DESENVOLVIMENTO E AVALIAÇÃO DE ELETRODOS DE DIFUSÃO GASOSA (EDG) PARA GERAÇÃO DE H2O2 IN SITU E SUA APLICAÇÃO NA DEGRADAÇÃO DO CORANTE REATIVO AZUL 19

DEVELOPMENT AND EVALUATION OF GAS DIFFUSION ELECTRODES (GDE) FOR GENERATION OF H2O2 IN SITU AND THEIR APPLICATION IN THE DEGRADATION OF REACTIVE BLUE 19 DYE. This work reports the development of GDE for electrogeneration of H2O2 and their application in the degradation process of Reactive Blue 19 dye. GDE produced by carbon black with 20% polytetrafluoroethylene generated up to 500 mg L-1 of H2O2 through the electrolysis of acidic medium at -0.8 V vs Ag/AgCl. Reactive Blue 19 dye was degraded most efficiently with H2O2 electrogenerated in the presence of Fe(II) ions, leading to removal of 95% of the original color and 39% of TOC at -0.8 V vs Ag/AgCl.

Phenol degradation in an anaerobic fluidized bed reactor packed with low density support materials

The objective of this research was to study phenol degradation in anaerobic fluidized bed reactors (AFBR) packed with polymeric particulate supports (polystyrene - PS, polyethylene terephthalate - PET, and polyvinyl chloride - PVC). The reactors were operated with a hydraulic retention time (HRT) of 24 h. The influent phenol concentration in the AFBR varied from 100 to 400 mg L-1, resulting in phenol removal efficiencies of similar to 100%. The formation of extracellular polymeric substances yielded better results with the PVC particles; however, deformations in these particles proved detrimental to reactor operation. PS was found to be the best support for biomass attachment in an AFBR for phenol removal. The AFBR loaded with PS was operated to analyze the performance and stability for phenol removal at feed concentrations ranging from 50 to 500 mg L-1. The phenol removal efficiency ranged from 90-100%.

Arthrospira platensis biomass with high protein content cultivated in continuous process using urea as nitrogen source

Aims: Arthrospira platensis has been studied for single-cell protein production because of its biomass composition and its ability of growing in alternative media. This work evaluated the effects of different dilution rates (D) and urea concentrations (N0) on A.similar to platensis continuous culture, in terms of growth, kinetic parameters, biomass composition and nitrogen removal. Methods and results: Arthrospira platensis was continuously cultivated in a glass-made vertical column photobioreactor agitated with Rushton turbines. There were used different dilution rates (0.040.44 day-1) and urea concentrations (0.5 and 5 mmol l-1). With N0 = 5 mmol l-1, the maximum steady-state biomass concentration was1415 mg l-1, achieved with D = 0.04 day-1, but the highest protein content (71.9%) was obtained by applying D = 0.12 day-1, attaining a protein productivity of 106.41 mg l-1 day-1. Nitrogen removal reached 99% on steady-state conditions. Conclusions: The best results were achieved by applying N0 = 5 mmol l-1; however, urea led to inhibitory conditions at D = 0.16 day-1, inducing the system wash-out. The agitation afforded satisfactory mixture and did not harm the trichomes structure. Significance and Impact of the Study: These results can enhance the basis for the continuous removal of nitrogenous wastewater pollutants using cyanobacteria, with an easily assembled photobioreactor.

A comparative study of the electrochemical oxidation of the herbicide tebuthiuron using boron-doped diamond electrode

