101 Guide to Cooling Tower Water Treatment

101 Guide to Cooling Tower Water Treatment

A combination of filtration technologies and chemical treatments help maintain the quality of water in the cooling tower and – if executed well – reduce the levels of bacteria, scale and mineral deposits, and corrosion. However, water treatment alone does not constitute an effective cooling tower maintenance program. Even the best-treated towers must be manually cleaned and disinfected as part of the cooling tower treatment program.

Filtration & Ultrafiltration

Most cooling towers use filtration systems as the first level of water treatment. In these filtration systems, the water passes through smaller and smaller spaces. Each filter has holes, with the first having the largest gaps. The mesh filter traps large particles like sediment, rust, and organic material as water passes through. A system of filters is necessary for your filtration when particles are smaller than gaps. Filters with an electrical charge can attract and hold minuscule particles in the final stages when the contaminants are microscopic. Clean,  polluted water is the result.

Make-up Water Intake

Cooling tower make-up water replaces evaporation, bleed, and leak losses. Sources include city water, well water, and even surface water. How clean your water is and the total volume of make-up water into the system will determine the level of water needed. You may need to adjust water hardness or soften it and balance the pH of the water here to prevent corrosion and regularly test for bacterial volume to mitigate any issues.

Ion Exchange & Water Softening

Mineral content in the cooling tower water, such as magnesium, calcium, or iron, can affect cooling tower lifespan and efficiency. Measuring and remediating “hard” or “soft” water is essential to overall system health and longevity. Lime or resin can be used to soften your water, but keep in mind that adding specific minerals – or removing them – will impact the overall quality of the water and may have undesired effects.

Blowdown Treatment

Blowdowns are part of the regular maintenance of cooling towers. The blowdown is a way to remove water from the system that has accumulated heavy mineral content or chemicals content. Water is then replaced with fresh water, and the spent water is disposed of. Some cooling towers may use reverse osmosis or other water recycling methods even when the water has already been cleaned, opening the tower to new contaminants. Demineral action is often used to remove contaminants that reenter water during treatment, and levels of minerals would be tested after blowdown.

Cooling Tower Cleaning

No matter how good your water treatment program is, your cooling towers will require manual cleaning as part of a maintenance program. Serious issues such as scale formations on the fill or Legionella bacterial growth within the system may become prevalent without proper cooling tower cleaning services. Ensure the cooling tower is appropriately cleaned and maintained to maintain optimum safety and operation.

Treating cooling tower water is akin to treating municipal drinking water. Without it, water quality suffers and can cause significant health and system damage. Treating cooling tower water with inhibitors, anti-bacterial agents, and other chemicals can help reduce health risks and reduce the time involved in cleaning. Dirty cooling tower water can be filled with slime, algae, sludge, and mud, all of which gather on the basin floor and can become a breeding ground for Legionella bacteria to thrive. Properly cleaning your cooling towers can help prevent this from happening and create the safety of your cooling tower. Dirty water can also negatively impact your chiller’s efficiency, which will, in turn, increase your energy costs. Cooling towers that perform at their optimum level achieve the best results. Minor defects or damage, however, can put a strain on an undertaking, leading to expensive repairs and high running costs if not addressed. We’ve broken down the steps to effectively treating your cooling tower water below. 

To disinfect, consider disinfecting the cooling tower surfaces after cleaning them with a product explicitly labeled for HVAC use, which is EPA registered. This can prevent microorganisms from flourishing between cleaning cycles. To prevent the development of Legionella bacteria, the BioSpray Tower works well on non-porous surfaces. The disinfectant kills 99.9% of the Legionella that develops in cooling towers. To descale, consider using a unique ultra cling formula that finds the mineral scale and dissolves it on contact. A descaler with low viscosity and an acidic base will adhere to and descale mineral deposits from cooling tower fill or other vertical surfaces.

