ABSTRACT The hydrodynamic behavior of an anaerobic fixed bed reactor (AFBR) was evaluated in the treatment of cattle slaughterhouse wastewater. The AFBR was operated at hydraulic retention time (HRT) of 14, 11 and 8 h. Stimulus-response assays were carried out with Eosin Y and the experimental data were adjusted to the single-parameter theoretical models of dispersion and N-continuous stirred tank reactors in series (N-CSTR). The experimental results of the residence time distribution curves showed that at lower flow rate, the reactor showed plug flow behavior with correlation coefficient (r) of 0.88 and number of dispersion of 0.2 for high dispersion (HD). However, at higher and intermediate flow rates, the AFBR behave as a complete mixture flow, (r) of 0.94 and 0.96, respectively. Residence time distribution curves in the AFBR showed a good approximation of the complete mixing model at hydraulic residence time of 11 and 8 h, with 5 and 2 N-CSTR reactors in series, respectively. The volume of dead zones corresponding to 43.0, 37.4 and 11.2% of the volume of the reactor for HRT of 14, 11 and 8 h, respectively, was noted, and hydraulic short circuiting were not confirmed.

RESUMO A adsorção tem sido estudada como alternativa para tratamento de efluentes têxteis contendo corantes tóxicos, carcinogênicos, mutagênicos e que interferem no equilíbrio dos ecossistemas aquáticos ao serem lançados no ambiente sem adequado tratamento prévio. Este problema é agravado pois até 50% da quantidade de corante aplicado nas etapas de tingimento e de lavagem não se fixa às fibras dos tecidos. O objetivo deste estudo foi avaliar a remoção de cor de uma solução aquosa contendo o corante direct blue, na concentração inicial de 5 g/L, através da adsorção em cerâmica vermelha. Para isto, foram selecionadas as faixas de diâmetro de 1,21 mm a 2,4 mm e de 2,41 mm a 4,8 mm e as massas de 200, 250 e 300 g do adsorvente para cada faixa. Os ensaios foram conduzidos sob agitação constante de 120 rpm a temperatura ambiente, com duração total de 5 horas, para avaliar o desempenho da adsorção a partir dos valores obtidos para remoção de cor. Além disto, os resultados foram ajustados aos modelos cinéticos de pseudo-primeira ordem e pseudo-segunda ordem de Lagergren. Em todas as configurações experimentais avaliadas, o equilíbrio se deu após a primeira hora de ensaio e as remoções de cor variaram de 98,2% a 99,5%. Do ponto de vista da capacidade de adsorção por massa de adsorvente, os melhores resultados foram verificados com massa de 200 g do adsorvente. Constatou-se ainda que os resultados foram moderadamente mais efetivos na faixa de menor de diâmetro com desempenho 0,5% superior à faixa de maiores diâmetros. O modelo cinético de pseudo-segunda ordem se ajustou melhor aos resultados experimentais quando comparado ao de pseudo-primeira ordem. Foi possível concluir através da pesquisa que a cerâmica de argila adquirida na Região Metropolitana de Curitiba foi um material efetivo na remoção do corante Direct Blue de uma solução aquosa.

ABSTRACT Adsorption has been studied as an alternative to the treatment of textile effluents containing toxic, carcinogenic, mutagenic dyes that also interfere in the equilibrium of aquatic ecosystems when discharged in the environment without proper previous treatment. This problem is as 50% of the amount of dye applied in the steps of dyeing and laundering does not attach to the fabric fibers. The aim of this study was to evaluate color removal from an aqueous solution containing blue direct dye at an initial concentration of 5 g/L, by the adsorption on ceramic clay. For this purpose, the ranges of diameter of 1.21 mm to 2.4 mm and 2.41 mm to 4.8 mm and the quantities mass of 200, 250 and 300 g of the adsorbent were selected for each range. Assays were carried out under constant agitation of 120 rpm at room temperature, with a total duration of 5 hours, to evaluate the performance of the adsorption from the values obtained for color removal. Furthermore, the results were adjusted to the kinetic pseudo-first order and pseudo-second order models of Lagergren. In all the experimental settings evaluated, the equilibrium was reached after the first hour of the assay and the color removals varied from 98.2% to 99.5%. Regarding the adsorption capacity by the mass of the adsorbent, the best results were verified with mass of 200 g of the adsorbent. It was also found that results were moderately effective at the lowest range of diameter (0.5% higher than the performance of larger diameters). The pseudo-second order kinetics model fits better to the experimental data when compared to the pseudo-first order. It was possible to conclude from the research that the red clay acquired in the Metropolitan Region of Curitiba was an effective material in the removal of the Direct Blue dye from an aqueous solution