The thiadiazolylurea derivative tebuthiuron (TBH) is commonly used as an herbicide even though it is highly toxic to humans. While various processes have been proposed for the removal of organic contaminants of this type from wastewater, electrochemical degradation has shown particular promise. The aim of the present study was to investigate the electrochemical degradation of TBH using anodes comprising boron-doped (5000 and 30000 ppm) diamond (BDD) films deposited onto Ti substrates operated at current densities in the range 10-200 mA cm(-2). Both anodes removed TBH following a similar pseudo first-order reaction kinetics with k(ap)p close to 3.2 x 10(-2) min(-1). The maximum mineralization efficiency obtained was 80%. High-pressure liquid chromatography with UV-VIS detection established that both anodes degraded TBH via similar intermediates. Ion chromatography revealed that increasing concentrations of nitrate ions (up to 0.9 ppm) were formed with increasing current density, while the formation of nitrite ions was observed with both anodes at current densities >= 150 mA cm(-2). The BDD film prepared at the lower doping level (5000 ppm) was more efficient in degrading TBH than its more highly doped counterpart. This unexpected finding may be explained in terms of the quantity of impurities incorporated into the diamond lattice during chemical vapor deposition. (C) 2012 Elsevier Ltd. All rights reserved.

Anion dopant effects on the structure and performance of polyethersulfone membranes

In this work, the effect of various casting solution salt dopants with similar cations, but different anions: (NaPO3)(6), Na2SO4, Na2CO3, NaCl, and NaF, on the morphology and performance of polyethersulfone ultrafiltration membranes was evaluated. The phase inversion process was used to produce all membranes using an 18% polyethersulfone in n-methylpyrrolidone casting solution and water as the non-solvent. Scanning electron microscopy (SEM) images of the membrane cross-section and surface pores were used to determine the specific anion effects on membrane morphology. The SEM images depicted significant changes to the membrane internal structure and pore size with respect to the type and concentration of the casting solution anion dopant. Membrane permeability, molecular weight cut-off, alginate retention, and susceptibility to fouling were evaluated using ultrapure water dead-end and ultrapure water, aqueous polyethylene glycol, aqueous sodium alginate, and natural surface water cross-flow filtration tests. Among the anions evaluated, hexametaphosphate doped at 1% w/w to the polymer resulted in the membrane with highest dead-end permeability at 490 LMH-bar (2- to 3-fold greater than the control), greatest alginate retention at 96.5%, and lowest susceptibility to fouling. The significant increase in membrane performance indicates that the hexametaphosphate anion has great potential to be used as a membrane casting solution dopant. It was also clearly demonstrated that membrane pore morphological characteristics can be effectively used to predict drinking water treatment performance. (C) 2012 Elsevier B.V. All rights reserved.

Effect of Feed Strategy on Methane Production and Performance of an AnSBBR Treating Effluent from Biodiesel Production

The aim of this work was to investigate the effect of different feeding times (2, 4 and 6 h) and applied volumetric organic loads (4.5, 6.0 and 7.5 gCOD L-1 day(-1)) on the performance of an anaerobic sequencing batch biofilm reactor (AnSBBR) treating effluent from biodiesel production. Polyurethane foam cubes were used as inert support in the reactor, and mixing was accomplished by recirculating the liquid phase. The effect of feeding time on reactor performance showed to be more pronounced at higher values of applied volumetric organic loads (AVOLs). Highest organic material removal efficiencies achieved at AVOL of 4.5 gCOD L-1 day(-1) were 87 % at 4-h feeding against 84 % at 2-h and 6-h feeding. At AVOL of 6.0 gCOD L-1 day(-1), highest organic material removal efficiencies achieved with 4-h and 6-h feeding were 84 %, against 71 % at 2-h feeding. At AVOL of 7.5 gCOD L-1 day(-1), organic material removal efficiency achieved with 4-h feeding was 77 %. Hence, longer feeding times favored minimization of total volatile acids concentration during the cycle as well as in the effluent, guaranteeing process stability and safety.

