ADM1 approach to the performance optimisation and biogas H2S prediction of a large-scale anaerobic reactor fed on sugarcane vinasse.

In this paper, we present extensions to the Anaerobic Digestion Model No. 1 (ADM1) to simulate hydrogen sulphide in biogas and solids retention efficiency. The extended model was calibrated and validated against data from a large-scale covered in-ground anaerobic reactor (CIGAR), processing sugarcane vinasse. Comparative scenarios and set-ups of a CIGAR with and without a settling tank unit (settler) were simulated to investigate the reactor's performance. Biogas flow, methane content, and yield with settler were 15,983 Nm3/d, 57%, and 0.198 Nm3CH4/kgCOD, respectively, which were 9.4%, 1.8%, and 11.64%, higher than without the settler. Improvements are combination of influent flow rate 116% higher and increased solids retention time by using a settler. The optimised modelled reactor, the volume of which was reduced by 50%, was able to produce 83% more methane per volume of reactor with half the retention time. After model calibration and validation, we assessed the quality of predictions and its utility. The overall quality of predictions was assessed as high accuracy quantitative for CH4 and medium for H2S and biogas flow. A practical demonstration of ADM1 to industrial application is presented here to identify the potential optimisation and behaviour of a large-scale anaerobic reactor, reducing, consequently, expenditure, risk, and time.

ADM1 modelling of large-scale covered in-ground anaerobic reactor treating sugarcane vinasse.

In this paper, we demonstrate in a clear procedure the application of the Anaerobic Digestion Model No. 1 (ADM1) to model a large-scale covered in-ground anaerobic reactor (Cigar), processing sugarcane vinasse from a biorefinery in Brazil. The biochemical make-up (carbohydrates, proteins, and lipids) of the substrate was analysed based on the food industry standards. Two distinct subsets of data, based on the sugarcane harvest season for bioethanol and sugar production in 2012 and 2014, were used to direct and cross validate the model, respectively. We fitted measured data by estimating two key parameters against biogas flow rate: the degradation extent (fd) and the first order hydrolysis rate coefficient (khyd). By cross validation we show that the fitted model can be generalised to represent the behaviour of the reactor under study. Therefore, motivated by practical and industrial application of ADM1, for both different reactors types and substrates, we show aspects on the implementation of ADM1 to a specific large-scale reactor for anaerobic digestion of sugarcane vinasse.

Giardia spp. and Cryptosporidium spp. removal efficiency of a combined fixed-film system treating domestic wastewater receiving hospital effluent.

Giardia and Cryptosporidium have caused numerous outbreaks of diarrhea as a result of the ingestion of water contaminated with sewage. In Brazil, the efficiency of Giardia and Cryptosporidium removal by combined fixed-film systems has rarely been studied. The aims of the present study were therefore to verify the removal efficiency of Giardia and Cryptosporidium by a combined system (anaerobic/anoxic filter and aerated submerged biofilter) and to perform the genetic characterization of these parasites. The (oo)cysts were detected by centrifuge concentration and membrane filtration from raw sewage, effluents, adhered biomass, and sludge samples. Immunofluorescence assay and differential interference contrast microscopy were used for the visualization of the (oo)cysts. Nested PCR was applied to confirm Giardia and Cryptosporidium. Giardia and Cryptosporidium were detected in 27% and 5.5% of the 144 analyzed samples of raw sewage and effluents, respectively. A total of 33,000 cysts/L were recovered in the adhered biomass samples (n = 25) from different points of the aerated submerged biofilter, while 6000 oocysts/L were registered in a single point. An average of 11,800 cysts/L were found in the sludge samples (n = 5). The combined system exhibited a removal efficiency of Giardia cysts of 1.8 ± 1.0 log removal. The C and BIV assemblages of Giardia were identified in the raw sewage while AII was found in the treated effluent sample. It was not possible to calculate the removal efficiency of Cryptosporidium oocysts by the combined system. The combined system exhibited some potential as a suitable treatment for the removal of parasites from sewage.

