Chitosan/albumin/CaCO3 as mimics for membrane bioreactor fouling: genesis of structural mineralized-EPS-building blocks and cake layer compressibility

Membrane bioreactor biofouling is usually described as an extracellular matrix in which biopolymers, inorganic salts and active microbes co-exist. For that reason, biomineralization (BM) models can be useful to describe the spatial organization and environmental constraints within the referred scenario. BM arguments were utilized as background in order to (1) evaluate CaCO₃ influence on flux decline; pore blocking and cake layer properties (resistance, permeability and compressibility) in a wide range of Chitosan/Bovine serum albumin (BSA) mixtures during step-pressure runs and, (2) perform membrane autopsies in order to explore the genesis of mineralized extracellular building blocks (MEBB) during cake layer build up. Using low molecular weight chitosan (LC) and BSA, 2 L of 5 LC/BSA mixtures (0.25-1.85 ratio) were pumped to an external ultra filtration (UF) membrane (23.5 cm², hydrophobic, piezoelectric, 100 kDa as molecular weight cut-off). Eight different pressure steps (40 ± 7 to 540 ± 21 kPa) were applied. Each pressure step was held for 900 s. CaCO₃ was added to LC/BSA mixtures at 0.5, 1.5 and 3 mM in order to create MEBB during the filtration tests. Membrane autopsies were performed after the filtration tests using thermo gravimetric, scanning microscopy and specific membrane mass (mg cm⁻²) analyses. Biopolymer-CaCO₃ step-pressure filtration created compressible cake layers (with inner voids). The formation of an internal skeleton of MEBB may contribute to irreversible fouling consolidation. A hypothesis for MEBB genesis and development was set forth.     

Phenol depletion by thermally activated peroxydisulfate at 70°C

The ability of thermal activated peroxydisulfate (PS) of mineralizing phenol at 70 °C from contaminated waters is investigated. Phenol in concentrations of 10⁻⁴ to 5 × 10⁻⁴ M is quantitatively depleted by 5 × 10⁻³ to 10⁻² M activated PS in 15 min of reaction. However, mineralization of the organic carbon is not observed. Instead, an insoluble phenol polymer-type product is formed. A reaction mechanism including the formation of phenoxyl radicals and validated by computer simulations is proposed. High molecular weight phenolic products are formed by phenoxyl radical H-abstraction reactions. This is not the case for the room temperature degradation of phenol by sulfate radicals where sulfate addition to the aromatic ring mainly leads to the generation of hydroxycyclohexadienyl radicals leading to hydroxybenzenes and oxidized open chain products. Therefore, a change in the reaction mechanism is observed with increasing temperature, and thermal activation of PS at 70 °C does not lead to the mineralization of phenol. Thus PS activation at 70 °C may be considered a potential method to reduce the load of phenol in polluted waters by polymerization.     

Biochemical biomarkers in Nile tilapia (Oreochromis niloticus) after short-term exposure to diesel oil, pure biodiesel and biodiesel blends

Fossil fuels such as diesel are being gradually replaced by biodiesel, a renewable energy source, cheaper and less polluting. However, little is known about the toxic effects of this new energy source on aquatic organisms. Thus, we evaluated biochemical biomarkers related to oxidative stress in Nile tilapia (Oreochromis niloticus) after two and seven exposure days to diesel and pure biodiesel (B100) and blends B5 and B20 at concentrations of 0.01 and 0.1 mL L⁻¹. The hepatic ethoxyresorufin-O-deethylase activity was highly induced in all groups, except for those animals exposed to B100. There was an increase in lipid peroxidation in liver and gills in the group exposed to the higher concentration of B5. All treatments caused a significant increase in the levels of 1-hydroxypyrene excreted in the bile after 2 and 7 d, except for those fish exposed to B100. The hepatic glutathione-S-transferase increased after 7 d in animals exposed to the higher concentration of diesel and in the gill of fish exposed to the higher concentration of pure diesel and B5, but decreased for the two tested concentrations of B100. Superoxide dismutase, catalase and glutathione peroxidase also presented significant changes according to the treatments for all groups, including B100. Biodiesel B20 in the conditions tested had fewer adverse effects than diesel and B5 for the Nile tilapia, and can be suggested as a less harmful fuel in substitution to diesel. However, even B100 could activate biochemical responses in fish, at the experimental conditions tested, indicating that this fuel can also represent a risk to the aquatic biota.     