RESUMO Compreender o comportamento hidrodinâmico de reatores biológicos pode auxiliar na detecção de problemas associados a falhas operacionais e de projeto, situações que prejudicam a eficiência do tratamento. Neste artigo, realizaram-se simulações da fluidodinâmica computacional (CFD) de escoamento de duas fases sólida-líquida de um reator anaeróbio de manta de lodo e fluxo ascendente (UASB), em escala piloto (160 L), com tempo de detenção hidráulica (TDH) de 10 h e vazão de 16 L.h-1. Um modelo Euler-Euler simplificado foi formulado para simular o comportamento hidrodinâmico da zona de reação, influenciada pela configuração do sistema de distribuição do afluente. Foram avaliadas quatro configurações do sistema de distribuição do afluente no reator: uma entrada na parte central (1) e duas entradas centrais (2), de fluxo ascendente; duas entradas nas laterais (3), de fluxo radial; e três entradas de fluxo descendente (4), utilizando geometrias bidimensionais e tridimensionais para verificar a formação de zonas mortas, curtos-circuitos hidráulicos e caminhos preferenciais. As melhores características hidrodinâmicas e a melhor distribuição do afluente foram verificadas na configuração 4, com melhor perfil de mistura do lodo com a fase líquida, na comparação com as demais configurações. Foi notada formação de vórtices na parte inferior do reator com maior concentração do lodo anaeróbio nessa configuração e de caminhos preferenciais nas laterais do reator na configuração 3, indicando mistura ineficiente do afluente com o lodo anaeróbio. O modelo demonstrou que a configuração do sistema de distribuição do afluente influencia significativamente o comportamento hidrodinâmico do reator UASB.

ABSTRACT Understanding the hydrodynamics behavior of biological reactors can help in the detection of problems related to operational failures and design that adversely affect the efficiency of the treatment. In this paper, computational fluid dynamics (CFD) simulations of two-phase liquid-solid flow were carried out in an upflow anaerobic sludge blanket reactor in pilot scale (160 L), with hydraulic retention time (HRT) of 10 h and flowrate 16 L.h-1. The Euler-Euler approach was formulated to simulate the reaction zone hydrodynamics. Four configurations of the influent distribution system in the reactor were evaluated: one central inlet (1) and two central inlets (2), upflow; two lateral inlets (3), radial flow; and three inlets, downflow (4), using two and three-dimensional geometries to verify the formation of dead zones, hydraulic short-circuiting and preferential pathways. Better influent distribution and greater mixture profile of the sludge with the liquid phase were found in the configuration 4, compared to the others by the formation of vortices in the bottom part of the reactor with higher concentration of anaerobic sludge. Formation of preferential pathways was noted in the lateral inlets of the reactor in the configuration 3, indicating an inefficient mixture of the influent with the sludge. The model demonstrates that the configuration of the influent distribution system significantly influences the hydrodynamics behavior of the UASB reactor.

O objetivo deste estudo foi avaliar o desempenho de um Reator Anaeróbio-Aeróbio de Leito Fixo (RAALF) com escoamento ascendente, no tratamento de efluente bruto de matadouro bovino, e obter constantes cinéticas aparentes da remoção de matéria orgânica. O RAALF foi operado sem recirculação (Etapa I) e com 50% de recirculação do efluente (Etapa II), com θ de 11 h e 8 h. Em termos de pH, alcalinidade a bicarbonato e ácidos voláteis, os resultados indicaram que o RAALF apresentou capacidade em manter condições favoráveis para os processos biológicos envolvidos na remoção de matéria orgânica, em ambas as etapas operacionais. As eficiências médias de remoção de matéria orgânica ao longo da altura do reator, expressa em termos de DQO bruta, foram de 49% e 68% na Etapa I e de 54% e 86% na Etapa II, para θ de 11 h e 8 h, respectivamente. Os resultados de DQO filtrada indicaram eficiências de remoção de 52% e k = 0,0857 h-1 para θ de 11 h e 42% e k = 0,0880 h-1 para θ de 8 h na Etapa I. Na Etapa II, as eficiências de remoção foram 59% e 51% para θ de 11 h e 8 h, com k = 0,1238 h-1 e k = 0,1075 h-1, respectivamente. O modelo cinético de primeira ordem indicou bom ajuste e descreveu adequadamente a cinética de remoção de matéria orgânica para θ de 11 h, com r² igual a 0,9734 e 0,9591 para as Etapas I e II, respectivamente.

This paper sought to evaluate the behavior of an upflow Anaerobic-Aerobic Fixed Bed Reactor (AAFBR) in the treatment of cattle slaughterhouse effluent and determine apparent kinetic constants of the organic matter removal. The AAFBR was operated with no recirculation (Phase I) and with 50% of effluent recirculation (Phase II), with θ of 11h and 8h. In terms of pH, bicarbonate alkalinity and volatile acids, the results indicated the reactor ability to maintain favorable conditions for the biological processes involved in the organic matter removal in both operational phases. The average removal efficiencies of organic matter along the reactor height, expressed in terms of raw COD, were 49% and 68% in Phase I and 54% and 86% in Phase II for θ of 11h and 8h, respectively. The results of the filtered COD indicated removal efficiency of 52% and k = 0.0857h-1 to θ of 11h and 42% and k = 0.0880h-1 to θ of 8h in the Phase I. In Phase II, the removal efficiencies were 59% and 51% to θ of 11h and 8h, with k = 0.1238h-1 and k = 0.1075 h-1, respectively. The first order kinetic model showed good adjustment and described adequately the kinetics of organic matter removal for θ of 11h, with r² equal to 0.9734 and 0.9591 to the Phases I and II, respectively.

An HPLC method was validated to assay lamivudine and zidovudine combined in tablets. The chromatographic separation was carried out using methanol and acetate buffer pH 6.5 (50:50 v/v) and a RP-18 column, as mobile and stationary phase, respectively. The UV detection was at 270 nm. The method was linear in the range of 24 - 36 µg/mL (lamivudine) and 48 - 72 µg/mL (zidovudine). The recovery (accuracy) ranged from 101.35% to 103.04% and the precision (repeatability and intermediate precision) was less than 2%. The method can be also applied to the quantification of these drugs in the dissolution test of tablets containing both drugs.