The UV tube: a family-shared water disinfection system in rural Sri Lanka

The UV tube: a family-shared water disinfection system in rural Sri Lank

AGENTES ASOCIADOS Y SU PAPEL EN LA DECLINACIÓN Y MUERTE DE ENCINOS (QUERCUS, FAGACEAE) EN EL CENTRO-OESTE DE MÉXICO

This study was carried out to identify bioticand abiotic agents and to determine theirrole in oak decline and death in five statesof the Mexican Republic: Aguascalientes,Colima, Guanajuato, Jalisco and Nayarit.Two 0.1-ha permanent plots wereestablished at the most representativeforested areas with tree death, diebackand bleeding cankers in these statesand sampled during 2003, 2004 and 2005(10 plots in total). Field observations weremade, and foliage, branch, trunk and soilsamples were collected to identify theassociated agents in each plot. Isolates frombleeding cankers were made in situ. Themost commonly found biotic agents were:Phytophthora cinnamomi, Pythium sp.,Hypoxylon antropunctatum, Ganodermaspp., Armillaria sp., Apiognomoniaquercina, the dwarf mistletoe(Phoradendron villosum), bark borers,insect defoliators and livestock overgrazing.Among the abiotic stress factors commonlyfound were the effects due to lowtemperature-lack of water and fire. Basedon their incidence, P. cinnamomi, H.antropunctatum and low temperature-lackof water were considered the most importantcontributors to the decline and death of theoaks. P. cinnamomi was identified in four ofthe 10 plots, mainly in Colima and Jalisco;H. antropunctatum was detected in sixplots, particularly in Nayarit andAguascalientes. Stem cankers (cracks) dueto low temperature-lack of water wereobserved in four plots, damaging 52% of the trees in Aguascalientes and 24% inGuanajuato. It was concluded that P.cinnamomi is killing some oak species, H.antropunctatum is colonizing weakenedtrees, and low temperature-lack of water iscausing stress and in some cases death inoaks.Este estudio tuvo como objetivo identificary determinar el papel tanto de los factoresbióticos como de los abióticos asociados ala declinación y muerte del encino en cincoestados de la República mexicana: Aguascalientes, Colima, Guanajuato, Jalisco yNayarit. Para esto, se establecieron dossitios permanentes de 0.1 ha en cada una delas áreas más representativas (con arboladomuerto, con muerte regresiva y cancros conexudado) de los estados mencionados (10sitios en total), los cuales fueron muestreados durante 2003, 2004 y 2005. Sehicieron observaciones y colectas en campode follaje, ramas, tronco y suelo, paraidentificar a los diferentes agentes de dañoen cada sitio. Se realizaron aislamientosin situ de cancros con exudado en mediosespecíficos. Los agentes bióticos máscomunes fueron: Phytophthora cinnamomi,Pythium sp., Hypoxylon antropunctatum,Ganoderma sp., Armillaria sp.,Apiognomonia quercina, el muérdagoenano (Phoradendron villosum), barrenadores, defoliadores y sobrepastoreo. Entre los abióticos causantes de estrés ymuerte, destacaron los daños ocasionadospor las bajas temperaturas-falta de aguay fuego. Con base en su incidencia, P.cinnamomi, H. antropunctatum y las bajastemperaturas-falta de agua son considerados los factores de mayor importanciaen la declinación y muerte del encino. P.cinnamomi fue identificado en cuatro delos diez sitios, particularmente de Colimay Jalisco; H. antropunctatum fué detectadoen seis de diez, principalmente en losrodales de Nayarit y Aguascalientes. Loscancros de troncos (rajaduras), debido a lasbajas temperaturas-falta de agua, seobservaron en cuatro sitios, afectando al52% de los árboles en Aguascalientes y24% en Guanajuato. Se concluye que P.cinnamomi está ocasionando la muertede algunas especies de encino, H.antropunctatum está coloni-zando árbolesdebilitados y las bajas temperaturas-faltade agua están participando como agentescausantes de estrés y muerte en algunoscasos