Salinity increases mobility of heavy metals in soils

The effect of salinity induced by CaCl₂, MgCl₂, NaCl and Na₂SO₄ on the mobility of Cu, Cd, Pb and Zn was studied. An increase of ionic strength by any salts promoted a higher release of Cd than the others metals. When CaCl₂ and NaCl were applied, Cd and Pb showed the highest degree of mobilization. When MgCl₂ was applied, Cd and Cu were mobilized the most. Finally, an increase of Na₂SO₄ also promoted the strongest mobilization of Cd and Cu.As the total heavy metal content was higher, the percentage of Pb and Cu released upon salinization decreased, indicating that these metals are strongly bound to soil constituents. An increase of carbonates in the soil promoted a higher release of Pb for all used salts and for Zn when MgCl₂ and NaCl were used. This indicates that Pb and Zn are adsorbed on the surface of carbonate crystals. An increase of fine particles promoted a decrease of percentage of released Cd for all salts, indicating that Cd is strongly retained in the fine fractions.The main mechanism regulating Pb and Cd mobility was competition with Ca²⁺ for sorption sites followed for metal chloro-complexation, association between the Cd/Pb-sulfates and competition with Mg²⁺. The main mechanism regulating Cu mobility was the formation of Cu-sulfate, followed by competition with cations (Mg > Ca) and chloride. For Zn, competition with Ca²⁺ for sorption sites was the most important process for its mobility; followed by Zn-sulfate association and, finally, chloride and competition with Mg with the same effect.     

Occurrence and distribution of pharmaceuticals in surface water, suspended solids and sediments of the Ebro river basin, Spain

The occurrence of 43 pharmaceuticals belonging to predominant therapeutic classes and their distribution in surface water, suspended solids and sediments has been investigated in the Ebro river basin in the Northeast of Spain. WWTP effluents were found to be a main source of contamination and the spatial distribution was affected by the river flow at the sampling point and corresponding dilution factor, resulting in higher concentrations and higher loads in small tributary rivers than in the Ebro river. The study showed that some compounds are preferentially found bound to suspended solids and not detected in river water. Generally, compounds with basic characteristics (pKa > 7) showed higher tendency to bind to suspended solids. The sediment samples generally presented lower concentrations than suspended solids.     

A national inventory to estimate release of polychlorinated dibenzo-p-dioxins and dibenzofurans in Portugal

Taking into account current environmental concerns, the main objective of this work focused a national inventory aiming to estimate the amount of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) released in Portugal in 2006. The methodology used was based on the Standardized Toolkit for Identification and Quantification of Dioxins and Furan Releases, developed by UNEP Chemicals, in 2005. The method allows the assessment of the amount of PCDD/PCDF released into the environment along five vectors involving air, water, land, products and residues. Facing some difficulties mainly regarding to the availability of data for some activities known to produce PCDD/PCDF, three scenarios (Sc1 to Sc3) corresponding to lower, central and upper estimates were established. The Sc1 scenario (lower estimate) includes the situations where in case of doubt or scarce information, reduced or none emission values were assumed, Sc2 refers to a central estimate, which is believed to be the most realistic for the Portuguese situation, while Sc3 corresponds to the worst case (upper estimate). The results obtained pointed out that the total amount of PCDD/PCDF emitted in Portugal during the period under analysis was in the range of 51.2-217.9 g TEQ year⁻¹, with the most likely value of 95.2 g TEQ year⁻¹ achieved under the Sc2 scenario. This study also showed that the methodology developed by UNEP Chemicals is a very simple one, and the main difficulty is the availability of data. The main indicators calculated in this study were 8.98 μg TEQ/(year person) by taking into account the total amount of PCDD/PCDF released, and 3.63 μg TEQ/(year person) when only air emissions were considered.     

