(IMO, US Coast Guard) by applications of discharged limits: · According to size of microorganisms (> 10 µm). · Microbial indicators according to human health (E.
EFFECTS OF DIFFERENT PHOTOCHEMICAL TREATMENTS ON MARINE BACTERIA: INACTIVATION AND POST-TREATMENT EVALUATION
Ballast Water
Global challenge and one of the most severe pollution problems faced by the world's oceans.
Application of disinfection treatments
Prevented by international regulations (IMO, US Coast Guard) by applications of discharged limits:
to ensure ship stability and buoyancy on oceangoing vessels
· According to size of microorganisms (> 10 µm) · Microbial indicators according to human health (E. coli, V. cholerae, Enterocci)
Transference 3–5 billion tons of BW yearly BW released into far ecosystems results in ecological threats and an enormous impact on human activities.
Invasive environmental microbes could alter the community structure and ecosystem functioning
AIMS: - To evaluate disinfection kinetics of three different marine-specific bacteria - To assess evolution after treatment through growth curves modelling
hν
2 ·OH
H2O2
Water discharge
Seawater with specific particularities: - high salinity, - low organic matter content,
BUT… WHAT ABOUT REST OF ORGANISMS < 10 µm?
- high microbiological activity and diversity
Roseobacter litoralis α-proteobacteria (Gram --) Water-associated Three different marine bacteria have been chosen among major groups of a natural marine ecosystem
Based on Survival organisms: Kinetic modelling according to: Shoulder + Log-Lineal + Tail
Inactivation kinetics
Pseudomonas litoralis γ-proteobacteria (Gram --) Water-associated
Membrane Filtration Method – Colony Counts
Evolution after treatment Kocuria rhizophila Actinobacteria (Gram +) Sediment-associated
0.75
Roseobacter litoralis Pseudomonas litoralis Kocuria rhizophila 0
0
-3 -4
-1
-2
-2
-3
-3
-4
0 10 20 30 40 UV-Dose (mJ·cm-2) 0 mJ 13.94 mJ
5.81 mJ 23.24 mJ
0.4
0
0.2
0.6
0.2
0.1
0
0 50
100 150 200
20
30
40
UV/H2O2
0.25 UV-C
UV-C
0 Pseudomonas litoralis
-4 0
0
UV/H2O2
Kocuria rhizophila
10 20 30 40 0 mJ
GROWTH MODELLING
0.4
0.3
10
+ H2O2
0.5 0.4 0.3 0 mJ 4.26 mJ 0.2 13.09 mJ 0.1 0 0 50 100 150 200
0 mJ 8.18 mJ 24.15 mJ
Treatment
50 100 150 200
Hours after treatment (h.)
UV-C
UV + H2O2
· Three different levels of resistance have been observed for different bacterial groups: Weakly resistant (Roseobacter), Medium (Pseudomonas) and highly resistant (Kocuria). · Growth modelling after UV-treatment shows some recovery after a lag-phase (24 h.) for both medium and highly resistant bacteria. · The application of UV/H2O2 process could accelerate the kinetics and decrease the maximum asymptotic limit of growth, specially on medium resistant bacteria. · K. rhizophila shows great resistance to both UV treatment and AOPs, suggesting an especially robust structure, even be able to inactivate reactive oxygen species originated in UV/H2O2. REFERENCES: · IMO. International Convention for the Control and Management of Ships’ Ballast Water and Sediments. BWM/CONF/36. (2004). · Cohen, A. N. & Dobbs, F. C. Failure of the public health testing program for ballast water treatment systems. Mar. Pollut. Bull. 91, 29–34 (2015). · Drillet, G. Food security: Protect aquaculture from ship pathogens. Nature 539, 31–31 (2016). · Geeraerd, A. H., Herremans, C. H. & Van Impe, J. F. Structural model requirements to describe microbial inactivation during a mild heat treatment. Int. J. Food Microbiol. 59, 185–209 (2000). · Nebot, E., Casanueva, J. F., Casanueva, T. & Sales, D. Model for fouling deposition on power plant steam condensers cooled with seawater: Effect of water velocity and tube material. Int. J. Heat Mass Transf. 50, 3351–3358 (2007). · De Schryver, P. & Vadstein, O. Ecological theory as a foundation to control pathogenic invasion in aquaculture. ISME J. 8, 2360–8 (2014).
UV-C
UV + H2O2
LagUV-Dose Maximum phase (mJ·cm-2 ) asymptotic limit (h.) Pseudomonas litoralis 0 < 24 0.52 13.09 24 0.50 20.68 24 0.44 0 < 24 0.45 7.71 24 0.24 15.42 24 0.32 Kocuria rhizophila 0
