Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 30
Filtrar
Mais filtros










Intervalo de ano de publicação
1.
J Hazard Mater ; 382: 121085, 2020 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-31465946

RESUMO

Here, we investigated the synergistic effect towards phenol degradation and mineralization between ozonation (O3) and electrochemical filtration (ECF) using perforated titanium as cathode and porous carbon nanotube (CNT) networks as anode. A flow rate of 1.6 mL min-1, 10 mM of sodium sulfate electrolyte, 1.0 mM of phenol (model aromatic compound), and an ozone dose of 12 mgO3 L-1 were used. Insight into the synergistic mechanism was achieved via carbon anode morphology characterization and phenol degradation kinetics analysis. Improved kinetic performance was observed for the combined process (O3-ECF) as compared to the sum of the individual processes, not only towards phenol degradation (3.2-fold increase), but also towards phenol mineralization (2.2-fold increase). Scanning electron microscopy revealed a significant decrease of polymer formation and deposition on CNT after the hybrid O3-ECF process as compared to the ECF alone. Voltage-dependent (0-2.5 V) ozone CNT functionalization was investigated at pH 7-11 to assist in elucidation of the synergistic mechanism. X-Ray photoelectron spectroscopy indicated increases up to 26-fold in CNT oxygen content post-ozonation at pH 7 comparing to fresh CNT. Various potential O3-ECF synergistic reaction mechanisms for organic aromatic oxidation and mineralization are discussed.

2.
Environ Sci Pollut Res Int ; 26(32): 33281-33293, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31520394

RESUMO

The main goal of this study was to evaluate the removal of bromate from drinking water using a heterogeneous photocatalytic mili-photoreactor, based on NETmix technology. The NETmix mili-reactor consists of a network of channels and chambers imprinted in a back slab made of acrylic (AS) or stainless steel (SSS) sealed, through mechanical compression and o-rings, with an UVA-transparent front borosilicate glass slab (BGS). A plate of UVA-LEDs was placed above the BGS window. TiO2-P25 thin films were immobilized on the BGS (back-side illumination, BSI) or SSS (front-side illumination, FSI) by using a spray deposition method. The photoreduction rate of a 200 µg L-1 (1.56 µM) BrO3- solution was assessed taking into account the following: (i) catalyst film thickness, (ii) catalyst coated surface and illumination mechanism (BSI or FSI), (iii) solution pH, (iv) type and dose of sacrificial agent (SA), (v) reactor material, and (vi) water matrix. In acidic conditions (pH 3.0) and in the absence of light/catalyst/SA, 28% and 36% of BrO3- was reduced into Br- only by contacting with AS and SSS during 2-h, respectively. This effect prevailed during BSI experiments, but not for FSI ones since back SSS was coated with the photocatalyst. The results obtained have demonstrated that (i) the molar rate of disappearance of bromates was similar to the molar rate of formation of bromides; (ii) higher BrO3- reduction efficiencies were reached in the presence of an SA using the FSI at pH 3.0; (iii) formic acid ([BrO3-]:[CH2O2] molar ratio of 1:3) presented higher performance than humic acids (HA = 1 mg C L-1) as SA; (iv) high amounts of HA impaired the BrO3- photoreduction reaction; (v) SSS coated catalyst surface revealed to be stable for at least 4 consecutive cycles, keeping its photonic efficiency. Under the best operating conditions (FSI, 18 mL of 2% wt. TiO2-P25 suspension, pH 3.0), the use of freshwater matrices led to (i) equal or higher reaction rates, when compared with a synthetic water in the absence of SA, and (ii) lower reaction rates, when compared with a synthetic water containing formic acid with a [BrO3-]:[CH2O2] molar ratio of 1:3. Notwithstanding, heterogeneous TiO2 photocatalysis, using the NETmix mili-reactor can be used to promote the reduction of BrO3- into Br-, attaining concentrations below 10 µg L-1 (guideline value) after 2-h reaction. Graphical Abstract .


Assuntos
Bromatos/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Bromatos/química , Brometos , Catálise , Água Potável , Poluentes Químicos da Água/química
3.
Waste Manag ; 89: 114-128, 2019 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-31079725

