RESUMO
Natural pozzolan is an amorphous silicate-based material of volcanic origin. In this work, the natural pozzolan was modified by using 3-aminopropyltriethoxysilane (APTES) as a grafting agent. This material was characterized by pHpzc, N2 adsorption/desorption curves, FTIR, TGA/DTG, DRUV, SEM, and elementary analysis. The functionalized materials were used for the removal of Reactive Black 5 (RB-5) and Brilliant Green 1 (BG-1) dyes from aqueous solutions using batch-contact adsorption. The characterization of modified pozzolan by FTIR, TGA/DTG, BET, and DRUV-vis revealed the effectiveness of grafting of amine functional group on pozzolan structure. The kinetic adsorption data were better fitted with general order for both dyes while for equilibrium models were better fitted by the Liu isotherm model. The maximum sorption capacities Q max (at 50 °C) obtained with the modified pozzolan were 350.6 and 300.9 mg g-1 for BG-1 and RB-5, at pH 9.0 and 2.0, respectively. The thermodynamic parameters show that the removal of dyes was spontaneous and endothermic. The modified material was also tested for the treatment of simulated dye house effluents showing very high efficiency.
Assuntos
Naftalenossulfonatos/isolamento & purificação , Propilaminas/química , Compostos de Amônio Quaternário/isolamento & purificação , Silanos/química , Adsorção , Corantes/química , Concentração de Íons de Hidrogênio , Cinética , Soluções , Termodinâmica , Água , Poluentes Químicos da Água/químicaRESUMO
Phenolic compounds biodegradation and its effect on the nitrification process were studied. A continuous stirrer tank reactor was operated in four stages, and phenolic compounds were fed as sequential way. In the first stage, at loading rate of 220 mg NH(4)(+)-N/Ld, the consumption efficiency was of 91%, being the product, nitrate. After that, p-cresol was fed at 53 mg C/Ld, reaching removal efficiencies for both substrates higher than 90%. In the third stage, p-hydroxybenzoate was fed at 56 mg C/Ld, and the removal efficiencies for all substrates remained high. In the last stage, the reactor was fed at 54 mg C/Ld of phenol, and it caused a diminishing on the ammonium removal efficiency; however, all phenolic compounds were efficiently removed. Kinetic results showed that the presence of each phenolic compound improved the ammonium oxidizing activity, but the nitrite oxidizing activity was not affected.
Assuntos
Reatores Biológicos , Cresóis/isolamento & purificação , Recuperação e Remediação Ambiental/instrumentação , Nitrificação , Parabenos/isolamento & purificação , Fenol/isolamento & purificação , Compostos de Amônio Quaternário/isolamento & purificação , Técnicas de Cultura Celular por Lotes , Biodegradação Ambiental , Reatores Biológicos/microbiologia , Carbono/análise , Consórcios Microbianos , Nitrogênio/isolamento & purificação , Reologia , Fatores de TempoRESUMO
A mathematical model was developed for a compact anoxic-anaerobic-aerobic filter reactor with liquid recirculation for the treatment of fishing effluents. The model includes denitrification, anaerobic digestion, aerobic carbon oxidation and nitrification steps, as well as an evaluation of the liquid gas mass transfer and pH. The model was calibrated using one experimental condition at a recycling ratio (R)=10, and was validated with R equal to 2 and 0, with an organic concentration of 554±24 mg TOCL(-1), salinity of 24 g L(-1) and hydraulic retention time (HRT) of 2 d. Carbon total removal is higher than 98%, while maximum nitrogen removal is 62% using total nitrification in the aerobic zone, due to a higher quantity of NO(x) produced which were recirculated to the anoxic zone. In the aerobic zone, simultaneous nitrification and denitrification processes occur, because the diffusion limitations cause a low oxygen penetration in the biofilm. In the anoxic-anaerobic zone, denitrification or methanogenesis inhibition by DO (caused by the recycled oxygen) is not observed.
