Moist heat as a promising method to decontaminate N95 masks: A large scale clinical study comparing four decontamination modalities-moist heat, steam, ultraviolet-C irradiation, and hydrogen peroxide plasma.

BACKGROUND: Early in the COVID-19 pandemic, there was a global shortage of masks. Although mask reprocessing was practiced, no clinical study has assessed systematically the impact of repeated cycles of wear and decontamination on the integrity of N95 filtering facepiece respirators (FFRs). METHODS: We evaluated mask fit assessed by qualitative respirator fit test (QRFT) after each cycle of wear and decontamination, as well as four measures of mask integrity-bacterial filtration efficacy, particle filtration efficacy, differential pressure, and splash resistance through five cycles of wear and decontamination using one of the four modalities (moist heat, steam, ultraviolet-C irradiation, and hydrogen peroxide plasma). RESULTS: A total of 60.6% (hydrogen peroxide plasma) to 77.5% (moist heat) of the FFRs passed five cycles of wear and decontamination, as assessed by the wearers passing QRFT all five times. Moist heat-decontaminated FFRs retained all technical measures of integrity through all five cycles. CONCLUSIONS: This is the first large-scale study to assess systematically the impact (clinically and quantitatively) on N95 FFR integrity of repeated cycles of wearing followed by decontamination. Our results suggest that moist heat is a promising method for decontaminating N95 FFRs. Performing QRFT after every cycle of wear and decontamination ensures wearer safety. Although there is currently no mask shortage, reprocessing may reduce medical waste and improve sustainability.

Pentachlorophenol dechlorination by an acidogenic sludge.

This study reports the feasibility of removing pentachlorophenol (PCP) by an acidogenic process in batch reactors. When the acidogenic sludge was first acclimated with 2,4,6-trichlorophenol (2,4,6-TCP) and developed 2,4,6-TCP dechlorinating activity, PCP could be ortho-dechlorinated to 3,4,5,-trichlorophenol (3,4,5-TCP) via 2,3,4,5-tetrachlorophenol as the intermediary. However, due to PCP's higher hydrophobicity and its higher expected Gibbs free energy yield, it was adsorbed to the sludge and dechlorinated preferentially to 2,4,6-TCP. This resulted in the inhibition of 2,4,6-TCP dechlorination. PCP removal under acidogenic condition was attributed to both reductive dechlorination and adsorption. At low PCP loads of 0.48micromoles/gMLVSS.d, dechlorination was the dominant removal mechanism (69% of total removal), while at the higher PCP load of 9.3micromoles/gMLVSS.d, adsorption was the main mechanism (82% of total removal). Attempts to induce meta or para position dechlorination of PCP failed when using meta position chlorophenols such as 2,3,6-TCP, 3,4,5-TCP and 3,5-DCP as the initial substrates. Overall, acidogenic biotreatment was an effective process in reducing PCP loads prior to downstream biological treatment.

Acidogenic sequencing batch reactor start-up procedures for induction of 2,4,6-trichlorophenol dechlorination.

Dechlorination of 2,4,6-trichlorophenol to 4-chlorophenol under acidogenic conditions (pH 5.6-6.5) was successfully induced by manipulating the start-up procedure of an acidogenic sequencing batch reactor (SBR). A stepwise pH reduction from neutral to acidic level during start-up was crucial for inducing dechlorination. Once induced, dechlorination can proceed at pH as low as 5.6 before inhibition occurs. Optimum pH for maximum dechlorination rate ranged from 6.0 to 6.3. High primary (sucrose) to secondary (2,4,6-trichlorophenol) substrate ratio failed to induce dechlorination. Instead, dechlorination occurred at primary to secondary substrate ratios of less than 103M/M. A specific maximum trichlorophenol loading rate of 60micromol/g MLVSSd was achieved before inhibition appeared with onset of acidogenic reactor failure. T-RFLP profile analysis gave evidence that the start-up procedure resulted in the selection of an appropriate microbial community, which resulted in the successful development of an acidogenic consortium capable of degrading 2,4,6-trichlorophenol.