Legionella in cooling tower

Since 2018, operators of evaporative cooling systems, cooling towers and scrubbers must have their cooling water regularly checked for microbiological impurities such as legionella or bacteria. This regulation was adopted after cases in the USA where people became infected with Legionella from cooling towers. Legionella are aerobic bacteria transmitted by water droplets. Under certain weather conditions, evaporation fumes from cooling towers remain close to the ground rather than rising, enabling infection transmission.

In Europe, regulations require own checks every 14 days and certified laboratory tests every 3 months. Limit values are 100, 1,000 and 10,000 CFU/100ml. If the highest stage exceeds 10,000 CFU, shock flushing with biocide must be performed.

The primary challenge in controlling legionella involves catching all bacteria. Biofilms serve as breeding grounds, and if biofilm isn't completely removed during treatment, bacteria regrow quickly. Traditional methods like biocides, heat sanitation, and UV systems only affect bacteria they directly contact, failing to reach protected bacteria within biofilm layers in dead pipes.

Merus technology addresses this limitation by reaching dead legs in pipes and machines through oscillations that move faster than water flow itself, removing biofilm from non-flowing pipe sections without requiring physical opening. This eliminates breeding grounds, reducing legionella below required thresholds and potentially allowing operators to reduce or eliminate biocides and thermal treatments.