Dietary uptake of polybrominated diphenyl ethers (PBDEs), occurrence and profiles, in aquacultured turbots (Psetta maxima) from Galicia, Spain

Polybromodiphenyl ethers (PBDEs) are one of the many toxic chemicals present in the environment and in the food we eat every day, being fish one of the main sources of persistent organic pollutants in our diet; like other lipid-related contaminants, they are of concern since they can bioaccumulate and biomagnify through the trophic chain. We published a study focused on the dietary uptake of dioxins and furans (PCDD/Fs) and dioxin-like polychlorobiphenyls (dl-PCBs) in a set of samples of Spanish farmed turbot (Blanco et al., 2007). In the present paper, we extend the study to PBDEs to provide more information about the uptake and transfer from feed to fish of halogenated contaminants. PBDEs in the feeds (2.35-4.76 ng g(-1)) were reflected in turbot fillets (0.54-2.05 ng g(-1)): predominant congeners were tetra-BDE 47, penta-BDEs 99 and 100. It is remarkable that tetra-BDE 49, accounting for only 2% in the feed, contributed to 15% of total PBDEs in turbot fillets. Dietary net accumulation values, 30-45%, showed that tri-, tetra-, penta- and hexa-BDEs were as efficiently transferred into turbot as dl-PCBs and tetra- and penta-chlorinated PCDD/Fs. Lipid-normalized biomagnification factors relating concentration in fish and in feed, BMFs>1 were obtained, except for BDE 209. BDE 49 accumulation, 90%, was possibly contributed by metabolism of higher brominated BDEs. Implication in aquaculture management is a need for uncontaminated fish feed to offer safe products.     

Temporal analysis of PM10 in Metropolitan Monterrey, México

The Monterrey Metropolitan Area (MMA) is the third largest city in Mexico. Few studies have been carried out regarding its air pollution. The aim of this study was to analyze the temporal behavior of PM10 (particulate matter < or =10 microm in aerodynamic diameter). Data reported by the "Sistema Integral de Monitoreo Ambiental" (Integrated Environmental Monitoring System) network from 2006 to 2008 were used. PM10 levels were compared among the stations by year, season, and day of week. A bootstrap technique was used to obtain subsamples to which Student's t test and ANOVA were applied. PM10 levels were high and exceeded the annual limit of 50 microg/m3 set up by the Mexican standard Norma Oficial Mexicana NOM-025-SSA1-1993. These levels could have serious health effects. The southwest zone of MMA had the highest levels of PM10 during the period studied. Winter was the most polluted season, and summer was the least polluted season. Thursday and Friday were the most polluted days, and Sunday was the least polluted day. The hours with the highest levels of PM10 were 8:00 to 10:00 a.m., whereas nighttime hours were the cleanest.     

Printed wiring boards for mobile phones: characterization and recycling of copper

The popularization of mobile phones, combined with a technological evolution, means a large number of scrap and obsolete equipment are discarded every year, thereby causing economic losses and environmental pollution. In the present study, the printed wiring boards scrap of mobile phones were characterized in order to recycle some of the device components, using techniques of mechanical processing, hydrometallurgy and electrometallurgy. The use of the techniques of mechanical processing (milling, particle size classification, magnetic and electrostatic separation) was an efficient alternative to obtain a concentrated fraction (mainly iron in the magnetic fraction and copper in the conductive fraction) and another fraction containing polymers and ceramics. At the end of mechanical processing, a concentrated fraction of metals could be obtained with an average concentration of 60% copper. This concentrated fraction in metals was dissolved in aqua regia and sent to electrowinning to recover 92% of the dissolved copper. The obtained cathodes have a copper content above 95%, which demonstrates the technical feasibility of recovery of copper using the techniques of mechanical processing, hydrometallurgy and electrometallurgy.