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Application of micronucleus test and comet assay to evaluate BTEX biodegradation

Mazzeo, Dânia Elisa Christofoletti; Matsumoto, Silvia Tamie; Levy, Carlos Emílio; de Angelis, Dejanira de Franceschi; Marin-Morales, Maria Aparecida
Tipo: Artigo de Revista Científica Formato: 1030-1036
Português
Relevância na Pesquisa
36.29%
The BTEX (benzene, toluene, ethylbenzene and xylene) mixture is an environmental pollutant that has a high potential to contaminate water resources, especially groundwater. The bioremediation process by microorganisms has often been used as a tool for removing BTEX from contaminated sites. The application of biological assays is useful in evaluating the efficiency of bioremediation processes, besides identifying the toxicity of the original contaminants. It also allows identifying the effects of possible metabolites formed during the biodegradation process on test organisms. In this study, we evaluated the genotoxic and mutagenic potential of five different BTEX concentrations in rat hepatoma tissue culture (HTC) cells, using comet and micronucleus assays, before and after biodegradation. A mutagenic effect was observed for the highest concentration tested and for its respective non-biodegraded concentration. Genotoxicity was significant for all non-biodegraded concentrations and not significant for the biodegraded ones. According to our results, we can state that BTEX is mutagenic at concentrations close to its water solubility, and genotoxic even at lower concentrations, differing from some described results reported for the mixture components...

Sugarcane bagasse ozonolysis pretreatment: Effect on enzymatic digestibility and inhibitory compound formation

Travaini, Rodolfo; Otero, Marian Derly Morales; Coca, Mónica; Da-Silva, Roberto; Bolado, Silvia
Tipo: Artigo de Revista Científica Formato: 332-339
Português
Relevância na Pesquisa
36.1%
Sugarcane bagasse was pretreated with ozone to increase lignocellulosic material digestibility. Bagasse was ozonated in a fixed bed reactor at room temperature, and the effect of the two major parameters, ozone concentration and sample moisture, was studied. Acid insoluble and total lignin decreased whereas acid soluble lignin increased in all experiments. Pretreatment barely attacked carbohydrates, with cellulose and xylan recovery rates being >92%. Ozonolysis increased fermentable carbohydrate release considerably during enzymatic hydrolysis. Glucose and xylose yields increased from 6.64% and 2.05%, for raw bagasse, to 41.79% and 52.44% under the best experimental conditions. Only xylitol, lactic, formic and acetic acid degradation compounds were found, with neither furfural nor HMF (5-hydroxymethylfurfural) being detected. Washing detoxification provided inhibitor removal percentages above 85%, increasing glucose hydrolysis, but decreasing xylose yield by xylan solubilization. SEM analysis showed structural changes after ozonization and washing. © 2013 Elsevier Ltd.

Electrochemical oxidation of wastewater containing aromatic amines using a flow electrolytic reactor

Moraes, Peterson B.; Bertazzoli, Rodnei; Bidoia, Ederio Dino
Tipo: Artigo de Revista Científica Formato: 1-14
Português
Relevância na Pesquisa
26.29%
Aromatic amines are environmental pollutants and represent one of the most important classes of industrial and natural chemicals. Some types of complex effluents containing these chemical species, mainly those originated from chemicals plants are not fully efficiently treated by conventional processes. In this work, the use of electrochemical technology through an electrolytic pilot scale flow reactor is considered for treatment of wastewater of a chemical industry manufacturer of antioxidant and anti-ozonant substances used in rubber. Experimental results showed that was possible to remove between 65% and 95% of apparent colour and chemical oxygen demand removal between 30 and 90% in 60 min of treatment, with energy consumption rate from 26 kWh m-3 to 31 kWh m-3. Absorbance, total organic carbon and toxicity analyses resulted in no formation of toxic by-products. The results suggest that the presented electrochemical process is a suitable method for treating this type of wastewater, mainly when pre-treated by aeration. Copyright © 2013 Inderscience Enterprises Ltd.

