Anion dopant effects on the structure and performance of polyethersulfone membranes

In this work, the effect of various casting solution salt dopants with similar cations, but different anions: (NaPO3)(6), Na2SO4, Na2CO3, NaCl, and NaF, on the morphology and performance of polyethersulfone ultrafiltration membranes was evaluated. The phase inversion process was used to produce all membranes using an 18% polyethersulfone in n-methylpyrrolidone casting solution and water as the non-solvent. Scanning electron microscopy (SEM) images of the membrane cross-section and surface pores were used to determine the specific anion effects on membrane morphology. The SEM images depicted significant changes to the membrane internal structure and pore size with respect to the type and concentration of the casting solution anion dopant. Membrane permeability, molecular weight cut-off, alginate retention, and susceptibility to fouling were evaluated using ultrapure water dead-end and ultrapure water, aqueous polyethylene glycol, aqueous sodium alginate, and natural surface water cross-flow filtration tests. Among the anions evaluated, hexametaphosphate doped at 1% w/w to the polymer resulted in the membrane with highest dead-end permeability at 490 LMH-bar (2- to 3-fold greater than the control), greatest alginate retention at 96.5%, and lowest susceptibility to fouling. The significant increase in membrane performance indicates that the hexametaphosphate anion has great potential to be used as a membrane casting solution dopant. It was also clearly demonstrated that membrane pore morphological characteristics can be effectively used to predict drinking water treatment performance. (C) 2012 Elsevier B.V. All rights reserved.

Hydrodynamic evaluation of a mechanical flocculation pilot unit

This work focused on the hydrodynamic research aiming at the short-circuiting evaluation for five different outlet configurations through the compartments of a vertical paddle flocculation pilot unit. The tests were carried out with variable and constant velocity gradients, including alternative rotation direction of the paddles. The research pointed out that the relevance of outlet configuration increases with the reduction of the number of compartments. In opposite, the velocity gradient and the rotation direction of paddles seem less significant features. These results open the perspective of viable increasing of performance, with low financial investments, mainly for flocculation units with three or two compartments installed in overloaded water treatment plants.

HEPATOTOXICITY ASSESSMENT OF THE AZO DYES DISPERSE ORANGE 1 (DO1), DISPERSE RED 1 (DR1,) AND DISPERSE RED 13 (DR13) IN HEPG2 CELLS

During the dyeing process in baths approximately 10 to 15% of the dyes used are lost and reach industrial effluents, thus polluting the environment. Studies showed that some classes of dyes, mainly azo dyes and their by-products, exert adverse effects on humans and local biota, since the wastewater treatment systems and water treatment plants were found to be ineffective in removing the color and reducing toxicity of some dyes. In the present study, the toxicity of the azo dyes disperse orange 1 (DO1), disperse red 1 (DR1), and disperse red 13 (DR13) was evaluated in HepG2 cells grown in monolayers or in three dimensional (3D) culture. Hepatotoxicity of the dyes was measured using 3-(4,5-dimethylthiazol-2yl)2,5-diphenyltetrazolium (MTT) and cell counting kit 8 (CCK-8) assays after 24, 48, and 72 h of incubation of cells with 3 different concentrations of the azo dyes. The dye DO1 only reduced the mitochondrial activity in HepG2 cells grown in a monolayer after 72 h incubation, while the dye DR1 showed this deleterious effect in both monolayer and 3D culture. In contrast, dye DR13 decreased the mitochondrial activity after 24, 48, and 72 h of exposure in both monolayer and 3D culture. With respect to dehydrogenase activity, only the dye DR13 diminished the activity of this enzyme after 72 h of exposure in both monolayer and 3D culture. Our results clearly demonstrated that exposure to the studied dyes induced cytotoxicity in HepG2 cells.

