Tratamiento de vinazas de alcohol de caña en un reactor UASB

Para la realización de este artículo, se evaluó el rendimiento del reactor UASB (Upflow Anaerobic Sludge Blanket) utilizando vinazas de alcohol de caña como sustrato.

Hidrogeología e hidrodinámica del acuífero de los manantiales de Gormaz y su importancia en el caudal base del río Duero, España = Hydrogeology and hydrodynamic of the Gormaz Springs Aquifer and its importance to the base flow of the Duero River, Spain

Se cuantifican las descargas subterráneas de un acuífero a un río que lo atraviesa utilizando correlaciones estadísticas. El río Duero, España, incrementa su caudal base en varios m3/s, al atravesar unos afloramientos carbonatados mesozoicos en un pequeño tramo de su cabecera; esto es de especial importancia en época de estiaje, cuando la mayor parte del caudal base del río procede de manantiales que allí se sitúan. Dichos afloramientos corresponden a uno de los dos acuíferos calcáreos confinados, que se desarrollan en paralelo y están hidráulicamente desconectados por una capa impermeable, que forman el sistema acuífero de los manantiales de Gormaz. Este sistema se encuentra en estado de régimen natural y está apenas explotado. Se define el modelo conceptual de funcionamiento hidrogeológico, considerando el papel hidrogeológico de la falla de Gormaz, situada en la zona de descarga del sistema. Analizando información geológica antecedente y la geofísica exploratoria realizada, se obtuvo un mejor conocimiento de la geometría y los límites de los acuíferos, definiéndose un sistema acuífero con una zona de recarga en el sur, correspondiente a los afloramientos calcáreos, los cuales se confinan hacia el norte bajo el Terciario, hasta intersecar con la falla normal de Gormaz. El salto de falla genera una barrera para las formaciones permeables situadas al extremo norte (margen derecha del río Duero); a su vez, el plano de falla facilita el ascenso del agua subterránea del sistema acuífero en estudio y pone en conexión hidráulica los dos acuíferos. Se estimaron, además, los parámetros hidráulicos de los acuíferos en los alrededores de la falla. La buena correlación entre los niveles piezométricos y las descargas subterráneas al río Duero han permitido la reconstrucción del hidrograma de los manantiales de Gormaz en el periodo 1992-2006. Se calcula así que la contribución subterránea al río Duero es de 135.9 hm3/año, que supone el 18.9% de la aportación total del río. In a short stretch of its headwaters, the base flow of the River Duero increases by several m3/s as it traverses some Mesozoic carbonate outcrops. This is of special importance during the dry season, when the majority of the base flow of the river proceeds from springs in this reach. The outcrops correspond to one of two confined calcareous aquifers that developed in parallel but which are not hydraulically connected because of an impermeable layer. Together, they constitute the aquifer system of the Gormaz Springs. The system is still in its natural regime and is hardly exploited. This study defines the conceptual model of hydrogeological functioning, taking into consideration the role of the Gormaz Fault, which is situated in the discharge zone of the system. Analysis of both antecedent geological information and geophysical explorations has led to a better understanding of the geometry and boundaries of the aquifers, defining an aquifer system with a recharge zone in the south corresponding to in the calcareous outcrops. These calcareous outcrops are confined to the north below Tertiary formations, as far as their intersection with the normal fault of Gormaz. The throw of the fault forms the barrier of the permeable formations situated in the extreme north (right bank of the River Duero). In turn, the fault plane facilitates the upflow of groundwater from the aquifer system and creates hydraulic connection between the two aquifers. In addition, the study estimated the hydraulic parameters of the aquifer around the fault. The close correlation between piezometric levels and the groundwater discharges to the River Duero has enabled the reconstruction of the hydrogram of Gormaz springs over the period 1992-2006. By this means, it is calculated that the groundwater contribution to the River Duero is 135.9 hm3/year, or 18.9% of the total river inflow.