RESUMO

This study aimed at developing an efficient multistage treatment strategy for a complex industrial landfill leachate: a leather tannery landfill leachate. Based on the leachate physicochemical characteristics, the following treatment train was delineated and tested: (i) initial biological process for removal of biodegradable organics, ammonium and alkalinity, (ii) coagulation/flocculation process for total removal of chromium and partial removal of recalcitrant organics and suspended solids, (iii) advanced oxidation process (AOP) or electrochemical AOP (EAOP) for degradation of recalcitrant organics and biodegradability enhancement, and (iv) final biological polishing step. Two initial biological treatment configurations were applied: one comprising nitrification and the other nitrification-denitrification. Coagulation/flocculation was optimized in terms of pH, coagulant dosage (iron(III) chloride) and flocculant nature and dosage. The following AOPs/EAOPs were tested: Fenton, photo-Fenton with UVA or UVC radiation (PF-UVA or PF-UVC), anodic oxidation (AO), electro-Fenton (EF) and photoelectro-Fenton with UVA radiation (PEF-UVA). The biological nitrification-denitrification was beneficial not only because it avoided the need for alkalinity addition during nitrification and decreased the amount of substrate added during denitrification, as expected. Over and above that, it reduced the acid consumption in the coagulation/flocculation, avoided the application of an additional stage comprising nitrites oxidation to nitrates prior to the AOP/EAOP, and improved the efficiency of Fenton's reaction based processes. Following nitrification-denitrification, the coagulation/flocculation was maximized at pH 3.0 and 400 mg Fe L-1 with no flocculant addition. The PEF-UVA process was the best AOP/EAOP. The final leachate fulfilled the discharge limits into waterbodies.


Assuntos
Poluentes Químicos da Água , Desnitrificação , Compostos Férricos , Peróxido de Hidrogênio , Ferro , Nitrificação , Oxirredução
4.
Sci Total Environ ; 678: 448-456, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31077923

RESUMO

This study reports the performance of a carbon nanotube (CNT) electrochemical filter applied to 17ß-estradiol (E2) and 17α-ethinylestradiol (EE2) degradation and their estrogenic activity removal (calculated in terms of E2 equivalent, EQ-E2). The performance of CNT electrochemical filter was assessed at different applied voltages (0-2.5 V) and aqueous matrices (ultrapure water and urban wastewater), using 37 µM of E2 and EE2, a flow rate of 1.5 mL min-1 and 10 mM of Na2SO4, used as supporting electrolyte. Surface characterization of CNT anodic filters was completed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) was used to investigate electron transfer mechanisms. The CNT electrochemical filter was successfully applied to E2 and EE2 degradation and removals higher than 95.3% (oxidative fluxes >2.94 ±â€¯0.05 mmol h-1 m-2) were achieved when 2.5 V was applied for both ultrapure water and urban wastewater. CV results indicate that the oxidation in the CNT electrochemical filter is an irreversible process. SEM and XPS results showed evidence of the polymer formation on the CNT surface after 300 min of reaction, which probably reduced the efficiency of the process under low applied voltages. Estrogenic activity was considerably reduced and minimal EQ-E2 levels were observed when 2.5 V was applied. A residual EQ-E2 was observed, likely due to the presence of estrogens, which suggests the non-formation of estrogenic intermediates. At 2.5 V total cell potential, the energy required to remove estrogenic activity was 0.014 ±â€¯0.001 kWh m-3 for ultrapure water and 0.021 ±â€¯0.001 kWh m-3 for post-secondary wastewater. These results suggest a CNT electrochemical filter may have potential to effectively and efficiently remove estrogenic activity and may be a feasible process for wastewater polishing treatment.


Assuntos
Estradiol/análise , Estrogênios/análise , Etinilestradiol/análise , Nanotubos de Carbono/química , Eliminação de Resíduos Líquidos/instrumentação , Poluentes Químicos da Água/análise , Técnicas Eletroquímicas , Filtração , Eliminação de Resíduos Líquidos/métodos
5.
Environ Sci Pollut Res Int ; 26(5): 4288-4299, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29717425

RESUMO

Pharmaceutically active compounds are carried into aquatic bodies along with domestic sewage, industrial and agricultural wastewater discharges. Psychotropic drugs, which can be toxic to the biota, have been detected in natural waters in different parts of the world. Conventional water treatments, such as activated sludge, do not properly remove these recalcitrant substances, so the development of processes able to eliminate these compounds becomes very important. Advanced oxidation processes are considered clean technologies, capable of achieving high rates of organic compounds degradation, and can be an efficient alternative to conventional treatments. In this study, the degradation of alprazolam, clonazepam, diazepam, lorazepam, and carbamazepine was evaluated through TiO2/UV-A, H2O2/UV-A, and TiO2/H2O2/UV-A, using sunlight and artificial irradiation. While using TiO2 in suspension, best results were found at [TiO2] = 0.1 g L-1. H2O2/UV-A displayed better results under acidic conditions, achieving from 60 to 80% of removal. When WWTP was used, degradation decreased around 50% for both processes, TiO2/UV-A and H2O2/UV-A, indicating a strong matrix effect. The combination of both processes was shown to be an adequate approach, since removal increased up to 90%. H2O2/UV-A was used for disinfecting the aqueous matrices, while mineralization was obtained by TiO2-photocatalysis.


