Décontamination | EPFL Graph Search

vignette|Travaux de décontamination sur l'arsenal de Redstone (Alabama, 1957). La décontamination est l'opération visant à extraire ou inerter des contaminants (dont produits chimiques industriels toxiques et/ou écotoxiques, contaminants d'origine agro-industrielle (pesticides), radionucléides, toxiques de guerre) d'un liquide, du sol, de l'habitat ou de l'environnement. Le décapage, l'extraction par solvants, la biodégradation (quand elle est possible), l'adsorption, la phytoremédiation, la fongoremédiation ou l'absorption sur divers supports sont utilisés. La recherche teste de nombreux moyens de décontaminer les solides ou les milieux gazeux ou liquides. Description Ainsi, en 2011, une étude a montré que des pollens (d'Ambrosia artemisiifolia) magnétisés sont efficaces pour éliminer des composés organiques hydrophobes (COHs) toxiques ou indésirables tels que des pesticides, des hydrocarbures aromatiques polycycliques (HAP) (ont été testés : acénaphtène, phénanthrène,

Modified full-face snorkel masks as reusable personal protective equipment for hospital personnel

Nitin Arora, Patrick Gerber, Mélanie Thérèse Marie Hannebelle

Here we adapt and evaluate a full-face snorkel mask for use as personal protective equipment (PPE) for health care workers, who lack appropriate alternatives during the COVID-19 crisis in the spring of 2020. The design (referred to as Pneumask) consists of a custom snorkel-specific adapter that couples the snorkel-port of the mask to a rated filter (either a medical-grade ventilator inline filter or an industrial filter). This design has been tested for the sealing capability of the mask, filter performance, CO2 buildup and clinical usability. These tests found the Pneumask capable of forming a seal that exceeds the standards required for half-face respirators or N95 respirators. Filter testing indicates a range of options with varying performance depending on the quality of filter selected, but with typical filter performance exceeding or comparable to the N95 standard. CO2 buildup was found to be roughly equivalent to levels found in half-face elastomeric respirators in literature. Clinical usability tests indicate sufficient visibility and, while speaking is somewhat muffled, this can be addressed via amplification (Bluetooth voice relay to cell phone speakers through an app) in noisy environments. We present guidance on the assembly, usage (donning and doffing) and decontamination protocols. The benefit of the Pneumask as PPE is that it is reusable for longer periods than typical disposable N95 respirators, as the snorkel mask can withstand rigorous decontamination protocols (that are standard to regular elastomeric respirators). With the dire worldwide shortage of PPE for medical personnel, our conclusions on the performance and efficacy of Pneumask as an N95-alternative technology are cautiously optimistic.

PUBLIC LIBRARY SCIENCE2021

Solar water purification with photocatalytic nanocomposite filter based on TiO2 nanowires and carbon nanotubes

Florian Frédéric Vincent Breider, László Forró, Miriam Gaál, Dominique Grandjean, Endre Horvath, Luca Rossi, Andrzej Sienkiewicz

Water contamination due to environmental conditions and poor waste management in certain areas of the world represents a serious problem in accessing clean and safe drinking water. This problem is especially critical in electricity-poor regions, where advanced water purification methods are absent. Here, we demonstrate that titanium dioxide nanowires (TiO2NWs)-based photocatalytic filters assisted only with sunlight can efficiently decontaminate water. Moreover, interweaving TiO2NWs with carbon nanotubes (CNTs) leads to the formation of a TiO2NWs/CNTs composite material and offers an additional water decontamination channel, that is of pasteurization with the visible part of the solar emission spectrum. Our results demonstrate that this nanoporous filter can successfully intercept various types of microbial pathogens, including bacteria and large viruses. In addition, photo-catalytically generated reactive oxygen species (ROS) on the surface of the TiO2NWs/CNTs-based filter material under exposure to sunlight contribute to an efficient removal of a broad range of organic compounds and infective microbes. A pilot study also yielded encouraging results in reducing traces of drugs and pesticides in drinking water.

2022

Robust and sustainable cultivation of microalgae: recycling of nitrogen from liquid digestate and control of biological contamination

Adrian Pulgarin

The present doctoral thesis aimed to achieve a robust cultivation of microalgae by recycling nitrogen from a liquid digestate. However, the use of non-sterile nutrient source increases the risks of contamination of undesired organisms such as bacteria, viruses, protozoa, and rotifers. Therefore, the thesis also aimed to develop a cheap and bio-compatible decontamination method, which can be applied to microalgae during their cultivation. To reach these objectives, three projects were carried out. In the first project, microalgae (Chlorella vulgaris) were successfully cultivated at high-density with liquid digestate from anaerobic digestion as a nitrogen source. The cultivation was carried out at laboratory and pilot scales in glass-column and thin-layer photobioreactors, respectively. Biomass dry weight and productivity reached values up to 18.6 grams per liter and 0.93 grams per liter per day, respectively. To obtain these results, a cultivation method was developed to overcome inherent issues associated to the use of liquid digestate such as the acidification of the water, ammonium toxicity, turbidity, and nutrient imbalance. The nitrogen mass balance was carried out during the cultivation and it shows that only 40 to 60 % of the nitrogen supplied to the cultures were assimilated in the biomass. Surprisingly, accumulation of nitrogen in the supernatant accounted only for approximatively 3 %. Therefore, a large fraction of the nitrogen was lost to the atmosphere.In the second project, a citrate-modified photo-Fenton (PF) process was used to treat microalgae cultures contaminated with the bacterium Escherichia coli. The aim was to set experimental conditions where physiological and morphological differences can be used to favor the inactivation of bacteria and to minimize the loss of microalgae. Results showed that the citrate-modified PF was more effective against bacteria than a solar light/hydrogen peroxide treatment, while being less effective against microalgae. If the treatment was applied at an early-stage contamination, bacteria were fully inactivated, while the microalgae loss of viable cells was about three orders of magnitude. In the third project, the citrate-modified PF process was used to treat microalgae cultures contaminated by the rotifer Brachionus calyciflorus, a predator of microalgae, which can lead cultures to failure due to its high consumption rate of algal cells. Then, treated cultures were cultivated up to 14 days to assess the efficacy of the treatment. Results show that the citrate-modified PF and solar light/hydrogen peroxide treatments had equivalent efficacy to inactivate rotifers. However, the PF process remained less harmful for microalgae. When the citrate-modified PF treatment was applied to an early-stage contamination (5 rotifers per mL), the decontamination was effective and no regrowth of rotifers was observed. However, the cultivation of contaminated cultures, which were not treated, failed due to an increasing rotifer population (>1000 individuals per mL after 14 days of cultivation).As a whole, the present doctoral thesis contributes to the development of more robust and sustainable cultures of microalgae. Methods were developed to cultivate microalgae at high-density with liquid digestate and to control biological contaminants. Finally, challenges and opportunities were discussed as a perspective for further works.

EPFL2021

Robust and sustainable cultivation of microalgae: recycling of nitrogen from liquid digestate and control of biological contamination

Adrian Pulgarin

EPFL2021