Maintaining quality of drinking water from the treatment plants to users is still a challenge, especially because of deteriorating transmission piping network. Residual disinfectants and corrosion inhibitors are frequently added to drinking water to prevent microbial growth and lead release, respectively. We performed a systematic study to determine the role of corrosion inhibitors on the porous structure, the stiffness, disinfectant reaction with biofilms, and the release of L. pneumophila from biofilms grown from simulated drinking water amended with silicate or phosphate corrosion inhibitors. We used optical coherent tomography coupled with image analysis to reconstruct the 3D porous structure of the studied biofilms. Compared to silicate corrosion inhibitor, phosphate and blend of phosphate can facilitate the growth of more porous biofilms. Large channels under thin layers of biomass were observed in the blends of phosphate biofilms, giving rise to multiple layers of the biofilms with different stiffness. More L. pneumophila adhered to and subsequently released from biofilms grown with phosphate corrosion inhibitors, compared to silicate biofilms. We also measured the mass transfer coefficients for chlorine decay in contact with these studied biofilms. These coefficients coupled with inactivation kinetics of L. pneumophila released from biofilms reported previously were integrated into a Monte Carlo framework to estimate the infection risk of biofilm-derived L. pneumophila from 1 to 48 h of stagnation. Overall, this study’s findings suggested that the presence of phosphate corrosion inhibitors could promote biofilms growth, induce disinfectant decay and consequently increase L. pneumophila infection risk.

Influence of corrosion inhibitors on infection risk of Legionella pneumophila released from drinking water biofilms

ACS Fall 2021

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