2,4-Dichlorophenoxyacetic acid (2,4-D) degradation promoted by nanoparticulate zerovalent iron (nZVI) in aerobic suspensions

Correia de Velosa, Adriana; Pupo Nogueira, Raquel F.
Tipo: Artigo de Revista Científica Formato: 72-79
Português
Relevância na Pesquisa
36.1%
Reactive species generated by Fe0 oxidation promoted by O2 (catalyzed or not by ligands) are able to degrade contaminant compounds like the herbicide 2,4-dichlorophenoxyacetic acid. The degradation of 2,4-D was influenced by the concentrations of zero valent iron (ZVI) and different ligands, as well as by pH. In the absence of ligands, the highest 2,4-D degradation rate was obtained at pH 3, while the highest percentage degradation (50%) was achieved at pH 5 after 120 min of reaction. Among the ligands studied (DTPA, EDTA, glycine, oxalate, and citrate), only ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) significantly enhanced oxidation of 2,4-D. This increase in oxidation was observed at all pH values tested (including neutral to alkaline conditions), indicating the feasibility of the technique for treatment of contaminated water. In the presence of EDTA, the oxidation rate was greater at pH 3 than at pH 5 or 7. Increasing the EDTA concentration increased the rate and percentage of 2,4-D degradation, however increasing the Fe0 concentration resulted in the opposite behavior. It was found that degradation of EDTA and 2,4-D occurred simultaneously, and that the new methodology avoided any 2,4-D removal by adsorption/coprecipitation. © 2013 Elsevier Ltd.

Photoelectrocatalysis based on Ti/TiO2 nanotubes removes toxic properties of the azo dyes Disperse Red 1, Disperse Red 13 and Disperse Orange 1 from aqueous chloride samples

Ferraz, E. R A; Oliveira, G. A R; Grando, M. D.; Lizier, T. M.; Zanoni, Maria Valnice Boldrin; Oliveira, D. P.
Tipo: Artigo de Revista Científica Formato: 108-114
Português
Relevância na Pesquisa
36.18%
This work describes the efficiency of photoelectrocatalysis based on Ti/TiO2 nanotubes in the degradation of the azo dyes Disperse Red 1, Disperse Red 13 and Disperse Orange 1 and to remove their toxic properties, as an alternative method for the treatment of effluents and water. For this purpose, the discoloration rate, total organic carbon (TOC) removal, and genotoxic, cytotoxic and mutagenic responses were determined, using the comet, micronucleus and cytotoxicity assays in HepG2 cells and the Salmonella mutagenicity assay. In a previous study it was found that the surfactant Emulsogen could contribute to the low mineralization of the dyes (60% after 4h of treatment), which, in turn, seems to account for the mutagenicity of the products generated. Thus this surfactant was not added to the chloride medium in order to avoid this interference. The photoelectrocatalytic method presented rapid discoloration and the TOC reduction was ?87% after 240min of treatment, showing that photoelectrocatalysis is able to mineralize the dyes tested. The method was also efficient in removing the mutagenic activity and cytotoxic effects of these three dyes. Thus it was concluded that photoelectrocatalysis was a promising method for the treatment of aqueous samples. © 2013 Elsevier Ltd.

Assessment of the Removal Capacity, Tolerance, and Anatomical Adaptation of Different Plant Species to Benzene Contamination

