Estimating decay kinetic parameters and persistence of bacteria in water is essential for future modelling

DOLORES GUTIÉRREZ CACCIABUE; VERÓNICA RAJAL

CHEMICAL ENGINEERING RESEARCH & DESIGN

INST CHEMICAL ENGINEERS

Año: 2022 vol. 179 p. 175 - 187

0263-8762

The aim of this work was to obtain decay kinetic parameters for bacteriasedimentation?resuspension in water. For that, synthetic water matrices preparedwith four particle sizes at 2.5 and 5 g/l, were spiked with Escherichia coli and Enterococcusfaecalis, selected as Gram-negative and -positive models, respectively. Matrices with bacteriawithout solids were used as controls. Turbidity was measured and culturable bacteria decaywas evaluated using membrane filtration over time. Also, the persistence of culturable E.faecalis and its DNA (detected by real-time PCR) was compared. When no colonies weredetected, water matrices were mixed to re-suspend sediments and surface samples werecollected and analysed. Spearman test was applied to find correlation between bacteriaand turbidity. A persistence coefficient (PC) was defined and several kinetic parameters(decay rate constants, R2, T90) were calculated from experimental data. While culturableE. coli disappeared from the surface of all water matrices with turbidity (p < 0.05), E. faecalisonly showed strong and positive correlation in matrices with higher turbidity and smallerparticles. E. coli decayed slower when interacting with smallest solids (149 m), being T90 3?4 times higher in the former. Also, it reappearedand persisted in the surface of all matrices after resuspension despite solid concentration(PC: 0.5−0.9). Instead, culturable E. faecalis, persisted less (lower PC values) in matriceswith 2.5 g/l than with 5 g/l and no logic relation was observed for any rate constant withparticle size. E. faecalis DNA remained in suspension for longer periods until the end ofthe experience as seen through their lower rate constants (kDNA < 0.05 h−1). Accuratedecay kinetic parameters, like the ones obtained here, are crucial for modelling the fateand transport of bacteria in water and to perform a robust and realistic quantitative riskassessment