Caratterizzazione di membrane da nanofiltrazione

Nanofiltration (NF) is a pressure-driven membrane process, intermediate between reverse osmosis and ultrafiltration. Commercially available polymeric membranes have been used in a wide range of applications, such as drinking, process industry and waste water treatment. For all the applications requiring high stability and harsh washing procedures inorganic membranes are preferred due to their high chemical inertia. Typically, γ – Al2O3 as well as TiO2 and ZrO2 selective layers are used; the latter show higher chemical stability in a wide range of pH and temperatures. In this work the experimental characterization of two different type of membrane has been performed in order to investigate permeation properties, separation performance and efficiency with aqueous solutions containing strong inorganic electrolytes. The influence of salt concentration and feed pH as well as the role of concentration polarization and electrolyte type on the membrane behavior are investigated. Experimentation was performed testing a multi–layer structured NF membrane in α-Al2O3, TiO2 and ZrO2, and a polymeric membrane, in polyamide supported on polysulfone, with binary aqueous solutions containing NaCl, Na2SO4 or CaCl2; the effect of salt composition and pH in the feed side was studied both on flux and salt rejection. All the NF experimental data available for the two membranes were used to evaluate the volumetric membrane charge (X) corresponding to each operative conditions investigated, through the Donnan Steric Pore Model and Dielectric Exclusion (DSPM&DE). The results obtained allow to understand which are the main phenomena at the basis of the different behaviors observed.

Caracterización del ensuciamiento en membranas de ultrafiltración mediante parámetros de medida de resistencia en operación de flujo cruzado

Programa de Doctorado: Ingeniería Ambiental y Desalinización

Synthesis, characterization and chemical modification of a cationic polyelectrolyte poly(methylene amine)

Polyamine polymers have attracted attention due to their ability to demonstrate pH dependent cationic nature and presence of highly reactive pendant amino groups. These amino groups make them suitable for a host of applications through cross-linking and derivatization. As a result the end use application of a polyamine is largely driven by the number of amino groups and the way they are attached to the polymer backbone. Thus, this piece of work describes the synthesis and investigation of properties of a novel aliphatic polyamine, poly(methylene amine); that carries maximum number of amino group on its backbone. The target polymer, poly(methylene amine); was synthesized via two major steps viz.1.synthesis of precursor polymers of poly(methylene amine) and 2. Hydrolysis of the precursor polymers to obtain poly(methylene amine). The precursor polymers poly (1,3-diacetylimidazole-2-one)(6) and poly(1,3-diformyldihydroimidazol-2-one)(7) were synthesized via radical polymerization of their respective monomers. The monomers were polymerized in bulk as well as in solution at different reaction conditions. The maximum molecular weights were achieved by polymerizing the monomers in bulk (Mn = 6.5 x 104 g/mol and Mw = 2.13 x 105 g/mol) of 6. The precursor polymers were hydrolyzed under strong reaction conditions in ethanol in presence of NaOH, LiCl at 170°C to yield poly(methylene amine). The process of hydrolysis was monitored by IR spectroscopy. The solution properties of poly(methylene amine) and its hydrochloride were investigated by viscosimetry and light scattering. The reduced viscosity of poly (methylene amine) hydrochloride as a function of polymer concentration demonstrated a behavior typical of cationic polyelectrolyte. With decrease in polymer concentration the reduced viscosity of poly(methylene amine) hydrochloride increased gradually. The dynamic light scattering studies also revealed behaviors of a polyelectrolyte. Poly(methylene amine) was reacted with electrophiles to yield novel materials. While the attachment of alkyl group onto the nitrogen would increase nucleophilicity, it would also impose steric hindrance. As a result the degree of substitution on poly(methylene amine) would be governed by both the factors. Therefore, few model reactions with electrophiles were performed on polvinylamine under similar reaction conditions in order to make a comparative evaluation. It was found that under similar reaction conditions the degree of substitution was higher in case of polyvinylamine in comparison with poly (methylene amine).This shows that the steric hindrance outweighs nucleophilicity while deciding degree of substitution of electrophiles on poly(methylene amine). The modification was further extended to its use as an initiator for ring opening polymerization of benzyloxy protected N-carboxyanhydride of z-Lysine. The resulting polymer had an interesting brush like architecture. The solid state morphology of this polymer was investigated by SAXS. The 2D-WAXS diffractograms revealed hexagonal morphology of peptide segments without formation of alpha helices.

