits and more.  If you’re ready to test and want to get started, place your order today.

Request a Quote