Campos, Valquiria de; Souto, L. S.; Medeiros, Thales Augusto de Miranda; Toledo, S. P.; Sayeg, I. J.; Ramos, R. L.; Shinzato, M. C.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 12
Português
Relevância na Pesquisa
36.1%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 12/05595-0; Processo FAPESP: 12/05982-3; Processo FAPESP: 12/08337-1; Processo FAPESP: 12/24832-2; The medium most directly affected by anthropic contamination is soil and, hence, groundwater (saturated and unsaturated zones). In the phytoremediation process, the direct absorption of soil contaminants through the roots is a surprising pollutant removal mechanism. Plants can act as a natural filter of shallow groundwater contamination, controlling and reducing the vertical percolation of contaminants into the soil, and after reaching the level of the water table, the roots can absorb contaminants dissolved in the water, thus reducing the size of the plume and protecting receptor sites (water supply wells, rivers, lakes) from possible contamination. In the first phase of the research, assays were performed to evaluate the tolerance of plant species to the direct injection of a benzene solution into the roots. Subsequent experiments involved direct absorption and spraying. The aim of this study was to evaluate the potential for tolerance and reaction to high levels of benzene. Three plant species were used...

Preparação e caracterização de argila oganofílica para adsorção de BTX; Preparation and characterization of organoclay for adsorption of BTX

Sidmara Bedin
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: dissertação de mestrado Formato: application/pdf
Publicado em 14/03/2014 Português
Relevância na Pesquisa
26.26%
Diariamente, uma grande quantidade de fluxos de água sofre contaminação por compostos orgânicos como, por exemplo, o benzeno, tolueno e xileno (BTX), os quais são compostos tóxicos e nocivos ao meio ambiente e aos seres humanos. Sendo assim, o estudo de técnicas de remoção e tratamento desses poluentes vem se tornando tema de muitas pesquisas. A adsorção tem se mostrado uma técnica bastante eficiente, pois atende aos limites da legislação, apresenta baixo consumo energético e custo de processo, ainda mais quando se faz uso de um adsorvente alternativo, como é o caso da argila organofílica. Nesse trabalho foi proposto avaliar a argila esmectítica sódica nacional Fluidgel, na forma natural e organofilizada, como materiais adsorventes alternativos na remoção dos compostos orgânicos BTX de soluções aquosas, em ensaios em sistema batelada e em sistema dinâmico. A argila organofílica foi preparada a partir da argila comercial e do sal quaternário de amônia HDTMA e se verificou a capacidade de troca catiônicas dos adsorventes. Foram realizadas técnicas de caracterização com a finalidade de determinar a área superficial do material, estrutura de poros, estrutura cristalina, morfologia de superfície, composição química...

Development of permeable biobarrier for the removal of PAH’s by Trichoderma longibrachiatum

Cobas, M.; Ferreira, L.; Tavares, M. T.; Sanromán, M. A.; Pazos, M.
Fonte: Pergamon Press Ltd. Publicador: Pergamon Press Ltd.
Tipo: Artigo de Revista Científica
Publicado em //2013 Português
Relevância na Pesquisa
36.18%
In this work, the formation of permeable reactive biobarriers (PRBBs) using Trichoderma longibrachiatum over nylon sponge as bioreactive medium for removal of polycyclic aromatic hydrocarbons (PAHs) was studied. Colony formation was pretested without PAH presence by inoculation of fungus into nylon sponge. The fungus formed a large quantity of strongly adhesive biofilm among nylon sponge. Afterwards, the ability of the developed bioreactive medium was tested to remediate phenanthrene in aqueous medium and in soil. In aqueous medium, a 90% of phenanthrene concentration reduction was observed after 14 d. However, the pollutant removal in soil requires previous fungus colonization and the attained level was around 70% after 28 d. Subsequently, the formed bioreactive material was used in a glass column reactor to evaluate its application as PRBBs. Mixtures of phenanthrene, benzo[a]anthracene and pyrene at several concentrations, from 100 to 400 ?M, were treated. In all cases, the performance of the PRBB was satisfactory and total PAH removals were achieved. These results suggest that PRBBs of T. longibrachiatum supported on nylon sponge can be an effective method for the treatment of PAHs.

