In Cooling Tower systems, water is continuously circulated and exposed to air while undergoing evaporation to reject heat. This process enables the cooling system to operate effectively, but it also changes water quality: dissolved minerals become increasingly concentrated, suspended solids accumulate, microorganisms grow, and the risks of scaling, corrosion, and fouling increase over time.

The most common approach today is to use scale inhibitors, corrosion inhibitors, biocides, and pH adjustment chemicals. However, chemical treatment also requires chemical storage tanks, dosing pumps, concentration control, chemical safety measures, and blowdown water management.

Therefore, chemical-free Cooling Tower water treatment is receiving increasing attention as an approach to reducing or partially replacing conventional chemical treatment programs. Technologies such as electromagnetic treatment, electrochemical treatment/electrolysis, mechanical filtration, ozone, and ion exchange water softening can be applied depending on the characteristics of the makeup water and the requirements of the system.

The important point to understand is that “chemical-free” does not mean that all water quality control activities can be eliminated. Each method addresses only one or several specific problems. The selection should be based on makeup water quality, circulating flow rate, system volume, concentration level, equipment materials, and the required control of scaling, corrosion, and microbiological growth.

1. Why Does Cooling Tower Water Need to Be Treated?

1.1. How Does Water Circulate in a Cooling Tower?

In a Cooling Tower system, hot water from the equipment requiring cooling is supplied to the tower. Here, the water is distributed over the surface of the fill material and comes into contact with the airflow.

A portion of the water evaporates to remove heat, while the remaining water is collected in the tower basin and continuously recirculated.

The process can be simply illustrated as:

Equipment Requiring Cooling → Hot Water → Cooling Tower → Cooled Water → Equipment

Because only the water that evaporates leaves the system while most dissolved substances remain, the concentration of minerals in the circulating water gradually increases.

This is an important cause of:

• Scale formation on heat-transfer surfaces.
• Increased electrical conductivity/TDS.
• Increased corrosion risk.
• Solids and sludge accumulation.
• Growth of algae and microorganisms.
• Reduced heat-transfer efficiency.
• Increased cleaning and maintenance requirements.

1.2. Main Problems That Need to Be Controlled

Cooling Tower water problems can generally be divided into four main groups:

Scaling

Mainly associated with Ca²⁺, Mg²⁺, bicarbonate, carbonate, silica, and other minerals.

Corrosion

Associated with pH, chloride, sulfate, dissolved oxygen, electrical conductivity, piping materials, and equipment materials.

Microbiological Growth

Including bacteria, algae, biofilm, and organic matter.

Suspended Solids

Dust from the air, corrosion products, mineral precipitates, and solids from the makeup water can accumulate in the basin and piping.

A chemical-free treatment system must be capable of controlling these factors to a level appropriate for the system.

2. Is It Possible to Treat Cooling Tower Water Completely Without Chemicals?

The answer is yes, under certain conditions and with certain technologies, but it should not be understood that every Cooling Tower can completely eliminate chemicals simply by installing one treatment device.

Electrochemical systems are currently being developed and tested for recirculating-water treatment without external chemical addition. A 2026 pilot-scale study tested an integrated electrochemical system for simultaneously controlling alkalinity, corrosion, and microbiological growth, with 45 days of operation and a stable concentration ratio above 6 under the specific test conditions.

However, this is the result of a specific system configuration and operating conditions and should not be directly applied to every Cooling Tower.

Therefore, three concepts should be distinguished:

2.1. No Chemical Dosing

The system does not use dosing pumps to continuously introduce scale inhibitors, corrosion inhibitors, or biocides into the circulating water.

2.2. Reduced Chemical Consumption

Physical or electrochemical treatment equipment is combined with a reduced chemical treatment program.

This is often a practical approach for large systems or systems with unstable makeup water quality.

2.3. Completely Chemical-Free Operation

This is more difficult to achieve and requires an integrated system, typically including:

• Makeup water quality control.
• Scale control.
• Solids filtration.
• Microbiological control.
• Conductivity/TDS control.
• Automatic blowdown.
• Periodic cleaning.
• Continuous or periodic water-quality monitoring.

Therefore, chemical-free operation does not mean that water treatment is no longer required.

3. Problems That Need to Be Controlled in Cooling Tower Water

3.1. Hardness – Calcium and Magnesium

Ca²⁺ and Mg²⁺ are two important ions associated with scale formation.

As water evaporates, these ions become increasingly concentrated. Under suitable chemical conditions, they can combine with carbonate/bicarbonate and form precipitates.

One of the most common types of scale is calcium carbonate – CaCO₃.

