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Search Results: 1 - 10 of 624039 matches for " S. M.;Zaiat "
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Effect of mixing mode on the behavior of an ASBBR with immobilized biomass in the treatment of cheese whey
Damasceno, L. H. S.;Rodrigues, José A. D.;Ratusznei, S. M.;Zaiat, M.;Foresti, E.;
Brazilian Journal of Chemical Engineering , 2008, DOI: 10.1590/S0104-66322008000200008
Abstract: a hydrodynamic study of a mechanically stirred anaerobic sequencing batch biofilm reactor (asbbr) containing immobilized biomass on polyurethane foam was performed with the aim to determine homogeneity of the reactor based on total mixing time. turbine or helix propellers were used for stirring at rotor speeds of 100, 200, 300 and 500 rpm. experimental values obtained were fitted to a boltzmann sigmoid. homogenization times of the reactor were negligible when compared to the 8-h cycle time for all conditions studied. at low propeller rotations the turbine propeller showed the best performance. for higher rotations total mixing times were similar for both propellers; however the helix propeller had better homogeneity conditions. at a subsequent stage the system was operated in batch mode treating cheese whey at concentrations of 500, 1000 and 2000 mgcod/l and rotations of 200, 300 and 500 rpm. in these assays the importance of the propeller became evident not only for mixing, but also for substrate flow across the bed containing immobilized biomass. due to axial flow, the helix propeller offered better mass transfer conditions, evidenced by improved organic matter conversion and lower production of total volatile acids.
Effect of ammonia load on efficiency of nitrogen removal in an SBBR with liquid-phase circulation
Canto, C. S. A.;Ratusznei, S. M.;Rodrigues, J. A. D.;Zaiat, M.;Foresti, E.;
Brazilian Journal of Chemical Engineering , 2008, DOI: 10.1590/S0104-66322008000200007
Abstract: the removal of biological nitrogen from a synthetic wastewater with different ammonium nitrogen concentrations (50 and 100 mgn-nh4+/l) by a nitrification and denitrification process using a sequencing batch biofilm reactor (sbbr) with liquid-phase circulation was studied. the system with a total working volume of 4.6 l (3.7 l in the reactor and 0.9 l in the reservoir) treated 2.1 l of synthetic wastewater in 12-h cycles. as inoculum two types of biomass were used: an anaerobic/anoxic one from an up-flow anaerobic sludge blanket reactor (uasb) and an aerobic one from a prolonged aeration activated sludge system. the system, maintained at 30 ± 1 oc, operated in batch mode followed by fed-batch mode and was aerated intermittently. during fed-batch operation the reactor was fed with an external carbon source as electron donor in the denitrifying step and with no aeration. when the reactor was fed with 50 mgn-nh4+/l, efficiencies of removal of ammonium nitrogen and total nitrogen from the effluent were 93.8 and 72.2%, respectively, and nitrite, nitrate and organic nitrogen concentrations were 0.07, 6.4 and 0.5 mg/l, respectively. on the other hand, when the influent ammonium nitrogen concentration was 100 mgn-nh4+/l, residual nitrite and nitrate were 0.17 and 20.4, respectively, and no n-org was found in the effluent. it should be mentioned that residual nitrate remained unaltered at the different c/n ratios used. consequently, efficiency of total nitrogen removal was reduced to 66.7%, despite efficiency of ammonium nitrogen removal exceeding 90%. these results show the potential of the proposed system in removing ammonium nitrogen from liquid effluents with a moderate ammonium nitrogen concentration.
