Spatio-temporal dynamics of virus and bacteria removal in dual-media contact-filtration for drinking water

Make it clean, make it safe: A review on virus elimination via adsorption

Recently, the potential dangers of viral infection transmission through water and air have become the focus of worldwide attention, via the spread of COVID-19 pandemic. The occurrence of large-scale outbreaks of dangerous infections caused by unknown pathogens and the isolation of new pandemic strains require the development of improved methods of viruses' inactivation. Viruses are not stable self-sustaining living organisms and are rapidly inactivated on isolated surfaces. However, water resources and air can participate in the pathogens' diffusion, stabilization, and transmission. Viruses inactivation and elimination by adsorption are relevant since they can represent an effective and low-cost method to treat fluids, and hence limit the spread of pathogen agents. This review analyzed the interaction between viruses and carbon-based, oxide-based, porous materials and biological materials (e.g., sulfated polysaccharides and cyclodextrins). It will be shown that these adsorbents can play a relevant role in the viruses removal where water and air purification mostly occurring via electrostatic interactions. However, a clear systematic vision of the correlation between the surface potential and the adsorption capacity of the different filters is still lacking and should be provided to achieve a better comprehension of the global phenomenon. The rationalization of the adsorption capacity may be achieved through a proper physico-chemical characterization of new adsorbents, including molecular modeling and simulations, also considering the adsorption of virus-like particles on their surface. As a most timely perspective, the results on this review present potential solutions to investigate coronaviruses and specifically SARS-CoV-2, responsible of the COVID-19 pandemic, whose spread can be limited by the efficient disinfection and purification of closed-spaces air and urban waters.

Some aspects of deep-bed filtration dynamics in QMRA for drinking water

Unlike most unit processes in drinking water treatment, the performance of deep-bed filtration processes vary systematically on short time-scales; the particle removal capacity changes with time since the previous backwash, even when the influent water quality is stable. For microorganisms, the removal efficiency may vary by orders of magnitude. In this note, the potential impact of such dynamics on microbial risk estimates is studied, using representative experimental filtration data for viruses and bacteria in conjunction with single-hit dose-response models for microbial infection. Assuming that filtration is the only source of variation in pathogen concentrations on the time-scale of a single filter cycle, it is concluded that such variations are unlikely to substantially affect risk estimates, except possibly in an outbreak situation with extremely high pathogen concentrations; it is generally sufficient to know the mean pathogen concentrations. Future studies should include concurrent variation in the performance of other unit processes and raw water pathogen concentrations. Experimental work should focus on capturing the variation in filtration performance in order to correctly estimate mean removal rates.