Scale can accumulate on:

• Heat-transfer tubes.
• Condensers.
• Plate Heat Exchangers.
• Piping.
• Nozzles.
• Cooling Tower fill.

Scale deposits increase thermal resistance and can reduce the heat-transfer efficiency of the equipment.

A study conducted in Vietnam on electrochemical treatment of cooling water for the condenser of a central Water-Cooled Chiller system reported a maximum total-hardness removal efficiency of 95% at a current density of 80 A/m² under the experimental conditions of that study.

3.2. TDS and Conductivity

TDS and conductivity are commonly used parameters for monitoring the accumulation of dissolved substances in circulating water.

As water evaporates:

Water evaporates → minerals remain → dissolved-solids concentration increases

If conductivity becomes excessively high, the system normally needs to perform blowdown to discharge a portion of the circulating water and add fresh makeup water.

3.3. Chloride and Sulfate

Chloride and sulfate can increase the risk of corrosion, particularly at high concentrations and when the system materials are not suitable.

Therefore, a chemical-free system still needs to monitor these ions rather than focusing only on scale control.

3.4. Microorganisms and Algae

Cooling Towers are directly exposed to air, creating favorable conditions for dust, microorganisms, and organic matter to enter the system.

If not properly controlled, the following may develop:

• Algae.
• Biofilm.
• Sludge.
• Bacteria.
• Organic deposits.

This is an area where some physical treatment methods such as electromagnetic treatment should not be considered a standalone solution.

4. Electromagnetic Treatment for Scale Control

4.1. Basic Principle

Water treatment using Electromagnetic Field – EMF or Pulsed Electromagnetic Field uses an electromagnetic field to act on the flowing water.

The primary objective of this technology is to influence the crystal-formation process of dissolved minerals, thereby reducing the tendency of crystals to firmly deposit on heat-transfer surfaces.

Recent reviews indicate that EMF can influence nucleation and crystal-growth processes; however, its effectiveness depends significantly on water chemistry, system configuration, field intensity, frequency, and flow velocity.

4.2. How Does an Electromagnetic Field Affect Scale Formation?

According to the mechanism used by electromagnetic water-treatment systems, the objective is not necessarily to completely remove Ca²⁺ and Mg²⁺ from the water.

Instead, the crystal-formation process is influenced to reduce the tendency of mineral crystals to firmly adhere to surfaces.

Some systems aim to promote precipitation within the water stream rather than allowing minerals to precipitate directly on heat-transfer surfaces.

Therefore, the system still requires:

• Filtration.
• Blowdown.
• Scale collection.
• Periodic cleaning.

4.3. Are Electromagnetic and Pulsed Electromagnetic Treatment the Same?

Not exactly.

Different systems may use:

• Fixed magnetic fields.
• Electromagnetic fields.
• Pulsed electromagnetic fields.

Different systems may also use:

• Different frequencies.
• Different waveform types.
• Different field intensities.
• Different exposure times.

Therefore, it is not appropriate to simply conclude that one technology is always better than another.

Performance must be evaluated based on the water source + flow rate + equipment configuration + operating conditions.

4.4. Advantages

• No need for chemical dosing for scale control.
• No chemical residual generated by continuous chemical dosing.
• The equipment can be installed on the piping.
• Can be combined with filtration.
• Can be used as part of a chemical-free water-treatment system.

4.5. Limitations

Electromagnetic treatment should not be considered a standalone solution for all Cooling Tower water problems.

In particular:

• It does not directly remove all dissolved ions.
• It does not completely replace blowdown.
• It does not effectively control all forms of microbiological growth.
• Its performance depends on water quality.
• Silica can be a difficult parameter to control.
• Large systems may require an appropriately sized and configured treatment system.

Therefore, electromagnetic treatment is generally more suitable when combined with filtration, blowdown control, and water-quality monitoring.

5. Electrochemical Treatment – Electrolysis and Scale Collection

This is one of the most notable methods when discussing chemical-free Cooling Tower water treatment.

5.1. Electrolysis Principle

The system uses electrodes and electrical current to generate electrochemical reactions in the water.

Basically, it consists of:

• Cathode – negative electrode.
• Anode – positive electrode.
• DC power supply.
• Electrochemical reactor or treatment chamber.

At the cathode, the local conditions can promote the formation of precipitates involving Ca²⁺, Mg²⁺, and related ions.

These precipitates are collected on the electrodes or within the treatment zone instead of continuing to circulate and deposit on equipment surfaces.

5.2. Electrochemical Scale Collection

The process can be illustrated as:

Circulating Water → Electrochemical Reactor → Mineral Precipitation → Scale Collection → Treated Water → Cooling Tower

The collected scale must be:

• Cleaned manually.
• Or automatically removed.
• Or combined with a filtration system.

