Evaluation of electrode separators and the external resistance in electrochemically assisted constructed wetlands.

A proton exchange membrane increases the electrical performance of a microbial fuel cell (MFC). New inexpensive materials should be sought, especially in a constructed wetland microbial fuel cell (CW-MFC). Here, in a laboratory-scale system of five CW-MFCs, wet clay, wet earth or mud, and non-woven cloth were used as inexpensive separators with long-term stability. The five CW-MFCs were planted with Typha latifolia, fed with synthetic wastewater, and packed with natural porous material. Graphite felt was used as electrodes and the experimental system had a hydraulic residence time of 3 days, operating under shade and natural conditions of temperature and light. Electrodes were connected to current collectors (copper wire) and to an external resistance, with a change every 20 days, starting in open-circuit and following with 20000, 18000, 15000, 10000, 5600, 1000, 560, and 10 Ω. These laboratory-scale CW-MFCs reduced concentrations of nitrates, ammonium ion, and sulfates without inhibiting electricity production. Microbiological analyses indicated that anaerobic, facultative, aerobic, and denitrifying bacteria may have caused these reductions. The reactor with the live plant and with the wet earth or mud separator achieved the highest production of electricity (22.6 mW/m2), and may be worth further attention.

Stevia rebaudiana Bertoni, an American plant used as sweetener: Study of its effects on body mass control and glycemia reduction in Wistar male and female rats.

Stevia rebaudiana Bertoni water extracts have been used as a natural sweetener and customary medicine by the indigenous inhabitants of South America for several hundred years. This plant was sent to Europe in the 16th century and was described by Peter Jacob Esteve in Spain. Recently the food industry has started to employ S. rebaudiana as sweetener using its glycosides after purification. Advertisement claims that Stevia glycosides is good for controling body mass and reducing glycemia. This study's objective was to evaluate the effect of S. rebaudiana leaf extract on Wistar rats as animal model to prove its effectiveness on body mass control, glycemia reduction, and other biochemical parameters. Three groups were randomly formed with 24 males and 24 females: A blank group without any sweetener, a control group drinking water with 10% glucose, and the test group ingesting a 0.94% water extract of S. rebaudiana. Body mass measurements as well as food and drink consumption were daily performed. The experiment lasted 120 days after the specimens were weaned and got used to eating solid food. Euthanasia was done and blood serum was collected to evaluate the following biochemical parameters: Glucose, triglycerides, cholesterol, insulin, glucagon, leptin, ghrelin, and glucose-dependent insulinotropic peptide, GIP. Results indicated that only female rats had statistical differences in body mass gain. No relevant effects either positive or negative were found in the biochemical parameters measured. The crude extracts of S. rebaudiana did not show any relevant changes in biochemical and hormonal profiles, changes nor body mass with respect to the blank and control groups of young and healthy rats in the age range of infancy to youth. According to the results obtained, the therapeutic properties that have been associated to S. rebaudiana consumption especially for body mass control and glycemia reduction, did not occur in young and healthy male and female rats in equivalent age to infants, young children, and youths.

Chronic intake of nutritive sweeteners and saccharin increases levels of glycolytic and lipogenic enzymes in rat liver.

There are doubts about the impact of non-nutritive sweeteners consumption on lipogenic and glycolytic metabolism. Therefore, the objective was to determine the effects of chronic consumption of sweeteners on the activity levels of the enzymes glucokinase (GK), phosphofructokinase-1 (PFK-1), pyruvate kinase (PKL), acetyl coenzyme A carboxylase (ACC), and fatty acid synthase (FAS) in livers' extracts. Groups of male and female Wistar rats drank solutions of sweeteners for 480 days: Sucrose 10%, glucose 14%, fructose 7%, acesulfame K 0.05%, aspartame:acesulfame mixture 1.55%, sucralose 0.017%, saccharin 0.033%, and a control group. The enzymatic activity in livers' extracts was determined. Likewise, the levels of glucose, triglycerides, insulin, glucagon, and leptin were determined. In both genders, there were significant differences in the levels of enzymatic activity, hormonal, and biochemical parameters due to sweeteners consumption. The highest glycolytic and lipogenic enzyme activity levels were observed in the groups that ingested nutritive sweeteners and saccharin.