Control of fruit postharvest diseases by thermotherapy: understanding the mechanisms of action by –omics approaches

In recent years the hot water treatment (HW) represents an effective and safe approach for managing postharvest decay. This study reported the effect of an HW (60°C for 60 s and 45°C for 10 min) on brown rot and blue mould respectively. Peaches was found more thermotolerant compared to apple fruit, otherwise Penicillium expansum was more resistant to heat with respect to Monilinia spp. In semi-commercial and commercial trials, the inhibition of brown rot in naturally infected peaches was higher than 78% after 6 days at 0°C and 3 days at 20°C. Moreover, in laboratory trials a 100% disease incidence reduction was obtained by treating artificially infected peaches at 6-12 h after inoculation revealing a curative effect of HW. The expression levels of some genes were evaluated by qRT-PCR. Specifically, the cell wall genes (β-GAL, PL, PG, PME) showed a general decrease of expression level whereas PAL, CHI, HSP70 and ROS-scavenging genes were induced in treated peaches compared to the control ones. Contrarily, HW applied on artificially infected fruit before the inoculum was found to increase brown rot susceptibility. This aspect might be due to an increase of fruit VOCs emission as revealed by PTR-ToF-MS analysis. In addition a microarray experiment was conducted to analyze molecular mechanisms underneath the apple response to heat. Our results showed a largest amount of induced Heat shock proteins (HSPs), Heat shock cognate proteins (HSCs), Heat shock transcription factors (HSTFs) genes found at 1 and 4 hours from the treatment. Those genes required for the thermotolerance process could be involved in induced resistance response. The hypothesis was confirmed by 30% of blue mold disease reduction in artificially inoculated apple after 1 and 4 hours from the treatment. In order to improve peaches quality and disease management during storage, an innovative tool was also used: Da-meter.

The evidence for groundwater as a source of enteric illness in developing countries: A systematic review of the literature

Groundwater constitutes approximately 30% of freshwater globally and serves as a source of drinking water in many regions. Groundwater sources are subject to contamination with human pathogens (viruses, bacteria and protozoa) from a variety of sources that can cause diarrhea and contribute to the devastating global burden of this disease. To attempt to describe the extent of this public health concern in developing countries, a systematic review of the evidence for groundwater microbially-contaminated at its source as risk factor for enteric illness under endemic (non-outbreak) conditions in these countries was conducted. Epidemiologic studies published in English language journals between January 2000 and January 2011, and meeting certain other criteria, were selected, resulting in eleven studies reviewed. Data were extracted on microbes detected (and their concentrations if reported) and on associations measured between microbial quality of, or consumption of, groundwater and enteric illness; other relevant findings are also reported. In groundwater samples, several studies found bacterial indicators of fecal contamination (total coliforms, fecal coliforms, fecal streptococci, enterococci and E. coli), all in a wide range of concentrations. Rotavirus and a number of enteropathogenic bacteria and parasites were found in stool samples from study subjects who had consumed groundwater, but no concentrations were reported. Consumption of groundwater was associated with increased risk of diarrhea, with odds ratios ranging from 1.9 to 6.1. However, limitations of the selected studies, especially potential confounding factors, limited the conclusions that could be drawn from them. These results support the contention that microbial contamination of groundwater reservoirs—including with human enteropathogens and from a variety of sources—is a reality in developing countries. While microbially-contaminated groundwaters pose risk for diarrhea, other factors are also important, including water treatment, water storage practices, consumption of other water sources, water quantity and access to it, sanitation and hygiene, housing conditions, and socio-economic status. Further understanding of the interrelationships between, and the relative contributions to disease risk of, the various sources of microbial contamination of groundwater can guide the allocation of resources to interventions with the greatest public health benefit. Several recommendations for future research, and for practitioners and policymakers, are presented.^

Clearence rates by Calanus finmarchicus and Calanus helgolandicus determined experimentally

