Cooling towers are a crucial component of industrial processes that provide efficient heat transfer and temperature regulation systems. However, their operation depends heavily on water quality. Untreated or poorly managed water can lead to scaling, corrosion, biofouling, and other issues. These problems compromise efficiency, equipment longevity, and even public health.
This comprehensive guide provides an in-depth investigation of water treatment principles, technologies, and best practices specifically designed for cooling towers. This manual will be helpful for facility managers, engineers, or any operator.
Table of Contents (Water Treatment for Cooling Towers)
Understand Water Treatment Cooling Systems
To talk about the latest methods and best practices of water treatment for cooling towers, let’s understand its basics and functionality. As water has high heat capacity and evaporative cooling properties, it is the primary source of heat transfer for cooling towers.
In the cooling tower system, water treatment is a series of methods or technologies that aare used to remove all types of impurities from the cooling tower’s feed water, blowdown, and circulation water. The water treatment process is critical for ensuring the quality of water and overall effective cooling tower management.
Before planning the water treatment system, focus on these essential points.
- The type of tour cooling tower.
- Feedwater quality
- Heat exchanger types
- What is the cycle of concentration?
- Required regulatory arrangements for discharge
- Chemistry of cooling tower water
- Cooling water impurities level
- Does your cooling tower components or equipment meet the manufacturer’s specifications?
Cooling tower treatments provide countless benefits to the overall cooling tower working efficiency, such as
Water Conservation: Effective and timely water treatment systems minimze water loss and ensure the better management of blowdown and recycling of water. They significantly reduce water consumption costs by effectively recycling them.
Improved Uptime: With time, the working ability of cooling towers is reduced due to build-ups of contaminants, corrosion, scaling, biological growth, or other factors. Keeping an eye on these issues and treating water before significant damage is a wise and proactive response that helps your cooling tower get maximum uptime and boost productivity.
Increased Components Lifespan: A planned water treatment decreases the risk of scaling and corrosion that can weaken the cooling tower parts. Repairing and replacing the cooling tower equipment costs highly. Proper water treatment minimizes these risks, enhances their lifespan, and increases their working abilities.
Safe Working: Dangerous chemical build-up and biological growth inside the cooling towers are dangerous for workers around them. So, water treatment helps to subside these health concerns.
Highly Recommended Cooling Tower Water Treatment Chemicals
Depending on the type of water contamination and impurities, several chemical treatments are used to treat water, and specific chemicals are used for each method. These chemicals effectively improve the cooling tower’s efficiency and reliability and solve many water-related concerns of the cooling towers.
- Anti-Foaming Agents
These anti-foaming agents eliminate foam production during treatment, as foam production can interfere with the cooling process. So, anti-foaming agents or chemicals inhibit foam production. For example, silicon-based deformers can be used in this regard.
- PH Adjusters
Quality water is required to run the essential cooling functions of cooling towers; a low or high water pH can only work sometimes. Different pH adjusters are available on the market to adjust the pH to reduce the chances of corrosion and other problems. Sulfonic acid and sodium hydroxide Can be used to balance the pH.
- Scale & Corrosion Inhibitors
Corrosion and scaling buildup can significantly affect the cooling tower components’ capability and cooling process. Corrosion and scale inhibitor chemicals can easily be removed, and the original shape of the equipment can be reformed. Zinc salt, silicate, phosphates, or phosphonates can be used in water treatment chemical processes.
- Biocides
Sometimes, bacteria, algae, fungi, or other microbes flourish in the cooling tower water due to their warm and moist environment. These microbiological factors impure the water and disturb its pH, and to inhibit its growth, some specific biocides are used. Some of the most used biocides include bromine, chlorine, and quats.
These are the typical chemicals used in cooling towers during water treatment processes; remember, the final chemical should be chosen after the complete water analysis.
Makeup Water Intake
The process of refilling or replenishing the lost water from cooling tower systems due to evaporation, blowdown, or drift is called makeup water intake. Water is essential to maintain the optimal operating level and ensure efficient heat transfer; therefore, its level and quality should be preferred.
