Study on the Degradation of a Semi-Synthetic Lignin–Acrylic Acid Hydrogel with Common Bacteria Found in Natural Attenuation Processes

In this study, lignin was chemically modified to promote hydrogel degradation as a source of carbon and nitrogen for a bacterial consortium consisting of P. putida F1, B. cereus and, B. paramycoides. A hydrogel was synthesized using acrylic acid (AA), acrylamide (AM), and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and cross-linked with the modified lignin. The structural changes and mass loss in the hydrogel, as well as its final composition, were evaluated as functions of the growth of the selected strains in a culture broth with the powdered hydrogel. The average loss was 18.4% wt. The hydrogel was characterized using FTIR spectroscopy, scanning electronic microscopy (SEM), elemental analysis (EA), and thermogravimetric analysis (TGA) before and after bacterial treatment. FTIR showed that the carboxylic groups present in both the lignin and the acrylic acid of the hydrogel decreased during bacterial growth. The bacteria showed a preference for the biomaterial components of the hydrogel. SEM demonstrated superficial morphological changes in the hydrogel. The results reveal that the hydrogel was assimilated by the bacterial consortium while preserving the water retention capacity of the material and that the microorganisms carried out a partial biodegradation of the hydrogel. The results of the EA and TGA confirm that the bacterial consortium not only degraded the biopolymer (lignin), but also used the synthetic hydrogel as a carbon source to degrade its polymeric chains and modified original properties. This modification with lignin as a crosslinker (which is a waste product of the paper industry) is therefore proposed to promote hydrogel degradation

Modeling Fate and Transport of Nutrients and Heavy Metals in the Waters of a Tropical Mexican Lake to Predict Pollution Scenarios

The tropical lake Chapala is an important source of drinking water in western Mexico since it supplies ~65% of the water consumed in the urban city of Guadalajara. To obtain different pollution scenarios, the presence of pollutants in this waterbody was modeled using a coupled hydraulic and transport model. Two water sampling campaigns were modeled. The governing equations were applied using the routines RMA2 and RMA4 in the Surface-Water Modeling System (SMS) software V 8.1. Hydraulic and transport models were calibrated to describe the water level, velocity, and fate of pollutants. The numerical model showed satisfactory results for the simulated data, analyzed against water level, current velocity, and pollutants measurement data through the Relative Percentage Deviation (RPD), except for ~20% of the sites and the 12-month simulation periods. The hydraulic calibrations showed that the dispersion coefficients were higher for nutrients compared to metals, indicating that the nutrients are dispersed throughout the lake and have a stronger impact on the lake’s water quality. The hydraulic model simulations indicated the presence of points in the central-eastern zone, the lowest concentration of PO43−, which can be attributed to the presence of vortexing. The metal simulations indicated that the dissolved Ni was the best approximation to the measured values. This is the first study on Lake Chapala regarding the modeling fate and transport of pollutants in relation to the prediction of pollution scenarios

El reto del abastecimiento de agua potable. Calidad del agua y su gestión

México se considera un país con disponibilidad de agua suficiente para cubrir las necesidades de la población, con más de 4300 m3 por habitante; pero, tal cantidad debe ajustarse por su distribución temporal y espacial, y características locales como el crecimiento urbano y suburbano, y actividades productivas que demandan cada vez de agua potable y el consecuente incremento del volumen de agua residual. En este contexto, los factores locales que más reducen la disponibilidad de agua es la contaminación de los cuerpos de agua por descargas continuas del drenaje doméstico e industrial, o durante los periodos de lluvias por los escurrimientos que se generan de los terrenos con uso agropecuario e instalaciones ganaderas. Según la Secretaría de Medio Ambiente para el Desarrollo Sustentable (SEMADES), todos los municipios de las regiones Altos sur y Altos norte de Jalisco, presentan problemas de contaminación de agua superficial, al verter aguas residuales sin tratamiento a la red fluvial y por desechos de granjas; aunque los sistemas de producción agropecuaria también se han identificado como fuentes de contaminación no puntual para los cuerpos de agua superficial. Más dramática es la situación de estos recursos hídricos contaminados de la región Alteña que están planeados para utilizarse en ciudades como Guadalajara, en Jalisco o León, en Guanajuato; las regiones Altos sur y Altos norte también reportan problemas de sobreexplotación de acuíferos, acentuados por la extracción de aguas subterráneas profundas con alto contenido de flúor, selenio y arsénico, con el consecuente efecto negativo en la salud de la población que consuma esta agua. El Cuerpo Académico (CA) N° 561 “Calidad del agua” del Centro Universitario de los Altos de la Universidad de Guadalajara, desde su formación planteó en sus metas el desarrollar el conocimiento para participar en la solución de la problemática de la sustentabilidad hídrica y así cumplir con el compromiso adquirido con la población Alteña. El CA requiere de acciones como la vinculación e intercambio de experiencias con otros investigadores, cuerpos académicos similares, e inclusive, instituciones que tienen al recurso hídrico y sus procesos de contaminación y tratamiento, como tema central de estudio