Assuntos
Desinfecção/métodos , Preparações Farmacêuticas/isolamento & purificação , Titânio/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/isolamento & purificação , Biodegradação Ambiental , Peróxido de Hidrogênio/química , Oxirredução , Preparações Farmacêuticas/química , Preparações Farmacêuticas/metabolismo , Processos Fotoquímicos , Luz Solar , Raios Ultravioleta , Águas Residuárias/química , Águas Residuárias/microbiologia , Poluentes Químicos da Água/química , Poluentes Químicos da Água/metabolismo
6.
Eng. sanit. ambient ; 23(5): 901-911, set.-out. 2018. tab, graf
Artigo em Português | LILACS-Express | LILACS | ID: biblio-975142

RESUMO

RESUMO Os lixiviados de áreas de disposição de resíduos municipais apresentam, em geral, alta complexidade, variabilidade, toxicidade, recalcitrância e alta concentração de nitrogênio amoniacal. Neste estudo, aplicaram-se técnicas combinadas para o tratamento de um lixiviado, a saber: coagulação/floculação (C/F), air stripping e ozonização, combinados com o tratamento por lodo ativado com/sem inserção de carvão ativado. O processo de C/F levou a uma redução na demanda química de oxigênio (DQO) de 58,1% e na cor, de 85,6%. O air stripping foi realizado em pH>12 e obteve-se diminuição dos níveis de nitrogênio amoniacal para abaixo de 60 mg.L-1. O processo de ozonização, com consumo de ozônio de 397 mgO3.L-1 e 2.376 mgO3.L-1, apresentou bons resultados, com aumento de 59,4% na relação DBO5/DQO e uma redução de toxicidade superior a 85%. Obteve-se melhor eficiência para o lodo ativado sem carvão ativado, com lixiviado pré-tratado por C/F + air stripping + ozonização (400 mgO3.L-1). Tal combinação resultou em uma redução de 90,6% na DQO do lixiviado e mais de 99% nos níveis de nitrogênio amoniacal.


ABSTRACT Leachate from waste disposal areas generally presents high complexity, variability, toxicity, recalcitrance and high concentration of ammonia nitrogen. In this work, combined techniques for the treatment of leachate were applied, namely: coagulation/flocculation, air stripping and ozonation combined with activated sludge treatment with/without activated carbon. The coagulation/flocculation process led to a COD reduction of 58.1% and color removal of 85.6%. The air stripping was performed at pH>12 and reduced ammonia levels below of 60 mg.L-1. The ozonation process (ozone consumption of 397 mgO3.L-1 and 2376 mgO3.L-1) presented good results. It was observed a BOD5/COD increase of 59.4% and a toxicity reduction of more than 85%. The best efficiency was observed with sludge activated without activated carbon for the pre-treated leachate by coagulation/flocculation + air stripping + ozonation (400 mgO3.L-1). This combination resulted in a COD reduction of 90.6% and more than 99% of ammonia nitrogen removal.

7.
Environ Sci Pollut Res Int ; 25(28): 27808-27818, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30132283

RESUMO

Polycyclic aromatic hydrocarbons (PAHs) are on the list of priority pollutants to be eliminated from the environment due to their carcinogenic and mutagenic action, chemical stability, and resistance to biodegradation. The aim of this study was to evaluate the degradation of fluorene, a well-known PAH, in aqueous solutions (0.03 and 0.08 mg L-1), by means of a solar-driven conventional (PF) and modified photo-Fenton mediated by ferrioxalate complexes (PFF). Photolysis was also employed for comparison purposes. PF reaction was evaluated at different pH values (2.8, 3.5, and 4.0) and iron concentrations (2, 5, 10, and 20 mg L-1). On the other hand, PFF studies were conducted at mild pH conditions (4.0, 5.0, and 6.0) and iron content of 2 mg L-1, keeping initial iron/oxalate molar ratio at 1:3. In both PF and PFF, the initial hydrogen peroxide/iron molar ratio was maintained at 5. In the presence of methanol as cosolvent for fluorene dissolution, the PF reaction was hampered and no consumption of H2O2 was observed during the reaction carried out at constant pH (2.8). This led to low degradation rates, similar to those achieved by photolysis. Under the same pH but using acetonitrile as cosolvent for fluorene dissolution, fluorene degradation was found to be proportional to the iron content used in the PF experiments. On the other hand, at an invariable iron concentration of 5 mg Fe2+ L-1, the increase in pH was accompanied by a decrease in the molar fraction of the most photoactive iron complex (FeOH2+) and ferric hydroxides precipitation, leading to a reduction in the fluorene degradation rate. With regard to the PFF tests, similar fluorene degradation performance was achieved at pH 4 and 5, while at pH 6 iron precipitation became relevant and the degradation rate was slightly slower. PFF has shown to be more efficient than the PF under the same pH (4) and iron concentration (2 mg L-1). Moreover, even at near neutral pH (6), fluorine degradation was shown to be feasible by using ferrioxalate complexes.


