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Cooling Tower Water Testing

Cooling towers are designed to remove heat from water by latent heat of evaporation. As water cascades over the surfaces in the tower fill, the cooler air draft causes evaporation, which conducts heat away from the water. Cooling towers efficiencies are measured by Delta T, the difference in water temperature from the top of the tower to the bottom.

The single largest user of cooling tower 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 good way to conduct 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 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 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 Langlier 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 programs 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 greatly reduce corrosion potential. When using softeners, Chloride level, Alkalinity and pH need to monitored daily. The softener should be tested every shift and if the resin is exhausted and hard water is entering the system, scale will begin forming almost 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

Legionella pneumophila serogroup 1 poses a threat for everyone. This bacterium proliferates in the lungs and can cause death if not properly treated. NY city and state 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 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 to create an anaerobic environment under the slime and allowing the SRBs to proliferate. The SRBs waste frees Iron from steel surfaces that feeds the IRBs, a perfect ecology until the structure bursts!

Monitoring Cooling Tower Systems With Tracers

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, since the compound is inert the level translates to ppm of product.

PTSA fluorescent dye is widely used now to trace cooling water products. A sample of the tower water is added to the cell, push the button and read. The PTSA level directly corresponds to the treatment level. Pyxis and Turner Deign offer superb PTSA testing meters, the method is very fast and very accurate.

AquaPhoenix: Your Single Source for Cooling Tower Water Test Kits

If you need reliable kits for testing 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- or next-day shipping for all in-stock items.

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