Passing the test with DMA

Without effective monitoring and control, cooling-tower water systems can suffer from microbiological contamination, which poses health and performance risks. Fortunately, testing techniques, such as differential microbial analysis (DMA) offer site managers greater insight into microorganism growth, enabling more informed decision-making.

Although packaged in many different shapes and sizes, cooling-tower water systems remain
fundamental to a number of important industrial processes.However, to function as efficiently as possible, cooling-towers must be kept free from the growth of microorganisms, such as bacteria and algae. If not, pathogens, such as Legionella, which spread Legionnaire’s Disease can develop.There also is the role microbes play in corrosion, structural damage, and performance to cooling systems.

The presence of the biological deposit prevents corrosion inhibitors from reaching the fouled surface, and the side effects of microbial growth include generation of corrosive acids with the ability to attack system surfaces, and reducing asset integrity.

Biofilms impact heat exchanger efficiency by acting as insulating barriers. Heat exchanger performance begins to deteriorate as soon as biofilm thickness exceeds that of flow rate. A thin layer of biofilm has a significant impact on heat exchanger efficiency, and therefore excessive utility costs.

Unfortunately, by virtue of their design, cooling-tower water systems provide a rich breeding ground for such microorganisms to thrive. Therefore, to prevent microbiological contamination, site managers must adhere to a strong commitment to maintenance.

Although routine microbial testing provide site managers with a snapshot of their system’s ‘general health’, there are techniques that offer far more detailed analysis. Arguably the most effective of these techniques is DMA. The test is able to identify separate species of microorganisms found in cooling water systems. This detail is important when looking to establish an effectively managed biocide programme.

With DMA, water samples are first taken from the cooling-tower system before being streaked onto specific agar plates and incubated to provide the microbes with optimum conditions for accelerated growth. As a result, cell cultures tend to form after a few days, with other algae and fungi
identifiable under a microscope in a similar time frame. By using DMA, site managers can figure out whether microbial populations within their systems are; stable, increasing, or decreasing. This
additional insight is not available with dip-slides and allows for more informed decision-making.

At Veolia Water Technologies, our team of experts are able to undertake this analysis, employing the highest standard of sampling techniques. What’s more, our in-depth technical capabilities mean we can provide a comprehensive interpretation of the analysis, helping site managers to harness on-site improvements from the data.

To this end, our team can use the information gained from DMA to develop individual treatment programmes for sites suffering with microbiological proliferation. Across our industry leading range of Hydrex biocide chemicals, we are able to create solutions to tackle any microbial growth
problem. Similarly, our team is on hand to provide a regular servicing programme to ensure that results last in the long term. As such, when looking to ensure the most effective maintenance on cooling-tower water systems, look to us.  


Jim Knight

About the Author

Jim Knight

Jim has over 25 years experience in the water treatment and cooling tower industry. The first 17 years were spent working for Nalco and Akzo Nobel in senior roles, working in account management and sales roles. His customer focused approach and chemical background made going into Veolia Water Technologies as a Business Development Manager a good fit. He has spent the last 8 years working in sales in the evaporative cooling industry having gained wealth of knowledge from the role, proving to be a valuable asset.