Influência da configuração da célula combustível microbiana na geração de energia elétrica a partir da degradação de compostos orgânicos

Nessa pesquisa foram testadas tanto CCM com membranas e sem membranas que tinham por característica reproduzir sistemas de tratamento de esgoto sanitário. A etapa experimental desse trabalho foi dividida entre o Brasil (ensaios com CCM sem a MTP e utilizando esgoto sanitário) e Portugal (ensaios com CCM tradicionais de uma e duas câmaras, utilizando água residuária sintética e a bactéria Lactobacillus pentosus). A execução em dois locais diferentes resultou em um maior aprofundamento e desenvolvimento da pesquisa. As CCM foram avaliadas principalmente quanto ao potencial elétrico e eficiência da degradação de compostos orgânicos (esgoto sanitário e água residuária sintética). Para os dados obtidos no Brasil, as três configurações apresentaram maior diferença na potência em função do modo de operação. A operação intermitente apresentou a maior potência (11 mW/m2) para a CCM cilíndrica de fluxo ascendente, enquanto que operação continua a maior potência (4,2 mW/m2) foi obtida para a CCM retangular de fluxo horizontal, a qual também apresentava uma maior facilidade na manutenção quanto aos eletrodos (adição/remoção). A CCM cúbica de fluxo ascendente devido a sua concepção simples demandava um sistema complementar para o aumento da remoção de DQO. Apesar da baixa potência mensurada para os ensaios realizados no Brasil há de se pontuar que os mesmos foram obtidos para reatores sem membranas e utilizando o esgoto sanitário, o qual apresentou grande sazonalidade. Para a etapa realizada em Portugal, foi possível realizar quinze diferentes ensaios e mais um ensaio específico de crescimento. A maior potência (10,37 mW/m2) foi obtida para CCM de câmara dupla operada de modo contínuo para um tempo de detenção hidráulico (TDH) de 20 horas. A maior potência obtida para a CCM de câmara única foi de 5,53 mW/m2 quando houve a adição do extrato de levedura (função teórica de mediador). A potência da CCM, na maioria das vezes, esteve relacionada à proporção de sólidos voláteis e totais, SV/ST, quantidade de bactérias, pH, características de operação e por fim a configuração da CCM. O ensaio de crescimento revelou a correlação da potência em função da quantidade de bactérias inseridas da massa do biofilme (SV) e mostra-se como uma ferramenta na avaliação da potência das CCM.

Avaliação do antagonismo do efeito do sódio sobre o tratamento de água residuária de Charqueada com elevada salinidade em reator anaeróbio de manta de lodo (UASB)

As águas residuárias provenientes da indústria do charque são conhecidas por apresentarem elevado teor de cloreto de sódio, aliado a grandes concentrações de matéria orgânica proveniente do sangue liberado ao longo do processo industrial. Esse tipo de água residuária apresenta potencial para degradação biológica, contudo, o cloreto de sódio, em concentração elevada, pode inibir a atividade dos microrganismos e, em alguns casos, levar sistemas biológicos à falência. No presente trabalho, foi avaliada a viabilidade de degradação anaeróbia de efluente sintético de Charqueada contendo elevado teor de cloreto de sódio, em reator anaeróbio tipo UASB (Upflow Anaerobic Sludge Blanket), em escala de laboratório. Foram utilizados 4 reatores, alimentados com água residuária sintética com características similares à água residuária de Charqueada. O reator 1 foi utilizado como controle, o reator 2 recebeu NaCl e os demais (3 e 4) foram operados na presença de NaCl acrescidos de: betaína e potássio com cálcio, respectivamente. Os compostos citados são conhecidos como antagonizantes, por possuirem capacidade de minimizar o efeito inibitório do sódio sobre o processo de digestão anaeróbia. Os reatores foram inoculados com lodo de reator UASB e submetidos à concentração de 5000 mg/L de matéria orgânica, como DQO. A carga orgânica aplicada foi de 5 Kg/m3.d e os reatores não suportaram tal carga. Reiniciou-se a operação com aumento progressivo da DQO de 500 a 2000 mg/L resultando em cargas orgânicas de 0,5 a 2,0 Kg/m3.d, respectivamente. Após estabilização dos reatores, iniciou-se a fase de introdução de cloreto de sódio (1.500 a 13.500 mg/L) e antagonizantes com aumento progressivo a cada fase. Na presença ou ausência de antagonizantes, os reatores 2, 3 e 4 não tiveram o desempenho alterado até a concentração de NaCl de 6000 mg/L. Na presença de 9000 mg/L de NaCl, a betaína se mostrou pouco efetiva como soluto compatível no reator 3 e os antagonizantes do reator 4, potássio e cálcio, apresentaram efeitos estimulatórios. As morfologias encontradas ao longo do experimento foram cocos, víbrios, bacilos, sarcinas, além de morfologias semelhantes a Methanosarcina sp. e Methanosaeta sp. O aumento da concentração de cloreto de sódio provocou a redição da população de Arqueas.