Assuntos
Reatores Biológicos/microbiologia , Modelos Biológicos , Compostos Orgânicos/metabolismo , Compostos de Amônio Quaternário/metabolismo , Ultrafiltração/instrumentação , Purificação da Água/instrumentação , Simulação por Computador , Desenho Assistido por Computador , Desnitrificação/fisiologia , Desenho de Equipamento , Análise de Falha de Equipamento , Nitrificação/fisiologia , Oxirredução , Compostos de Amônio Quaternário/isolamento & purificaçãoRESUMO
This work applied PCR amplification method and Fluorescence in situ hybridisation (FISH) with primers and probes specific for the anammox organisms and aerobic ammonia-oxidising beta-Proteobacteria in order to detect these groups in different samples from a wastewater treatment system comprised by UASB reactor and three polishing (maturation) ponds in series. Seven primer pairs were used in order to detect Anammox bacteria. Positive results were obtained with three of them, suggesting that Anammox could be present in polishing pond sediments. However, Anammox bacteria were not detected by FISH, indicating that they were not present in sediment samples, or they could be present but below FISH detection limit. Aerobic ammonia- and nitrite-oxidising bacteria were verified in water column samples through Most Probable Number (MPN) analysis, but they were not detected in sediment samples by FISH. Ammonia removal efficiencies occurred systematically along the ponds (24, 32, and 34% for polishing pond 1, 2, and 3, respectively) but the major reaction responsible for this removal is still unclear. Some nitrification might have occurred in water samples because some nitrifying bacteria were present. Also Anammox reaction might have occurred because Anammox genes were detected in the sediments, but probably this reaction was too low to be noticed. It is important also to consider that some of the ammonia removal observed might be related to NH(3) stripping, associated with the pH increase resulting from the intensive photosynthetic activity in the ponds (mechanism under investigation). Therefore, it can be concluded that more than one mechanism (or reaction) might be involved in the ammonia removal in the polishing ponds investigated in this study.
Assuntos
Bactérias/metabolismo , Compostos de Amônio Quaternário/metabolismo , Eliminação de Resíduos Líquidos/métodos , Aerobiose , Anaerobiose , Bactérias/genética , Betaproteobacteria/genética , Betaproteobacteria/metabolismo , Reatores Biológicos , Primers do DNA , DNA Bacteriano/genética , DNA Bacteriano/isolamento & purificação , Desenho de Equipamento , Amplificação de Genes , Oxirredução , Reação em Cadeia da Polimerase , Probabilidade , Compostos de Amônio Quaternário/isolamento & purificação , Eliminação de Resíduos Líquidos/instrumentaçãoRESUMO
In this work a set of experiments was undertaken in a pilot-scale WSP system to determine the importance of organic nitrogen sedimentation on ammonium and total nitrogen removals in maturation ponds and its seasonal variation under British weather conditions, from September 2004 to May 2007. The nitrogen content in collected sediment samples varied from 4.17% to 6.78% (dry weight) and calculated nitrogen sedimentation rates ranged from 273 to 2868 g N/ha d. High ammonium removals were observed together with high concentrations of chlorophyll-a in the pond effluent. Moreover, chlorophyll-a had a very good correlation with the corresponding increment of VSS (algal biomass) and suspended organic nitrogen (biological nitrogen uptake) in the maturation pond effluents. Therefore, when ammonium removal reached its maximum, total nitrogen removal was very poor as most of the ammonia taken up by algae was washed out in the pond effluent in the form of suspended solids. After sedimentation of the dead algal biomass, it was clear that algal-cell nitrogen was recycled from the sludge layer into the pond water column. Recycled nitrogen can either be taken up by algae or washed out in the pond effluent. Biological (mainly algal) uptake of inorganic nitrogen species and further sedimentation of dead biomass (together with its subsequent mineralization) is one of the major mechanisms controlling in-pond nitrogen recycling in maturation WSP, particularly when environmental and operational conditions are favourable for algal growth.
