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Ozonation as pre-treatment of activated sludge process of a wastewater containing benzalkonium chloride and NiO nanoparticles
No full textThe continuous ozonation of benzalkonium chloride (BAC) and nickel oxide nanoparticles (NiO-NPs) has been performed in a synthetic water matrix and in a sewage treatment plant influent. This study aims to assess ozonation as pre-treatment of an activated sludge process, with emphasis on the toxicity of treated water. BAC was completely removed in synthetic matrix independently of the presence of NiO-NPs, although the ozone dose was influenced by NPs co-occurrence. The extent of mineralization was limited and a number of intermediate transformation products (TPs) appeared, twelve of which could be identified. The degradation pathway was shown to initiate both on the hydrophobic (alkyl chain) and hydrophilic (benzyl and ammonium moiety) region of the surfactant. The reactions on the hydrophilic region were affected by the presence of NiO-NPs as a consequence of the adsorption of BAC onto NP surface via the aromatic group. Water matrix strongly influenced BAC depletion. The aquatic toxicity of treated mixtures was assessed using a biotest battery composed of single species (the bacteria Vibrio fischeri and Pseudomonas putida and the protozoan Tetrahymena thermophila), as well as a whole biological community assay using activated sludge. Although, BAC showed considerable aquatic toxicity in all bioassays, ozonation decreased the toxic effects of treated water samples at ozone dosages below those required for total BAC depletion. Further treatment would not be justified, neither for a significant increase in BAC abatement nor concerning the toxicity of treated wastewater, which increased as a result of nickel leaching from the NPs
Parent lithology and organic matter influence the hyporheic biota of two Mediterranean rivers in central Spain
No full textThe hyporheic zone of stream ecosystems, located at the transition between surface channel and ground waters, exhibits patchy discontinuity on a longitudinal transect and induces changes in the structure and functioning of biotic communities. Nevertheless, the factors that influence biotic communities along spatial and temporal gradients remain poorly understood. This study aimed to characterise the diversity and spatial pattern distribution of Cyclopoida and Ostracoda from the hyporheic zone in relation to the riverbed sediment structure and the quantity of organic matter in two second-order rivers in central Spain, whose alluvium is derived from materials of contrasting geology (siliceous vs. carbonates). Both streams were found to be characterised by marked habitat heterogeneity along the hyporheic flow path, as reflected by the different lithology, riverbed permeability and distinct hyporheic biota assemblages. The results indicate that the alluvium riverbeds dominated by carbonates rocks and associated with high permeable riverbeds had slightly diverse hyporheic assemblages (25 species in all) with species of mixed ecology (stygobites / stygophiles / stygoxenes). Conversely, the siliceous alluvium riverbeds with low mineralised waters, associated with reduced permeability and relatively less active surface/ground water exchanges, displayed slightly lower diversity (23 species) with assemblages exclusively composed of stygophiles/stygoxenes. The results highlight the role of the riverbed substratum for the hyporheic biota and provide forthcoming approaches for depicting surface-subsurface hydrological exchanges
Monitoring priority substances, other organic contaminants and heavy metals in a volcanic aquifer from different sources and hydrological processes
No full textIrrigation with reclaimedwater (R) is necessary to guarantee the sustainability of semi-arid areas. Results obtained
during a two years monitoring network (2009–2011) in Gran Canaria are presented, including the analysis of
chemical parameters, N and S isotopes, priority substances (2008/105/EC, 2013/39/EU), other organic contaminants
and heavy metals in groundwater and R used to irrigate a golf course. The aims of thiswork are to evaluate
the contamination in a volcanic aquifer, relate the presence of organic contaminants and heavy metals with the
hydrogeochemistry and identify pollution sources in the area. No priority substance exceeded the EU thresholds
for surface water, although seventeen were detected in R. The most frequent compounds were hexachlorobenzene,
chlorpyrifos ethyl, fluorene, phenanthrene and pyrene. These compounds were detected at low concentration,
except chlorpyrifos. Chlorpyrifos ethyl, terbuthylazine, diuron, terbutryn, procymidone, atrazine and
propazine exceeded the European threshold concentration for pesticides in groundwater (100 ng L−1). Therefore,
the priority substances chlorpyrifos ethyl and diuron must be included in monitoring studies. The priority