Nutrição mineral da cana‑de‑açúcar irrigada com efluente de esgoto tratado, em área com aplicação de fosfogesso

O objetivo deste trabalho foi quantificar o aporte e a remoção de nutrientes em sistemas de cultivo  de cana‑de‑açúcar irrigados, ou não, com efluente de estação de tratamento de esgoto (EETE), com e sem  adição  de fosfogesso,  bem  como  avaliar  os  efeitos  desses sistemas  de  cultivo  no  estado  nutricional  das  plantas. Foram avaliados tratamentos sem irrigação e com irrigação a 100 e 150% da necessidade hídrica da  cultura. Os tratamentos com fosfogesso foram aplicados em área de terceiro corte, irrigada com EETE desde  o plantio. As  avaliações foram realizadas em duas safras. Os tratamentos não afetaram os rendimentos de  colmos. O tratamento com EETE e fosfogesso apresentou efeito sinérgico sobre o conteúdo de nitrogênio e de  enxofre nas plantas. O EETE beneficiou a nutrição das plantas quanto ao fósforo, mas não causou melhorias  na nutrição com potássio e enxofre. A nutrição com ferro, zinco e manganês não foi influenciada pelo aporte  desses micronutrientes pelo EETE. O  fósforo e o nitrogênio aportados na irrigação com EETE devem ser  considerados na recomendação de adubação. Porém, potássio, enxofre, ferro, zinco e manganês do efluente não  são fontes eficientes desses nutrientes para as plantas.

Adsorption of phosphate from aqueous solution by hydrous zirconium oxide

Synthetic ZrO2 center dot nH(2)O was used for phosphate removal from aqueous solution. The optimum adsorbent dose obtained for phosphate adsorption on to hydrous zirconium oxide was 0.1 g. The kinetic process was described very well by a pseudo-second-order rate model. The phosphate adsorption tended to increase with the decrease in pH. The adsorption capacity increased from 61 to 66 mg g(-1) when the temperature was increased from 298 to 338 K. A phosphate desorption of approximately 74% was obtained using water at pH 12.

Effect of Substrate Concentration on Dark Fermentation Hydrogen Production Using an Anaerobic Fluidized Bed Reactor

The effect of substrate (glucose) concentration on the stability and yield of a continuous fermentative process that produces hydrogen was studied. Four anaerobic fluidized bed reactors (AFBRs) were operated with a hydraulic retention time (HRT) from 1 to 8 h and an influent glucose concentration from 2 to 25 gL(-1). The reactors were inoculated with thermally pre-treated anaerobic sludge and operated at a temperature of 30 degrees C with an influent pH around 5.5 and an effluent pH of about 3.5. The AFBRs with a HRT of 2 h and a feed strength of 2, 4, and 10 gL(-1) showed satisfactory H-2 production performance, but the reactor fed with 25 gL(-1) of glucose did not. The highest hydrogen yield value was obtained in the reactor with a glucose concentration of 2 gL(-1) when it was operated at a HRT of 2 h. The maximum hydrogen production rate value was achieved in the reactor with a HRT of 1 h and a feed strength of 10 gL(-1). The AFBRs operated with glucose concentrations of 2 and 4 gL(-1) produced greater amounts of acetic and butyric acids, while AFBRs with higher glucose concentrations produced a greater amount of solvents.

Performance and composition of bacterial communities in anaerobic fluidized bed reactors for hydrogen production: Effects of organic loading rate and alkalinity

This study evaluated the effects of the organic loading rate (OLR) and pH buffer addition on hydrogen production in two anaerobic fluidized bed reactors (AFBRs) operated simultaneously. The AFBRs were fed with glucose, and expanded clay was used as support material. The reactors were operated at a temperature of 30 degrees C, without the addition of a buffer (AFBR1) and with the addition of a pH buffer (AFBR2, sodium bicarbonate) for OLRs ranging from 19.0 to 140.6 kg COD m(-3) d(-1) (COD: chemical oxygen demand). The maximum hydrogen yields for AFBR1 and AFBR2 were 2.45 and 1.90 mol H-2 mol(-1) glucose (OLR of 84.3 kg COD m(-3) d(-1)), respectively. The highest hydrogen production rates were 0.95 and 0.76 L h(-1) L-1 for AFBR1 and AFBR2 (OLR of 140.6 kg COD m(-3) d(-1)), respectively. The operating conditions in AFBR1 favored the presence of such bacteria as Clostridium, while the bacteria in AFBR2 included Clostridium, Enterobacter, Klebsiella, Veillonellaceae, Chryseobacterium, Sporolactobacillus, and Burkholderiaceae. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Hydrogen production and consumption of organic acids by a phototrophic microbial consortium

