The use of a protozoal predator of Legionella to replace chemical biocides in the control of Legionella in evaporative cooling systems: A 12 months study in a cooling tower application

Legionella pneumophila has a complex growth cycle including a free living, largely inactive, state and a reproductive stage involving invasion and parasitic attack of phagocytic protozoa. One protozoan species (Willaertia magna C2c Maky) has been shown to resist attack by Legionella and to reduce number of viable Legionella in vitro studies . This study examines the use of this protozoan as an alternative to chemical biocides in cooling towers.

Samples for analysis by culture (n-=134, NFT 90-431) were all negative from both planktonic and sessile samples over an 12 month period. Legionella DNA was detectable throughout the study but the proportion of positive results was lower during periods of biological treatment than during chemical treatments before and after the biological treatment was applied

TVC rate goes under the median of total values recorded for the period.Green Biocide treatment delivered a 2 log reduction in TVC after 12 months of continous treament.

Willaertia magna C2c Maky has reduced the corrosion rate from 10um/year to 0,06um/year!

The data suggests that use of the Amoeba Willaertia magna C2c Maky as a biocide is effective in controlling both planktonic and sessile Legionella populations in these cooling systems.