pesticides chlorfenvinphos and diazinon were always detected in R but rarely in groundwater. Besides, the existence of contaminants not related to the current R irrigation has been identified. Absence of environmental
problems related to heavy metals can be expected. The relationship among contaminant presence,
hydrogeochemistry, including the stable isotopic prints of δ18O, δ15N and δ34S and preferential recharge paths
has been described. The coastal well shows high values of EC, nitrate, a variable chemistry, and 50% of organic
contaminants detected above 100 ng L−1. Thewell located in the recharge area presents a stable hydrochemistry,
the lowest value of δ15N and the lowest contaminants occurrence. The area is an example of a complex volcanic
media with several sources of contaminants such as leakages from septic tanks and sewerage, agriculture practices,
irrigation with reclaimed water or urban runoff
Stimulating soil microorganisms for mineralizing the herbicide isoproturon by means of microbial electroremediating cells
No full textThe absence of suitable terminal electron acceptors (TEA) in soil might limit the oxidative metabolism of environmental microbial populations. Microbial electroremediating cells (MERCs) consist in a variety of bioelectrochemical devices that aim to overcome electron acceptor limitation and maximize metabolic oxidation with the purpose of enhancing the biodegradation of a pollutant in the environment. The objective of this work was to use MERCs principles for stimulating soil bacteria to achieve the complete biodegradation of the herbicide 14C-isoproturon (IPU) to 14CO2 in soils. Our study concludes that using electrodes at a positive potential [+600 mV (versus Ag/AgCl)] enhanced the mineralization by 20-fold respect the electrode-free control. We also report an overall profile of the 14C-IPU metabolites and a 14C mass balance in response to the different treatments. The remarkable impact of electrodes on the microbial activity of natural communities suggests a promising future for this emerging environmental technology that we propose to name bioelectroventing
Improvement of resilience of urban areas by integrating social perception in flash-flood risk management
No full textSistema bioelectroquímico para depurar aguas residuales con cátodo de esferas conductoras flotantes
No full textSistema bioelectroquímico para depurar aguas residuales, que comprende una cámara anaerobia anódica, en la que se produce la oxidación de materia orgánica por microorganismos, y una cámara aerobia catódica, donde el cátodo de dicha cámara aerobia catódica consiste en esferas conductoras flotantes
A novel profiled core–shell nanofibrous membrane for wastewater treatment by direct contact membrane distillation
No full textInspired by the profiled structure of polar bear hair that possesses excellent thermal insulation properties, a novel profiled polyacrylonitrile-polystyrene (PAN-PS) core-shell nanofibrous membrane with peculiar groove structures and excellent direct contact membrane distillation (DCMD) performance was designed and manufactured by using an eccentric-axial electrospinning technique. Fiber surface morphology analyses indicated the major contributing role of applied voltage and the shell feeding rate in determining the stability of the electrospinning fluid jet, groove length and width, and membrane structural characteristics. The superhydrophobic properties resulting from the surface hierarchical roughness, prominent void volume fraction, fabulous gas permeability, appropriate mean flow pore (MFP) size and relatively considerable liquid entry pressure of water (LEPw) of the free-standing electrospun nanofibrous membranes (ENMs) could completely satisfy the requirements of the MD process. The resultant choreographed PAN-PS core-shell ENMs with a delicate groove morphology presented an outstanding permeate flux of 60.1 kg m(-2) h(-1) and high quality water permeate (20 g L-1 NaCl and 1000 ppm Sunset Yellow FCF aqueous solution as feed, Delta T = 40 degrees C) over a DCMD test period of 36 h without detection of membrane pore wetting. This result was better than those of typical commercial PVDF membranes and exhibited considerable competitiveness as compared with the well-designed ENMs reported so far, suggesting the grooved PAN-PS core-shell ENMs as promising alternatives for MD applications
Presence or absence of mlr genes and nutrient concentrations co-determine the microcystin biodegradation efficiency of a natural bacterial community
No full textThe microcystin biodegradation potential of a natural bacterial community coexisting with a toxic cyanobacterial bloom was investigated in a water reservoir from central Spain.
The biodegradation capacity was confirmed in all samples during the bloom and an increase of mlrA gene copies was found with increasing microcystin concentrations. Among the 24 microcystin degrading strains isolated from the bacterial community, only 28% showed presence of mlrA gene, strongly supporting the existence and abundance of alternative microcystin degradation pathways in nature. In vitro degradation assays with both mlr+ and ml