A Stepped Wedge, Cluster-Randomized Trial of a Household UV-Disinfection and Safe Storage Drinking Water Intervention in Rural Baja California Sur, Mexico

In collaboration with a local non-profit organization, this study evaluated the expansion of a program that promoted and installed Mesita Azul, an ultraviolet-disinfection system designed to treat household drinking water in rural Mexico. We conducted a 15-month, cluster-randomized stepped wedge trial by randomizing the order in which 24 communities (444 households) received the intervention. We measured primary outcomes (water contamination and diarrhea) during seven household visits. The intervention increased the percentage of households with access to treated and safely stored drinking water (23–62%), and reduced the percentage of households with Escherichia coli contaminated drinking water (risk difference (RD): −19% [95% CI: −27%, −14%]). No significant reduction in diarrhea was observed (RD: −0.1% [95% CI: −1.1%, 0.9%]). We conclude that household water quality improvements measured in this study justify future promotion of the Mesita Azul, and that future studies to measure its health impact would be valuable if conducted in populations with higher diarrhea prevalence

Estimation of treatment efficacy with complier average causal effects (CACE) in a randomized stepped wedge trial.

Complier average causal effects (CACE) estimate the impact of an intervention among treatment compliers in randomized trials. Methods used to estimate CACE have been outlined for parallel-arm trials (e.g., using an instrumental variables (IV) estimator) but not for other randomized study designs. Here, we propose a method for estimating CACE in randomized stepped wedge trials, where experimental units cross over from control conditions to intervention conditions in a randomized sequence. We illustrate the approach with a cluster-randomized drinking water trial conducted in rural Mexico from 2009 to 2011. Additionally, we evaluated the plausibility of assumptions required to estimate CACE using the IV approach, which are testable in stepped wedge trials but not in parallel-arm trials. We observed small increases in the magnitude of CACE risk differences compared with intention-to-treat estimates for drinking water contamination (risk difference (RD) = -22% (95% confidence interval (CI): -33, -11) vs. RD = -19% (95% CI: -26, -12)) and diarrhea (RD = -0.8% (95% CI: -2.1, 0.4) vs. RD = -0.1% (95% CI: -1.1, 0.9)). Assumptions required for IV analysis were probably violated. Stepped wedge trials allow investigators to estimate CACE with an approach that avoids the stronger assumptions required for CACE estimation in parallel-arm trials. Inclusion of CACE estimates in stepped wedge trials with imperfect compliance could enhance reporting and interpretation of the results of such trials

UVC inactivation of MS2-phage in drinking water – Modelling and field testing

UVC disinfection has been recognised by the WHO as an effective disinfection treatment to provide decentralized potable water. Under real conditions there are still unknowns that limit this application including the influence of suspended solids and natural organic matter. This work aims to investigate the influence of two key parameters, suspended solids and natural organic matter, on the efficiency of UVC disinfection of surface water to achieve the drinking water quality requirements established by the WHO for point of use (POU) technologies. Kaolinite (turbidity agent) and humic acids (HA, model of organic matter) were used in a factorial design of experiments (Turbidity from 0 to 5 NTU, and HA from 0 to 3.5 mg/L) to investigate their effect on UVC inactivation of MS2 phage in surface water. A collimated beam (12 W) and a commercial UVC disinfection flow system (16 W) designed to provide drinking water at households were used. The UVC flow system both in the laboratory and in the field was able to achieve the reduction requirements established by WHO (LRV >3.5 for all tested conditions), confirming the good performance of the studied UVC disinfection system. The results found in the lab were used to establish a numerical model that predicts the disinfection rate constant as a function of water turbidity and transmittance at 254 nm (confidence level>95%). The model permitted to elucidate the critical effect of low concentrations of HA in reducing the inactivation rate by 40% for 3.5 mg/L-HA compared with 0, the non-significant detrimental effect of turbidity lower than 5 NTU, and the lack of synergistic effects between both parameters at these levels. The UVC flow system was also tested in the field, in Tzabalho, Chiapas (Mexico), and Antioquia (Colombia), with spiked MS2 into natural surface water. This investigation opens a potential application to monitor the performance of UVC systems with surface water by monitoring transmittance at 254 nm as a tool to control UVC domestic systems to deliver safe drinking water in a household without the need of expensive and laborious biological monitoring tools