Pós-tratamento físico-químico por flotação de efluentes de reatores anaeróbios de manta de lodo (UASB)

O emprego da flotação por ar dissolvido (FAD) para o pós-tratamento de efluentes de reatores anaeróbios aparenta ser atraente considerando algumas características desse processo físico-químico. A FAD é reconhecidamente um processo de alta taxa, particularmente eficiente na remoção de material particulado em suspensão e de flocos produzidos pela coagulação química de águas residuárias. Além disso, há produção de lodo espesso e provavelmente arraste de parcela de gases e de compostos voláteis, presentes nos efluentes anaeróbios. Entretanto, a concepção de sistemas de FAD deve ser precedida por ensaios em unidades de flotação em escala de laboratório, permitindo a determinação dos principais parâmetros do processo. Neste trabalho, são apresentados e discutidos os resultados obtidos em laboratório e em instalação piloto de flotação com escoamento contínuo recebendo efluente de reator anaeróbio de manta de lodo (UASB), com 18 m3 de volume, tratando esgoto sanitário. Os ensaios em unidade em escala de laboratório foram realizados utilizando diferentes dosagens de cloreto férrico (entre 30 e 110 mg/L) ou de polímero catiônico (entre 1,0 e 16,0 mg/L), atuando como coagulantes. Além disso, foram estudadas as condições de floculação (tempo de 15 e de 25 min, e gradiente médio de velocidade de floculação entre 30 e 100 s-1) e diferentes valores de quantidade de ar fornecido ao processo (S*, entre 4,7 e 28,5 g de ar por m3 de efluente). Com a instalação piloto de FAD foram realizados apenas ensaios preliminares variando-se a taxa de aplicação superficial (140 e 210 m3/m2/d) para diferentes valores de S* (14,8 a 29,5 g de ar por m3 de efluente). Com o emprego de dosagem de 65 mg/L de cloreto férrico, de tempo de 15 min e gradiente médio de velocidade de floculação de 80 s-1 e de 19 g de ar por m3 de efluente, foram observados excelentes resultados em laboratório, com elevadas remoções de DQO (89%), de fosfato total (96%), de sólidos suspensos totais (96%), de turbidez (98%), de cor aparente (91%), de sulfetos (não detectado) e NTK (47%). Considerando o sistema UASB e FAD, nos testes em laboratório, foram observadas remoções globais de 97,7% de DQO, de 98,0% de fosfato total, de 98,9% de SST, de 99,5% de turbidez, de 97,8% de cor aparente e de 59,0% de NTK. Nos ensaios com a instalação piloto de FAD, o sistema apresentou remoções de 93,6% de DQO, de 87,1% de SST, de 90% de sulfetos e de 30% de NTK.

The influence of substrate kinetics on the microbial community structure in granular anaerobic biomass

The development of a strong, active granular sludge bed is necessary for optimal operation of upflow anaerobic sludge blanket reactors. The microbial and mechanical structure of the granules may have a strong influence on desirable properties such as growth rate, settling velocity and shear strength. Theories have been proposed for granule microbial structure based on the relative kinetics of substrate degradation, but contradict some observations from both modelling and microscopic studies. In this paper, the structures of four granule types were examined from full-scale UASB reactors, treating wastewater from a cannery, a slaughterhouse, and two breweries. Microbial structure was determined using fluorescence in situ hybridisation probing with 16S rRNA-directed oligonucleotide probes, and superficial structure and microbial density (volume occupied by cells and microbial debris) assessed using scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The granules were also modelled using a distributed parameter biofilm model, with a previously published biochemical model structure, biofilm modelling approach, and model parameters. The model results reflected the trophic structures observed, indicating that the structures were possibly determined by kinetics. Of particular interest were results from simulations of the protein grown granules, which were predicted to have slow growth rates, low microbial density, and no trophic layers, the last two of which were reflected by microscopic observations. The primary cause of this structure, as assessed by modelling, was the particulate nature of the wastewater, and the slow rate of particulate hydrolysis, rather than the presence of proteins in the wastewater. Because solids hydrolysis was rate limiting, soluble substrate concentrations were very low (below Monod half saturation concentration), which caused low growth rates. (C) 2003 Elsevier Ltd. All rights reserved.