Kinetic modeling and microbial assessment by fluorescent in situ hybridization in anaerobic sequencing batch biofilm reactors treating sulfate-rich wastewater
Silva, A. J.;Domingues, M. R.;Hirasawa, J. S.;Varesche, M. B.;Foresti, E.;Zaiat, M.;
Brazilian Journal of Chemical Engineering , 2011, DOI: 10.1590/S0104-66322011000200005
Abstract: this paper reports the results of applying anaerobic sequencing batch biofilm reactors (ansbbr) for treating sulfate-rich wastewater. the reactor was filled with polyurethane foam matrices or with eucalyptus charcoal, used as the support for biomass attachment. synthetic wastewater was prepared with two ratios between chemical oxygen demand (cod) and sulfate concentration (cod/so42-) of 0.4 and 3.2. for a cod/so42- ratio of 3.2, the ansbbr performance was influenced by the support material used; the average levels of organic matter removal were 67% and 81% in the reactors filled with polyurethane foam and charcoal, respectively, and both support materials were associated with similar levels of sulfate reduction (above 90%). in both reactors, sulfate-reducing bacteria (srb) represented more than 65% of the bacterial community. the kinetic model indicated equilibrium between complete- and incomplete-oxidizing srb in the reactor filled with polyurethane foam and predominantly incomplete-oxidizing srb in the reactor filled with charcoal. methanogenic activity seems to have been the determining factor to explain the better performance of the reactor filled with charcoal to remove organic matter at a cod/so42- ratio of 3.2. for a cod/so42- ratio of 0.4, low values of sulfate reduction (around 32%) and low reaction rates were observed as a result of the small srb population (about 20% of the bacterial community). although the support material did not affect overall performance for this condition, different degradation pathways were observed; incomplete oxidation of organic matter by srb was the main kinetic pathway and methanogenesis was negligible in both reactors.
Enhancement of the performance of an anaerobic sequencing batch reactor treating low-strength wastewater through implementation of a variable stirring rate program
Rodrigues, J. A. D.;Pinto, A. G.;Ratusznei, S. M.;Zaiat, M.;Gedraite, R.;
Brazilian Journal of Chemical Engineering , 2004, DOI: 10.1590/S0104-66322004000300007
Abstract: this work focuses on enhancement of the performance of an anaerobic sequencing batch reactor with a six-vertical-blade-disk-turbine impeller, containing granulated biomass treating low-strength synthetic wastewater, through a study of the feasibility of implementing a variable stirring rate program. the reactor was operated at 30oc and a six-hour cycle was used to treat approximately 2.0 l of the synthetic substrate with a chemical oxygen demand (cod) of nearly 500 mg/l. two different stirring rate program were implemented: a constant rate of 50 rpm and a variable rate consisting of 75 rpm for one hour, 50 rpm for four hours and 25 rpm for 0.5 hour. the last 0.5 hour of the cycle was used for the settling step. in both cases, a very short start-up period and unfiltered and filtered substrate removal efficiencies of 81% and 88%, respectively, were attained. however, use of the variable stirring rate enhanced efficiency of the reactor dynamics without impairing biomass morphology, thus resulting in a reduction in the total cycle time and a possible decrease in energy consumption. additionally, a simplified model of the anaerobic metabolic activity, using apparent kinetic parameters, was proposed as a consecutive first-order kinetic model with substrate and total volatile acid residual concentrations in order to analyze how the variable stirring rate affects reactor performance.
Aplica??o de espumas ceramicas produzidas via "gelcasting" em biorreator para tratamento anaeróbio de águas residuárias
Ortega, F. S.;Rocha, K. M.;Zaiat, M.;Pandolfelli, V. C.;
Ceramica , 2001, DOI: 10.1590/S0366-69132001000400006
Abstract: the development of anaerobic biotechnology for treatment of wastewater has led to new configurations of bioreactors, which have as an important feature the establishment of favorable conditions for the fixation of biomass that will degrade organic material present in wastewaters. characteristics such as high resistance to biological degradation and high mechanical strength, coupled to cellular structure make ceramic foams an excellent option for the production of supports for biomass immobilization. in this work, the gelcasting process in association with the aeration of a ceramic suspension was used as a route to produce ceramic foam supports. alumina and caulinite, which are materials that have, respectively, positive and negative surface charges at the ph range used in bioreactors, were used as raw materials. after sintering, the foams had their porosity and permeability characterized, and then were submitted to a cycle of 35 days in a differential reactor, fed with synthetic domestic wastewater. other materials, like expanded clay and ethylene-propylene rubber (epr) were also submitted to the same tests for the purpose of comparison. results allowed the evaluation of advantages and disadvantages of ceramic foams as supports for the immobilization of microorganisms in comparison to other materials.