Water might come from different sources such as rivers, lakes, municipal supplies, etc. Each head has its specific characteristics and requires tailored treatment approaches. The quality of water significantly impacts the overall performance and durability of the cooling tower. Hence, it should be free from contaminants, sediments, and minerals that otherwise can cause corrosion or scaling.
The quality and origin of water determine the treatment process, which may include filtration, softening, chemical treatment, etc. This proactive approach helps identify potential issues before they impact the system.
Clean makeup water also extends equipment life by reducing erosion and scaling.
This decreases maintenance and replacement costs over time. Furthermore, effective treatment minimizes biological growth, reducing maintenance needs and a more reliable system.
Upgrade the Filtration System of the Cooling Tower
Filtration is the first process of the cooling tower water treatment system, which removes suspended particles in the cooling tower water. It is considered one of the most important and challenging (time-consuming) tasks as it needs to filter all types of sediments, rust, and organic matter.
Water passes through the smaller spaces or holes, leaving behind the big suspended particles that easily trap in the mesh filter that is later removed. The advanced filtration process uses Multiple types of filters, such as charge filters, sand filters, and multimedia filters.
Sand Filters: The latest filters have several layers of graded sand that take off the dangled particles from the cooling tower water to purify it. As water moves on the sand filter bed, contaminants are trapped and clear the water of the cooling towers. However, systemic media replacement is also essential to retaining maximum filtration efficiency.
Multimedia Filters: It has the exact working mechanism as the sand filter but has different filter media like garnet, anthracite, or sand. Because of the supreme combination of the press, it is considered more effective than a sand filter.
Charged Filters: The latest filtration process is highly operative as it can remove smaller particles, even less than one micron in size, from the water stream. Charged filters attract the microscopic particles in the last filtration stage and provide clean and unpolluted water.
Ion-Exchange System
It is a process in which ions in the water are exchanged with desirable ions, most commonly on resins. In this strategy, harmful ions, such as scaling ions, induce corrosion, and heavy metals are removed, continuously hindering cooling towers’ performance and efficiency.
There are different type of polluted are various types of this exchange system;
Cation-exchange: It removes positively charged particles from the water, just like Ca2+ and Mg2+.
Anion exchange: As the name suggests, this system extracts negative charge carriers, such as SO4 2-and Cl-.
Mixed-bed: It is the type in which both categories are used to remove cations and anions to treat cooling tower water.
The components of the exchange system involve resins, exchange columns, valves, and a regeneration system. The waxes or resins serve as the medium for the exchange process, while exchange columns house the resin. Valves control flow and regeneration, which ultimately restore resin capacity.
This process operates in three steps: service, regeneration, and rinse. Water flows through the system during the first phase, and ions exchange during this glide. During the second stage, reins will be restored with salt (NaCl) or acid, while the rinse cycle removes excess regenerant.
This technique improves water quality, reduces scaling and corrosion, increases equipment life, enhances system efficiency, and provides cost savings.
Adjust the PH Level
Imbalancing the water pH is a clear sign of contamination or impurities. The standard and neutral pH of water is 7, and if it decreases, then 7, water ie acidic, and if it’s enhanced from 7, water is supposed to be essential.
Several factors are responsible for disturbing the cooling tower water pH, like mixing minerals, rust, sediments, or other impurities. Dissolving calcium carbonates, sodium hydroxide, or calcium hydroxide increases the pH from 7, making it more basic or alkaline.
Similarly, the addition of acids such as hydrochloric acid, ascorbic acid, or sulphuric acids reduces the pH, making ot more acidic, and this water is highly harmful to the primary cooling tower’s effectiveness.
Different cooling towers’ allowed pH levels vary depending on their types, materials used, and designs. Adjusting pH is mandatory to prevent corrosion and ensure the water quality of the cooling towers.
Anti-Corrosion and Anti-Scaling Treatments
The primary goal of the anti-corrosion treatment in the water treatment system is to protect the metal cooling tower components from being damaged and weakened. Some chemical methods extend the equipment’s lifespan and avoid future corrosion build-up.
Some corrosion inhibitors (silicates or zinc salt) and pH controller chemicals (Hcl, NaOH, or KOH) are used to avoid rusting and all types of corrosion. Additionally, oxidizing biocides or bio-killers are employed to prevent corrosion risk.
