Enhanced treatment of perfluoroalkyl acids in groundwater by membrane separation and electrochemical oxidation

This work explores the treatment of poly- and perfluoroalkyl acids (PFAAs) in groundwater by coupling membrane separation and electrochemical oxidation (ELOX). A process system engineering approach based on modelling and empirical data was followed. Two nanofiltration (NF90) and reverse osmosis (BW30) membranes were characterized for treating an electrolyte (NaCl and CaSO4) mixture of perfluorocarboxylic acids (PFCAs) containing PFOA, PFHpA, PFHxA, PFPeA and PFBA with initial concentrations of 10 µg L−1 each. Membrane surface charge shielding and concentration polarization negatively influenced NF90 performance, and the BW30 membrane was selected. Electrochemical oxidation with boron doped diamond anodes treated the PFCAs mixture amended with PFOS and 6:2 FTSA, emulating previously pre-concentrated feed and non-preconcentrated feed conditions. Working at different current densities (J) between 20 and 350 A m−2, the removal of PFOA, PFOS and 6:2 FTSA followed first order apparent kinetics, although shorter chain PFCAs initially showed increasing trends because of their simultaneous electrogeneration and degradation. Overall, ΣPFAA electrolysis followed first order kinetics linearly correlated to J in the full range of testing. Unexpectedly, PFAAs electrolysis was faster for the low conductive non-preconcentrated feed, a result that was ascribed to the enhanced direct electron transfer mechanism resulting from the higher cell voltage. For 99.9% PFAAs removal, the total specific cost of treatment was minimized using a cascade of four RO stages and ELOX treatment of the concentrate, to reach ΣPFAA below the Health Advisory Levels recommended by the USEPA in drinking water (<70 ng L−1 sum of PFOA and PFOS).Financial support by the Spanish Ministry of Economy and Compet- itiveness through projects CTM2016-75509-R (MINECO, SPAIN-FEDER 2014-2020) and PID2019-105827RB-I00 (AEI, Spain) is gratefully acknowledged

BDD anodic treatment of 6:2 fluorotelomer sulfonate (6:2 FTSA). Evaluation of operating variables and by-product formation

The concerns about the undesired impacts on human health and the environment of long chain perfluorinated alkyl substances (PFASs) have driven industrial initiatives to replace PFASs by shorter chain fluorinated homologues. 6:2 fluorotelomer sulfonic acid (6:2 FTSA) is applied as alternative to PFOS in metal plating and fluoropolymer manufacture. This study reports the electrochemical treatment of aqueous 6:2 FTSA solutions on microcrystalline BDD anodes. Bench scale batch experiments were performed, focused on assessing the effect of the electrolyte and the applied current density (5-600 A m-2) on the removal of 6:2 FTSA, the reduction of total organic carbon (TOC) and the fluoride release. Results showed that at the low range of applied current density (J=50 A m-2), using NaCl, Na2SO4 and NaClO4, the electrolyte exerted a minimal effect on removal rates. The formation of toxic inorganic chlorine species such as ClO4- was not observed. When using Na2SO4 electrolyte, increasing the applied current density to 350-600 A m-2 promoted a notable enhancement of the 6:2 FTSA removal and defluorination rates, pointing to the positive contribution of electrogenerated secondary oxidants to the overall removal rate. 6:2 FTSA was transformed into shorter-chain PFCAs, and eventually into CO2 and fluoride, as TOC reduction was >90%. Finally, it was demonstrated that diffusion in the liquid phase was controlling the overall kinetic rate, although with moderate improvements due to secondary oxidants at very high current densities.Support from MINECO and SPAIN-FEDER 2014–2020 to project CTM2016-75509-R and to the Spanish Excellence Network E3TECH (CTQ2015-71650-RDT) is acknowledged. J. Carrillo-Abad thanks the Generalitat Valenciana for granting a post doctoral fellowship (APOSTD/2015/019). The authors are thankful to Dr. R. Buck (Chemours Co.) for kindly providing samples of Capstone FS10

Efficient treatment of perfluorohexanoic acid by nanofiltration followed by electrochemical degradation of the NF concentrate

