In industrial cooling towers, biofilm growth can cause serious problems, both contributing to the deterioration of materials and, most important, increasing the risk of harmful microbiological contaminations (e.g. Legionella). For these reasons, large amounts of chemical substances (biocides) are used to limit microbiological growth in such systems. A new application case, illustrating what happens when chlorination does not work as expected, can be download from the ALVIM Biofilm Sensors page.