Assuntos
Fluorenos/análise , Peróxido de Hidrogênio/química , Ferro/química , Oxalatos/química , Luz Solar , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Biodegradação Ambiental , Fluorenos/efeitos da radiação , Concentração de Íons de Hidrogênio , Ácido Oxálico , Oxirredução , Fotólise , Poluentes Químicos da Água/efeitos da radiação
8.
Environ Sci Pollut Res Int ; 25(28): 27796-27807, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29696544

RESUMO

In the present work, a facile method to prepare translucent anatase thin films on cellulose acetate monolithic (CAM) structures was developed. A simple sol-gel method was applied to synthesize photoactive TiO2 anatase nanoparticles using tetra-n-butyl titanium as precursor. The immobilization of the photocatalyst on CAM structures was performed by a simple dip-coating method. The translucent anatase thin films allow the UV light penetration through the CAM internal walls. The photocatalytic activity was tested on the degradation of n-decane (model volatile organic compound-VOC) in gas phase, using a tubular lab-scale (irradiated by simulated solar light) and pilot-scale (irradiated by natural solar light or UVA light) reactors packed with TiO2-CAM structures, both equipped with compound parabolic collectors (CPCs). The efficiency of the photocatalytic oxidation (PCO) process in the degradation of n-decane molecules was studied at different operating conditions at lab-scale, such as catalytic bed size (40-160 cm), TiO2 film thickness (0.435-0.869 µm), feed flow rate (75-300 cm3 min-1), n-decane feed concentration (44-194 ppm), humidity (3 and 40%), oxygen concentration (0 and 21%), and incident UV irradiance (18.9, 29.1, and 38.4 WUV m-2). The decontamination of a bioaerosol stream was also evaluated by the PCO process, using Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive) as model bacteria. A pilot-scale unit was operated day and night, using natural sunlight and artificial UV light, to show its performance in the mineralization of n-decane air streams under real outdoor conditions. Graphical abstract Normally graphics abstract are not presented with captions/legend. The diagram is a collection of images that resume the work.


Assuntos
Poluentes Atmosféricos/análise , Alcanos/análise , Celulose/análogos & derivados , Nanopartículas/química , Titânio/química , Compostos Orgânicos Voláteis/análise , Aerossóis , Alcanos/efeitos da radiação , Catálise , Celulose/química , Modelos Teóricos , Oxirredução , Projetos Piloto , Pseudomonas aeruginosa/efeitos da radiação , Staphylococcus aureus/efeitos da radiação , Luz Solar , Propriedades de Superfície , Raios Ultravioleta , Compostos Orgânicos Voláteis/efeitos da radiação
9.
Environ Sci Pollut Res Int ; 24(7): 6353-6360, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-27044292

RESUMO

Contaminated soil has become a growing issue in recent years. The most common technique used to remove contaminants (such as metals) from the soil is the soil washing process. However, this process produces a final effluent containing chelating agents (i.e., ethylenediaminedisuccinic acid, also known as EDDS) and extracted metals (i.e., Cu, Fe, and Zn) at concentrations higher than discharge limits allowed by the Italian and Brazilian environmental law. Therefore, it is necessary to develop further treatments before its proper disposal or reuse. In the present study, soil washing tests were carried out through two sequential paths. Moreover, different artificial sunlight-driven photocatalytic treatments were used to remove Cu, Zn, Fe, and EDDS from soil washing effluents. Metal concentrations after the additional treatment were within the Brazilian and Italian regulatory limits for discharging in public sewers. The combined TiO2-photocatalytic processes applied were enough to decontaminate the effluents, allowing their reuse in soil washing treatment. Ecotoxicological assessment using different living organisms was carried out to assess the impact of the proposed two-step photocatalytic process on the effluent ecotoxicity. Graphical Abstract ᅟ.


Assuntos
Descontaminação/métodos , Processos Fotoquímicos , Poluentes do Solo/química , Poluentes do Solo/isolamento & purificação , Solo/química , Luz Solar , Catálise , Etilenodiaminas/química , Etilenodiaminas/isolamento & purificação , Etilenodiaminas/toxicidade , Metais Pesados/química , Metais Pesados/isolamento & purificação , Metais Pesados/toxicidade , Poluentes do Solo/toxicidade , Succinatos/química , Succinatos/isolamento & purificação , Succinatos/toxicidade
10.
Environ Sci Pollut Res Int ; 24(7): 6195-6204, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26555882