Alternative fuel sources have been extensively studied. Hydrogen gas has gained attention because its combustion releases only water, and it can be produced by microorganisms using organic acids as substrates. The aim of this study was to enrich a microbial consortium of photosynthetic purple non-sulfur bacteria from an Upflow Anaerobic Sludge Blanket reactor (UASB) using malate as carbon source. After the enrichment phase, other carbon sources were tested, such as acetate (30 mmol l(-1)), butyrate (17 mmol l(-1)), citrate (11 mmol l(-1)), lactate (23 mmol l(-1)) and malate (14.5 mmol l(-1)). The reactors were incubated at 30 degrees C under constant illumination by 3 fluorescent lamps (81 mu mol m(-2) s(-1)). The cumulative hydrogen production was 7.8, 9.0, 7.9, 5.6 and 13.9 mmol H-2 l(-1) culture for acetate, butyrate, citrate, lactate and malate, respectively. The maximum hydrogen yield was 0.6, 1.4, 0.7, 0.5 and 0.9 mmol H-2 mmol(-1) substrate for acetate, butyrate, citrate, lactate and malate, respectively. The consumption of substrates was 43% for acetate, 37% for butyrate, 100% for citrate, 49% for lactate and 100% for malate. Approximately 26% of the clones obtained from the Phototrophic Hydrogen-Producing Bacterial Consortium (PHPBC) were similar to Rhodobacter, Rhodospirillum and Rhodopseudomonas, which have been widely cited in studies of photobiological hydrogen production. Clones similar to the genus Sulfurospirillum (29% of the total) were also found in the microbial consortium. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Treatment of Domestic Sewage in an Anaerobic-Aerobic Fixed-bed Reactor with Recirculation of the Liquid Phase

This study reports the performance of a combined anaerobic-aerobic packed-bed reactor that can be used to treat domestic sewage. Initially, a bench-scale reactor was operated in three experimental phases. In the first phase, the anaerobic reactor was operated with an average organic matter removal efficiency of 77% for a hydraulic retention time (HRT) of 10 h. In the second phase, the reactor was operated with an anaerobic stage followed by an aerobic zone, resulting in a mean value of 91% efficiency. In the third and final phase, the anaerobic-aerobic reactor was operated with recirculation of the effluent of the reactor through the anaerobic zone. The system yielded mean total nitrogen removal percentages of 65 and 75% for recycle ratios (r) of 0.5 and 1.5, respectively, and the chemical oxygen demand (COD) removal efficiencies were higher than 90%. When the pilot-scale reactor was operated with an HRT of 12 h and r values of 1.5 and 3.0, its performance was similar to that observed in the bench-scale unit (92% COD removal for r = 3.0). However, the nitrogen removal was lower (55% N removal for r = 3.0) due to problems with the hydrodynamics in the aerobic zone. The anaerobic-aerobic fixed-bed reactor with recirculation of the liquid phase allows for concomitant carbon and nitrogen removal without adding an exogenous source of electron donors and without requiring any additional alkalinity supplementation.

Application of succinylated sugarcane bagasse as adsorbent to remove methylene blue and gentian violet from aqueous solutions - Kinetic and equilibrium studies

In a previous work, succinylated sugarcane bagasse (SCB 2) was prepared from sugarcane bagasse (B) using succinic anhydride as modifying agent. In this work the adsorption of cationic dyes onto SCB 2 from aqueous solutions was investigated. Methylene blue, MB, and gentian violet, GV, were selected as adsorbates. The capacity of SCB 2 to adsorb MB and GV from aqueous single dye solutions was evaluated at different contact times, pH, and initial adsorbent concentration. According to the obtained results, the adsorption processes could be described by the pseudo-second-order kinetic model. Adsorption isotherms were well fitted by Langmuir model. Maximum adsorption capacities for MB and GV onto SCB 2 were found to be 478.5 and 1273.2 mg/g, respectively. (C) 2011 Elsevier Ltd. All rights reserved.