Assuntos
Biomassa , Nitrogênio/isolamento & purificação , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Biodegradação Ambiental , Eucariotos/metabolismo , Resíduos Industriais , Nitrogênio/química , Compostos de Amônio Quaternário/química , Compostos de Amônio Quaternário/isolamento & purificação , Estações do Ano , Esgotos , Fatores de Tempo , Reino Unido , Poluentes Químicos da Água/químicaRESUMO
A polyurethane packed-bed-biofilm sequential batch reactor was fed with synthetic substrate simulating the composition of UASB reactor effluents. Two distinct ammonia nitrogen concentrations (125 and 250 mg l(-1)) were supplied during two sequential long-term experiments of 160 days each (320 total). Cycles of 24h under intermittent aeration for periods of 1h were applied, and ethanol was added as a carbon source at the beginning of each anoxic period. Nitrite was the main oxidized nitrogen compound which accumulated only during the aerated phases of the batch cycle. A consistent decrease of nitrite concentration started always immediately after the interruption of oxygen supply and addition of the electron donor. Removal to below detection limits of all nitrogen soluble forms was always observed at the end of the 24h cycles for both initial concentrations. Polyurethane packed-bed matrices and ethanol amendments conferred high process stability. Microbial investigation by cloning suggested that nitrification was carried out by Nitrosomonas-like species whereas denitrification was mediated by unclassified species commonly observed in denitrifying environments. The packed-bed batch bioreactor favored the simultaneous colonization of distinct microbial groups within the immobilized microbial biomass. The biofilm was capable of actively oxidizing ammonium and denitrification at high ratios in intermittent intervals within 24h cycles.
Assuntos
Reatores Biológicos/microbiologia , Nitratos/metabolismo , Nitritos/metabolismo , Compostos de Amônio Quaternário/metabolismo , Esgotos/microbiologia , Poluentes Químicos da Água/metabolismo , Purificação da Água/métodos , Nitratos/isolamento & purificação , Nitritos/isolamento & purificação , Compostos de Amônio Quaternário/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificaçãoRESUMO
Acid mine drainage (AMD) is a widespread environmental problem associated with both working and abandoned mining operations, resulting from the microbial oxidation of pyrite in presence of water and air, affording an acidic solution that contains toxic metal ions. The generation of AMD and release of dissolved heavy metals is an important concern facing the mining industry. The present study aimed at evaluating the use of low-cost sorbents like coal fly ash, natural clinker and synthetic zeolites to clean-up AMD generated at the Parys Mountain copper-lead-zinc deposit, Anglesey (North Wales), and to remove heavy metals and ammonium from AMD. pH played a very important role in the sorption/removal of the contaminants and a higher adsorbent ratio in the treatment of AMD promoted the increase of the pH, particularly using natural clinker-based faujasite (7.70-9.43) and the reduction of metal concentration. Na-phillipsite showed a lower efficiency as compared to that of faujasite. Selectivity of faujasite for metal removal was, in decreasing order, Fe>As>Pb>Zn>Cu>Ni>Cr. Based on these results, the use of these materials has the potential to provide improved methods for the treatment of AMD.
Assuntos
Ácidos/química , Carbono/química , Carvão Mineral , Recuperação e Remediação Ambiental/métodos , Metais Pesados/isolamento & purificação , Mineração , Material Particulado/química , Poluentes Químicos da Água/isolamento & purificação , Zeolitas/química , Adsorção , Cinza de Carvão , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de Varredura , Compostos de Amônio Quaternário/isolamento & purificação , Difração de Raios XRESUMO
In the summer of 2003, a microalga strain was isolated from a massive green microalgae bloom in wastewater stabilization ponds at the treatment facility of La Paz, B.C.S., Mexico. Prevailing environmental conditions were air temperatures over 40 degrees C, water temperature of 37 degrees C, and insolation of up to 2400 micromol m2 s(-1) at midday for several hours at the water surface for four months. The microalga was identified as Chlorella sorokiniana Shih. et Krauss, based on sequencing its entire 18S rRNA gene. In a controlled photo-bioreactor, this strain can grow to high population densities in synthetic wastewater at temperatures of 40-42 degrees C and light intensity of 2500 micromol m2 s(-1) for 5h daily and efficiently remove ammonium from the wastewater under these conditions better than under normal lower temperature (28 degrees C) and lower light intensity (60 micromol m2 s(-1)). When co-immobilized with the bacterium Azospirillum brasilense that promotes growth of microalgae, the population of microalga grew faster and removed even more ammonium. Under exposure to extreme growth conditions, the quantity of four photosynthetic pigments increased in the co-immobilized cultures. This strain of microalga has potential as a wastewater treatment agent under extreme conditions of temperature and light intensity.
