Biotic and abiotic particles protect marine heterotrophic bacteria during UV and ozone disinfection

Abstract

Disinfection of water is required for a range of applications, including ballast water treatment and land-based fish farming. Bacteria attached to or embedded in particles can be protected from the disinfectant by various mechanisms. We investigated inactivation of marine heterotrophic bacteria in the presence of biotic and abiotic particles. In one set of experiments with the planktonic rotifer Brachionus 'Nevada', water was exposed to increasing UV and ozone dose, and we examined inactivation of free-living and particle-associated heterotrophic bacteria. An estimated 99.9% inactivation of free-living bacteria was obtained compared to only 91.4% inactivation (3 of 4 experiments) of particle-associated bacteria at the same ozone dose. For the UV experiments, a 6-fold increase in disinfection dose was required to obtain 99.9% inactivation of the particle-associated compared to the free-living bacteria. In a second set of experiments we investigated the protective effect of biotic (rotifers) and abiotic (ceramic clay) particles as a function of particle concentration. Increased particle concentration resulted in reduced disinfection efficiency of free-living bacteria with both UV and ozone. Rotifers protected slightly better against UV disinfection than ceramic clay particles, while such a relationship was not evident for the ozone disinfection. The results suggest a complex bacterial inactivation mechanism in the presence of particles, and will have implications for the treatment strategy used for ballast water and land-based fish farming.

Bacterioneuston Community Structure in the Southern Baltic Sea and Its Dependence on Meteorological Conditions

“…This suggests that increasing exposure to UVinduced stress alters the community composition of nonattached, active bacterioneuston members, which again is favored during low wind conditions. In contrast, variability in the particle-attached fingerprints was not related to changing levels of radiation, probably due to the sheltering from UV exposure conferred by particle association (22,53).…”

Disinfection of Seawater: Application of UV and Ozone

“…. ) as reported in literature (Hess-Erga et al 2008;Summerfelt 2003) but UV radiation appears as an effective technology for microorganism elimination seawater. To apply the minimum UV dose of 320 J L −1 , seawater flow for continuous mode experiments were set at 200 L h −1 .…”

Inactivation of dinoflagellateScripsiella trochoideain synthetic ballast water by advanced oxidation processes

“…Because of the covalently bound pyrimidine residues, replication of the nucleic acid is hampered or completely blocked, the effect of which could be temporal or lethal depending on the repair mechanisms and the degree of UV resistance. [43] In this study it seems that within 24 h of regrowth period, the S. trochoidea cells could not overcome the negative effect of UV and achieve recovery. However, the inactivation of S. trochoidea cells by UV mostly exhibited as the lack of movement of the cells, which might not be equal to cell death.…”