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Assessment of groundwater circulation in La Gomera aquifers (Canary Islands, Spain) from their hydrochemical features
No full textLa Gomera (Canary Islands, Spain) does not show water scarcity like other islands of the Archipelago. However, the study of its aquifers is paramount as nearly 60 % of the water supplies are covered with spring water. According to the currently accepted hydrogeological model, La Gomera presents an upper aquifer consisting of perched groundwater bodies. Below this hydrogeological unit, the General Saturated Zone or basal groundwater is placed. The model also establishes the presence of flows through them. Many perched groundwater bodies are located under Garajonay National Park where most of the springs are found. Therefore, if upper and lower aquifers are truly connected and new wells are built, the new extractions could affect Garajonay ecosystems. With the aim of identifying spring groups and related potential areas of water transfer, hydrochemical and statistical analyses (principal component analysis and cluster analysis) have been applied. This study shows the great compositional variability of groundwaters, precluding the identification of spring groups, hydrochemical patterns and, therefore, the transfer areas with no possibility of assessing the potential impact of a water demand increase on the Garajonay National Park ecosystems from the present data. Only the springs belonging to group II of the cluster analysis could indicate a transfer area. The lack of conclusive results could be due to: (1) great compositional variability of volcanic materials; (2) unequal influence of marine aerosols; (3) irregular distribution of rainfall; (4) different grades of soils development; and (5) the occurrence of partially disconnected water bodies giving as a result a complex hydrogeological system
Presence and spatial distribution of emerging contaminants (drugs of abuse) in protected agroecological systems (L’Albufera de Valencia Coastal Wetland, Spain)
No full textThe Mediterranean wetlands are unique in biological diversity and provide multiple benefits, constituting a great water reserve for the planet and producing biomass and nutrients for the trophic chain. However, the increasing human impact and socio-economic development in recent decades have caused important losses in these ecosystems. This work was carried out in the Natural Park of L’Albufera (Valencia, Spain), which includes a coastal lagoon, marshlands, dunes and pinewoods, surrounded by rice fields and orchard in its non-urbanized part. Despite this great ecological value, it suffers impacts derived from the high human and industrial occupation and the hydrological contributions of the connected irrigation systems. The study focused on the development of a combined methodology, based on environmental forensics principles, with the aim of identifying the presence, flow paths and spatial distribution of illicit drugs entering the Natural Park. It is organized around two major procedures: analysis of 16 water samples and application of Geographical Information Systems (GIS) integrating different sources and data formats, as analysis of 14 drugs of abuse by Liquid Chromatography-Mass Spectrometry techniques, and social and environmental data in either GIS layers or tabular digital formats. Results show that, at present, most analyzed drugs have been identified in all sample points. Besides the population distribution pattern, the traditional irrigation system connected to sewage treatment plant (STP) locations is the way by which illicit substances are introduced into the Natural Park water
Sorption/desorption of non-hydrophobic and ionisable pharmaceutical and personal care products from reclaimed water onto/from a natural sediment
No full textIn the present work, the sorption of pharmaceutical and personal care products (PPCPs) (acetaminophen, atenolol,
carbamazepine, caffeine, naproxen and sulphamethoxazole) onto the natural organic matter (NOM) and the
inorganic surfaces of a natural sandy loam sediment was quantified separately. The quantification was based on
the PPCP charge, their degree of ionisation, their octanol–water partitioning coefficient (KOW) and the sediment
organic carbon fraction (ƒOC). PPCP desorption from the sediment was examined under conditions of infiltrating
water containing a high concentration of inorganic ions (mimicking infiltrating reclaimedwater), and a lowconcentration
(and smaller diversity) of inorganic ions (mimicking rainwater infiltration). Batch tests were performed
using a sediment/water ratio of 1:4 and a PPCP initial concentration ranging from 1 to 100 μg L−1. The
results showed the type and degree of PPCP ionisation to strongly influence the sorption of these compounds
onto the sediment. The sorption of cationic species onto the sediment was higher than that of anionic species
andmostly reversible; the sorption of neutral specieswas negligible. The anionic species sorbed less onto the sediment,
but also desorbed less easily.More than 70% of the total sorptionwas due to interaction with mineral surfaces.