Assuntos
Adaptação Fisiológica , Chlorella/metabolismo , Chlorella/efeitos da radiação , Temperatura Alta , Compostos de Amônio Quaternário/isolamento & purificação , Luz Solar , Eliminação de Resíduos Líquidos , Adaptação Fisiológica/efeitos da radiação , Alginatos/metabolismo , Azospirillum brasilense/metabolismo , Biodegradação Ambiental , Células Imobilizadas , Chlorella/citologia , Chlorella/crescimento & desenvolvimento , Ácido Glucurônico/metabolismo , Ácidos Hexurônicos/metabolismo , Microesferas , Fotossíntese/efeitos da radiação , Pigmentos Biológicos/metabolismoRESUMO
We evaluated ammonium nitrogen removal and nitrogen transformations in three-year-old, batch-operated, subsurface wetland microcosms. Treatments included replicates of Typha latifolia, Carex rostrata, and unplanted controls when influent carbon was excluded, and C. rostrata with an influent containing organic carbon. A series of 10-day batch incubations were conducted over a simulated yearlong cycle of seasons. The presence of plants significantly enhanced ammonium removal during both summer (24 degrees C, active plant growth) and winter (4 degrees C, plant dormancy) conditions, but significant differences between plant species were evident only in summer when C. rostrata outperformed T. latifolia. The effect of organic carbon load was distinctly seasonal, enhancing C. rostrata ammonium removal in winter but having an inhibitory effect in summer. Season did not influence ammonium removal in T. latifolia or unplanted columns. Net production of organic carbon was evident year-round in units without an influent organic carbon source, but was enhanced in summer, especially for C. rostrata, which produced significantly more than T. latifolia and unplanted controls. No differences in production were evident between species in winter. COD values for C. rostrata microcosms with and without influent organic carbon converged within 24 hours in winter and 7 days in summer. Gravel sorption, microbial immobilization and sequential nitrification/denitrification appear to be the major nitrogen removal mechanisms. All evidence suggests differences between season and species are due to differences in seasonal variation of root-zone oxidation.
Assuntos
Carbono/química , Compostos de Amônio Quaternário/isolamento & purificação , Purificação da Água/métodos , Adsorção , Biodegradação Ambiental , Fluoretos Tópicos/química , Compostos de Amônio Quaternário/química , Estações do Ano , Typhaceae/químicaRESUMO
A combination of microalgae (Chlorella vulgaris or C. sorokiniana) and a microalgae growth-promoting bacterium (MGPB, Azospirillum brasilense strain Cd), co-immobilized in small alginate beads, was developed to remove nutrients (P and N) from municipal wastewater. This paper describes the most recent technical details necessary for successful co-immobilization of the two microorganisms, and the usefulness of the approach in cleaning the municipal wastewater of the city of La Paz, Mexico. A. brasilense Cd significantly enhanced the growth of both Chlorella species when the co-immobilized microorganisms were grown in wastewater. A. brasilense is incapable of significant removal of nutrients from the wastewater, whereas both microalgae can. Co-immobilization of the two microorganisms was superior to removal by the microalgae alone, reaching removal of up to 100% ammonium, 15% nitrate, and 36% phosphorus within 6 days (varied with the source of the wastewater), compared to 75% ammonium, 6% nitrate, and 19% phosphorus by the microalgae alone. This study shows the potential of co-immobilization of microorganisms in small beads to serve as a treatment for wastewater in tropical areas.