  1. Turn off all water treatment chemicals, pH & conductivity meters. Once the ScaleBreak is added to the basin, it will give false readings to these devices, and in turn, they will try to make corrections to the system. You do not want a blowdown of the system initiated where the ScaleBreak will be needlessly purged out. It is equally important to shut off or disconnect any non-chemical systems, especially alternating high-frequency electric types, as leaving this technology can cause unintended damage to the unit during cleaning.
  2. Close the make-up water valve to the basin.
  3. If possible, lower the water volume of the basin, but be cautious that you avoid cavitation of the pump. This action will minimize the dilution level of your ScaleBreak once in the system and allow it to dissolve the scale deposits faster.
  4. If the basin contains loose scale or debris, it is good to remove it before a descaling. This can be accommodated by utilizing our Cooling Tower Vacuum (CTV), so the ScaleBreak is not needlessly wasted on these deposits.
  5. If possible, turn off the fan during the duration of your cleaning. It is possible that the foam generated as a result of the ScaleBreak dissolving the scale could be sucked up and blown out the top.
  6. Slowly start to add the prescribed amount of ScaleBreak to the water in the basin, preferably on the opposite side of the pump suction. This action will allow the ScaleBreak to dilute first with the water. Please note: do not pour ScaleBreak onto the hot deck. Only add it to the basin with the water.
  7. The foaming reaction is a natural occurrence when ScaleBreak dissolves the scale deposits in the system.
  8. If you have a heavily scaled unit, add 25% of the recommended amount, wait 20 minutes and add the next 25%. Follow this procedure until all the ScaleBreak is in the system. If you encounter a substantial foaming reaction, you can wait 30-45 minutes or until the foaming subsides to controllable amounts before adding more ScaleBreak. Defoamers are not recommended as the foaming can be controlled by minimizing the overall concentration of ScaleBreak within the system.
  9. During your ScaleBreak cleaning, you will want to ensure your solution remains active. Please follow our “Testing ScaleBreak’s Effectiveness” procedure for this step.
  10. Should all your ScaleBreak become neutralized during the cleaning process, this is an indication you had more scale in the system than anticipated. Additional ScaleBreak will be required to complete your cleaning. What happens is every descaling product has a saturation point. Once it dissolves its maximum ability, it becomes neutralized.
  11. Upon completing the cleaning, shut off the pump and check the pH of the cleaning solution in your basin. Though ScaleBreak is a biodegradable solution, most facilities need to conform to pH discharge limits. ScaleBreak Neutralizer can be utilized to safely elevate your pH to meet your discharge limit so it can be flushed to the drain. Please follow the instructions for this process in the ScaleBreak Neutralizer information sheet.
  12. If you need to neutralize your remaining solution, shut off the tower pump and add a neutralizer to the basin. Once the solution meets your release limit, the basin can be drained. Caution: do not run the neutralizer thru the entire system as the dissolved scale solids can fall out of suspension upon a quick elevation of the pH value.
  13. Once the system has been flushed, you can reestablish pH & conductivity meters turn on non-chemical treatment systems, or water treatment chemical feeds.
  14. After the cleaning, if some heavy debris were released and is now in the bottom of the basin, you can utilize our Cooling Tower Vacuum (CTV) to vacuum this debris out.
  1. Inspect monthly. Examine surfaces for sediment, scale, and biofilm – commonly known as slime. Overall system cleanliness minimizes the buildup that provides food and shelter for LDB – the slime and scale where they thrive and multiply.
  2. Clean tower basin regularly. Clean the basin when slime, scale, and sediment are visible. Remove these solids and microorganisms, and you eliminate the bacteria’s food and hiding places. Some of our customers clean monthly to keep them ahead of contaminants. Goodway’s powerful TowerVac® makes it easy to clean frequently. It effectively removes contaminants from your system while it’s online – there’s no need to drain the system or shut it down. Our compatible F2 filter system scrubs the wastewater and returns it to the cooling tower to minimize water and chemical loss.
  3. Implement a water treatment schedule. Work with a qualified water treatment contractor to develop a custom water treatment program for your cooling towers. This will include using a variety of treatments, including biocides, that will help manage Legionella outbreaks. Water treatment is an important part of managing cooling tower health; however, it cannot keep cooling towers clean and clear of biological and scale buildup alone.
  4. Clean the towers fill. Clean dirty, crusty, scale-filled cooling tower fill with Goodway’s TFC-200. Use this all-in-one system with our ScaleBreak®-Gel descaling solution to effectively remove scale, increase water flow and control the growth of mold, mildew, and dangerous biological buildup in your cooling system.
  5. Maintain low water temperature. OSHA recommends water temperatures be kept at or below 20°C (68°F) to minimize LDB colonization.
  6. Don’t forget side-arm and dead-let piping. These provide a haven for bacteria colonization. Eliminate stagnant water areas in your system, or be sure to clean them frequently.

Click here for the complete line of Cooling Tower Maintenance Solutions from Goodway

Watch our webinar on Cooling Tower Fill Descaling 

Read up on our 9 tips to controlling Legionella in your cooling towers

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