Principales microorganismos sulfato reductores (MSR) de reactores anaerobios alimentados con efluentes ácidos, una revisión bibliográfica / Main sulfate-reducing microorganisms (SRM) present in anaerobic reactors fed with acid effluents, a review

RESUMEN En esta investigación bibliográfica se encontraron reportes sobre una gran variedad de especies responsables de precipitar a cuatro metales de interés (Cu, Pb, Zn y Fe). En la mayoría de las investigaciones no solamente se considera la precipitación de estos metales, sino también la de otros elementos que están presentes en cada efluente estudiado. Los artículos aquí mencionados tienen una relación directa con el efluente proveniente de la operación unitaria de flotación. Aportan conocimiento acerca del proceso de sulfato-reducción, comprendiendo el mecanismo mediante microorganismos con características específicas, especialmente su versatilidad pues se desarrollan en diferentes ecosistemas. Se muestra que varias especies, como Desulfobacter o Desulfovibrio son comunes pues tienen condiciones relativamente sencillas para desarrollarse. Los microorganismos sulfato reductores (MSR) son eficientes para reducir la acidez del agua (de la operación unitaria de flotación de una mina, de cocinas, de corrientes marinas, etc.). También lo son para precipitar diferentes elementos pues no requieren de algún agente externo salvo en contadas ocasiones donde debe actuar un catalizador. Hay investigaciones sobre los nutrientes que deben adicionarse para incrementar su actividad. Los reportes de investigación revisados identificaron las variables a controlar para obtener buenos resultados en la remoción de metales y menores impactos en el ambiente. Es de gran importancia el desarrollo de proyectos que tomen en cuenta un sistema natural, como la degradación anaerobia, para alcanzar un punto en el cual la tecnología y el ambiente puedan complementarse logrando bienes de consumo necesarios para la población sin causar daños irreparables a la naturaleza.

ABSTRACT In this bibliographical research, reports were found on a great variety of species responsible for precipitating four metals of interest (Cu, Pb, Zn and Fe). In most of the investigations, not only the precipitation of these metals is considered, but also that of other elements that are present in each effluent studied. The items mentioned here have a direct relationship with the effluent from the flotation unit operation. They provide knowledge about the sulfate-reduction process, understanding the mechanism through microorganisms with specific characteristics, especially their versatility as they develop in different ecosystems. It is shown that several species, such as Desulfobacter or Desulfovibrio, are common because they have relatively simple conditions to develop. Sulfate-reducing microorganisms (SRM) are efficient in reducing the acidity of water (from the flotation unit operation of a mine, kitchens, ocean currents, etc.). They are also used to precipitate different elements since they do not require any external agent except on rare occasions when a catalyst must act. There is research on the nutrients that should be added to increase its activity. The research reports reviewed identified the variables to control to obtain good results in the removal of metals and less impact on the environment. The development of projects that take into account a natural system, such as anaerobic degradation, is of great importance in order to reach a point where technology and the environment can complement each other, achieving necessary consumer goods for the population without causing irreparable damage to nature.

Effects on weaned male Wistar rats after 104, 197, and 288 days of chronic consumption of nutritive and non-nutritive additives in water.

ABSTRACT: It has been suggested that the consumption of artificial sweeteners is related to greater body mass gain and diverse metabolic alterations. In this study, the effect of chronic consumption of nutritive sweeteners (fructose 7% and sucrose 10%) and non-nutritive or low-calorie sweeteners (acesulfame 0.015%, aspartame 0.3%, aspartame:acesulfame mixture 0.04%, saccharin 0.3%, and sucralose 0.19%), in drinking water, as well as a control group with no sweeteners, was evaluated. Body mass gain and glucose, insulin, triglycerides, and total cholesterol levels in blood were the parameters considered. For this purpose, 120 weaned male Wistar rats of the HsdHan:WIST line were used, 15 per group in first stage, then 10 and 5 per group for 2nd and 3rd stages, respectively. Body mass gain, food intake, and beverage consumption were daily quantified. After 104, 197, and 288 days of experimentation the concentrations of glucose, triglycerides, cholesterol, and insulin were determined. Only in the first stage there were significant differences in the body mass gain. In the three stages there were significant differences in the patterns of beverage intake and food consumption. The trend was the same in all 3 stages: rats drank more in the groups of drinks sweetened with nutritive sweeteners and ate more in the groups that drank non-nutritive artificial sweeteners. Regarding the biochemical profile, no sweetener either nutritive or non-nutritive caused that the serum levels of glucose, triglycerides, and cholesterol were at pathological levels. It is concluded that the sweeteners by themselves can modify certain biochemical parameters but not at a pathological level. Furthermore, by themselves they are not capable of triggering excess of body mass or obesity in the early and medium stages of life when consumed together with a balanced diet.

Consumption of sweeteners at different stages of life: effects on body mass, food and drink intake in male and female Wistar rats.