RESUMO

The present study aims to assess the removal of 3-amino-5-methylisoxazole (AMI), a recalcitrant by-product resulting from the biological breakdown of some pharmaceuticals, applying a solar photo-Fenton process assisted by ferrioxalate complexes (SPFF) (Fe3+/H2O2/oxalic acid/UVA-Vis) and classical solar photo-Fenton process (SPF) (Fe2+/H2O2/UVA-Vis). The oxidation ability of SPFF was evaluated at different iron/oxalate molar ratios (1:3, 1:6, and 1:9, with [total iron] = 3.58 × 10-2 mM and [oxalic acid] = 1.07 × 10-1, 2.14 × 10-1 and 3.22 × 10-1 mM, respectively) and pH values (3.5-6.5), using low iron contents (2.0 mg Fe3+ L-1). Additionally, the use of other organic ligands such as citrate and ethylenediamine-N,N'-disuccinic acid (EDDS) was tested. The oxidation power of the classical SPF was assessed at different pH values (2.8-4.0) using 2.0 mg Fe2+ per liter. Furthermore, the effect of AMI concentration (2-20 mg L-1), presence of inorganic ions (Cl-, SO42-, NO3-, HCO3-, NH4+), and radical scavengers (sodium azide and D-mannitol) on the SPF method at pH 3.5 was also assessed. Experiments were done using a lab-scale photoreactor with a compound parabolic collector (CPC) under simulated solar radiation. A pilot-scale assay was conducted using the best operation conditions. While at near neutral pH, an iron/oxalate molar ratio of 1:9 led to the removal of 72 % of AMI after 90 min of SPFF, at pH 3.5, an iron/oxalate molar ratio of 1:3 was enough to achieve complete AMI degradation (below the detection limit) after 30 min of reaction. The SPF process at pH 3.5 underwent a slower AMI degradation, reaching total AMI degradation after 40 min of reaction. The scale up of SPF process showed a good reproducibility. Oxalic and oxamic acids were identified as the main low-molecular-weight carboxylic acids detected during the pilot-scale SPF reaction. Graphical abstract ᅟ.


Assuntos
Resíduos de Drogas/química , Peróxido de Hidrogênio/química , Ferro/química , Isoxazóis/química , Processos Fotoquímicos , Concentração de Íons de Hidrogênio , Ácido Oxálico/química , Oxirredução
11.
Environ Sci Pollut Res Int ; 24(7): 6307-6316, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-27388593

RESUMO

In this study, an aqueous solution containing the azo dye Reactive Orange 16 (RO16) was subjected to two sequential treatment processes, namely: ozonation and biological treatment in a moving-bed biofilm reactor (MBBR). The most appropriate ozonation pretreatment conditions for the biological process and the toxicity of the by-products resulting from RO16 ozone oxidation were evaluated. The results showed that more than 97 % of color removal from the dye solutions with RO16 concentrations ranging from 25 to 100 mg/L was observed in 5 min of ozone exposure. However, the maximum total organic carbon removal achieved by ozonation was only 48 %, indicating partial mineralization of the dye. Eleven intermediate organic compounds resulting from ozone treatment of RO16 solution were identified by LC/MS analyses at different contact times. The toxicity of the dye-containing solution decreased after 2 min of ozonation, but increased at longer contact times. The results further demonstrated that the ozonolysis products did not affect the performance of the subsequent MBBR, which achieved an average chemical oxygen demand (COD) and ammonium removal of 93 ± 1 and 97 ± 2 %, respectively. A second MBBR system fed with non-ozonated dye-containing wastewater was run in parallel for comparison purposes. This reactor also showed an appreciable COD (90 ± 1 %) and ammonium removal (97 ± 2 %), but was not effective in removing color, which remained practically invariable over the system. The use of short ozonation times (5 min) and a compact MBBR has shown to be effective for the treatment of the simulated textile wastewater containing the RO16 azo dye.


Assuntos
Compostos Azo/química , Compostos Azo/metabolismo , Biofilmes , Ozônio/química , Têxteis , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Compostos Azo/isolamento & purificação , Compostos Azo/toxicidade , Biodegradação Ambiental , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos/microbiologia , Corantes/química , Corantes/isolamento & purificação , Corantes/metabolismo , Corantes/toxicidade , Oxirredução
12.
Environ Sci Pollut Res Int ; 24(7): 6372-6381, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-27357708

RESUMO

In the last decade, environmental risks associated with wastewater treatment plants (WWTPs) have become a concern in the scientific community due to the absence of specific legislation governing the occupational exposure limits (OEL) for microorganisms present in indoor air. Thus, it is necessary to develop techniques to effectively inactivate microorganisms present in the air of WWTPs facilities. In the present work, ultraviolet light A radiation was used as inactivation tool. The microbial population was not visibly reduced in the bioaerosol by ultraviolet light A (UVA) photolysis. The UVA photocatalytic process for the inactivation of microorganisms (bacteria and fungi, ATCC strains and isolates from indoor air samples of a WWTP) using titanium dioxide (TiO2 P25) and zinc oxide (ZnO) was tested in both liquid-phase and airborne conditions. In the slurry conditions at liquid phase, P25 showed a better performance in inactivation. For this reason, gas-phase assays were performed in a tubular photoreactor packed with cellulose acetate monolithic structures coated with P25. The survival rate of microorganisms under study decreased with the catalyst load and the UVA exposure time. Inactivation of fungi was slower than resistant bacteria, followed by Gram-positive bacteria and Gram-negative bacteria. Graphical abstract Inactivation of fungi and bacteria in gas phase by photocatalitic process performed in a tubular photoreactor packed with cellulose acetate monolith structures coated with TiO2.