Sugarcane water use from shallow water tables: implications for improving irrigation water use efficiency

The resource potential of shallow water tables for cropping systems has been investigated using the Australian sugar industry as a case study. Literature concerning shallow water table contributions to sugarcane crops has been summarised, and an assessment of required irrigation for water tables to depths of 2 m investigated using the SWIMv2.1 soil water balance model for three different soils. The study was undertaken because water availability is a major limitation for sugarcane and other crop production systems in Australia and knowledge on how best to incorporate upflow from water tables in irrigation scheduling is limited. Our results showed that for the three soils studied (representing a range of permeabilities as defined by near-saturated hydraulic conductivities), no irrigation would be required for static water tables within 1 m of the soil surface. Irrigation requirements when static water tables exceeded 1 m depth were dependent on the soil type and rooting characteristics (root depth and density). Our results also show that the near-saturated hydraulic conductivities are a better indicator of the ability of water tables below 1 m to supply sufficient upflow as opposed to soil textural classifications. We conclude that there is potential for reductions in irrigation and hence improvements in irrigation water use efficiency in areas where shallow water tables are a low salinity risk: either fresh, or the local hydrology results in net recharge. (C) 2003 Elsevier B.V. All rights reserved.

Integration of sulphate reduction, autotrophic denitrification and nitrification to achieve low-cost excess sludge minimisation for Hong Kong sewage

An integrated anaerobic-aerobic treatment system of sulphate-laden wastewater was proposed here to achieve low sludge production, low energy consumption and effective sulphide control. Before integrating the whole system, the feasibility of autotrophic denitrification utilising dissolved sulphide produced during anaerobic treatment of sulphate rich wastewater was studied here. An upflow anaerobic sludge blanket reactor was operated to treat sulphate-rich synthetic wastewater (TOC = 100 mg/L and sulphate = 500 mg/L) and its effluent with dissolved sulphide and external nitrate solution were fed into an anoxic biofilter. The anaerobic reactor was able to remove 77-85% of TOC at HRT of 3 h and produce 70-90 mg S/L sulphide in dissolved form for the subsequent denitrification. The performance of anoxic reactor was stable, and the anoxic reactor could remove 30 mg N/L nitrate at HRT of 2 h through autotrophic denitrification. Furthermore, sulphur balance for the anoxic filter showed that more than 90% of the removed sulphide was actually oxidised into sulphate, thereby there was no accumulation of sulphur particles in the filter bed. The net sludge productions were approximately 0.15 to 0.18 g VSS/g COD in the anaerobic reactor and 0.22 to 0.31 g VSS/g NO3--N in the anoxic reactor. The findings in this study will be helpful in developing the integrated treatment system to achieve low-cost excess sludge minimisation.

