Efficient cooling tower operation at alkaline pH for the control of Legionella pneumophila and other pathogenic genera

Efficient control of pathogenic bacteria, specifically Legionella pneumophila, is one the main concerns when operating industrial cooling towers. Common practices to limit proliferation involves use disinfectants, leading formation disinfection by-product and increase in water corrosiveness. A disinfectant-free method would make industry more environmentally friendly. pilot-scale tower (1 m3/h) operated with demineralized was used investigate potential high-pH conditioning as a alternative for L. pneumophila other pathogens. One experiment performed under standard full-scale operation involving sodium hypochlorite dosage. Thereafter 3 alkaline pHs were tested: 9.0, 9.4 9.6. The tests lasted between 25 35 days. from basins analysed total cell count by flow cytometry, concentration plate occasional qPCR analyses targeting mip-gene, bacterial eukaryotic community 16S 18S rRNA gene amplicon sequencing, relative abundance prokaryotic DNA gene. showed considerable growth at pH 9.0 but maintained below detection (< 100 CFU/L) 9.6 without disinfection. Interestingly, results correlated overall protozoa samples not directly specific reported protozoan hosts Legionella. pathogenicity based on sequencing decreased increasing strong decline 9.4, 7.1% 1.6% genera respectively. shift microbiome observed each tested reproducibility confirmed duplicate test lasting 80 High-pH ≥ therefore considered an efficient pathogenicity, including pneumophila.