New water treatment technologies are giving industrial facilities additional options for preventing Legionella and biofilm formation in cooling tower systems while reducing reliance on traditional chemical treatment.
Cooling towers are essential to industrial operations across sectors including chemical and pharmaceutical manufacturing, power generation, food and beverage processing and refining. However, the warm and recirculating water conditions within these systems can create an environment where Legionella bacteria and biofilm can develop.
For facility operators, effective water management is therefore critical to maintaining equipment performance while protecting workers, visitors and surrounding communities.
Why Cooling Towers Can Support Legionella Growth
Cooling towers operate by exposing warm water to moving air, allowing a portion of the water to evaporate and remove heat before the remaining water is recirculated.
This process can increase the concentration of minerals in the water while maintaining temperatures that can support bacterial growth.
Biofilm formation can further complicate treatment. Scale, organic material and microorganisms can accumulate on wetted surfaces, providing protection and nutrients for bacteria.
Poor circulation or taking a cooling tower offline for maintenance can also increase the risk of bacterial growth.
Limitations of Traditional Biocide Treatment
Biocides have traditionally been used to control bacterial growth in cooling tower systems. While chemical treatment can be effective, it can also introduce additional operational and maintenance requirements.
Facilities may need regular treatment cycles and cleaning programmes to control biofilm. Certain chemicals can also affect downstream processes, equipment and water-discharge requirements.
Biofilm presents another challenge because it can shield bacteria from treatment, potentially reducing the effectiveness of chemical disinfection.
The cost and availability of treatment chemicals can also create additional operational pressures for facilities managing large cooling-water systems.
New Approaches to Legionella Control
Advances in water treatment technology are providing facilities with additional options for controlling Legionella and reducing the conditions that allow bacteria to establish themselves.
Three technologies highlighted for cooling tower applications include ultraviolet (UV) treatment, ozone generation and catalytic water treatment (CWT).
Each technology operates differently and can provide advantages depending on a facility’s water chemistry, operating conditions and treatment objectives.
UV Treatment Targets Bacteria
UV treatment can be applied through a sidestream loop, using ultraviolet light to target microorganisms in the process water.
The technology is well established and can provide direct disinfection. However, UV treatment does not necessarily eliminate the scaling and biofilm that can provide protection for bacteria.
This means UV may form part of a wider water-treatment strategy rather than addressing every factor contributing to Legionella growth.
Ozone Treatment Controls Bacteria and Biofilm
Ozone generation provides another approach to controlling Legionella and biofilm.
As an oxidising agent, ozone can attack microorganisms while also helping break down biofilm when appropriately applied.
The technology can be generated on site using oxygen and can leave relatively little residual material in the treatment process.
However, facility operators need to consider factors such as oxygen availability, system requirements and the operating conditions of the cooling-water circuit when evaluating ozone treatment.
Catalytic Water Treatment Supports Proactive Prevention
Catalytic water treatment (CWT) takes a different approach by focusing on the water chemistry and conditions that contribute to biofilm formation rather than directly killing Legionella.
CWT can be installed upstream of the cooling tower, within the cooling circuit or in a sidestream configuration, potentially allowing facilities to integrate the technology without major modifications to existing cooling-tower infrastructure.
By targeting the conditions that support biofilm development, CWT can help make the cooling-water environment less favourable for Legionella to establish and grow.
However, CWT does not directly eliminate Legionella and should not be considered a standalone response to an active outbreak. Facilities may need to combine preventative technologies with appropriate disinfection and monitoring programmes.
Moving Towards Proactive Water Management
The development of reduced-chemical water treatment technologies is changing how industrial facilities approach Legionella management.
Rather than relying exclusively on reactive chemical treatment, operators can combine water-quality monitoring, proactive biofilm control and targeted disinfection to build more resilient cooling-water management programmes.
The appropriate strategy will depend on factors such as water chemistry, cooling-tower design, operating conditions, regulatory requirements and the specific risks facing each facility.
For industrial operators, the combination of improved water treatment technology and effective maintenance can help support equipment reliability, water efficiency and safer cooling-tower operations.