We studied the response in development times of Calanus finmarchicus and Calanus helgolandicus to changes in temperature and food conditions. The ingestion response to temperature was determined in the laboratory, where the copepods C. finmarchicus and C. helgolandicus were fed the diatom Thalassiosira weissflogii (cultivated at 18°C-20°; 12 : 12 light :dark cycle; exponential growth). C. finmarchicus was obtained for experiments from the Gullmar fjord. C. finmarchicus was incubated at in situ temperature (5°C) until the experiments were performed. First-generation cultures were grown in the laboratory at 15°C from the eggs from the Sta. L4 females. During growth both C. finmarchicus and C. helgolandicus cultures were fed a mixture of the cryptophyte Rhodomonas salina, the diatom Thalassiosira weissflogii, and the dinoflagellate Prorocentrum minimum. Five 600-mL glass bottles containing 1400 cells mL**-1 or 5 mg chlorophyll a (Chl a) L**-1 of T. weissflogii (200 mg C) and 1-2 C. finmarchicus or C. helgolandicus copepodite stage 5 (CV) or females were incubated in darkness at series of temperatures between 1°C and 21 ± 0.5°C. Three bottles without copepods served as control. In the C. helgolandicus experiment, T. weissflogii cells were counted at the beginning and end of the experiment in the grazing bottles and controls using a Coulter CounterH (MultisizerTM 3, Beckman Coulter). In the C. finmarchicus experiment, phytoplankton reduction was determined by Chl a measurements. The reduction in phytoplankton during any of the experiments was generally below 20% and never more than 32%. Clearance rates were calculated following Harris et al. (2000).

Uso de aguas residuales urbanas en el riego de colza (Brassica napus L.) con destino a biocombustible

El aceite de colza es comestible pero también puede utilizarse en la producción de biodiesel. Cuando el destino es el energético, el cultivo puede regarse con aguas residuales urbanas o cloacales. La mayor proporción del uso de éstas en el mundo ocurre en regiones áridas donde otras fuentes de agua son escasas, situación que se plantea en los oasis irrigados de Mendoza. En este trabajo se comparó el rendimiento de un cultivar invernal de colza regado con agua cloacal (AC) y agua subterránea (AS), y su potencial para producir biodiesel. La experiencia se llevó a cabo en una planta de tratamiento de agua cloacal de Obras Sanitarias en el departamento Tunuyán (33° 32’ 89’’ S; 69° 00’ 80’’ O; 859 m snm). El rendimiento de semilla de AC fue significativamente mayor que el de AS (7690 y 3886 kg/ha, respectivamente). La cantidad de biodiesel factible de producir por cada hectárea de cultivo asciende a 2800 kg en el tratamiento AC y a 1400 kg en AS. El uso de aguas residuales urbanas genera un nicho interesante para la producción de biocombustibles, utilizando un recurso hídrico con limitaciones para producir alimentos.

The nitrogen costs of photosynthesis in a diatom under current and future pCO2

With each cellular generation, oxygenic photoautotrophs must accumulate abundant protein complexes that mediate light capture, photosynthetic electron transport and carbon fixation. In addition to this net synthesis, oxygenic photoautotrophs must counter the light-dependent photoinactivation of Photosystem II (PSII), using metabolically expensive proteolysis, disassembly, resynthesis and re-assembly of protein subunits. We used growth rates, elemental analyses and protein quantitations to estimate the nitrogen (N) metabolism costs to both accumulate the photosynthetic system and to maintain PSII function in the diatom Thalassiosira pseudonana, growing at two pCO2 levels across a range of light levels. The photosynthetic system contains c. 15-25% of total cellular N. Under low growth light, N (re)cycling through PSII repair is only c. 1% of the cellular N assimilation rate. As growth light increases to inhibitory levels, N metabolite cycling through PSII repair increases to c. 14% of the cellular N assimilation rate. Cells growing under the assumed future 750 ppmv pCO2 show higher growth rates under optimal light, coinciding with a lowered N metabolic cost to maintain photosynthesis, but then suffer greater photoinhibition of growth under excess light, coincident with rising costs to maintain photosynthesis. We predict this quantitative trait response to light will vary across taxa.

