Bubble-enhanced cold plasma improves microbial inactivation in water under scalable conditions.
8 affiliations
- 1MARE - Marine and Environmental Sciences Centre, ARNET - Aquatic Research Network Associate Laboratory, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal. [email protected].
- 2MARE - Marine and Environmental Sciences Centre, ARNET - Aquatic Research Network Associate Laboratory, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal.
- 3Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
- 4Department for Public Health Microbiology, National Laboratory of Health, Environment and Food, Ljubljana, Slovenia.
- 5CEFITEC - Centre of Physics and Technological Research, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal.
- 6Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia. [email protected].
- 7Institute of Sustainable Processes, University of Valladolid, Paseo Prado de La Magdalena 3-5, Valladolid, 47011, Spain.
- 8Department of Chemical Engineering and Environmental Technology, University of Valladolid, Paseo Prado de La Magdalena 3-5, Valladolid, 47011, Spain.
Abstract
Cold atmospheric plasma (CAP) is emerging as an environmentally friendly disinfection technology, but most plasma-liquid systems remain confined to millilitre‑scale volumes, limiting their applicability as bioprocesses for water treatment. Here, we designed and evaluated a bubble‑enhanced dielectric barrier discharge reactor, the Spiral Plasma Aeration Reactor Column (SPARC), as an environmental technology approach for litre‑scale inactivation of model bacteria in water. Direct CAP exposure achieved rapid, near‑complete inactivation of Escherichia coli and Bacillus subtilis in 200 µL, but performance decreased sharply at 100 mL, confirming strong volume dependence under surface‑limited plasma-liquid contact. Coupling CAP with gas bubbling (2 L·min⁻¹) in SPARC markedly enhanced inactivation at 250-500 mL, achieving approximately 2-3 log reductions (≥ 99-99.9%) for E. coli and B. subtilis within 60 min, whereas non-aerated CAP remained below ≈0.8-log (≤ 60%) reduction under identical conditions. At 1 L under high initial loads (~ 10⁶-10⁷ CFU·100 mL⁻¹), bubble-assisted CAP yielded ~ 4-log inactivation of E. coli and 3-3.5-log reduction of B. subtilis, including continued post-treatment inactivation consistent with plasma-activated water effects. In a protein‑rich organic matrix, early‑stage inactivation was attenuated, but SPARC still achieved ≈2-3‑log reductions, indicating robust yet matrix‑sensitive performance under wastewater‑like conditions. At fixed electrical input (34.5 W), specific energy consumption ranged from 60 kWh·m⁻³ (250 mL, 30 min, > 99% E. coli inactivation) to 30 kWh·m⁻³ (1 L, 60 min, ≈4‑log E. coli inactivation), corresponding to ≈7.5 kWh·log₁₀⁻¹·m⁻³. These results position bubble‑assisted CAP as a promising environmental biotechnology and bioprocess platform for water disinfection and emphasise the central role of reactor and contactor design in determining microbial efficacy and energy demand. KEY POINTS: • Direct CAP exposure in microlitre-scale water (200 µL) produces rapid ≥ 3-log₁₀ (> 99.9%) inactivation of E. coli and B. subtilis, but performance deteriorates at 100 mL, confirming strong volume dependence under surface-limited plasma-liquid contact. • The bubble-enhanced DBD reactor SPARC, operated at 250-500 mL, achieves ≈2-3-log₁₀ (≥ 99-99.9%) bacterial reductions within 60 min, whereas non-aerated CAP under identical electrical conditions generally remains below ≈0.8-log₁₀ (≤ 60%) reduction. • At 1 L, bubble-assisted SPARC attains ~ 4-log₁₀ (E. coli) and 3-3.5-log₁₀ (B. subtilis) inactivation under high initial loads, with specific energy consumption between 30 and 60 kWh·m⁻³ (≈7.5 kWh·log₁₀⁻¹·m⁻³) for the laboratory prototype.
