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.

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.

Um reator em bateladas sequenciais com biomassa em suspensão e volume útil de 5L, aplicado para remoção de nutrientes e matéria orgânica, foi operado em escala de bancada, nas condições ótimas obtidas a partir de um delineamento composto central rotacional (DCCR), tempo de ciclo (TC) de 16 h (10h15 fase aeróbia e 4h35 fase anóxica) e relação carbono:nitrogênio (DQO/N-NO2-+N-NO3-) de 6. Avaliaram-se 20 ciclos completos, nitrificação seguida de desnitrificação, com o objetivo de efetuar o estudo do comportamento cinético de degradação da matéria orgânica (DQO) e nitrogenada (N-NH4+, N-NO2- e N-NO3-) presentes no efluente proveniente do abate e industrialização de aves, bem como avaliar a estabilidade do reator através de gráficos de controle Shewhart para medidas individuais. Os resultados apontaram valores médios de remoção de nitrogênio inorgânico total (N-NH4++N-NO2-+N-NO 3-) de 84,32±1,59% (C.V.=1,89%) e de matéria orgânica (DQO) de 53,65±8,48% (CV= 15,81%), no processo completo (nitrificação-desnitrificação), estando o processo sob controle estatístico. A atividade nitrificante estimada, durante a fase aeróbia, pela determinação dos parâmetros cinéticos, apresentou valores médios para K1 e K2, de 0,00381±0,00043 min-1 e 0,00249±0,00056 min-1, respectivamente. A avaliação do comportamento cinético de conversão do nitrogênio indicou possível redução no TC da fase anóxica, uma vez que foram alcançadas remoções de N-NO2- e N-NO3-, superiores a 90%, em apenas uma hora de desnitrificação.

A sequential batch reactor with suspended biomass and useful volume of 5 L was used in the removal of nutrients and organic matter in workbench scale under optimal conditions obtained by central composite rotational design (CCRD), with cycle time (CT) of 16 h (10.15 h, aerobic phase, and 4.35 h, anoxic phase) and carbon: nitrogen ratio (COD/NO2--N+NO3--N) equal to 6. Complete cycles (20), nitrification followed by denitrification, were evaluated to investigate the kinetic behavior of degradation of organic (COD) and nitrogenated (NH4+-N, NO2--N and NO3--N) matter present in the effluent from a bird slaughterhouse and industrial processing facility, as well as to evaluate the stability of the reactor using Shewhart control charts of individual measures. The results indicate means total inorganic nitrogen (NH4+-N+NO2- -N+NO3--N) removal of 84.32±1.59% and organic matter (COD) of 53.65±8.48% in the complete process (nitrification-denitrification) with the process under statistical control. The nitrifying activity during the aerobic phase estimated from the determination of the kinetic parameters had mean K1 and K2 values of 0.00381±0.00043 min-1 and 0.00381±0.00043 min-1, respectively. The evaluation of the kinetic behavior of the conversion of nitrogen indicated a possible reduction of CT in the anoxic phase, since removals of NO2--N and NO3--N higher than 90% were obtained with only 1 h of denitrification.