Development of permeable reactive biobarrier for the removal of PAHs by Trichoderma longibrachiatum

Cobas, M.; Ferreira, L.; Tavares, M. T.; Sanromán, M. A.; Pazos, M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 01/01/2013 Português
Relevância na Pesquisa
36.18%
In this work, the formation of permeable reactive biobarriers (PRBBs) using Trichoderma longibrachiatum over nylon sponge as bioreactive medium for removal of polycyclic aromatic hydrocarbons (PAHs) was studied. Colony formation was pretested without PAH presence by inoculation of fungus into nylon sponge. The fungus formed a large quantity of strongly adhesive biofilm among nylon sponge. Afterwards, the ability of the developed bioreactive medium was tested to remediate phenanthrene in aqueous medium and in soil. In aqueous medium, a 90% of phenanthrene concentration reduction was observed after 14 d. However, the pollutant removal in soil requires previous fungus colonization and the attained level was around 70% after 28 d. Subsequently, the formed bioreactive material was used in a glass column reactor to evaluate its application as PRBBs. Mixtures of phenanthrene, benzo[a]anthracene and pyrene at several concentrations, from 100 to 400 ?M, were treated. In all cases, the performance of the PRBB was satisfactory and total PAH removals were achieved. These results suggest that PRBBs of T. longibrachiatum supported on nylon sponge can be an effective method for the treatment of PAHs.

Bionanocomposites of Fe3O4/SiO2 and alginate for magnetic removal of Cr(III) species from water; Bionanocompositos de Fe3O4/SiO2 e alginatopara remoção magnética de espécies de Cr(III) em água

Busse, Marta Julia
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: masterthesis
Português
Relevância na Pesquisa
46.26%
The aim of the present work was to study the removal of Cr (III) species from aqueous solutions by adsorption process, using magnetic nanoparticles functionalized with amine groups and with the polysaccharide alginate. Heavy metal pollution is serious environmental and public health problem worldwide. Chromium is one of the most toxic metal endangering human life. Cr(III) is often used in industry which caused water pollution. Therefore, increased interest by the researchers to employ nanomaterials for the removal contamination and explore adsorbents to replace expensive materials, particularly low-cost raw materials such as, residual polymers materials or agricultural by-products. The work included the preparation of magnetic nanoparticles, coating them with amorphous silica shell functionalized with amine groups and the covalent attachment of alginate to the magnetic nanoparticle. The properties of the nanoparticles were assessed by a number of experimental techniques namely x-ray diffraction, infrared spectroscopy, elemental analysis, thermogravimetry and zeta potential measurements. Silica coated magnetic nanoparticles functionalized with amine groups were investigated for the uptake of Cr(III)/EDTA complexes from water, while the nanoparticles attached to the alginate molecules were tested for the removal of aqueous Cr(III) ions. The kinetic results were fitted to models of pseudo first and pseudo second order and the equilibrium adsorption results were adjusted to suitable isotherm models such as Langmuir and Freundlich. The composite nanoparticles revealed affinity to the Cr(III) species. Due to its properties...

Adsorption Properties of Activated Carbons Prepared from Recycled PET in the Removal of Organic Pollutants from Aqueous Solutions

Cansado, IPP; Galacho, Cristina; Nunes, AS; Ribeiro Carrott, MML; Carrott, PJM
Fonte: Multiscience Publicador: Multiscience
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.26%
Activated carbons (ACs) were prepared from recycled polyethylene terephthalate (PET) by chemical activation with KOH and used successfully for the removal of 4-chloro-2-methylphenoxyacetic acid (MCPA) and Methylene Blue (MB) from aqueous media. In order to improve the adsorption capacity towards pollutant removal, the AC was submitted to different post-treatments. After oxidation, the sample exhibited an increase in MB adsorption capacity but showed a decreased MCPA adsorption removal extent. High-temperature treatment was not favourable for increasing the MB or MCPA adsorption capacity. However, after treatment with sodium hydroxide or urea, the samples showed a significant increase in their MCPA adsorption capacities. Normalisation of the MB and MCPA adsorption data with respect to the micropore volume led to a clearer understanding of the influence of the textural and chemical characteristics of the AC on the removal of MB and MCPA. The MB and MCPA adsorption isotherms were analysed via the Langmuir and Freundlich models, with the calculated parameters accurately fitting the experimental data and exhibiting good agreement between them.