The present study was aimed at the development of a strategy for removing and degrading perfluorohexanoic acid (PFHxA) from industrial process waters at concentrations in the range 60–200 mg L-1. The treatment train consisted of nanofiltration (NF) separation followed by electrochemical degradation of the NF concentrate. Using a laboratory-scale system and working in the total recirculation mode, the DowFilm NF270 membrane provided PFHxA rejections that varied in the range 96.6–99.4% as the operating pressure was increased from 2.5 to 20 bar. The NF operation in concentration mode enabled a volume reduction factor of 5 and increased the PFHxA concentration in the retentate to 870 mg L-1. Results showed that the increase in PFHxA concentration and the presence of calcium sulfate salts did not induce irreversible membrane fouling. The NF retentate was treated in a commercial undivided electrochemical cell provided with two parallel flow-by compartments separated by bipolar boron doped diamond (BDD) electrode, BDD counter anode, and counter cathode. Current densities ranging from 20 to 100 A m-2 were examined. The electrochemical degradation rate of PFHxA reached 98% and was accompanied by its efficient mineralization, as the reduction of total organic carbon was higher than 95%. Energy consumption, which was 15.2 kWh m-3 of treated NF concentrate, was minimized by selecting operation at 50 A m-2. While most of the previous research on the treatment of perfluoroalkyl substances (PFASs) focused on the removal of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), these compounds have been phased out by chemical manufacturers. Our findings are relevant for the treatment of PFHxA, which appears to be one of the present alternatives to long-chain PFASs thanks to its lower bioaccumulative potential than PFOA and PFOS. However, PFHxA also behaves as a persistent pollutant. Moreover, our results highlight the potential of combining membrane separation and electrochemical oxidation for the efficient treatment of PFAS-impacted waters.Financial support from projects CTM2013-44081-R and CTM2016-75509-R (MINECO, SPAIN-FEDER 2014e2020) is gratefully acknowledged

Membrane preconcentration as an efficient tool to reduce the energy consumption of perfluorohexanoic acid electrochemical treatment

One of the key points for the large-scale implementation of electrochemical water treatment technologies lies in the need of reducing the energy consumption. The present work analyzes the removal of persistent perfluorohexanoic acid (PFHxA, 204 mg L−1) from industrial process waters using a strategy that combines membrane pre-concentration followed by electrooxidation of the concentrate. A mathematical model describing the nanofiltration (NF) system was developed and complemented with new and background experimental data of PFHxA and ion species rejections and total permeate flux through the NF270 and NF90 membranes. Similarly, the kinetics of PFHxA electrolysis on boron doped diamond anodes was determined at laboratory scale. Later, the model was used to simulate the NF-ELOX integrated process, where a commercial spiral wound unit (membrane area 7.6 m2) was implemented and the electrooxidation unit was scaled-up to pilot plant (anode area 1.05 m2). The obtained energy savings depended on a combination of the target PFHxA removal ratio at the end of the treatment train, the separation performance of the commercial membrane and the reduction of the electrolyte ohmic resistance in the electrooxidation stage, that was attained as a result of the increase of salts content in the concentrate. Only the tight NF90 membrane allowed to achieve high (99%) PFHxA removal ratios in the integrated NF-ELOX process, and the specific energy consumption was estimated at 11.6 kWh m−3, 59.2% less than when electrolysis alone was applied. Still, the electrolysis is the most energy demanding step, with 85.9% contribution to the total energy consumption. The strategy of combining membrane pre-concentration with electrochemical degradation could be extended to the treatment of other highly persistent organic compounds.Financial support from projects CTM2013-44081-R, CTM2016-75509-R and CTQ2016-75158-R (MINECO, SPAIN-FEDER 2014–2020) and to the Spanish Excellence Network E3TECH (CTQ2015-71650-RDT) is gratefully acknowledged

EL TLC CON ESTADOS UNIDOS: EFECTOS Y RETOS PARA LA CADENA LÁCTEA DE NARIÑO

En este artículo se presenta una descripción general de la Cadena Láctea en Colombia y en la cuenca lechera del departamento de Nariño e igualmente se mencionan las posibles consecuencias que se derivarán, para este importante sector de la economía regional, cuando entren en vigencia los puntos acordados en el Tratado de Libre Comercio con los Estados Unidos. Como elementos imprescindibles para el análisis se incluyen los indicadores que determinan, en buena medida, la competitividad del renglón lácteo de Colombia y Nariño, los contingentes asignados a cada país, las condiciones acordadas para el libre comercio de productos lácteos, las potencialidades de los productos colombianos, los problemas y dificultades que actualmente limitan la productividad en Nariño y los retos que tendrán que afrontar todos los eslabones de la cadena láctea por efecto del TLC

Relationship of the compositional content and sanitary quality of Holstein cows’ milk of the high tropic of Nariño

Agricultural production seeks to obtain high quality, safe products for human consumption- a great concern for the dairy chain. The present investigation seeks to identify the correlation between the compositional and sanitary quality of raw milk (SCC/mL). The investigation was carried out in three districts of the Department of Nariño, Colombia. For this purpose, sampling and information collection was executed throughout the years 2016 and 2017. To determine the relationship between composition and sanitary quality, an analysis was made of the principal components of the milk, and a design of mixed models was creating using selected variables. The analysis showed that there is a relationship between the compositional variables, and the mixed model indicated that there is a significant relationship between the somatic cell count and the milk quality of the region. It was concluded that a somatic cell count above 500,000 CFU/mL has negative effects on protein, casein, and milk production

Validity evidence of the Alcohol, Smoking and Substance Involvement Screening Test (ASSIST) in Chile

