Removal of trihalomethane precursors in drinking water treatment processes.

In this study the removal efficiency of humic substances by conventional drinking water treatment processes was studied in a full scale operating plant in Windsor, Ontario, Canada over a period of 16 months. A comparison of the removal efficiency of humic substances between conventional and advanced treatment processes such as ozonation (used as an oxidant before filtration) and the addition of granular activated carbon (GAC) was also carried out for the same water source (Detroit River) in a pilot scale treatment plant at the same location. The performance of different treatment processes in removing humic substances was evaluated through the quantification of humic substances and their apparent molecular size distributions (AMSD) in samples taken from the raw water and after each treatment process. The dissolved organic carbon (DOC) and the concentration of the non-humic substances for the water source (Detroit River) were also determined. Results indicate that seasonal variations in humic substances concentration occurred, showing a maximum level during the month of April when the spring turn-over of water bodies took place. These seasonal variations were associated with the corresponding changes in THM concentrations observed during the same period. The fulvic and humic acid composition of humic substances and their THM formation potential (THMFP) were quantified. Their AMSD were determined by the gel permeation chromatography (GPC) and the high performance size exclusion chromatography (HPSEC). The humic substances from the Detroit River were found to be less reactive in forming THMs ($\mu$g THM/mg C) when compared with the standard humic substances provided by the International Humic Substances Society (IHSS). Coagulation-sedimentation was the most efficient process of the conventional treatment options in the removal of humic substances. The GAC greatly improved the removal efficiency of not only the humic substances but also of a large fraction of the non-humic substances. The removal of humic substances by the use of ozone as an oxidant before filtration was similar to that obtained by the conventional treatment with prechlorination. The THMFP was determined on water samples from different processes and on their corresponding non-humic fractions. Precursor removal after each process effectively reduced the THMFP in the treated water. The non-humic fractions appeared to be potential contributors to the formation of THMs for high chlorine dosages. Source: Dissertation Abstracts International, Volume: 56-01, Section: B, page: 0389. Adviser: Nihar Biswas. Thesis (Ph.D.)--University of Windsor (Canada), 1994

Des conflits socio-environnementaux aux vulnérabilités sociétales liés à l'eau au Mexique (Puebla-Chihuahua) : première approche par l'analyse de la presse quotidienne régionale (PQR)

International audienceAu Mexique, au cours des dernières décennies, les cas de conflits liés à l’eau se sont multipliés entraînant de fortes mobilisations sociales. L’étude de ces conflit présente un intérêt dans le sens où ces conflits traduisent ou génèrent une vulnérabilité : leur connaissance, ainsi que celle des facteurs associés, peut aider à la réduction de cette vulnérabilité. Le travail présenté s’appuie sur l’étude deux régions du Mexique (Puebla et Chihuahua) jugées pertinentes et intéressantes pour l’étude des conflits du fait de leurs conditions naturelles (disponibilité, accessibilité, qualité naturelle) et de leurs dynamiques (évolution démographique, diversité des usages et des acteurs liés à l’eau, etc.). Il s’appuie sur l’analyse des conflits présentés dans la presse quotidienne régionale (analyses qualitatives d’articles de presse de janvier 2011-avril 2013, sur la base d’une grille d’analyse diagnostic du conflit : causes, manifestation, acteurs, secteurs agricoles/industriels/urbains, etc.). Il permet de dresser un tableau local et ponctuel de conflits liés à l’eau, de mettre en évidence le rôle des interactions entre dynamiques environnementales, pratiques locales et politiques publiques à l’échelle des estados, et, enfin, de mettre en avant certaines initiatives locales ou interventions institutionnelles permettant la résolution de conflits vers une réduction de la vulnérabilité ou à contrario le blocage et l’accentuation de la vulnérabilité

VAMOS A QUEDAR Vulnérabilités, Aléas Au Mexique : Obstacles et Stratégies en QUêtes à Durango d'Approches de Résiliences.

International audienc

Occurrence and treatment of arsenic in groundwater and soil in northern Mexico and southwestern USA

This review focuses on the occurrence and treatment of arsenic (As) in the arid region of northern Mexico (states of Chihuahua and Coahuila) and bordering states of the southwestern US (New Mexico, Arizona, and Texas), an area known for having high As concentrations. Information assembled and assessed includes the content and probable source of As in water, soil, and sediments and treatment methods that have been applied in the area. High As concentrations were found mainly in groundwater, their source being mostly from natural origin related to volcanic processes with significant anthropogenic contributions near mining and smelting of ores containing arsenic. The affinity of As for solid phases in alkaline conditions common to arid areas precludes it from being present in surface waters, accumulating instead in sediments and shifting its threat to its potential remobilization in reservoir sediments and irrigation waterways. Factors such as oxidation and pH that affect the mobility of As in the subsurface environment are mentioned. Independent of socio-demographic variables, nutritional status, and levels of blood lead, cognitive development in children is being affected when exposed to As. Treatments known to effectively reduce As content to safe drinking water levels as well as those that are capable of reducing As content in soils are discussed. Besides conventional methods, emergent technologies, such as phytoremediation, offer a viable solution to As contamination in drinking water

A spatial application of the water poverty index (WPI) in the State of Chihuahua, Mexico

International audienc

Emerging mitigation needs and sustainable options for solving the arsenic problems of rural and isolated urban areas in Latin America - a critical analysis