Assuntos
Microbiologia do Ar , Raios Ultravioleta , Bactérias/isolamento & purificação , Catálise , Celulose/análogos & derivados , Celulose/química , Fungos/isolamento & purificação , Viabilidade Microbiana/efeitos da radiação , Fotólise , Titânio/química , Águas Residuárias/microbiologia , Purificação da Água , Óxido de Zinco/química
13.
Environ Sci Pollut Res Int ; 23(22): 22947-22956, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27578092

RESUMO

This paper comes out from the need to provide an improvement in the current oil refinery wastewater treatment plant (WWTP) aiming to generate water for reuse. The wastewater was pretreated and collected in the WWTP after the biological treatment unit (bio-disks) followed by sand filtration. Ozonation (ozone concentration from 3.0-60 mgO3 L-1), UV (power lamp from 15 to 95 W), H2O2 (carbon:H2O2 molar ratio of 1:1, 1:2, and 1:4), and two advanced oxidation processes (UV/O3 and UV/H2O2) were investigated aiming to reduce the wastewater organic matter and generate water with suitable characteristics for the reverse osmosis operation and subsequent industrial reuse. Even after the biological and filtration treatments, the oil refinery wastewater still presented an appreciable amount of recalcitrant organic matter (TOC of 12-19 mgC L-1) and silt density index (SDI) higher than 4, which is considered high for subsequent reverse osmosis due to membrane fouling risks. Experiments using non combined processes (O3, H2O2, and UV only) showed a low degree of mineralization after 60 min of reaction, although the pretreatment with ozone had promoted the oxidation of aromatic compounds originally found in the real matrix, which suggests the formation of recalcitrant compounds. When the combined processes were applied, a considerable increase in the TOC removal was observed (max of 95 % for UV/O3 process, 55 W, 60 mgO3 L-1), likely due the presence of higher amounts of reactive species, specially hydroxyl radicals, confirming the important role of these species on the photochemical degradation of the wastewater compounds. A zero-order kinetic model was fitted to the experimental data and the rate constant values (k, mgC L-1 h-1) ranged from 4.8 < k UV/O3 < 11 ([O3]0 = 30-60 mg L-1), and 8.6 < k UV/H2O2 < 11 (C:H2O2 from 1:1 to 1:4). The minimum and maximum electrical energy per order (E EO) required for 60 min of treatment were calculated as 5.4 and 81 Wh L-1, respectively, for UV/O3 (15 W, 60 mgO3 L-1) and UV/H2O2 (95 W, 1C:1H2O2). Good results in terms of water conditioning for reverse osmosis operation were obtained using UV/H2O2 process with initial molar ratio of 1 C:2 H2O2 (UV lamp 55 W) and 1 C:4 H2O2 (UV lamp 95 W), and total organic carbon (TOC) removals of 62 % (SDI15 = 1.8) and 74 % (SDI15 = 2.0) were achieved, respectively, after 60 min. The treated wastewater followed to the reverse osmosis system, which operated with an adequate flux of permeate, was very efficient to remove salt and generate a permeate water with the required quality for industrial reuse.


Assuntos
Compostos Orgânicos/isolamento & purificação , Águas Residuárias/química , Água/química , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Compostos Orgânicos/química , Oxirredução , Ozônio/química , Raios Ultravioleta , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Purificação da Água/métodos
14.
Environ Sci Pollut Res Int ; 23(19): 19626-33, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27392628

RESUMO

Petrochemical industries generate wastewaters containing pollutants that can severely impact the biological treatment systems. Some streams from specific production units may contain nonbiodegradable or toxic compounds that impair the performance of the wastewater treatment plant and should be segregated and treated by specific techniques. In this work, the utilization of chemical oxidation (H2O2/UV) was investigated for removing 4-vinylcyclohexene (VCH) from a liquid stream coming from the production of hydroxylated liquid polybutadiene (HLPB). Besides VCH, this stream also contains ethanol, hydrogen peroxide, and many other organic compounds. Experiments were carried out in a small-scale photochemical reactor (0.7 L) using a 25-W low-pressure mercury vapor lamp. The photochemical reactor was operated in batch, and the reaction times were comprised between 10 and 60 min. Assays were also performed with a synthetic medium containing VCH, H2O2, and ethanol to investigate the removal of these substances in a less complex aqueous matrix. By-products formed in the reaction were identified by gas chromatography and mass spectroscopy (GC-MS). VCH was significantly removed by the oxidation process, in most assays to undetectable levels. Ethanol removal varied from 16 to 23 % depending on the reaction conditions. Acetic acid, acetaldehyde, and diols were detected as by-products of the industrial wastewater stream oxidation. A drop on the toxicity of the industrial stream was also observed in assays using the organism Artemia salina.