Effects of Copper Sulfate on Productive, Reproductive Performance and Blood Constituents of Laying Japanese Quail Fed Optimal and Sub-Optimal Protein
I.M. Abaza,W. Ezzat,M.S. Shoeib,A.A. El- Zaiat
International Journal of Poultry Science , 2009,
Abstract: A (3X3) factorial design experiment was conducted to study the effect of three levels of crude protein (16, 18 and 20%) and three levels of copper sulfate (0, 100 and 200 mg/kg diet) as a growth promoter on productive and reproductive performances, egg quality, blood serum constituents and economical efficiency of laying quail hens through 8 weeks. A total number of 270 hens and 135 males of Japanese quail at 8 weeks of age with nearly equal body weight and average rate of laying were randomly divided into 9 groups (30 hens and 15 males each). Each group of birds was sub divided into 3 replicates (10 hens and 5 males) and each replicate was housed in one wire cage. The results showed that the layer body weights at 12 or 16 weeks and weight gain at 12-16 and 8-16 weeks of age were significantly increased with increasing crude protein level from 16-18 or 20%, while there were no significant differences between the groups fed 18 and 20% crude protein throughout the experimental intervals and the whole period. Egg number, rate of laying and egg mass of laying quail hens increased with increasing crude protein at levels 16-18 or 20% (except at 12-16 week of age), while insignificant differences were found between the groups fed 18 and 20% crude protein throughout the experimental intervals and the whole period. Addition of copper sulfate at levels of 100 and 200 mg/kg to laying quail diets significantly improved egg number, rate of laying, egg mass and feed conversion ratio except at 8-12 weeks of age as compared with group non-supplemented with copper sulfate during the experimental period. The highest values of body weight and egg mass were recorded with 20 % protein plus 100 mg copper sulfate/kg diet, while, the best values of feed conversion and The highest values of egg number and rate of laying were recorded with 20 % protein plus 200 mg copper sulfate/kg diet from 8-16 weeks of age for quail layer as compared with other treatments. Laying quails hens fed diet contained copper sulfate levels significantly increased hatchability of fertile eggs percentage (except at 12 wks of age) as compared with those un-supplemented group. Various levels of crude protein or copper sulfate containing diets did not significantly affect on egg quality parameters, while egg yolk cholesterol was significantly decreased with increased copper sulfate levels. The highest values for total serum protein and serum albumin were recorded with experimental groups fed 18 or 20% protein levels compared with those received 16% protein diet, while serum cholesterol values were signifi
Aplica o de espumas ceramicas produzidas via "gelcasting" em biorreator para tratamento anaeróbio de águas residuárias
Ortega F. S.,Rocha K. M.,Zaiat M.,Pandolfelli V. C.
Ceramica , 2001,
Abstract: O desenvolvimento da biotecnologia anaeróbia de tratamento de águas residuárias, resultou em novas configura es de biorreatores, nas quais uma importante característica é a existência de condi es favoráveis à imobiliza o de biomassa ativa responsável pela degrada o biológica de resíduos poluentes. Características como a resistência à degrada o biológica e boa resistência mecanica associadas a uma estrutura celular fazem das espumas ceramicas excelentes candidatas à fabrica o de suportes para imobiliza o da biomassa. Neste trabalho, utilizou-se o processo "gelcasting" associado à aera o de uma suspens o para produzir suportes de espuma ceramica. Foram utilizadas alumina e caulinita, materiais estes em que predominam cargas superficiais positiva e negativa, respectivamente, na faixa de pH 7, em que operam os reatores. Após a queima, as espumas foram caracterizadas quanto à densidade aparente e à permeabilidade, e em seguida submetidas a um ciclo de 35 dias em reator diferencial alimentado com esgoto sanitário sintético. Materiais como argila expandida e borracha de etileno-propileno (EPR) foram submetidos a ciclo similar e comparados aos materiais ceramicos. Os resultados permitem avaliar as vantagens e desvantagens das espumas ceramicas como suporte para a imobiliza o de microorganismos frente a outros materiais.
Enhancement of the performance of an anaerobic sequencing batch reactor treating low-strength wastewater through implementation of a variable stirring rate program
Rodrigues J. A. D.,Pinto A. G.,Ratusznei S. M.,Zaiat M.