In this work, current information about the contamination of ground- and surface-water resources by arsenic from geogenic sources in Latin America is presented together with possible emerging mitigation solutions. The problem is of the same order of magnitude as other world regions, such as SE Asia, but it is often not described in English. Despite the studies undertaken by numerous local researchers, and the identification of proven treatment methods for the specific water conditions encountered, no technologies have been commercialized due to a current lack of funding and technical assistance.Emerging, low-cost technologies to mitigate the problem of arsenic in drinking water resources that are suitable for rural and urban areas lacking centralized water supplies have been evaluated. The technologies generally use simple and low-cost equipment that can easily be handled and maintained by the local population. Experiences comprise (i) coagulation/filtration with iron and aluminum salts, scaled-down for small community- and household-scale-applications, (ii) adsorption techniques using low-cost arsenic sorbents, such as geological materials (clays, laterites, soils, limestones), natural organic-based sorbents (natural biomass), and synthetic materials. TiO2-heterogeneous photocatalysis and zerovalent iron, especially using nanoscale particles, appear to be promising emergent technologies. Another promising innovative method for rural communities is the use of constructed wetlands using native perennial plants for arsenic rhizofiltration. Small-scale simple reverse osmosis equipment (which can be powered by wind or solar energy) that is suitable for small communities can also be utilized.The individual benefits of the different methods have been evaluated in terms of (i) size of the treatment device, (ii) arsenic concentration and distribution of species, chemical composition and grade of mineralization in the raw water, (iii) guidelines for the remaining As concentration, (iv) economical constrains, (v) complexity of installation and maintenance, and infrastructure constraints (e.g. electricity needs)

Co-occurrence of arsenic and fluoride in groundwater of semi-arid regions in Latin America: genesis, mobility and remediation

Several million people around the world are currently exposed to excessive amounts of arsenic (As) and fluoride (F) in their drinking water. Although the individual toxic effects of As and F have been analyzed, there are few studies addressing their co-occurrences and water treatment options. Several studies conducted in arid and semi-arid regions of Latin America show that the co-occurrences of As and F in drinking water are linked to the volcaniclastic particles in the loess or alluvium, alkaline pH, and limited recharge. The As and F contamination results from water–rock interactions and may be accelerated by geothermal and mining activities, as well as by aquifer over-exploitation. These types of contamination are particularly pronounced in arid and semi-arid regions, where high As concentrations often show a direct relationship with high F concentrations. Enrichment of F is generally related to fluorite dissolution and it is also associated with high Cl, Br, and V concentrations. The methods of As and F removal, such as chemical precipitation followed by filtration and reverse osmosis, are currently being used at different scales and scenarios in Latin America. Although such technologies are available in Latin America, it is still urgent to develop technologies and methods capable of monitoring and removing both of these contaminants simultaneously from drinking water, with a particular focus towards small-scale rural operations

Seven potential sources of arsenic pollution in Latin America and their environmental and health impacts

This review presents a holistic overview of the occurrence, mobilization, and pathways of arsenic (As) from predominantly geogenic sources into different near-surface environmental compartments, together with the respective reported or potential impacts on human health in Latin America. The main sources and pathways of As pollution in this region include: (i) volcanism and geothermalism: (a) volcanic rocks, fluids (e.g., gases) and ash, including large-scale transport of the latter through different mechanisms, (b) geothermal fluids and their exploitation; (ii) natural lixiviation and accelerated mobilization from (mostly sulfidic) metal ore deposits by mining and related activities; (iii) coal deposits and their exploitation; (iv) hydrocarbon reservoirs and co-produced water during exploitation; (v) solute and sediment transport through rivers to the sea; (vi) atmospheric As (dust and aerosol); and (vii) As exposure through geophagy and involuntary ingestion. The two most important and well-recognized sources and mechanisms for As release into the Latin American population's environments are: (i) volcanism and geothermalism, and (ii) strongly accelerated As release from geogenic sources by mining and related activities. Several new analyses from As-endemic areas of Latin America emphasize that As-related mortality and morbidity continue to rise even after decadal efforts towards lowering As exposure. Several public health regulatory institutions have classified As and its compounds as carcinogenic chemicals, as As uptake can affect several organ systems, viz. dermal, gastrointestinal, peptic, neurological, respiratory, reproductive, following exposure. Accordingly, ingesting large amounts of As can damage the stomach, kidneys, liver, heart, and nervous system; and, in severe cases, may cause death. Moreover, breathing air with high As levels can cause lung damage, shortness of breath, chest pain, and cough. Further, As compounds, being corrosive, can also cause skin lesions or damage eyes, and long-term exposure to As can lead to cancer development in several organs

Clínica Integrada - ME210 - 202101

Curso de especialidad, de la carrera de medicina, de carácter teórico- práctico del ciclo 7, en el que los estudiantes integran conocimientos previos con la anamnesis, el examen físico y establecen el diagnostico por síndromes o problemas y el plan de trabajo. El curso de Clínica integrada busca desarrollar las competencias generales de comunicación escrita y comunicación oral(nivel 2) y las competencias específicas de práctica clínica-diagnóstico (nivel 2) y profesionalismo-sentido ético y legal y responsabilidad profesional(nivel 2). La integración de conocimientos en la historia clínica, permitirá al estudiante, plantear un adecuado diagnóstico, plan de trabajo para la atención de su futuro paciente