Assuntos
Peróxido de Hidrogênio/química , Resíduos Industriais/análise , Raios Ultravioleta , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Purificação da Água/métodos , Indústria de Petróleo e Gás , Oxirredução , Poluentes Químicos da Água/química
15.
Water Res ; 80: 90-8, 2015 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-25996756

RESUMO

In moving bed biofilm reactors (MBBR), the removal of pollutants from wastewater is due to the substrate consumption by bacteria attached on suspended carriers. As a biofilm process, the substrates are transported from the bulk phase to the biofilm passing through a mass transfer resistance layer. This study proposes a methodology to determine the external mass transfer coefficient and identify the influence of the mixing intensity on the conversion process in-situ in MBBR systems. The method allows the determination of the external mass transfer coefficient in the reactor, which is a major advantage when compared to the previous methods that require mimicking hydrodynamics of the reactor in a flow chamber or in a separate vessel. The proposed methodology was evaluated in an aerobic lab-scale system operating with COD removal and nitrification. The impact of the mixing intensity on the conversion rates for ammonium and COD was tested individually. When comparing the effect of mixing intensity on the removal rates of COD and ammonium, a higher apparent external mass transfer resistance was found for ammonium. For the used aeration intensities, the external mass transfer coefficient for ammonium oxidation was ranging from 0.68 to 13.50 m d(-1) and for COD removal 2.9 to 22.4 m d(-1). The lower coefficient range for ammonium oxidation is likely related to the location of nitrifiers deeper in the biofilm. The measurement of external mass transfer rates in MBBR will help in better design and evaluation of MBBR system-based technologies.


Assuntos
Biofilmes , Reatores Biológicos/microbiologia , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/microbiologia , Purificação da Água/métodos , Algoritmos , Compostos de Amônio/química , Compostos de Amônio/metabolismo , Bactérias/crescimento & desenvolvimento , Bactérias/metabolismo , Biomassa , Cinética , Modelos Teóricos , Oxirredução , Oxigênio/química , Oxigênio/metabolismo , Águas Residuárias/química
16.
Ecotoxicol Environ Saf ; 120: 41-7, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26024813

RESUMO

The estrogenicity of waters collected from an important hydrological system in Brazil (Paraiba do Sul and Guandu Rivers) was assessed using the yeast estrogen screen (YES) assay. Sampling was performed in rivers and at the outlets of conventional water treatment plants (WTP). The removal of estrogenic activity by ozonation and chlorination after conventional water treatment (clarification and sand filtration) was investigated employing samples of the Guandu River spiked with estrogens and bisphenol A (BPA). The results revealed a preoccupying incidence of estrogenic activity at levels higher than 1ngL(-1) along some points of the rivers. Another matter of concern was the number of samples from WTPs presenting estrogenicity surpassing 1ngL(-1). The oxidation techniques (ozonation and chlorination) were effective for the removal of estrogenic activity and the combination of both techniques led to good results using less amounts of oxidants.


Assuntos
Estrogênios/análise , Saccharomyces cerevisiae/metabolismo , Poluentes Químicos da Água/análise , Compostos Benzidrílicos/análise , Bioensaio/métodos , Brasil , Estrogênios não Esteroides/análise , Estrona , Água Doce/química , Fenóis/análise , Rios , Purificação da Água/métodos
17.
Environ Technol ; 33(4-6): 695-701, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22629645

RESUMO

Organic micropollutants are often found in domestic and industrial effluents. Thus, it is important to learn their fate, the metabolites generated and their sorption during biological treatment processes. This work investigated the biodegradation of 14C-dicofol organochloride during wastewater aerobic treatment and sludge anaerobic biodigestion. The performance of these processes was evaluated by physical-chemical parameters. Radioactivity levels were monitored in both treatments, and residues of dicofol (DCF) and dichlorobenzophenone (DBP) were quantified by HPLC/UV. The efficiency of the aerobic and anaerobic processes was slightly reduced in the presence of DCF and DBP. After aerobic treatment, only 0.1% of DCF was mineralized, and 57% of radioactivity remained sorbed on biological sludge as DBP. After 18 days of anaerobiosis, only 3% of DCF and 5% of DBP were detected in the sludge. However, 70% of radioactivity remained in the sludge, probably as other metabolites. Dicofol was biodegraded in the investigated process, but not mineralized.


Assuntos
Bactérias Aeróbias/metabolismo , Bactérias Anaeróbias/metabolismo , Dicofol/metabolismo , Herbicidas/metabolismo , Resíduos Industriais/prevenção & controle , Esgotos/microbiologia , Purificação da Água/métodos , Biodegradação Ambiental , Radioisótopos de Carbono/isolamento & purificação , Radioisótopos de Carbono/metabolismo , Dicofol/isolamento & purificação , Herbicidas/isolamento & purificação , Marcação por Isótopo , Poluentes Químicos da Água/isolamento & purificação , Poluentes Químicos da Água/metabolismo
18.
Appl Microbiol Biotechnol ; 93(3): 1281-94, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21744134