The consumption of non-nutritive sweeteners has increased in the last decades. However, there are doubts about its consumption and its impact on body mass and metabolic alterations. For this reason, this study investigates the effects of the consumption of nutritive and non-nutritive sweeteners on body mass in different life stages of male and female Wistar rats: Childhood, adolescence, young adult, adulthood, and aged. For this purpose, 8 groups of male and female rats were used (10 per group/gender): sucrose 10%, glucose 14%, fructose 7%, acesulfame K 0.05%, aspartame:acesulfame mixture 1.55%, sucralose 0.017%, saccharin 0.033%, and a control group. Only in aged male rats (504 days) there were significant differences in body mass. In both genders, there were differences in food, drink, and energy intake along all life stage. It is concluded that non-nutritive sweeteners when consumed together with a balanced diet did not cause a greater body mass gain.

Chitosan from shrimp residues with a saturated solution of calcium chloride in methanol and water.

Calcium chloride, methanol, and water in stoichiometric amounts were used for the extraction of chitosan from shrimp residues (Farfantepenaeus aztecus). Chitosan was characterized by FT-IR, TGA, XRD, SEM, elemental analysis, and 13C-NMR. The yield of chitosan with medium molecular mass was 65.90% (mass of extracted chitosan/mass of shrimp residues when the extraction was assisted with stirring at 60 °C for 20 min and ultrasound at 60 °C for 30 min. The extracted chitosan had a % DD of 64.06 and 65.87% (13C-NMR and FT-IR, respectively), thermal decomposition stage at 375 °C, porous on its surface, and calcite as the main mineral found. The experimental results revealed that the saturated solution of calcium chloride in methanol and water could be an alternative for the extraction of mineralized chitosan from shrimp residues with thermal stability and porosity.

Fate of mercury in a terrestial biological lab process using Polypogon monspeliensis and Cyperus odoratus.

Mercury has been extracted in Queretaro, Mexico since the 1960s. The mining wastes were open-air disposal and these mercury wastes have polluted the zone. The aim of this research was to evaluate mercury's fate in lab scale terrestrial reactors considering the following mercury species: soluble, interchangeable, strongly bound, organic, and residual ones. Soils were sampled in two former mines of Pinal de Amoles, Queretaro, Mexico (N 20° 58' to 21° 21' and West 99° 26' to 99° 43') with initial mercury concentrations were 424 ± 29 and 433 ± 12 mg kg-1 for "La Lorena" and "San Jose" former mines, respectively. Two vegetal species Polypogon monspeliensis and Cyperus odoratus were used and 20 reactors were constructed for the lab process. Total mercury was removed to 49-79% from both soils. Mercury elemental, exchangeable, and organic species had the most removal or exchange in the process. Metal uptake, by the plants, was of 5-6% for P. monspeliensis and 5-15% for C. odoratus. Also, mercury fate was estimated to the atmosphere to be 3.3-4.5 mg m-2 h-1 for both soils.

Plant and microorganisms support media for electricity generation in biological fuel cells with living hydrophytes.

Plant support media may impact power output in a biological fuel cell with living plants, due to the physical and biochemical processes that take place in it. A material for support medium should provide the suitable conditions for the robust microbial growth and its metabolic activity, degrading organic matter and other substances; and, transferring electrons to the anode. To consider the implementation of this type of bio-electrochemical systems in constructed wetlands, this study analyzes the electrochemical behavior of biological fuel cells with the vegetal species Phragmites australis, by using two different support media: graphite granules and a volcanic slag, commonly known as tezontle (stone as light as hair, from the Aztec or Nahuatl language). Derived from the results, both, graphite and tezontle have the potential to be used as support medium for plants and microorganisms supporting a maximum power of 26.78mW/m(2) in graphite reactors. These reactors worked under mixed control: with ohmic and kinetic resistances of the same order of magnitude. Tezontle reactors operated under kinetic control with a high activation resistance supplying 9.73mW/m(2). These performances could be improved with stronger bacterial populations in the reactor, to ensure the rapid depletion of substrate.

Accumulation and Distribution of Lead and Chromium in Laboratory-Scale Constructed Wetlands Inoculated with Metal-Tolerant Bacteria.

The accumulation and distribution of lead and chromium was tested in a laboratory-scale constructed wetland (CW) inoculated with metal-tolerant bacteria. Two non-inoculated systems also were evaluated, one planted and the other unplanted. Mass balances indicated that 57% of chromium input was accumulated into inoculated CW after 151 days of operation. The distribution was similar in support media and vegetation, in which 78% was transferred to aerial part. Similarly Pb was accumulated 29% in the support media and 39% in vegetation, which was distributed 52% in rhizome and 48% in aerial part. Significantly lower amounts of heavy metals were accumulated in non-inoculated systems than in the inoculated wetlands (p < 0.005). In addition, a markedly higher proportion of chromium in aerial vegetation and of lead in the suspended fraction of the effluent was exhibited, which raises a subsequent recovery of the metal by harvest and settling, respectively. Results indicate that CW inoculated with metal-tolerant bacteria might be a suitable option for treating wastewater with content of lead and chromium.