Competitive co-adsorption of bacteriophage MS2 and natural organic matter onto multiwalled carbon nanotubes

Céline Jacquin; Diya Yu; Michael Sander; Kamila W Domagala; Jacqueline Traber; Eberhard Morgenroth; Timothy R Julian

doi:10.1016/j.wroa.2020.100058

Competitive co-adsorption of bacteriophage MS2 and natural organic matter onto multiwalled carbon nanotubes

Water Res X. 2020 Jun 10:9:100058. doi: 10.1016/j.wroa.2020.100058. eCollection 2020 Dec 1.

Authors

Céline Jacquin¹, Diya Yu¹, Michael Sander², Kamila W Domagala^{3

4}, Jacqueline Traber¹, Eberhard Morgenroth^{1

5}, Timothy R Julian^{1

6

7}

Affiliations

¹ Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600, Dübendorf, Switzerland.
² Institute of Biogeochemistry and Pollutant Dynamics (IBP), Department of Environmental Systems Science, ETH Zürich, 8092, Zürich, Switzerland.
³ Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for High Performance Ceramics, Überlandstrasse 129, 8600, Dübendorf, Switzerland.
⁴ AGH, University of Science and Technology, Faculty of Materials Science and Ceramics, al. Mickiewicza 30, 30-059, Krakow, Poland.
⁵ ETH Zürich, Institute of Environmental Engineering, 8093, Zürich, Switzerland.
⁶ Swiss Tropical and Public Health, P.O. Box, 4001, Basel, Switzerland.
⁷ University of Basel, P.O. Box, 4002, Basel, Switzerland.

Abstract

A leading challenge in drinking water treatment is to remove small-sized viruses from the water in a simple and efficient manner. Multi-walled carbon nanotubes (MWCNT) are new generation adsorbents with previously demonstrated potential as filter media to improve virus removal. This study therefore aimed to evaluate the field applicability of MWCNT-filters for virus removal in water containing natural organic matter (NOM) as co-solute to viruses, using batch equilibrium experiments. Contrary to previous studies, our results showed with MS2 bacteriophages single-solute systems that the affinity of MWCNT for MS2 was low, since after 3 h of equilibration only 4 log₁₀ reduction value (LRV) of MS2 (20 mL at an initial concentration of 10⁶ PFU MS2/mL) were reached. Single solute experiments with Suwannee river NOM (SRNOM) performed with environmentally-relevant concentrations showed MWCNT surface saturation at initial SRNOM concentrations between 10 and 15 mgC/L, for water pH between 5.2 and 8.7. These results suggested that at NOM:virus ratios found in natural waters, the NOM would competitively suppress virus adsorption onto MWCNT, even at low NOM concentrations. We confirmed this expectation with SRNOM-MS2 co-solute experiments, which showed an exponential decrease of the MS2 LRV by MWCNT with an increase in the initial SRNOM concentration. More interestingly, we showed that pre-equilibrating MWCNT with a SRNOM solution at a concentration as low as 0.4 mgC/L resulted in a LRV decrease of 3 for MS2, due to the formation of a negatively charged SRNOM adlayer on the MWCNT surface. Complementary batch experiments with natural NOM-containing waters and competition experiments with SRNOM in the presence of CaCl₂ confirmed that the presence of NOM in waters challenges virus removal by MWCNT-filters, irrespective of the concentration and type of NOM and also in the presence of Ca²⁺. We therefore conclude that MWCNT-filters produced with commercially available pristine MWCNT cannot be considered as a viable technology for drinking water virus removal.

Keywords: Competitive adsorption; Drinking water; Multiwalled carbon nanotubes; Natural organic matter; Virus treatment.