Desenvolvimento de lodo granular aeróbio em reatores em batelada sequencial com baixa velocidade de sedimentação / Development of aerobic granular sludge in sequencing batch reactors with low sedimentation speed

RESUMO Diversos trabalhos têm mostrado a formação de lodo granular aeróbio em reatores nos quais são impostas elevadas velocidades de sedimentação, da ordem de 10 a 12 m.h−1. Aparentemente, quando a velocidade de sedimentação é inferior a 3,8 m.h−1, a fração de lodo floculado é predominante, visto que o lodo suspenso não é eliminado de forma efetiva do reator. Outros estudos, entretanto, mostram a formação de lodos granulares aeróbios para velocidades menores que essa, apontando a possibilidade da formação desse tipo de biomassa em velocidades ainda menores. Assim, este trabalho avaliou a formação desse tipo de lodo em reatores que tratam esgoto sanitário, com relação altura/diâmetro unitária, para velocidades de sedimentação de 1,8 e 1,2 m.h−1, verificando as eficiências de remoção de matéria orgânica e nitrogênio. Os resultados obtidos indicaram que é possível formar lodo aeróbio granular para a faixa de velocidade de estudo, porém com baixa estabilidade estrutural para diâmetros de 1,2 mm ou mais. Essa instabilidade dos grânulos contribui para a baixa eficiência de remoção de matéria orgânica e nitrogênio nos reatores.

ABSTRACT Several studies have shown the formation of aerobic granular sludge in reactors where high sedimentation rates are imposed, varying from 10 to 12 m.h−1. Apparently, when the settling velocity is less than 3.8 m.h−1, the fraction of flocculated sludge is predominant, since the suspended sludge is not effectively eliminated from the reactor. Other studies, however, show the formation of aerobic granular sludge at velocities lower than this, pointing to the possibility of formation of this type of biomass at even lower speeds. Thus, this work evaluated the efficacy of this type of sludge in reactors treating sewage, with H/D ratio (height/diameter), for sedimentation velocities of 1.8 and 1.2 mh−1, verifying the efficiencies of organic matter and nitrogen. The results indicated that it is possible to form aerobic granular sludge for the study velocity range, but with low structural stability from diameters of approximately 1.2 mm. This instability of the granules contributes to the low efficiency of removal of organic matter and nitrogen in the reactors.

Tratamento de esgoto sanitário por escoamento superficial no solo: remoção de metais / Wastewater treatment by overland flow: removal of metals

RESUMO Com o objetivo de avaliar a remoção e a concentração dos metais cádmio (Cd), cromo (Cr), cobre (Cu), chumbo (Pb), ferro (Fe), níquel (Ni) e zinco (Zn) em águas residuais municipais, foram conduzidos ensaios de campo utilizando o método do escoamento em duas taxas de aplicação superficial, 0,30 e 0,20 m3.m-1.h-1, em uma rampa de 4,25 × 40 m, com 3,5% de declividade, plantada com Tifton 85 (Cynodon spp.). Em amostras coletadas durante o estudo de 15 meses, apenas Cu, Cr e Pb excederam os limites de lançamento de acordo com a Resolução do Conselho Nacional do Meio Ambiente (CONAMA) nº 430/2011 (BRASIL, 2011). A taxa de aplicação não influencia na remoção superficial de Cd, Cr, Cu, Fe, Ni e Pb, no entanto maior remoção de Zn ocorreu ao empregar taxas de aplicação superficial de 0,30 m3.m-1.h-1. A taxa de aplicação não influencia a incorporação de Cd, Cr, Fe, Ni e Zn na biomassa, porém maior incorporação de Pb ocorreu ao aplicar 0,20 m3.m-1.h-1.

ABSTRACT In order to evaluate the removal and concentration of the metals cadmium (Cd), chrome (Cr), copper (Cu), lead (Pb), iron (Fe), nickel (Ni) and zinc (Zn) in municipal wastewater, we conducted field tests using the method of overland flow under two rates of surface application, 0.30 and 0.20 m3.m-1.h-1, on a ramp of 4.25 × 40 m with a slope of 3.5%, planted with Tifton 85 (Cynodon spp.). In samples collected during the 15-month study, only Cu, Cr and Pb exceeded the discharge limit according to the National Environment Council (CONAMA) Resolution n. 430/2011 (BRASIL, 2011). The application rate does not influence the surface removal of Cd, Cr, Cu, Fe, Ni and Pb; however, higher Zn removal occurred by applying rates of surface application of 0.30 m3.m-1.h-1. The rate of application does not influence the incorporation of Cd, Cr, Fe, Ni and Zn in the biomass, but greater incorporation of Pb occurred when applying 0.20 m3.m-1.h-1.