This holds especially true for cationic species (atenolol and caffeine) which sorption was enhanced by the
negative surface charge of the sediment. The presence of inorganic ions had no impact on the desorption of the
PPCPs from the sediment. According to the calculated percentages of removal, the mobility followed the order:
carbamazepine N acetaminophen N naproxen N atenolol N sulfamethoxazole N caffeine
Hydrophilic porous asymmetric ultrafiltration membranes of aramid-g-PEO copolymers
No full textA series of experimental aramid-g-PEO copolymers was employed to fabricate ultrafiltration (UF) membranes by the conventional method of phase inversion, using N,N-dimethylformamide as the solvent and water as the coagulating medium. By adjusting the dope concentration for each polymer, porous membranes were attained which were suitable for UF operations and were tested using a laboratory-scale cross-flow test unit. The water flux of the membranes showed a strong dependency on the chemical composition, with water permeability increasing with increasing PEO content in the copolymer. Their separation potentials were investigated using standard solutions of poly(ethylene oxide) (PEO) as the feed, and the performance of the membranes in UF operations was systematically compared. A relationship between the dope concentration and the molecular weight cut-off (MWCO) could be observed, with higher concentrations resulting in a lower MWCO. In contrast, it was observed that the higher the content of PEO in the copolymer the greater the MWCO. In fouling tests performed using a bovine serum albumin (BSA) solution, aramid-g-PEO UF membranes exhibited very good antifouling properties compared to a commercially sourced polysulfone membrane and to polyamide UF membranes. The results of this work indicate that aramid-g-PEO copolymers are promising materials for the fabrication of fouling resistant membranes for biomacromolecules' separations
Advances in Geoconservation in Cuba: Assessment of the Guaniguanico Range and Guanahacabibes Plain (Pinar del Río)
No full textThe application of geoconservation concepts in Cuba is very recent, despite the wide body of knowledge accumulated through the study of Cuban geology. Recently, the establishment and consolidation of a National System of Protected Areas that stresses interaction with scientific institutions has greatly helped initiate geoconservation in Cuba. In this study, we review the geoconservation criteria used in the management of protected areas, their precedents and administrative framework. We used the methodology proposed by Bruschi (2007) for the characterisation, assessment and management of geodiversity resources, and modified its criteria for use in selecting geosites. We have applied the methodology to assess the Guaniguanico Range and the Guanahacabibes Plain where 162 geosites were defined. Of the 162 geosites assessed, 107 were at Viñales National Park, so it could be a potential area to become the first Caribbean Geopark
Study of Asymmetric Capacitive Deionization Cells for Water Treatment Applications
No full textCapacitive Deionization (CDI) is one of the emerging water technologies attracting interest in recent years. CDI works by removing ions present in water by applying a constant voltage or current between two electrodes immersed into solution. When the removal step is complete, the electrodes are regenerated by short-circuiting the system or reversing the sign of the voltage or current. During regeneration, the ions that were previously adsorbed on the electrodes undergo a desorption process and are returned to solution as a wastewater. One of the reasons for a high degree of interest in CDI research is the possibility of storing energy in the electrochemical double layer (EDL) of the electrodes while treating water. Hence, CDI systems might also be described as a non-ideal EDL capacitor that removes ions from water in the charging step and releases this energy during discharge. In addition to this attractive feature (saving energy while delivering clean water), CDI is a low-pressure method of water treatment in contrast with typical membrane technologies (Reverse Osmosis, Electrodyalisis). This results in a decrease in energy consumption. Moreover, aspects such as the high water recovery that diminishes the volume of brine, the low cost and high availability of carbon materials and the lack of post-treatment, that reduces the consumption of chemical compounds, are additional benefits of this technology. Thus, many studies have been performed in order to evaluate the potential of CDI being employed in a variety of applications such as: desalinating brackish waters, water softening and the removal of specific contaminants. In addition, extensive research has been performed focusing on the development of CDI electrodes having better performance with respect to the electrosorption of ions. In this thesis, new materials based on coating carbon substrates with nanoporous metal oxides developed by the Environmental Chemistry and Technology Program of University of Wisconsin-Madison were employed. Accordingly, the cathode was coated with a thin-film of nanoporous SiO2 whereas the anode with a nanoporous layer of aluminum oxide. This kind of configuration was named Asymmetric Capacitive Deionization (ACDI) in contrast with systems where the two electrodes are identical or can be described as being symmetric.
In this thesis work, the application of this type of ACDI system for water treatment applications such as water softening and brackish water desalination has been evaluated. Firstly, the influence of metal oxide coatings on CDI performance was studied. This effect was evaluated in two different ways: material characterization (BET surface area, Pore Size Distribution (PSD), Microscopy) and electrochemical behavior (Cyclic Voltammetry (CV) and Zeta Potential analysis). Moreover, ion electrosorption mechanisms were investigated using methods of analysis specific for each of the ions being removed and by correlating this data to changes or lack of change in pH. This method allowed us to identify ion removal processes such as electrosorption in the EDL, specific adsorption on the metal oxides or carbon support. Furthermore, the effect of these different ion removal mechanisms on electrode regeneration was also studied. In this sense, different electrode regeneration strategies were attempted. In order to complete the research, the occurrence of faradaic (oxidation-reduction) reactions was examined. These can be parasitic in nature possibly reducing electrochemical efficiencies.
Moreover, the impact of operational parameters such as applied voltage, the concentration and type of electrolyte in the inlet solution or the regeneration mechanisms on ion removal was widely analyzed using a medium size prototype (10 cells, 12 x 12 cm electrodes, 400 ml) reactor. These experiments included examining the symmetry of the removing of anions and cations, the occurrence of parasitic reactions and the effect of removal and regeneration on pH change. Besides the effect of these parameters on ion adsorption/desorption, an important part of the research was dedicated to the influence of those variables on the charge efficiency and the energy consumption of this ACDI device.
As a final contribution, the effect of a long-term performance of an ACDI device was evaluated. Particular attention was paid to electrode stability (corrosion, surface acidification, electrode capacitance). This kind of analysis is essential if one wants to demonstrate the feasibility of CDI systems competing with other water treatment techniques in real world scenarios.
The results from this thesis suggest that CDI systems outfitted with carbon electrodes coated asymmetrically with different metal oxides could be potentially applied for water softening as well as for brackish water desalination. In addition, this study has shown the ability of ACDI to be optimized by altering operational parameters according to the product specifications required for given treatment scenarios. Moreover, this thesis stresses the importance of CDI studies that are coupled to specific methods of analysis in coordination with pH measurements if one hopes to obtain useful information concerning ion removal mechanisms. Additionally, long-term experiments emphasize the role of the parasitic reactions with respect to the reduction of CDI performance and an increasing energy demand
Evaluation of Operational Parameters for a Capacitive Deionization Reactor Employing Asymmetric Electrodes
No full textCapacitive deionization is a potential technology for water softening. In this study, low-cost high surface area carbons coated with two different metal oxides (SiO2 on the cathode and Al2O3 on the anode) were employed. CaSO4 removal was investigated using a 400 ml reactor in a ‘single-pass’ mode. Influence of applied voltage and flow rate on ion removal/regeneration, charge efficiency, and energy consumption was determined. High potentials (> 1.2 V) led to pH acidification and increased likelihood of faradaic reactions affecting ion electrosorption and charge efficiency. CaSO4 removal amounted 4.38 mg·g-1 of electrode material after 15 minutes of cell polarization at 1.2 V. Charge efficiencies of 60 % and an energy consumption of 0.12 KWh·mol-1 of salt removed were obtained. Different regeneration modes (open circuit, short-circuit (SC) and reverse voltage (RV)) were studied. SC regeneration resulted in the highest ion regeneration efficiency while short applications of RV increased water recovery values but also increased energy cost. Oxide coatings avoided ion crossover when short circuit or low reverse voltage were used in regeneration. Ca2+ and SO42- ions adsorbed specifically on SiO2 and Al2O3, respectively with Ca2+ also adsorbing specifically to carbon alone. These chemical affinities directly influence the desorption proces
Novel and emerging membranes for water treatment by hydrostatic pressure and vapour pressure gradient membrane processes
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