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BibTeX
@article{goncalves2026bubbleenhanced,
title = {{Bubble-enhanced cold plasma improves microbial inactivation in water under scalable conditions.}},
author = {José Gonçalves and João Pequeno and Jure Žigon and Tom Koritnik and Filipe Ferreira da Silva and Davor Kržišnik and Marija Trkov and Israel Diaz and Elisa Rodriguez and Sebastian Dahle and Andrej Steyer and Rita Maurício and Graça Martinho},
journal = {Applied microbiology and biotechnology},
year = {2026},
month = aug,
doi = {10.1007/s00253-026-13979-8},
url = {https://europepmc.org/article/MED/42909657},
note = {CC BY},
}
RIS
TY - JOUR
TI - Bubble-enhanced cold plasma improves microbial inactivation in water under scalable conditions.
AU - José Gonçalves
AU - João Pequeno
AU - Jure Žigon
AU - Tom Koritnik
AU - Filipe Ferreira da Silva
AU - Davor Kržišnik
AU - Marija Trkov
AU - Israel Diaz
AU - Elisa Rodriguez
AU - Sebastian Dahle
AU - Andrej Steyer
AU - Rita Maurício
AU - Graça Martinho
PY - 2026
DA - 2026/08/01
JO - Applied microbiology and biotechnology
DO - 10.1007/s00253-026-13979-8
UR - https://europepmc.org/article/MED/42909657
AB - Cold atmospheric plasma (CAP) is emerging as an environmentally friendly disinfection technology, but most plasma-liquid systems remain confined to millilitre‑scale volumes, limiting their applicability as bioprocesses for water treatment. Here, we designed and evaluated a bubble‑enhanced dielectric barrier discharge reactor, the Spiral Plasma Aeration Reactor Column (SPARC), as an environmental technology approach for litre‑scale inactivation of model bacteria in water. Direct CAP exposure achieved rapid, near‑complete inactivation of Escherichia coli and Bacillus subtilis in 200 µL, but performance decreased sharply at 100 mL, confirming strong volume dependence under surface‑limited plasma-liquid contact. Coupling CAP with gas bubbling (2 L·min⁻¹) in SPARC markedly enhanced inactivation at 250-500 mL, achieving approximately 2-3 log reductions (≥ 99-99.9%) for E. coli and B. subtilis within 60 min, whereas non-aerated CAP remained below ≈0.8-log (≤ 60%) reduction under identical conditions. At 1 L under high initial loads (~ 10⁶-10⁷ CFU·100 mL⁻¹), bubble-assisted CAP yielded ~ 4-log inactivation of E. coli and 3-3.5-log reduction of B. subtilis, including continued post-treatment inactivation consistent with plasma-activated water effects. In a protein‑rich organic matrix, early‑stage inactivation was attenuated, but SPARC still achieved ≈2-3‑log reductions, indicating robust yet matrix‑sensitive performance under wastewater‑like conditions. At fixed electrical input (34.5 W), specific energy consumption ranged from 60 kWh·m⁻³ (250 mL, 30 min, > 99% E. coli inactivation) to 30 kWh·m⁻³ (1 L, 60 min, ≈4‑log E. coli inactivation), corresponding to ≈7.5 kWh·log₁₀⁻¹·m⁻³. These results position bubble‑assisted CAP as a promising environmental biotechnology and bioprocess platform for water disinfection and emphasise the central role of reactor and contactor design in determining microbial efficacy and energy demand. KEY POINTS: • Direct CAP exposure in microlitre-scale water (200 µL) produces rapid ≥ 3-log₁₀ (> 99.9%) inactivation of E. coli and B. subtilis, but performance deteriorates at 100 mL, confirming strong volume dependence under surface-limited plasma-liquid contact. • The bubble-enhanced DBD reactor SPARC, operated at 250-500 mL, achieves ≈2-3-log₁₀ (≥ 99-99.9%) bacterial reductions within 60 min, whereas non-aerated CAP under identical electrical conditions generally remains below ≈0.8-log₁₀ (≤ 60%) reduction. • At 1 L, bubble-assisted SPARC attains ~ 4-log₁₀ (E. coli) and 3-3.5-log₁₀ (B. subtilis) inactivation under high initial loads, with specific energy consumption between 30 and 60 kWh·m⁻³ (≈7.5 kWh·log₁₀⁻¹·m⁻³) for the laboratory prototype.
SN - 0175-7598
SN - 1432-0614
ER -