A Stepped Wedge, Cluster-Randomized Trial of a Household UV-Disinfection and Safe Storage Drinking Water Intervention in Rural Baja California Sur, Mexico

In collaboration with a local non-profit organization, this study evaluated the expansion of a program that promoted and installed Mesita Azul, an ultraviolet-disinfection system designed to treat household drinking water in rural Mexico. We conducted a 15-month, cluster-randomized stepped wedge trial by randomizing the order in which 24 communities (444 households) received the intervention. We measured primary outcomes (water contamination and diarrhea) during seven household visits. The intervention increased the percentage of households with access to treated and safely stored drinking water (23–62%), and reduced the percentage of households with Escherichia coli contaminated drinking water (risk difference (RD): −19% [95% CI: −27%, −14%]). No significant reduction in diarrhea was observed (RD: −0.1% [95% CI: −1.1%, 0.9%]). We conclude that household water quality improvements measured in this study justify future promotion of the Mesita Azul, and that future studies to measure its health impact would be valuable if conducted in populations with higher diarrhea prevalence

Estimation of treatment efficacy with complier average causal effects (CACE) in a randomized stepped wedge trial.

Complier average causal effects (CACE) estimate the impact of an intervention among treatment compliers in randomized trials. Methods used to estimate CACE have been outlined for parallel-arm trials (e.g., using an instrumental variables (IV) estimator) but not for other randomized study designs. Here, we propose a method for estimating CACE in randomized stepped wedge trials, where experimental units cross over from control conditions to intervention conditions in a randomized sequence. We illustrate the approach with a cluster-randomized drinking water trial conducted in rural Mexico from 2009 to 2011. Additionally, we evaluated the plausibility of assumptions required to estimate CACE using the IV approach, which are testable in stepped wedge trials but not in parallel-arm trials. We observed small increases in the magnitude of CACE risk differences compared with intention-to-treat estimates for drinking water contamination (risk difference (RD) = -22% (95% confidence interval (CI): -33, -11) vs. RD = -19% (95% CI: -26, -12)) and diarrhea (RD = -0.8% (95% CI: -2.1, 0.4) vs. RD = -0.1% (95% CI: -1.1, 0.9)). Assumptions required for IV analysis were probably violated. Stepped wedge trials allow investigators to estimate CACE with an approach that avoids the stronger assumptions required for CACE estimation in parallel-arm trials. Inclusion of CACE estimates in stepped wedge trials with imperfect compliance could enhance reporting and interpretation of the results of such trials

Structure of neutron-rich Br and Nb nuclei populated in fission experiments

International audienceSpectroscopic information on exotic Br and Nb nuclei, with odd and even masses around A=100, respectively, was obtained by analyzing fission fragments data collected with AGATA+VAMOS++ at GANIL and the FIPPS spectrometer at ILL. The complementarity of these two state-of-the art setups has been used, for the first time, to investigate the structure of these neutron-rich fission fragments via gamma-ray spectroscopy. Details on the two fission experiments will be given, as well as examples of high-resolution gamma-ray spectra used for the reconstruction of the level schemes. The active fission target, used in the neutron-induced fission experiment at ILL, allowed for high-statistics prompt-delayed coincidences for the analysis of a new isomeric state in $^{100}$Nb. Evidence for a spherical isomeric state in $^{100}$Nb will be shown and discussed within the systematic of neighbouring nuclei