How Can the Functioning of Treatment Wetlands be Enhanced?

Dordio, Ana; Carvalho, A. J. Palace
Fonte: Nova Science Publishers Publicador: Nova Science Publishers
Tipo: bookpart
Português
Relevância na Pesquisa
26.28%
Wetlands have already been recognized to hold the capacity for efficiently reducing or removing large amounts of pollutants from point sources (e.g. municipal and certain industrial effluents) as well as non-point sources (e.g. mining, agricultural and urban runoff) including organic matter, suspended solids, excess of nutrients, pathogens, metals and other micropollutants. This pollutants removal is accomplished by the interdependent action of several physical, chemical and biological processes which include sedimentation, filtration, chemical precipitation, sorption, biodegradation, and plants uptake among others. The mechanisms and the interdependences among the wetlands’ components (water, substrate and biota) are complex and not yet entirely understood, although some progresses have been achieved in the latest years as the awareness to the water depurative functions of wetlands becomes more widespread. In fact, studies have led to both a greater understanding of the potential of natural wetland ecosystems for pollutants assimilation and the design of new natural water treatment systems inspired in these natural systems, the constructed wetlands systems (CWS). These CWS can be defined as man-made systems that have been designed and constructed to utilize the natural processes involving wetland vegetation...

How can the Functioning of Treatment Wetlands be Enhanced?

Dordio, Ana; Carvalho, A.J. Palace
Fonte: Nova Science Publishers Publicador: Nova Science Publishers
Tipo: bookpart
Português
Relevância na Pesquisa
26.28%
Wetlands have already been recognized to hold the capacity for efficiently reducing or removing large amounts of pollutants from point sources (e.g. municipal and certain industrial effluents) as well as non-point sources (e.g. mining, agricultural and urban runoff) including organic matter, suspended solids, excess of nutrients, pathogens, metals and other micropollutants. This pollutants removal is accomplished by the interdependent action of several physical, chemical and biological processes which include sedimentation, filtration, chemical precipitation, sorption, biodegradation, and plants uptake among others. The mechanisms and the interdependences among the wetlands’ components (water, substrate and biota) are complex and not yet entirely understood, although some progresses have been achieved in the latest years as the awareness to the water depurative functions of wetlands becomes more widespread. In fact, studies have led to both a greater understanding of the potential of natural wetland ecosystems for pollutants assimilation and the design of new natural water treatment systems inspired in these natural systems, the constructed wetlands systems (CWS). These CWS can be defined as man-made systems that have been designed and constructed to utilize the natural processes involving wetland vegetation...

Removal of Antibiotics by “Green” Clay Sorbents

Dordio, A. V.; Miranda, Susana; Carvalho, A. J. Palace
Fonte: International Congress on Water, Waste and Energy Management Publicador: International Congress on Water, Waste and Energy Management
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.31%
Contamination of water resources with pharmaceuticals has been one of the top concerns of environmental sciences in the latest years [1], the matter having received very significant media coverage recently [2]. Antibiotics in particular have been gathering considerable attention and are amongst the most serious worries due to the development of antibiotic resistant bacteria as result of prolonged exposure [1, 2]. Because most wastewater treatment plants were only designed for removing bulk pollutants, many other more specific pollutant types that are present in low concentrations in the wastewaters are often inefficiently treated and end up being released into receiving water bodies. Although in many cases these contaminants are detected only at small concentrations in environmental samples, the large variety of such compounds and the high potential for adverse interactions with living organisms (due to the nature of their action) is a matter of serious concern. Several advanced technologies have been evaluated as options to treat these contaminants, e.g. advanced oxidative processes or membrane filtration, but despite the sometimes high removal efficiencies attained, these technologies are too expensive to be considered as viable solutions on a large scale. Adsorption...