A study in Vietnam reported that electrolysis could significantly reduce water hardness under the experimental conditions; the highest reported efficiency was 95% at a current density of 80 A/m² for the pulse condition.

This indicates that electrochemical treatment has potential for controlling one of the major causes of scale formation in Cooling Tower systems.

5.3. Can Electrolysis Control Microorganisms?

Certain electrochemical configurations can generate oxidizing species during the treatment process and support microbiological control.

A 2026 pilot study using an integrated electrochemical system combined alkalinity treatment, corrosion control, and disinfection, achieving operation without chemical addition under the tested conditions.

However, it should be noted that microbiological-control performance depends on reactor design, electrical current, contact time, and water quality.

The results of one specific system should not be directly applied to all Cooling Towers.

6. Water Softening Using Ion Exchange Resin

6.1. Principle

A Water Softener uses Ion Exchange Resin to remove or reduce Ca²⁺ and Mg²⁺ from the water.

The basic process is:

Ca²⁺/Mg²⁺ in water → retained by the resin → Na⁺ exchanged into the water

By reducing hardness, the risk of CaCO₃ scale formation in the system can be significantly reduced.

A typical water softener consists of:

• Resin vessel.
• Control valve.
• Brine tank.
• Brine suction system.
• Water inlet and drain lines.

The U.S. Department of Energy also identifies makeup-water softening by ion exchange as an option when hardness limits the concentration cycles of a Cooling Tower.

6.2. Is This a “Chemical-Free” Method?

Not completely.

This is an important point.

During operation, the resin needs to be regenerated using a NaCl brine solution.

Therefore:

A Water Softener can reduce the need for direct chemical treatment of Cooling Tower water, but the resin regeneration process still uses salt.

Therefore, if the objective is “no chemical dosing into the Cooling Tower circulating water,” a softener can be an appropriate pretreatment solution.

However, if the objective is “zero chemicals throughout the entire water-treatment system,” a conventional softener should not be classified as a completely chemical-free solution.

7. Mechanical and Automatic Filtration

A chemical-free water-treatment system still needs to pay particular attention to Suspended Solids – TSS.

Sources of TSS may include:

• Airborne dust.
• Solids from makeup water.
• Corrosion products.
• Mineral precipitates.
• Biofilm.
• Sludge accumulated in the Cooling Tower basin.

If not removed, these substances can form sludge and reduce system performance.

7.1. Side-Stream Filtration

A common approach is to divert a portion of the circulating water through a filter:

Cooling Tower Basin → Side-stream Filter → Cleaner Water → Return

It is not always necessary to filter the entire circulating flow.

Side-stream filtration can reduce the amount of solids accumulated in the system and support other scale-control technologies.

7.2. Automatic Filtration

For industrial systems, the following may be used:

• Automatic self-cleaning filters.
• Automatic backwash filters.
• Screen filters.
• Disc filters.
• Sand/media filters, depending on water quality.

The advantage is reduced dependence on manual cleaning.

In particular, if electromagnetic or electrochemical treatment promotes mineral precipitation in the reactor or water stream, the downstream filtration system can play an important role in removing the generated particles.

8. Ozone in Cooling Tower Water Treatment

Ozone – O₃ is a strong oxidizing agent and can be generated on-site using an ozone generator.

Unlike chemicals such as chlorine or biocides supplied from a chemical storage tank, ozone is generated directly at the treatment equipment.

Its main objectives include:

• Oxidizing organic matter.
• Supporting microbiological control.
• Reducing biofilm.
• Supporting odor control.
• Reducing the demand for certain types of chemicals.

However, ozone is not a primary solution for removing Ca²⁺/Mg²⁺.

Therefore, if the main problem in a Cooling Tower is scale caused by high hardness, ozone cannot completely replace a hardness-control solution.

In addition, the ozone system must be properly designed and controlled because oxidizing agents can affect materials and corrosion behavior if the system is not properly operated.

9. Comparison of Chemical-Free Water-Treatment Methods

Method	Scale Control	Hardness	TSS	Microbiological Control	Requires Chemical Addition
Electromagnetic Treatment	Good under suitable conditions	Does not completely remove	No	Limited	No
Electrochemical/Electrolysis	Good	Can reduce	Requires filtration/scale collection	Can provide support	No direct dosing
Ion Exchange	Very good for Ca/Mg	Very good	No	No	Requires regeneration salt
Mechanical Filtration	Not directly	No	Very good	Partial	No
Ozone	Not the primary target	No	Limited	Good	No direct dosing
Blowdown	Reduces dissolved-solids accumulation	Reduces accumulation	Partial	Limited	No

No single method can solve all problems.