Chemical and isotopic composition of carbonate veins from ODP Leg 209

Carbonate veins hosted in ultramafic basement drilled at two sites in the Mid Atlantic Ridge 15°N area record two different stages of fluid-basement interaction. A first generation of carbonate veins consists of calcite and dolomite that formed syn- to postkinematically in tremolite-chlorite schists and serpentine schists that represent gently dipping large-offset faults. These veins formed at temperatures between 90 and 170 °C (oxygen isotope thermometry) and from fluids that show intense exchange of Sr and Li with the basement (87Sr/86Sr = 0.70387 to 0.70641, d7Li L-SVEC = + 3.3 to + 8.6 per mil). Carbon isotopic compositions range to high d13C PDB values (+ 8.7 per mil), indicating that methanogenesis took place at depth. The Sr-Li-C isotopic composition suggests temperatures of fluid-rock interaction that are much higher (T > 350-400 °C) than the temperatures of vein mineral precipitation inferred from oxygen isotopes. A possible explanation for this discrepancy is that fluids cooled conductively during upflow within the presumed detachment fault. Aragonite veins were formed during the last 130 kyrs at low-temperatures within the uplifted serpentinized peridotites. Chemical and isotopic data suggest that the aragonites precipitated from cold seawater, which underwent overall little exchange with the basement. Oxygen isotope compositions indicate an increase in formation temperature of the veins by 8-12 °C within the uppermost ~ 80 m of the subseafloor. This increase corresponds to a high regional geothermal gradient of 100-150 °C/km, characteristic of young lithosphere undergoing rapid uplift.

Kelvin-Helmholtz instability in solar chromospheric jets: theory and observation

Using data obtained by the high-resolution CRisp Imaging SpectroPolarimeter instrument on the Swedish 1 m Solar Telescope, we investigate the dynamics and stability of quiet-Sun chromospheric jets observed at the disk center. Small-scale features, such as rapid redshifted and blueshifted excursions, appearing as high-peed jets in the wings of the Hα line, are characterized by short lifetimes and rapid fading without any descending behavior. To study the theoretical aspects of their stability without considering their formation mechanism, we model chromospheric jets as twisted magnetic flux tubes moving along their axis, and use the ideal linear incompressible magnetohydrodynamic approximation to derive the governing dispersion equation. Analytical solutions of the dispersion equation indicate that this type of jet is unstable to Kelvin–Helmholtz instability (KHI), with a very short (few seconds) instability growth time at high upflow speeds. The generated vortices and unresolved turbulent flows associated with the KHI could be observed as a broadening of chromospheric spectral lines. Analysis of the Hα line profiles shows that the detected structures have enhanced line widths with respect to the background. We also investigate the stability of a larger-scale Hα jet that was ejected along the line of sight. Vortex-like features, rapidly developing around the jet’s boundary, are considered as evidence of the KHI. The analysis of the energy equation in the partially ionized plasma shows that ion–neutral collisions may lead to fast heating of the KH vortices over timescales comparable to the lifetime of chromospheric jets.

Nitrogen removal and sustainability of vertical flow constructed wetlands for small scale wastewater treatment

The challenge for wastewater professionals is to design and operate treatment processes that support human well being and are environmentally sensitive throughout the life-cycle. This research focuses on one technology for small-scale wastewater treatment: the vertical flow constructed wetland (VFCW), which is herein investigated for the capacity to remove ammonium and nitrate nitrogen from wastewater. Hydraulic regime and presence/absence of vegetation are the basis for a three-phase bench scale experiment to determine oxygen transfer and nitrogen fate in VFCWs. Results show that 90% NH4+-N removal is achieved in aerobic downflow columns, 60% NO3--N removal occurs in anaerobic upflow columns, and 60% removal of total nitrogen can be achieved in downflow-upflow in-series. The experimental results are studied further using a variably saturated flow and reactive transport model, which allows a mechanistic explanation of the fate and transport of oxygen and nitrogen. The model clarifies the mechanisms of oxygen transport and nitrogen consumption, and clarifies the need for readily biodegradable COD for denitrification. A VFCW is then compared to a horizontal flow constructed wetland (HFCW) for life cycle environmental impacts. High areal emissions of greenhouse gases from VFCWs compared to HFCWs are the driver for the study. The assessment shows that because a VFCW is only 25% of the volume of an HFCW designed for the same treatment quality, the VFCW has only 25-30% of HFCW impacts over 12 impact categories and 3 damage categories. Results show that impacts could be reduced by design improvements. Design recommendations are downflow wetlands for nitrification, upflow wetlands for denitrification, series wetlands for total nitrogen removal, hydraulic load of 142 L/m2d, 30 cm downflow wetland depth, 1.0 m upflow wetland depth, recycle, vegetation and medium-grained sand. These improvements will optimize nitrogen removal, minimize gaseous emissions, and reduce wetland material requirements, thus reducing environmental impact without sacrificing wastewater treatment quality.