Seawater carbonate chemistry and calcification rate in flume experiment

Ocean acidification (OA) poses a severe threat to tropical coral reefs, yet much of what is know about these effects comes from individual corals and algae incubated in isolation under high pCO2. Studies of similar effects on coral reef communities are scarce. To investigate the response of coral reef communities to OA, we used large outdoor flumes in which communities composed of calcified algae, corals, and sediment were combined to match the percentage cover of benthic communities in the shallow back reef of Moorea, French Polynesia. Reef communities in the flumes were exposed to ambient (400 ?atm) and high pCO2 (1300 ?atm) for 8 weeks, and calcification rates measured for the constructed communities including the sediments. Community calcification was reduced by 59% under high pCO2, with sediment dissolution explaining ~ 50% of this decrease; net calcification of corals and calcified algae remained positive but was reduced by 29% under elevated pCO2. These results show that, despite the capacity of coral reef calcifiers to maintain positive net accretion of calcium carbonate under OA conditions, reef communities might transition to net dissolution as pCO2 increases, particularly at night, due to enhanced sediment dissolution.

Synergistic effects of pCO2 and iron availability on nutrient consumption ratio of the Bering Sea phytoplankton community

Little is known concerning the effect of CO2 on phytoplankton ecophysiological processes under nutrient and trace element-limited conditions, because most CO2 manipulation experiments have been conducted under elements-replete conditions. To investigate the effects of CO2 and iron availability on phytoplankton ecophysiology, we conducted an experiment in September 2009 using a phytoplankton community in the iron limited, high-nutrient, low-chlorophyll (HNLC) region of the Bering Sea basin . Carbonate chemistry was controlled by the bubbling of the several levels of CO2 concentration (180, 380, 600, and 1000 ppm) controlled air, and two iron conditions were established, one with and one without the addition of inorganic iron. We demonstrated that in the iron-limited control conditions, the specific growth rate and the maximum photochemical quantum efficiency (Fv/Fm) of photosystem (PS) II decreased with increasing CO2 levels, suggesting a further decrease in iron bioavailability under the high-CO2 conditions. In addition, biogenic silica to particulate nitrogen and biogenic silica to particulate organic carbon ratios increased from 2.65 to 3.75 and 0.39 to 0.50, respectively, with an increase in the CO2 level in the iron-limited controls. By contrast, the specific growth rate, Fv/Fm values and elemental compositions in the iron-added treatments did not change in response to the CO2 variations, indicating that the addition of iron canceled out the effect of the modulation of iron bioavailability due to the change in carbonate chemistry. Our results suggest that high-CO2 conditions can alter the biogeochemical cycling of nutrients through decreasing iron bioavailability in the iron-limited HNLC regions in the future.

Colony-specific investigations reveal highly variable responses among individual corals to ocean acidification and warming

As anthropogenic climate change is an ongoing concern, scientific investigations on its impacts on coral reefs are increasing. Although impacts of combined ocean acidification (OA) and temperature stress (T) on reef-building scleractinian corals have been studied at the genus, species and population levels, there are little data available on how individual corals respond to combined OA and anomalous temperatures. In this study, we exposed individual colonies of Acropora digitifera, Montipora digitata and Porites cylindrica to four pCO2-temperature treatments including 400 µatm-28 °C, 400 µatm-31 °C, 1000 µatm-28 °C and 1000 µatm-31 °C for 26 days. Physiological parameters including calcification, protein content, maximum photosynthetic efficiency, Symbiodinium density, and chlorophyll content along with Symbiodinium type of each colony were examined. Along with intercolonial responses, responses of individual colonies versus pooled data to the treatments were investigated. The main results were: 1) responses to either OA or T or their combination were different between individual colonies when considering physiological functions; 2) tolerance to either OA or T was not synonymous with tolerance to the other parameter; 3) tolerance to both OA and T did not necessarily lead to tolerance of OA and T combined (OAT) at the same time; 4) OAT had negative, positive or no impacts on physiological functions of coral colonies; and 5) pooled data were not representative of responses of all individual colonies. Indeed, the pooled data obscured actual responses of individual colonies or presented a response that was not observed in any individual. From the results of this study we recommend improving experimental designs of studies investigating physiological responses of corals to climate change by complementing them with colony-specific examinations.