Brazilian Journal of Chemical Engineering , 2004,
Abstract: This work focuses on enhancement of the performance of an anaerobic sequencing batch reactor with a six-vertical-blade-disk-turbine impeller, containing granulated biomass treating low-strength synthetic wastewater, through a study of the feasibility of implementing a variable stirring rate program. The reactor was operated at 30oC and a six-hour cycle was used to treat approximately 2.0 L of the synthetic substrate with a chemical oxygen demand (COD) of nearly 500 mg/L. Two different stirring rate program were implemented: a constant rate of 50 rpm and a variable rate consisting of 75 rpm for one hour, 50 rpm for four hours and 25 rpm for 0.5 hour. The last 0.5 hour of the cycle was used for the settling step. In both cases, a very short start-up period and unfiltered and filtered substrate removal efficiencies of 81% and 88%, respectively, were attained. However, use of the variable stirring rate enhanced efficiency of the reactor dynamics without impairing biomass morphology, thus resulting in a reduction in the total cycle time and a possible decrease in energy consumption. Additionally, a simplified model of the anaerobic metabolic activity, using apparent kinetic parameters, was proposed as a consecutive first-order kinetic model with substrate and total volatile acid residual concentrations in order to analyze how the variable stirring rate affects reactor performance.
Development and validation of a HPLC method for the determination of aldicarb, aldicarb sulfoxide and aldicarb sulfone in liquid samples from anaerobic reactors
Damasceno, Leonardo H. S.;Adorno, M. Angela T.;Hirasawa, Julia S.;Varesche, M. Bernadete A.;Zaiat, Marcelo;
Journal of the Brazilian Chemical Society , 2008, DOI: 10.1590/S0103-50532008000600016
Abstract: this study describes the development and validation of a high-performance liquid chromatography (hplc) method for detecting aldicarb and its residues in liquid samples without pretreatment. the hplc system was equipped with a c-18 column and the mobile phase was composed of a mixture of water and acetonitrile using a linear gradient elution. the uv detector was utilized at 210 nm. methomyl was used as an internal standard. water and synthetic medium were used as solvents. the method was linear from 0.49-15.0 mg l-1 (r2 > 0.9985), 0.1-5.0 mg l-1 (r2 > 0.9974) and 0.1-5.0 mg l-1 (r2 > 0.9987) for aldicarb, aldicarb sulfoxide and aldicarb sulfone, respectively. the linearity of the method was confirmed by the anova f-test through adjustment of the linear model, validity of the regression and efficiency of the regression tests. the limit of detection in water and synthetic medium were of 0.391/0.440 mg l-1, 0.069/0.192 mg l-1 and 0.033/0.068 mg l-1 for aldicarb, aldicarb sulfoxide and aldicarb sulfone, respectively. total time of analysis was of 22 min. in the application of the method, the aldicarb degradation in horizontal-flow anaerobic immobilized biomass (haib) reactor was evaluated under different conditions (methanogenic, sulfidogenic and denitrifying).
Treatment of low-strength wastewater using immobilized biomass in a sequencing batch external loop reactor: influence of the medium superficial velocity on the stability and performance
Camargo, E.F.M.;Ratusznei, S.M.;Rodrigues, J.A.D.;Zaiat, M.;Borzani, W.;
Brazilian Journal of Chemical Engineering , 2002, DOI: 10.1590/S0104-66322002000300001
Abstract: an anaerobic sequencing batch bioreactor with external circulation of the liquid phase wherein the biomass was immobilized on a polyurethane foam matrix was analyzed, focussing on the influence of the liquid superficial velocity on the reactor's stability and efficiency. eight-hour cycles were carried out at 30oc treating glucose-based synthetic wastewater around 500 mgdqo/l. the performance of the reactor was assessed without circulation and with circulating liquid superficial velocity between 0.034 and 0.188 cm/s. the reactor attained operating stability and a high organic matter removal was achieved when liquid was circulated. a first order model was used to evaluate the influence of the liquid superficial velocity (vs), resulting in an increase in the apparent first order parameter when vs increased from 0.034 to 0.094 cm/s. the parameter value remained unchangeable when 0.188 cm/s was applied, indicating that beyond this value no improvement on liquid mass transfer was observed. moreover, the necessary time to reach the final removal efficiency decreased when liquid circulation was applied, indicating that a 3-hour cycle could be enough.
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