Anti-scaling chemical treatment is an alternative method of ion exchange treatment, offering an advanced level of protection from mineral build-up or scaling. Phosphoric acid is the main ingredient that is widely used in cooling towers’ water systems for calcium, magnesium, potassium, phosphorus, and all other mineral deposition. Advanced water softening techniques are available to soften the complex ions from the cooling tower water through the ion exchange action and improve the heat exchanger efficiency.
Blowdown Treatment
This process is not a technical treatment approach as it comes under regular maintenance of cooling towers. However, the blowdown method is essential in overall cleaning and maintaining procedures. In this method, water is removed from the system in which heavy metals and chemical contents are accumulated. Freshwater replaces spent water after treatment, with used water being disposed of. Some towers use reverse osmosis or recycling methods despite potential recontamination. Demineralization removes reentering impurities, and mineral levels are tested post-blowdown.
Bleeding from the tower is an essential stage that prevents scaling and corrosion. This procedure also reduces water consumption, lowers water generation, and protects equipment. These strategies are crucial in maintaining optimal water quality and controlling expensive repairs.
The cooling towers manage water circulation to ensure optimal capacity. To conserve water, especially in water-deficient areas, plants implement post-treatment technologies like reverse osmosis or ion exchange. These methods concentrate and remove liquid and solid waste, allowing treated water to be reused in the tower, minimizing waste, and reducing water consumption.
Microbiological Treatment
It is a crucial aspect to control microbial growth and prevent associated problems. Disease-causing bacteria in the water can cause biofouling and corrosion and pose health risks, including Legionella. You can use germicides, disinfectants, and helpful flora to avert these. Moreover, beneficial flora can also be employed to outcompete harmful ones.
Standard treatment chemicals include chlorine, bromine, ozone, aldehydes, and quaternary ammonium compounds. However, microbiological control remedies also present challenges and considerations. These include water quality variability, resistance development, chemical handling and storage, regulatory compliance, and environmental impact. Therefore, by understanding microbiological treatment principles and implementing effective strategies, cooling tower operators can ensure a safe, efficient, and reliable system.
Basic Terms of Water Treatment of Cooling Tower System
Here are the basic and most used terms for cooling towers you need to know. Understanding the cooling tower treatment process is complicated, so understanding these terms can help you with a detailed conception.
Biocides: They are microbes’ killer or their growth inhibitors. Cooling towers in moist and warm environments is ideal for microorganisms flourishing. Biocides are used in the water treatment process to stop their growth.
Alkalinity: Determining alkalinity is an essential step in water treatment; it shows the amount of calcium, magnesium, sodium, or carbonate in the water.
Cycle of Concentration: COC is the ratio of the concentration of the diffuse solids in the recirculating water(blow-down) relative to the make-up water. It is used to examine how much mineral content increased.
Make-up: Due to the evaporation process, drift, or blow down, some portion of water is lost. To replace it, fresh water is added to the cooling tower called make-up water.
Blowdown: The cooling tower system removes the impure from the cooling tower, known as a blowdown. Sometimes, leaks, windage, or drift are also included in the cooling tower blowdown.
Heat Load: The amount of heat energy required to remove from the cooling tower process. It is measured in the BTUs per hour.
Total Dissolved Salts: The exact amount of organic and inorganic matter dissolved in the cooling tower process water, represented as TDS.
Windage: Windage is the loss of water in the form of water droplets from the cooling tower when the wind blows.
Mass Balance: Water balance or mass balance is the equal amount of water make-up and blow-down plus evaporation.
Tons: The cooling tower system’s capacity size is referred to as tons. 1 Ton=12,000 BTU per hour.
Conclusion
Effective water treatment is the backbone of efficient and reliable cooling tower operation. Understanding the basic working principles, technologies, and best practices mentioned in this encyclopedic guide will help operators and engineers optimize cooling tower performance.
As you apply the knowledge from this guide, remember that water treatment is an ongoing process requiring continuous monitoring, maintenance, and improvement. Stay informed, adapt to changing regulations and technologies, and strive for excellence in cooling tower water management.
For expert water treatment solutions, trust our team of seasoned professionals. We offer tailored services to meet your unique needs. Contact us today for remarkable quality and reliability.