El objetivo del estudio fue analizar la validez de la versión chilena de un instrumento para la identificación de diferentes niveles de riesgo asociado al consumo de alcohol, tabaco, marihuana y cocaína (Alcohol, Smoking and Substance Involvement Screening Test, ASSIST). Se evaluó la fiabilidad y consistencia del instrumento además de la validez concurrente y discriminante. La muestra fue de 400 usuarios de servicios de tratamiento drogas y alcohol ambulatorios y residenciales de la atención primaria de salud, comisarías y empresas. La consistencia interna obtenida fue alta (Alcohol α= .86. marihuana α= .84 y cocaína α= .90). El coeficiente de correlación intraclase (CCI) con la comparación test-retest fue buena para Alcohol (CCI = .66), marihuana (CCI = .74) y cocaína (CCI =.80). Se observó una buena correlación entre los puntajes del ASSIST el puntaje del AUDIT (r de Pearson = .85), ASI-Lite (r entre .66 y .83 para tabaco, alcohol, marihuana y cocaína) y SDS (r = .65). El punto de corte original para la detección del riesgo alto es de 27 puntos, sin embargo, considerando un mejor balance entre sensibilidad y especificidad se modificó ese corte a 21. Los resultados obtenidos en éste estudio demostraron las buenas propiedades psicométricas del ASSIST para la detección de distintos niveles de riesgo asociados al consumo de sustancias en población general de Chile.This study aims to psychometrically validate the Chilean version of the Alcohol, Smoking and Substance Involvement Screening Test ASSIST. Specifically, this study is interested in evaluating the reliability, consistency and concurrent and discriminant validity of this instrument. The sample was composed for a total of 400 people from four different settings: treatment centers (residential and ambulatories), primary health care, police stations and companies. The reliability of the ASSIST was high (α = .86 for Alcohol, α = .84 for marijuana and α = .90 for cocaine). The intra class correlation coefficient (ICC) with test-retest comparison was statistically significant for Alcohol (ICC = .66), marijuana (ICC = .74) and cocaine (ICC = .80). There were statistically significant correlations between the ASSIST and the AUDIT score (Pearson?s r = .85), the ASSIST and the ASI-Lite score (r between .66 and .83 for tobacco, alcohol, marijuana and cocaine), and the ASSIST and the SDS score (r = .65). The original cutoff point for high risk detection was 27 points, however, in order to have a better balance between sensitivity and specificity the cut was changed to 21 points. The ASSIST presents good psychometric properties and therefore is a reliable and valid instrument to be used as a mechanism to detect risk levels of substance use in the Chilean population.Fil: Soto Brandt, Gonzalo. Servicio Nacional para la Prevención y Rehabilitación del Consumo de Drogas y Alcohol; ChileFil: Portilla Huidobro, Rodrigo. Servicio Nacional para la Prevención y Rehabilitación del Consumo de Drogas y Alcohol; ChileFil: Huepe Artigas, David. Universidad Diego Portales; ChileFil: Rivera Rei, Álvaro. Universidad Diego Portales; ChileFil: Escobar, María Josefina. Universidad Diego Portales; ChileFil: Salas Guzmán, Natalia. Universidad Diego Portales; ChileFil: Canales Johnson, Andrés. Universidad Diego Portales; ChileFil: Ibáñez Barassi, Agustín Mariano. Universidad Diego Portales; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Martínez Guzmán, Claudio. Universidad Diego Portales; ChileFil: Castillo Carniglia, Álvaro. Servicio Nacional para la Prevención y Rehabilitación del Consumo de Drogas y Alcohol; Chil

El ultrasonido gástrico en la determinación del estado prandial preoperatorio

Introduction: Gastric content aspiration represents the main cause of death related to anesthesia. Gastric ultrasound seems to be useful for studying gastric content, especially in situations where fasting conditions do not exist or are unknown. Objective: To describe the usefulness of ultrasound for the evaluation of gastric content. Methods: A structured search was carried out with the descriptors: fasting; anesthesia; general anesthesia; ultrasounds, ultrasonography, stomach (MeSH), in the databases: Pubmed, Embase, SciELO and Cochrane Library. Results: About 29 articles were found with relevant information for the development of this review. Conclusions: Although gastric ultrasound appears to be a useful technique for the study of gastric content, the impact that this may have on the incidence of pneumonic aspiration is unknown, so more studies are needed to promote its routine use in clinical practice.  Introducción: La aspiración de contenido gástrico representa la principal causa de muerte relacionada con la anestesia. El ultrasonido gástrico parece ser útil para el estudio del contenido gástrico, en especial en situaciones donde no existen o se desconocen las condiciones de ayuno. Objetivo: Describir la utilidad del ultrasonido para la valoración del contenido gástrico preoperatorio.   Metodología: Se realizó una búsqueda estructurada en las bases de datos Pubmed, Embase, SciELO y Cochrane Library con los descriptores fasting; anesthesia; anesthesia, general; ultrasonics, ultrasonography, stomach (MeSH) Resultados: Se encontraron alrededor de 29 artículos con información relevante para el desarrollo de la presente revisión. Conclusiones: Aunque el ultrasonido gástrico parece ser una técnica útil para el estudio del contenido gástrico, se desconoce su impacto en  la incidencia de aspiración neumónica, por lo que se necesitan más estudios para promover su uso rutinario en la práctica clínica