Analysis of constructed wetland performance for irrigation reuse

Marecos do Monte, H.; Albuquerque, A.
Fonte: IWA Publicador: IWA
Tipo: Artigo de Revista Científica
Publicado em //2010 Português
Relevância na Pesquisa
26.31%
Most of the wastewater treatment systems in small rural communities of the Cova da Beira region (Portugal) consist of constructed wetlands (CW) with horizontal subsurface flow (HSSF). It is believed that those systems allow the compliance of discharge standards as well as the production of final effluents with suitability for reuse. Results obtained in a nine-month campaign in an HSSF bed pointed out that COD and TSS removal were lower than expected. A discrete sampling also showed that removal of TC, FC and HE was not enough to fulfill international irrigation goals. However, the bed had a very good response to variation of incoming nitrogen loads presenting high removal of nitrogen forms. A good correlation between mass load and mass removal rate was observed for BOD5, COD, TN, NH4-N, TP and TSS, which shows a satisfactory response of the bed to the variable incoming loads. The entrance of excessive loads of organic matter and solids contributed for the decrease of the effective volume for pollutant uptake and therefore, may have negatively influenced the treatment capability. Primary treatment should be improved in order to decrease the variation of incoming organic and solid loads and to improve the removal of COD, solids and pathogenic. The final effluent presented good physical–chemical quality to be reused for irrigation...

Cultivation of microalgae Spirulina platensis (Arthrospira platensis) from biological treatment of swine wastewater

Mezzomo,Natália; Saggiorato,Adriana Galon; Siebert,Rochele; Tatsch,Pihetra Oliveira; Lago,Maria Cristina; Hemkemeier,Marcelo; Costa,Jorge Alberto Vieira; Bertolin,Telma Elita; Colla,Luciane Maria
Fonte: Sociedade Brasileira de Ciência e Tecnologia de Alimentos Publicador: Sociedade Brasileira de Ciência e Tecnologia de Alimentos
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2010 Português
Relevância na Pesquisa
36.23%
The microalgae biomass production from swine wastewater is a possible solution for the environmental impact generated by wastewater discharge into water sources. The biomass can be added to fish feed, which can be used in the formulation of meat products. This work addresses the adaptation of the microalgae Spirulina platensis (Arthrospira platensis) in swine wastewater and the study of the best dilution of the wastewater for maximum biomass production and for removal of Chemical Oxygen Demand (COD), ammonia and phosphorous to the microalgae. The cultivation of Spirulina platensis, strain Paracas presented maximum cellular concentrations and maximum specific growth rates in the wastewater concentration of 5.0 and 8.5%. The highest COD removals occurred with 26.5 and 30.0% of wastewater in the medium. The maximum removal of total phosphorous (41.6%), was with 8.5% of wastewater, which is related to the microalgae growth. The results of Spirulina culture in the swine wastewater demonstrated the possibility of using these microalgae for the COD and phosphorous removal and for biomass production.

A Previously Unexposed Forest Soil Microbial Community Degrades High Levels of the Pollutant 2,4,6-Trichlorophenol

Sánchez, M. A.; Vásquez, M.; González, B.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: text
Publicado em /12/2004 Português
Relevância na Pesquisa
26.45%
2,4,6-Trichlorophenol (2,4,6-TCP) is a hazardous pollutant that is efficiently degraded by some aerobic soil bacterial isolates under laboratory conditions. The degradation of this pollutant in soils and its effect on the soil microbial community are poorly understood. We report here the ability of a previously unexposed forest soil microbiota to degrade high levels of 2,4,6-TCP and describe the changes in the soil microbial community found by terminal restriction fragment length polymorphism (T-RFLP) analysis. After 30 days of incubation, about 50% degradation of this pollutant was observed in soils amended with 50 to 5,000 ppm of 2,4,6-TCP. The T-RFLP analysis showed that the soil bacterial community was essentially unchanged after exposure to up to 500 ppm of 2,4,6-TCP. However, a significant decrease in richness was found with 2,000 and 5,000 ppm of 2,4,6-TCP, even though the removal of this pollutant remained high. The introduction of Ralstonia eutropha JMP134 or R. eutropha MS1, two efficient 2,4,6-TCP degraders, to this soil did not improve degradation of this pollutant, supporting the significant bioremediation potential of this previously unexposed, endogenous forest soil microbial community.