Degradação de formaldeído tratado em conjunto com esgoto sanitário em sistema combinado anaeróbio-aeróbio / Degradation of formaldehyde treated in conjunction with municipal sewage in combined anaerobic-aerobic system

O estudo visou a investigação da degradação de formaldeído em um sistema combinado anaeróbio-aeróbio, de fluxo ascendente e com biomassa imobilizada, constituindo-se por um filtro anaeróbio seguido de biofiltro aerado submerso. As concentrações de formaldeído aplicadas ao sistema variaram de 26 a 1.055 mg HCHO.L-1, resultando em eficiências de remoção de formaldeído de 97±3% e de DQO de 90±6%. A partir dos resultados obtidos, conclui-se que o sistema combinado se apresentou adequado para o tratamento de esgoto sanitário contendo formaldeído, uma vez que além de eficiências de remoção representativas, apresentou estabilidade de operação durante o decorrer do estudo.

The study aimed to investigate the degradation of formaldehyde in an anaerobic-aerobic combined system, upflow and with immobilized biomass, consisting of an Anaerobic Filter (AF) followed by Aerated Submerged Biofilter (ASB). The concentrations of formaldehyde applied to the system ranged from 26 to 1,055 mg HCHO.L-1, resulted in a removal efficiency of formaldehyde of 97±3% and chemical oxygen demand (COD) of 90±6%. From the results, it is concluded that the combined system was suitable for treating wastewater containing formaldehyde, since besides representative removal efficiencies; operation was stable during the course of the study.

Remoção de nitrogênio em sistema combinado anóxico-aeróbio com biomassa imobilizada / Nitrogen removal in combined anoxic-aerobic system with imobilized biomass

Este trabalho visa estudar o desempenho de um sistema combinado na remoção de matéria orgânica e nitrogênio de esgoto sanitário, por meio da recirculação interna do efluente. Os reatores, em escala de bancada, foram: filtro anóxico (32,6 L), biofiltro aerado submerso (17,6 L) e decantador secundário (7,2 L). As razões de recirculação foram 0,5; 1,5; 2,0 e 4,0 sem adição de carbono externo ou alcalinizante. Na razão de recirculação de 4,0 foram aplicadas taxas de carregamento orgânico e de nitrogênio ao sistema de 0,7±0,3 Kg DQO.m-3.d-1 e 0,08±0,02 kg N-NH4 +.m-3.d-1, atingindo remoções de demanda química de oxigênio e nitrogênio total de 92±4% e 83±8%, respectivamente. Os resultados mostram viabilidade do uso da recirculação do efluente, uma vez que as concentrações finais de nitrogênio total (12±3 mg N.L-1) estão abaixo do valor estipulado pela Resolução CONAMA nº 430/2011.

This work aims to study the performance of a combined system in the removal of organic matter and nitrogen from sanitary sewage through internal recirculation of the effluent. The bench scale reactors were: anoxic filter (32.6 L), submerged aerated biofilter (17.6 L) and secondary settler (7.2 L). The recirculation rates were 0.5; 1.5; 2.0 and 4.0 without added external-carbon or alkalising. In 4.0 recirculation rate, the organic and nitrogen loading rates applied to the system were 0.7±0.3 kg chemical oxygen demand.m-3.d-1 and 0.08±0.02 kg N-NH4 +.m-3.d-1, reaching removals of chemical oxygen demand and total nitrogen of 92±4% and 83±8%, respectively. The results show the feasibility of using recirculation of effluent, once the final concentrations of total nitrogen (12±3 mg.L-1) are below the value stipulated by CONAMA Resolution nº 430/2011.