ABSTRACT
Abstract Potable water supply and sanitization in rural areas in developing countries are still inadequate. The main risk associated with unsafe drinking water is the infection with pathogenic microorganisms. Objective: In this study, we investigate the bacterial diversity and the potentially pathogenic bacteria in water samples from diffe rent points of distribution in three rural villages from the Andean region of Colombia. Methods: Illumina libraries for water samples were prepared and sequenced using 300 bp paired-end MiSeq protocol, the bioinformatic analyses were performed with Mothur pipeline and the phyloseq package in Rstudio. Results: The mi crobial community composition showed statistically significant differences according to the village and the sample origin. Alpha, Beta, and Gammaproteobacteria were the dominant class detected in all water samples. The most relevant pathogenic genera detected in the surface were Legionella, Mycobacterium, Yersinia, Burkholderia, and Rickettsia. In the tap water samples, potential pathogens like Streptococcus, Staphylococcus, Corynebacterium, Nocardia, and Escherichia/Shige lla were detected.
Resumen El suministro y potabilización del agua de consumo humano en las zonas rurales de los países en vías de desarrollo sigue siendo limitado. El principal riesgo asociado con el uso de agua no potable es la infección con microorganismos patógenos. Objetivo: En este estudio se investigó la diversidad bacteriana y la presencia de bacterias potencialmente patógenas en muestras de agua de diferentes puntos de distribución en tres asentamientos rurales de la región andina de Colombia. Métodos: Se prepararon y secuenciaron bibliotecas de amplicones (rDNA 16S) para muestras de agua utilizando la plataforma Illumina MiSeq con lecturas pareadas de 300 bases. Los análisis bioinformáticos se realizaron con el programa Mothur y el paquete estadístico Phyloseq en Rstudio. Resultados: La composición de la comunidad microbiana mostró diferencias estadísticamente significativas según el sitio y el origen de la muestra. Alfa, Beta y Gammaproteobac terias fueron las clase dominantes detectadas en todas las muestras de agua. Los géneros patógenos más relevantes detectados fueron Legionella, Mycobacterium, Yersinia, Burkholderia y Rickettsia. En las muestras de agua del grifo se detectaron patógenos potenciales como Streptococcus, Staphylococcus, Corynebacterium, Nocardia y Escherichia /Shigella.
ABSTRACT
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.
Subject(s)
Drinking Water , Water Purification , Disinfection , Levivirus , Ultraviolet RaysABSTRACT
In this study, disinfection of urban wastewater (UWW) with two solar processes (H2O2 -20 mg/L and photo-Fenton 10 mg/L-Fe2+/20 mg/L-H2O2 at natural water pH) at pilot scale using a 60 L compound parabolic collector reactor for irrigation of two raw-eaten vegetables (lettuce and radish) has been investigated. Several microbial targets (total coliforms, Escherichia coli, Salmonella spp., and Enterococcus spp.) naturally occurring in UWW and 74 organic microcontaminants (OMCs) were monitored. Disinfection results showed no significant differences between both processes, showing the following inactivation resistance order: Salmonella spp. < E. coli < total coliforms < Enterococcus spp. Reductions of target microorganisms to concentrations below the limit of detection (LOD) was achieved in all cases with cumulative solar UV energy per volume (QUV) ranged from 12 to 40 kJ/L (90 min to 5 h). Solar photo-Fenton showed a reduction of 66% of OMCs and solar/H2O2 of 56% in 5 h treatment. Irrigation of radish and lettuce with solar treated effluents, secondary effluents, and mineral water was performed for 6 and 16 weeks, respectively. The presence of bacteria was monitored in surfaces and uptake of leaves, fruit, and also in soil. The bacterial concentrations detected were below the LOD in the 81.2% (lettuce) and the 87.5% (radish) of the total number of samples evaluated. Moreover, uptake of OMCs was reduced above 70% in crops irrigated with solar treated effluents in comparison with secondary effluents of UWW.
Subject(s)
Raphanus , Wastewater , Escherichia coli , Hydrogen Peroxide , LactucaABSTRACT
The interest in developing alternative water disinfection methods that increase the access to irrigation water free of pathogens for agricultural purposes is increasing in the last decades. Advanced Oxidation Processes (AOPs) have been demonstrated to be very efficient for the abatement of several kind of pathogens in contaminated water. The purpose of the current study was to evaluate and compare the capability of several solar AOPs for the inactivation of resistant spores of agricultural fungi. Solar photoassisted H2O2, solar photo-Fenton at acid and near-neutral pH, and solar heterogeneous photocatalysis using TiO2, with and without H2O2, have been studied for the inactivation of spores of Curvularia sp., a phytopathogenic fungi worldwide found in soils and crops. Different concentrations of reagents and catalysts were evaluated at bench scale (solar vessel reactors, 200mL) and at pilot plant scale (solar Compound Parabolic Collector-CPC reactor, 20L) under natural solar radiation using distilled water (DW) and real secondary effluents (SE) from a municipal wastewater treatment plant. Inactivation order of Curvularia sp. in distilled water was determined, i.e. TiO2/H2O2/sunlight (100/50mgL-1)>H2O2/sunlight (40mgL-1)>TiO2/sunlight (100mgL-1)>photo-Fenton with 5/10mgL-1 of Fe2+/H2O2 at pH3 and near-neutral pH. For the case of SE, at near neutral pH, the most efficient solar process was H2O2/Solar (60mgL-1); nevertheless, the best Curvularia sp. inactivation rate was obtained with photo-Fenton (10/20mgL-1 of Fe2+/H2O2) requiring a previous water adicification to pH3, within 300 and 210min of solar treatment, respectively. These results show the efficiency of solar AOPs as a feasible option for the inactivation of resistant pathogens in water for crops irrigation, even in the presence of organic matter (average Dissolved Organic Carbon (DOC): 24mgL-1), and open a window for future wastewater reclamation and irrigation use.
Subject(s)
Ascomycota/pathogenicity , Disinfection/methods , Sunlight , Wastewater/microbiology , Agricultural Irrigation , Hydrogen Peroxide/chemistry , Iron/chemistry , Plant Diseases/microbiology , Titanium/chemistry , Water PurificationABSTRACT
Un método analítico para el análisis de leche líquida sin pasteurizar para siete pesticidas fue desarrollado. El método involucra una extracción líquido-líquido y extracción en fase sólida, utilizando cartuchos de florisil para seis pesticidas organofosforados (diazinon, dimetoato, metilparation, malation, etilparation y sulprofos)y un piretroide (lamnda cihalotrina). Los limites de cuantificación fueron menores de 0.1ppm. La linealidad en el instrumento fue observada para todos los pesticidas con un valor máximo de 0.5 ppm. Las recuperaciones promedio para la leche fortificada se encontraron en un rango de 64 - 101 por ciento para los pesticidas organofosforados y del 55.3 por ciento para la piretrina
Subject(s)
Pesticides , Pesticide Utilization , Milk , Food ContaminationABSTRACT
El software DRYLABRGC es un simulador que optimiza las separaciones por cromatografía gaseosa. El software predice las separaciones en función de las condiciones experimentales. Las separaciones cromatográficas pueden ser predichas isotérmicas o con temperatura programada. Con el software se optimizó la separación de una mezcla de pesticidas organofosforados y una piretrina (diazinon, dimetoato, metil paration, paration, malation, sulprofos y lambda cihalotrina)