Hydrogen and Methane Production, Energy Recovery, and Organic Matter Removal from Effluents in a Two-Stage Fermentative Process

This study evaluates the potential for using different effluents for simultaneous H-2 and CH4 production in a two-stage batch fermentation process with mixed microflora. An appreciable amount of H-2 was produced from parboiled rice wastewater (23.9 mL g(-1) chemical oxygen demand [COD]) and vinasse (20.8 mL g(-1) COD), while other effluents supported CH4 generation. The amount of CH4 produced was minimum for sewage (46.3 mL g(-1) COD), followed by parboiled rice wastewater (115.5 mL g(-1) COD) and glycerol (180.1 mL g(-1) COD). The maximum amount of CH4 was observed for vinasse (255.4 mL g(-1) COD). The total energy recovery from vinasse (10.4 kJ g(-1) COD) corresponded to the maximum COD reduction (74.7 %), followed by glycerol (70.38 %, 7.20 kJ g(-1) COD), parboiled rice wastewater (63.91 %, 4.92 kJ g(-1) COD), and sewage (51.11 %, 1.85 kJ g(-1) COD). The relatively high performance of vinasse in such comparisons could be attributed to the elevated concentrations of macronutrients contained in raw vinasse. The observations are based on kinetic parameters of H-2 and CH4 production and global energy recovery of the process. These observations collectively suggest that organic-rich effluents can be deployed for energy recovery with sequential generation of H-2 and CH4.

Soil properties in a sugarcane plantation after the application of treated sewage effluent and phosphogypsum in Brazil

In a field experiment performed in Lins County (Sao Paulo State, Brazil), treated sewage effluent (TSE) irrigation increased sugarcane yield but caused an excessive increase in the exchangeable sodium percentage (ESP) and clay dispersion after 16 months due to an intense irrigation regime (2500 mm/16 months) with sodium rich effluents. After two additional complete cycles with lower TSE irrigation rates (1200 mm year(-1)), 1700 kg ha(-1) of phosphogypsum was added to a section of the irrigated plots to evaluate its residence time and its implications on Na+ dynamics and other soil properties. Undisturbed soil cores were taken 2 years after phosphogypsum application to verify soil physical properties up to 0.2 m depth, and disturbed soil samples were taken every year up to 1 m depth for chemical analyses. After 5 years of consecutive TSE irrigation (2005-2010), soil acidity (pH approximate to 5) and basic cations (Ca approximate to 12, Mg approximate to 6 and K approximate to 2 mmol(c) kg(-1)) were maintained in adequate conditions for plant development without the necessity of liming, while acidity was increased (pH approximate to 4.5) and Ca (approximate to 9 mmol(c) kg(-1)), and the Mg (approximate to 4.5 mmol(c) kg(-1)) concentration decreased in the rainfed without phosphogypsum treatment. An increase in water retention capacity at -30 (from 0.14 to 0.17 m(3) m(-3)) and -1500 kPa (from 0.08 to 0.12 m(3) m(-3)) potentials was also observed in all TSE irrigated treatments. The plots with a phosphogypsum treatment showed average increases of 2 mmol(c) kg(-1) of Ca2+ and 7 mg kg(-1) of S-SO42- in all soil profiles and an average reduction of 2 mmol(c) kg(-1) of Na+ up to 0.4 m from 2008 to 2009. However, the extent of the chemical effects was greater after the first year compared to the second year. The high concentration of Na+ found in previous studies performed in the same area returned to low concentrations after continued TSE irrigation at lower rates, even without the phosphogypsum application. An unusual phosphorus migration was observed to the 0.4-0.8 m soil layer as a result of TSE irrigation, most likely due to a high pH and a Na carbonate-dominated TSE. (C) 2012 Elsevier B.V. All rights reserved.