Therefore, in practical applications, effective solutions generally involve combining multiple technologies.

10. Combined Solutions for Chemical-Free Cooling Tower Systems

10.1. Electromagnetic Treatment + Filtration + Blowdown

Suitable for systems that prioritize scale control while having relatively stable water quality.

Process:

Makeup Water → Cooling Tower → Electromagnetic Treatment → Filtration → Blowdown Control

Electromagnetic treatment supports scale-control processes.

The filter removes suspended solids.

Blowdown controls the accumulation of dissolved substances.

10.2. Electrochemical Treatment + Scale Collection + Filtration

This is a notable configuration for systems with hardness-related problems.

Process:

Cooling Tower Basin → Electrochemical Reactor → Scale Collector → Filter → Cooling Tower

In this configuration:

• The reactor promotes precipitation.
• The collector captures scale.
• The filter retains remaining particles.
• Blowdown controls dissolved-solids accumulation.

Studies on electrochemical Cooling Tower treatment indicate that hardness control through electrolysis can achieve significant performance under suitable experimental conditions.

10.3. Electrochemical Treatment + Ozone + Filtration

If the system simultaneously has:

• Hardness.
• Biofilm.
• Algae.
• Organic matter.

a combined configuration can be considered:

Electrochemical Treatment + Ozone + Filtration

Electrochemical treatment focuses on minerals and scale formation.

Ozone supports microbiological and organic-matter control.

Filtration removes suspended solids.

10.4. Softener + Filtration + Cooling Tower Control

When the makeup water has very high hardness, another approach is to pretreat the makeup water before it enters the Cooling Tower:

Raw Water → Softener → Filter → Cooling Tower

This is not a “zero-chemical” solution in the absolute sense because the resin requires NaCl for regeneration.

However, it can significantly reduce the amount of Ca²⁺ and Mg²⁺ entering the system.

11. Parameters to Survey Before System Design

Water-treatment equipment should not be selected solely based on Cooling Tower capacity.

At least the following parameters should be surveyed:

Makeup Water Quality

• pH.
• Conductivity.
• TDS.
• Total Hardness.
• Calcium.
• Magnesium.
• Alkalinity.
• Silica.
• Chloride.
• Sulfate.
• TSS.
• Fe.
• Mn.
• TOC, if required.

Circulating Water Quality

• pH.
• Conductivity.
• TDS.
• Hardness.
• Alkalinity.
• Chloride.
• Sulfate.
• Silica.
• TSS.
• Microbiological parameters.
• Scale condition.
• Corrosion condition.

System Parameters

• Circulating flow rate.
• Makeup water flow rate.
• Blowdown flow rate.
• System water volume.
• Cooling Tower capacity.
• Water inlet/outlet temperatures.
• Piping materials.
• Heat exchanger/condenser materials.
• Operating hours.
• Current concentration cycles.

Technical Cooling Tower guidance also emphasizes that makeup water quality, system design, materials, flow rate, temperature, contaminants, and environmental conditions all influence the selection of an appropriate water-treatment program.

12. Operation and Control of a Chemical-Free System

A common mistake is to assume that once chemical-free treatment equipment has been installed, the system can operate without water-quality monitoring.

In reality, the opposite is true.

12.1. Monitor Conductivity

Increasing conductivity is an indication that dissolved substances are accumulating in the circulating water.

Appropriate operating limits should be established, and blowdown should be controlled accordingly.

12.2. Monitor Hardness

When electrochemical or electromagnetic treatment is used, hardness should be measured before and after treatment to evaluate actual performance.

The system should not be evaluated solely through visual inspection.

12.3. Monitor pH

pH directly affects:

• Scale formation.
• Corrosion.
• Electrochemical treatment performance.
• Microbiological activity.

Therefore, suitable control limits should be established for each system.

In the electrolysis study of a Water-Cooled Chiller system in Vietnam, the water pH under the tested current-density conditions ranged from approximately 7.4 to 7.9. However, this was a result obtained from a specific experimental system and should not be considered a universal operating limit for all Cooling Towers.

12.4. Clean the Scale Collector

If an electrolysis/scale-collector system is used, the amount of collected scale will increase over time.

The following should be checked:

• Scale accumulation.
• Electrode cleanliness.
• Electrode condition.
• Electrical current.
• Flow rate through the reactor.

12.5. Clean the Cooling Tower

Even when a chemical-free treatment system is used, the tower basin, fill, strainers, and piping still need to be inspected and cleaned periodically.

Scale and biofilm should not be allowed to accumulate for extended periods before corrective action is taken.

