With a unique and large size of testing results of 1,842 samples collected from 12 wastewater treatment plants (WWTP) for 14 months through from low to high prevalence of COVID-19,the sensitivity of RT-qPCR detection ...With a unique and large size of testing results of 1,842 samples collected from 12 wastewater treatment plants (WWTP) for 14 months through from low to high prevalence of COVID-19,the sensitivity of RT-qPCR detection of SARS-CoV-2 RNA in wastewater that correspond to the communities was computed by using Probit analysis.This study determined the number of new COVID-19 cases per 100,000 population required to detect SARS-CoV-2RNA in wastewater at defined probabilities and provided an evidence-based framework of wastewater-based epidemiology surveillance (WBE).Input data were positive and negative test results of SARS-CoV-2 RNA in wastewater samples and the corresponding new COVID-19 case rates per 100,000 population served by each WWTP.The analyses determined that RT-qPCR-based SARS-CoV-2 RNA detection threshold at 50%,80%and 99%probability required a median of 8 (range:4-19),18 (9-43),and 38 (17-97) of new COVID-19 cases/100,000,respectively.Namely,the positive detection rate at 50%,80%and 99%probability were 0.01%,0.02%,and 0.04%averagely for new cases in the population.This study improves understanding of the performance of WBE SARS-CoV-2 RNA detection using the large datasets and prolonged study period.Estimated COVID-19 burden at a community level that would result in a positive detection of SARS-CoV-2 in wastewater is critical to support WBE application as a supplementary warning/monitoring system for COVID-19 prevention and control.展开更多
Acid mine drainage presents an important threat to cementitious structures.This study is aimed at investigating the effect of cellulose nanocrystals(CNCs)on the acid resistance of cementitious composites.CNCs were add...Acid mine drainage presents an important threat to cementitious structures.This study is aimed at investigating the effect of cellulose nanocrystals(CNCs)on the acid resistance of cementitious composites.CNCs were added to mortar mixtures as additives at cement volume ratios of 0.2vol%,0.4vol%,1.0vol%,and 1.5vol%.After 28 d of standard curing,the samples were immersed in a sulfuric acid with a pH value of 2 for 75 d.The unconfined compressive strength(UCS)test,the density,water absorption,void volume test,and thermogravimetric analysis were carried out to investigate the properties of CNC mixtures before sulfuric acid immersion.It was found that the addition of CNC reduced the volume of permeable voids and increased the hydration degree and mechanical strength of the samples.Changes in mass and length were monitored during immersion to evaluate the acid resistance of mixtures.The mixture with 0.4vol%CNC showed a reduced mass change and length change indicating its improved acid resistance.展开更多
基金supported by research grants from the Canadian Institutes of Health Research [grant number VR5-172701, 2020]Alberta Innovates and Alberta Health [grant number RES0051047, 2020]。
文摘With a unique and large size of testing results of 1,842 samples collected from 12 wastewater treatment plants (WWTP) for 14 months through from low to high prevalence of COVID-19,the sensitivity of RT-qPCR detection of SARS-CoV-2 RNA in wastewater that correspond to the communities was computed by using Probit analysis.This study determined the number of new COVID-19 cases per 100,000 population required to detect SARS-CoV-2RNA in wastewater at defined probabilities and provided an evidence-based framework of wastewater-based epidemiology surveillance (WBE).Input data were positive and negative test results of SARS-CoV-2 RNA in wastewater samples and the corresponding new COVID-19 case rates per 100,000 population served by each WWTP.The analyses determined that RT-qPCR-based SARS-CoV-2 RNA detection threshold at 50%,80%and 99%probability required a median of 8 (range:4-19),18 (9-43),and 38 (17-97) of new COVID-19 cases/100,000,respectively.Namely,the positive detection rate at 50%,80%and 99%probability were 0.01%,0.02%,and 0.04%averagely for new cases in the population.This study improves understanding of the performance of WBE SARS-CoV-2 RNA detection using the large datasets and prolonged study period.Estimated COVID-19 burden at a community level that would result in a positive detection of SARS-CoV-2 in wastewater is critical to support WBE application as a supplementary warning/monitoring system for COVID-19 prevention and control.
基金financially supported by the Natural Sciences and Engineering Research Council of Canada(No.RGPIN-2017-05537)the Alberta Innovates CNC Challenge 3.0 Grant(No.BFC 18009)。
文摘Acid mine drainage presents an important threat to cementitious structures.This study is aimed at investigating the effect of cellulose nanocrystals(CNCs)on the acid resistance of cementitious composites.CNCs were added to mortar mixtures as additives at cement volume ratios of 0.2vol%,0.4vol%,1.0vol%,and 1.5vol%.After 28 d of standard curing,the samples were immersed in a sulfuric acid with a pH value of 2 for 75 d.The unconfined compressive strength(UCS)test,the density,water absorption,void volume test,and thermogravimetric analysis were carried out to investigate the properties of CNC mixtures before sulfuric acid immersion.It was found that the addition of CNC reduced the volume of permeable voids and increased the hydration degree and mechanical strength of the samples.Changes in mass and length were monitored during immersion to evaluate the acid resistance of mixtures.The mixture with 0.4vol%CNC showed a reduced mass change and length change indicating its improved acid resistance.