Enhancing the Production of Hydroxyl Radicals by Pleurotus eryngii via Quinone Redox Cycling for Pollutant Removal?

Gómez-Toribio, Víctor; García-Martín, Ana B.; Martínez, María J.; Martínez, Ángel T.; Guillén, Francisco
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: text
Português
Relevância na Pesquisa
36.29%
The induction of hydroxyl radical (OH) production via quinone redox cycling in white-rot fungi was investigated to improve pollutant degradation. In particular, we examined the influence of 4-methoxybenzaldehyde (anisaldehyde), Mn2+, and oxalate on Pleurotus eryngii OH generation. Our standard quinone redox cycling conditions combined mycelium from laccase-producing cultures with 2,6-dimethoxy-1,4-benzoquinone (DBQ) and Fe3+-EDTA. The main reactions involved in OH production under these conditions have been shown to be (i) DBQ reduction to hydroquinone (DBQH2) by cell-bound dehydrogenase activities; (ii) DBQH2 oxidation to semiquinone (DBQ?) by laccase; (iii) DBQ? autoxidation, catalyzed by Fe3+-EDTA, producing superoxide (O2?) and Fe2+-EDTA; (iv) O2? dismutation, generating H2O2; and (v) the Fenton reaction. Compared to standard quinone redox cycling conditions, OH production was increased 1.2- and 3.0-fold by the presence of anisaldehyde and Mn2+, respectively, and 3.1-fold by substituting Fe3+-EDTA with Fe3+-oxalate. A 6.3-fold increase was obtained by combining Mn2+ and Fe3+-oxalate. These increases were due to enhanced production of H2O2 via anisaldehyde redox cycling and O2? reduction by Mn2+. They were also caused by the acceleration of the DBQ redox cycle as a consequence of DBQH2 oxidation by both Fe3+-oxalate and the Mn3+ generated during O2? reduction. Finally...

Temporary Storage or Permanent Removal? The Division of Nitrogen between Biotic Assimilation and Denitrification in Stormwater Biofiltration Systems

Payne, Emily G. I.; Fletcher, Tim D.; Russell, Douglas G.; Grace, Michael R.; Cavagnaro, Timothy R.; Evrard, Victor; Deletic, Ana; Hatt, Belinda E.; Cook, Perran L. M.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: text
Publicado em 26/03/2014 Português
Relevância na Pesquisa
36.44%
The long-term efficacy of stormwater treatment systems requires continuous pollutant removal without substantial re-release. Hence, the division of incoming pollutants between temporary and permanent removal pathways is fundamental. This is pertinent to nitrogen, a critical water body pollutant, which on a broad level may be assimilated by plants or microbes and temporarily stored, or transformed by bacteria to gaseous forms and permanently lost via denitrification. Biofiltration systems have demonstrated effective removal of nitrogen from urban stormwater runoff, but to date studies have been limited to a ‘black-box’ approach. The lack of understanding on internal nitrogen processes constrains future design and threatens the reliability of long-term system performance. While nitrogen processes have been thoroughly studied in other environments, including wastewater treatment wetlands, biofiltration systems differ fundamentally in design and the composition and hydrology of stormwater inflows, with intermittent inundation and prolonged dry periods. Two mesocosm experiments were conducted to investigate biofilter nitrogen processes using the stable isotope tracer 15NO3? (nitrate) over the course of one inflow event. The immediate partitioning of 15NO3? between biotic assimilation and denitrification were investigated for a range of different inflow concentrations and plant species. Assimilation was the primary fate for NO3? under typical stormwater concentrations (?1–2 mg N/L)...