RESUMO

The effect of salinity on the activity of nitrifying bacteria, floc characteristics, and microbial community structure accessed by fluorescent in situ hybridization and polymerase chain reaction-denaturing gradient gel electrophoresis techniques was investigated. Two sequencing batch reactors (SRB1 and SBR2) treating synthetic wastewater were subjected to increasing salt concentrations. In SBR1, four salt concentrations (5, 10, 15, and 20 g NaCl/L) were tested, while in SBR2, only two salt concentrations (10 and 20 g NaCl/L) were applied in a more shock-wise manner. The two different salt adaptation strategies caused different changes in microbial community structure, but did not change the nitrification performance, suggesting that regardless of the different nitrifying bacterial community present in the reactor, the nitrification process can be maintained stable within the salt range tested. Specific ammonium oxidation rates were more affected when salt increase was performed more rapidly and dropped 50% and 60% at 20 g NaCl/L for SBR1 and SBR2, respectively. A gradual increase in NaCl concentration had a positive effect on the settling properties (i.e., reduction of sludge volume index), although it caused a higher amount of suspended solids in the effluent. Higher organisms (e.g., protozoa, nematodes, and rotifers) as well as filamentous bacteria could not withstand the high salt concentrations.


Assuntos
Adaptação Fisiológica , Bactérias/efeitos dos fármacos , Reatores Biológicos/microbiologia , Nitrificação/efeitos dos fármacos , Esgotos/microbiologia , Cloreto de Sódio/farmacologia , Amônia/metabolismo , Bactérias/classificação , Bactérias/genética , Bactérias/metabolismo , Eletroforese em Gel de Ágar/métodos , Hibridização in Situ Fluorescente , Reação em Cadeia da Polimerase/métodos , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Esgotos/química , Cloreto de Sódio/química , Eliminação de Resíduos Líquidos
19.
Environ Technol ; 32(7-8): 837-46, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21879558

RESUMO

Nitrification of wastewaters from chemical industries can pose some challenges due to the presence of inhibitory compounds. Some wastewaters, besides their organic complexity present variable levels of salt concentration. In order to investigate the effect of salt (NaCl) content on the nitrification of a conventional biologically treated industrial wastewater, a bench scale moving-bed biofilm reactor was operated on a sequencing batch mode. The wastewater presenting a chloride content of 0.05 g l(-1) was supplemented with NaCl up to 12 g Cl(-) l(-1). The reactor operation cycle was: filling (5 min), aeration (12 or 24h), settling (5 min) and drawing (5 min). Each experimental run was conducted for 3 to 6 months to address problems related to the inherent wastewater variability and process stabilization. A PLC system assured automatic operation and control of the pertinent process variables. Data obtained from selected batch experiments were adjusted by a kinetic model, which considered ammonia, nitrite and nitrate variations. The average performance results indicated that nitrification efficiency was not influenced by chloride content in the range of 0.05 to 6 g Cl(-) l(-1) and remained around 90%. When the chloride content was 12 g Cl(-) l(-1), a significant drop in the nitrification efficiency was observed, even operating with a reaction period of 24 h. Also, a negative effect of the wastewater organic matter content on nitrification efficiency was observed, which was probably caused by growth of heterotrophs in detriment of autotrophs and nitrification inhibition by residual chemicals.


Assuntos
Biofilmes/crescimento & desenvolvimento , Reatores Biológicos/microbiologia , Resíduos Industriais/prevenção & controle , Membranas Artificiais , Cloreto de Sódio/farmacologia , Poluentes Químicos da Água/metabolismo , Purificação da Água/instrumentação , Biofilmes/efeitos dos fármacos , Relação Dose-Resposta a Droga , Desenho de Equipamento , Análise de Falha de Equipamento , Nitrificação/efeitos dos fármacos , Nitrificação/fisiologia , Poluentes Químicos da Água/isolamento & purificação
20.
J Hazard Mater ; 185(1): 242-8, 2011 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-20933327

RESUMO

Nitrification of saline wastewaters was investigated in bench-scale moving-bed biofilm reactors (MBBR). Wastewater from a chemical industry and domestic sewage, both treated by the activated sludge process, were fed to moving-bed reactors. The industrial wastewater contained 8000 mg Cl(-)/L and the salinity of the treated sewage was gradually increased until that level. Residual substances present in the treated industrial wastewater had a strong inhibitory effect on the nitrification process. Assays to determine inhibitory effects were performed with the industrial wastewater, which was submitted to ozonation and carbon adsorption pretreatments. The latter treatment was effective for dissolved organic carbon (DOC) removal and improved nitrification efficiency. Nitrification percentage of the treated domestic sewage was higher than 90% for all tested chloride concentrations up to 8000 mg/L. Results obtained in a sequencing batch reactor (SBR) were consistent with those attained in the MBBR systems, allowing tertiary nitrification and providing adequate conditions for adaptation of nitrifying microorganisms even under stressing and inhibitory conditions.


Assuntos
Biofilmes , Reatores Biológicos , Resíduos Industriais/análise , Nitrificação , Esgotos/análise , Eliminação de Resíduos Líquidos , Amônia/química , Biomassa , Carbono/análise , Carbono/química , Indústria Química , Cloretos/química , Ozônio/química , Cloreto de Sódio
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA