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Soil amendment using poplar woodchips to enhance the treatment of wastewater-originated nutrients
No full textVegetation filters, a nature based wastewater regeneration technology, have been reported as a feasible solution for small municipalities and scattered populations with limited access to sewage networks. However even when such a treatment is properly planned, the leaching of contaminants through the unsaturated zone may occur. The amendment of soil with a readily-labile source of carbon is supposed to ameliorate the removal of contaminants by stimulating microbial activity and enhancing sorption processes. In this study, lab-scale leaching column experiments were carried out to explore if the addition of woodchips to the soil could be a feasible strategy to be integrated in a vegetation filter. Two different types of arrangement of soil and woodchips layers were tested. The soil was collected from an operating vegetation filter treating wastewater of an office building characterised by a high nutrient load. Daily pulse of synthetic wastewater were applied into the columns and effluent samples were collected and analyzed for major ions, total nitrogen (NT), total phosphorous (PT) and chemical oxygen demand (COD). By the end of the experiment, NT, NO3-N and PT soil contents were also measured. Results indicate that amendments with woodchips enhance the elimination of wastewater-originated contaminants. NT removal in the columns with woodchips reaches a value of 99.4%. The main processes responsible for this elimination are NH4-N sorption and nitrification/denitrification. This latter fostered by the reduced redox conditions due to the enhanced microbial activity. High removal of PT (99%) is achieved independently of the woodchips presence due to retention and/or precipitation phenomena. The COD removal efficiency is not affected by the presence of the woodchips. The leaching of organic carbon occurs only during the experimental start-up period
Modeling and optimization of a solar forward osmosis pilot plant by response surface methodology
No full textForward osmosis (FO) is a water treatment/separation technology of emerging interest. Due to its complex nature involving various operating parameters, modeling of this separation process is challenging. A solar thermal and photovoltaic-powered FO pilot plant has been optimized by means of a statistical experimental design and response surface methodology. Predictive models were developed for simulation and optimization of different responses such as the water permeate flux, the reverse solute permeate flux and the FO specific performance index that includes the water and reverse solute permeate fluxes together with the energy consumption. The considered input variables of the FO pilot plant were the feed flow rate, the permeate flow rate and the temperature. The developed response models have been tested using the analysis of variance. A Monte Carlo Simulation method has been conducted to determine the optimum operating conditions of the FO pilot plant. The obtained optimum parameters were confirmed experimentally. Regeneration of the draw solution can be performed by means of an optimized solar powered reverse osmosis (RO) pilot plant with an optimum FO specific performance index ranging from 25.79 to 0.62 L/g kW h achieved under the FO optimal conditions, 0.83 L/min feed flow rate, 0.31 L/min draw solution flow rate and 32.65 degrees C temperature. The FO energy consumption is only 14.1% the total energy consumption of the FO/RO hybrid system
Clean Water from Clean Energy: Decentralised Drinking Water Production Using Wind Energy Powered Electrodialysis
No full textSupply of potable water requires energy and unfortunately most of the countries with minimal access to safe drinking water are also poor in terms of access to reliable energy grids. However, many of such regions have access to other sources of water (such as brackish and groundwater) that can be treated for producing drinking water if correct treatment systems are put in place. Moreover, many of the electrically remote areas are rich in terms of renewable energy (RE) resources (such as wind and solar) which can be potentially employed as the main source of energy for powering water purification systems. Therefore, development and implementation of off‐grid RE powered contaminant removal systems, for producing freshwater from available resources (such s brackish and groundwater), can be considered as an effective and potentially sustainable solution for overcoming the drinking water scarcity issue in remote regions
of developing countries. This chapter revises the state of the art related to desalination systems using electrodialysis technology powered by wind energy for decentralised water production
Physiological and Operation Strategies for Optimizing Geobacter-based Electrochemical Systems
No full textEsta tesis doctoral explora nuevas estrategias para mejorar el funcionamiento de las METs (Microbial Electrochemical Technologies), mediante el análisis de parámetros tanto a escala micro como a escala pre-piloto.
Si analizamos las METs, a escala micro, G.sulfurreducens (microorganismo electroactivo modelo) es capaz de transferir los electrones de la oxidación del acetato a un electrodo en un proceso conocido como transferencia extracelular de electrones directa (DEET, Direct Extracellular Electron Transfer). En esta tesis se presenta un protocolo basado en utilizar el stress salino como factor para estimular el proceso DEET y, por tanto, la electroactividad de células planctónicas de G.sulfurreducens. Se han presentado evidencias de la contribución de sustancias poliméricas extracelulares (EPS, Extracellular Polymeric Substances), en el proceso DEET potenciado pudiendo ser propuestas como una red electroactiva capaz de conectar a las células planctónicas de G. sulfurreducens con electrodos.
Nuestros estudios revelan como el estado fisiológico del inóculo bacteriano es clave para el funcionamiento de las METs, no sólo en cuanto a la producción de corriente, sino también a la reducción de los períodos de operación. Usando un prototipo tipo filtro prensa, a escala pre-piloto, se ensayaron aguas residuales reales y aguas sintéticas suplidas con acetato, así como dos inóculos con fisiología diferente Se pudo demostrar como la fisiología adquirida en un quimiostato bajo limitación de aceptor de electrones resultó óptima para reducir, en casi 20 veces, el tiempo de arranque del sistema. Además, se identificó el papel del citocromo C (proteínas redox) del tipo OmcB en el fenotipo electroactivo de estas células planctónicas.
En la plataforma de las METs, las celdas de combustible microbianas (MFC, Microbial Fuel Cell) son los principales dispositivos que explotan la capacidad de los microorganismos electroactivos para generar energía eléctrica. En este contexto, una tecnología prometedora, derivada de las MFC, son las celdas microbianas de desalinización (MDC, Microbial Desalination Cell). Las MDC son dispositivos capaces de tratar agua residual y desalinizar agua salobre. Como tecnología derivada, el protocolo convencional de puesta en marcha implica la operación del sistema como MFC antes de poder desalinizar. En esta tesis se presenta un protocolo optimizado basado en integrar la electroquímica de Geobacter sulfurreducens en una electrodiálisis convencional con el objeto de reducir los tiempos de arranque. Tanto el protocolo de puesta en marcha como el diseño del sistema propuesto se confirman como una tecnología de bajo consumo, viable y escalable para poder operar de forma autónoma, como pre-tratamiento combinada con otras tecnologías de desalinización como la ósmosis reversa
An assessment of chemical and biological product use in aquaculture in Bangladesh
No full textThe aim of this study is to describe current chemical use practices in the aquaculture sector of Bangladesh and to identify the factors that influence them. A survey on the use of chemical and biological products was conducted between November 2011 and June 2012 using structured questionnaires administered to operators of nine farm groups, including homestead ponds, carps, tilapias, koi fish, shrimps, shrimps and prawns, prawns, rice and fish, and pangas. Farm type and farm owner characteristics were used as independent variables to explain observed chemical use. Forty-six chemical and biological products (7 water and sediment treatment compounds, 13 disinfectants, 7 antibiotics, 7 pesticides, 8 fertilizers and 4 feed additives and probiotics) were reported to be applied in aquaculture. The use of disinfectants and antibiotics was found to be highest in intensive koi and pangas farms as compared to other farm groups, whereas the use of fertilizers was lowest in these farm groups. A higher percentage of prawn and shrimp/prawn farmers applied pesticides than other farm groups. A multivariate analysis showed that patterns of use of chemical and biological products were significantly different across aquaculture farm groups, with the largest number of chemical compounds used by the intensive koi farm group. The study shows that, despite rapid expansion of commercial aquaculture in Bangladesh, use of chemical and biological products is still relatively low compared to other aquaculture producing countries in Asia. However, despite this finding, the study identified a large number of compounds that are currently in use, and that require further regulation and evaluation regarding their potential environmental and human health impacts, as already done in most developed countries
The role of sorption and biodegradation in the removal of acetaminophen, carbamazepine, caffeine, naproxen and sulfamethoxazole during soil contact: A kinetics study
No full textIn countries like Spain, where water is a limited resource, reusing effluents from wastewater treatment plants may imply the introduction of incompletely eliminated pollutants into the environment. Therefore, this work identified the role of sorption and biodegradation in attenuating pharmaceutical compounds (acetaminophen, carbamazepine, caffeine, naproxen and sulfamethoxazole) in natural soil. It also determined which sorption and removal (“sorption + biodegradation”) kinetics models describe the behaviour of these substances in the water-soil system. Presence of potential transformation products (TPs) as a result of pharmaceuticals biodegradation was also studied. To this end, serial batch-type experimentswere performedwith a soil:water ratio of 1:4 and an initial pharmaceutical concentration of 100 μg L−1. Despite results are dependent on soil characteristics, they revealed that, for those substances with a higher affinity to the soil used (loamy sand), sorption seems to play a key role during the first 48 h of contactwith soil, and gives way to biodegradation afterwards. The sorption of the pharmaceuticals studied follows a pseudo second-order kinetics. Caffeine and sulfamethoxazole displayed the fastest initial sorption velocities (h=2055 and h=228 μg kg−1 h−1, respectively). The removal kinetics experiments, satisfactorily simulated by the first-order kinetics model, indicated the presence of potential microbial adaptation to degradation. Indeed, half-lives decreased from 1.6- to 11.7-fold with respect to initial values. The microbial capacity to degrade sulfamethoxazole could be a matter of concern if bacteria have developed resistance to this antibiotic. Caffeine, acetaminophen and sulfamethoxazole were mitigated to a greater extent, whereas the removal of naproxen and carbamazepine was more limited. The appearance of epoxycarbamazepine andN4-acetyl-sulfamethoxazole as possible TPs of carbamazepine and sulfamethoxazole, respectively, indicated that biodegradationwas incomplete and showed the capacity of soil microbes to transform these substances
The variation of stygofauna along a gradient of salinization in a coastal aquifer: the variation of stygofauna along a gradient of salinization in coastal aquifer
No full textWe examined the variation of stygofauna composition collected in wells, along a gradient in groundwater salinity/conductivity in a coastal aquifer from southern Portugal. The studied coastal aquifer is considered vulnerable to salinization due to seawater intrusion, caused by overexploitation of the aquifer. Knowing the response of the stygofauna species to present levels of groundwater salinity makes it possible to understand and measure the effects of saltwater intrusion on stygofauna, rendering them potential bioindicators of this environmental pressure. Biotic and abiotic sampling was conducted in six shallow wells located in the fresh–saltwater interface of the Arade estuary along the salinity gradient established in the groundwater from the estuary to inland locations (microSiemens/cm). Groundwater salinity was highly correlated with taxa distribution. The stygobites Eucyclops hadjebensis and Acanthocyclops sensitivus, the cosmopolitan Megacyclops viridis and Cypria ophtalmica were particularly associated with low-salinity conditions, whereas Eucyclops graeteri, Megacyclops brachypus and Daphnia pulicaria were related to high-salinity waters. Multivariate analyses indicated that stygofauna assemblages varied significantly with location. We suggest that stygofauna composition and structure can be a useful complementing tool for monitoring seawater intrusion into coastal aquifers, where reduction or deterioration in groundwater resources is predicted
Toxicological assessment of third generation (G3) poly (amidoamine) dendrimers using the Allium cepa test
No full textDespite the expected increase of nanotechnology applications, limited information is currently available on the occurrence, fate and negative impact of engineered nanosizecl particles in the environment. Plants arc an integral and essential part of the ecosystems and their response to nanomaterials exposure is therefore of great interest. In this work, different parameters including root growth, mitotic index and chromosome aberrations were used to estimate the potential ecotoxicity of low generation (G3) hydroxyl- and amine-terminated poly(amicloamine) dendrimers using the Allium cepa test.
The findings of the present study indicate that both tested clendrimers produce toxic effects in a higher plant system. The analysis of macroscopic parameters, used in testing for general toxicity, revealed reduction of mean root length in bulbs exposed to high concentrations. In parallel, we observed a decrease in the mitotic activity of root meristerns which was associated with severe defects in chromosome segregation. Our results may greatly contribute to characterize the toxicological profile and risk of these potentially emerging pollutants in the environment
Relative influence of chemical and non-chemical stressors on invertebrate communities: a case study in the Danube River
No full textA key challenge for the ecological risk assessment of chemicals has been to evaluate the relative contribution of chemical pollution to the variability observed in biological communities, as well as to identify multiple stressor groups. In this study we evaluated the toxic pressure exerted by > 200 contaminants to benthic macroinvertebrates in the Danube River using the Toxic Unit approach. Furthermore, we evaluated correlations between several stressors (chemical and non-chemical) and biological indices commonly used for the ecological status assessment of aquatic ecosystems. We also performed several variation partitioning analyses to evaluate the relative contribution of contaminants and other abiotic parameters (i.e. habitat characteristics, hydromorphological alterations, water quality parameters) to the structural and biological trait variation of the invertebrate community. The results of this study show that most biological indices significantly correlate to parameters related to habitat and physico-chemical conditions, but showed limited correlation with the calculated toxic pressure. The calculated toxic pressure, however, showed little variation between sampling sites, which complicates the identification of pollution-induced effects. The results of this study show that the variation in the structure and trait composition of the invertebrate community are mainly explained by habitat and water quality parameters, whereas hydromorphological alterations play a less important role. Among the water quality parameters, physico-chemical parameters such as suspended solids, nutrients or dissolved oxygen explained a larger part of the variation in the invertebrate community as compared to metals or organic contaminants. Significant correlations exist between some physico-chemical measurements (e.g. nutrients) and some chemical classes (i.e. pharmaceuticals, chemicals related to human presence) which constitute important multiple stressor groups. This study demonstrates that, in large rivers like the Danube, the variation in the invertebrate community seems to be more related to varying habitat and physico-chemical conditions than to chemical pollution
Merging microbial electrochemical systems with conventional reactor designs for treating wastewater
No full textLa electroquímica microbiana ha surgido como una nueva subdisciplina de la biotecnología basada en el estudio de las interacciones entre microorganismos y electrodos. Las propiedades catalíticas de estos microorganismos son muy versátiles y una diversidad de campos pueden beneficiarse de ellas a través del desarrollo de las tecnologías electroquímicas microbianas (METs). La aplicación de las METs a escala real depende de la resolución de desafíos microbiológicos, tecnológicos y económicos. En esta tesis se han explorado nuevos escenarios y estrategias para superar los cuellos de botella tecnológicos de las METs en su aplicación para el tratamiento de aguas residuales. Para ello, se ha investigado la fusión de configuraciones de reactores clásicos, como la de lecho fluidizado o la de lodos activados, con tecnologías electroquímicas microbianas. El uso de este tipo de diseños permitiría operar prototipos sencillos de instalar a gran escala para evaluar tecnologías novedosas como las METs, que, de otro modo, estarían estancadas en escala laboratorio