13. When Should Chemical-Free Treatment Be Considered?

Chemical-free treatment can be particularly worth considering when:

• The plant wants to reduce chemical consumption.
• Chemical costs and wastewater-treatment costs are high.
• Chemical storage in the operating area is undesirable.
• The system needs to reduce blowdown volume.
• There are environmental requirements.
• Makeup water quality is relatively stable.
• Adequate water-quality monitoring is available.
• Filtration and automatic blowdown can be integrated.

Evaluation programs in the United States have also reported the potential of chemical-free Cooling Tower treatment technologies to reduce water consumption and blowdown volumes, although performance depends on the specific system and application conditions.

14. When Should Chemicals Not Be Completely Eliminated?

Not every system is suitable for a “Zero Chemical” objective.

Particular caution is required when:

• Makeup water has very high hardness.
• Silica concentration is high.
• Chloride/sulfate concentrations are high.
• TSS is high.
• Water quality fluctuates significantly.
• The Cooling Tower has a large capacity.
• The surrounding environment contains significant amounts of dust.
• Operating temperature is high.
• Strict microbiological control is required.
• The system already has severe corrosion.
• Piping or heat exchangers already have thick scale deposits.
• No water-quality monitoring system is available.

In these cases, a hybrid solution – combining chemical-free technologies with a controlled amount of chemical treatment – may be more practical.

15. Common Mistakes When Applying Chemical-Free Water Treatment

15.1. Assuming Electromagnetic Treatment Can Solve Every Problem

Electromagnetic treatment is primarily used to influence scale-formation processes.

It does not mean that the system completely removes:

• Chloride.
• Sulfate.
• TDS.
• TSS.
• Microorganisms.
• Dissolved oxygen.

15.2. Ignoring Blowdown

Regardless of the treatment technology used, water continues to evaporate and dissolved substances continue to accumulate.

Therefore, blowdown remains an important part of Cooling Tower water management.

15.3. Failing to Analyze Water Quality Before Installation

This is one of the main causes of inappropriate technology selection.

Two plants with the same Cooling Tower capacity may have completely different makeup water quality.

15.4. Considering a Softener as Completely “Chemical-Free”

A softener uses ion exchange resin but requires NaCl for regeneration.

Therefore, it is necessary to clearly distinguish:

No chemical dosing into the circulating water ≠ No chemicals used anywhere in the entire water-treatment system.

15.5. Failing to Control Microbiological Growth

If the system focuses only on scale control while ignoring microbiological control, it may still experience:

• Algae.
• Biofilm.
• Sludge.
• Bacteria.

Therefore, a chemical-free solution must include an appropriate microbiological-control strategy.

16. Conclusion

Chemical-free Cooling Tower water treatment is a promising approach to reducing dependence on chemicals, reducing blowdown volume, and improving Cooling Tower water management. However, this is not a problem that can be solved simply by installing one treatment device.

The technologies that can be considered include:

• Electromagnetic Field: supports control of scale-formation processes.
• Electrochemical/Electrolysis Treatment: promotes precipitation and collection of scale-forming ions, while certain configurations may also support microbiological control.
• Ion Exchange: effectively reduces hardness but requires salt for regeneration.
• Mechanical Filtration: removes TSS, mineral particles, and sludge.
• Ozone: supports microbiological and organic-matter control.
• Blowdown: controls the accumulation of dissolved substances in circulating water.

For a practical system, the optimal solution is generally not to select a single technology but to combine different treatment methods according to water quality and operating objectives.

For example:

Electromagnetic Treatment + Filtration + Blowdown Control

or:

Electrochemical Treatment + Scale Collection + Filtration + Blowdown

or, for high-hardness makeup water:

Softener + Filtration + Circulating Water Treatment Technology

The most important point is to survey makeup water quality, circulating water quality, flow rate, system volume, equipment materials, temperature, conductivity/TDS, hardness, silica, chloride, sulfate, TSS, and microbiological conditions before selecting the treatment technology.

In other words, the objective of Cooling Tower water treatment is not simply “to eliminate chemicals,” but to build a system capable of controlling scale, corrosion, microbiological growth, suspended solids, and circulating-water quality in a stable, safe, and application-specific manner.

Recent studies indicate that electrochemical treatment has significant potential for Cooling Tower applications, including chemical-free pilot operation; however, these results still need to be evaluated according to each water source, system scale, and system configuration before practical implementation.

ANCES can use actual water-analysis results and operating conditions to develop a suitable treatment solution, from water filtration, softening, electrochemical/electrolysis treatment, scale control to Cooling Tower circulating-water management, rather than applying one fixed technology to every system.