RESUMEN
This study aims at evaluating the performance of a two-chambered continuously fed microbial fuel cell with new Ti-TiO2 electrodes for bioelectricity generation from young landfill leachate at varying strength of wastewater (1-50 COD g/L) and hydraulic retention time (HRT, 0.25-2 days). The COD removal efficiency in the MFC increased with time and reached 45 % at full-strength leachate (50 g/L COD) feeding. The current generation increased with increasing leachate strength and decreasing HRT up to organic loading rate of 100 g COD/L/day. The maximum current density throughout the study was 11 A/m² at HRT of 0.5 day and organic loading rate of 67 g COD/L/day. Coulombic efficiency (CE) decreased from 57 % at feed COD concentration of 1 g/L to less than 1 % when feed COD concentration was 50 g/L. Increase in OLR resulted in increase in power output but decrease in CE.
Asunto(s)
Fuentes de Energía Bioeléctrica , Eliminación de Residuos Líquidos/métodos , Biodegradación Ambiental , Bioingeniería , Análisis de la Demanda Biológica de Oxígeno , Electricidad , Electrodos , Eliminación de Residuos , TitanioRESUMEN
Electrode materials play a key role in enhancing the electricity generation in the microbial fuel cell (MFC). In this study, a new material (Ti-TiO(2)) was used as an anode electrode and compared with a graphite electrode for electricity generation. Current densities were 476.6 and 31 mA/m(2) for Ti-TiO(2) and graphite electrodes, respectively. The PCR-DGGE analysis of enriched microbial communities from estuary revealed that MFC reactors were dominated by Shewanella haliotis, Enterococcus sp., and Enterobacter sp. Bioelectrochemical kinetic works in the MFC with Ti-TiO(2) electrode revealed that the parameters by non-linear curve fitting with the confidence bounds of 95% gave good fit with the kinetic constants of η (difference between the anode potential and anode potential giving one-half of the maximum current density) = 0.35 V, K (s) (Half-saturation constant) = 2.93 mM and J (max) = 0.39 A/m(2) for T = 298 K and F = 96.485 C/mol-e(-). From the results observed, it is clear that Ti-TiO(2) electrode is a promising candidate for electricity generation in MFC.
Asunto(s)
Fuentes de Energía Bioeléctrica , Electrodos , Secuencia de Bases , Cartilla de ADN , Electroforesis en Gel de Gradiente Desnaturalizante , Enterobacter/metabolismo , Enterococcus/metabolismo , Grafito , Cinética , Reacción en Cadena de la Polimerasa , Shewanella/metabolismoRESUMEN
Batch experiments were conducted to investigate the thermophilic biohydrogen production using an enrichment culture from a Turkish hot spring. Following the enrichment, the culture was heat treated at 100 degrees C for 10 min to select for spore-forming bacteria. H(2) production was accompanied by production of acetate, butyrate, lactate and ethanol. H(2) production was associated by acetate-butyrate type fermentation while accumulation of lactate and ethanol negatively affected the H(2) yield. H(2) production was highest in the temperature range from 49.6 to 54.8 degrees C and optimum values for initial pH and concentrations of iron, yeast extract and glucose were 6.5, 40 mg/l, 4-13.5 g/l, respectively. PCR-DGGE profiling showed that the heat treated culture consisted of species closely affiliated to genus Thermoanaerobacterium.
Asunto(s)
Manantiales de Aguas Termales/microbiología , Hidrógeno/química , Acetatos/química , Anaerobiosis , Butiratos/química , Relación Dosis-Respuesta a Droga , Fermentación , Glucosa/química , Calor , Concentración de Iones de Hidrógeno , Hierro/química , Cinética , Reacción en Cadena de la Polimerasa , Thermoanaerobacterium/metabolismo , Microbiología del AguaRESUMEN
Using magnesit (MgCO(3)) as a low cost source of magnesium ions in the struvite precipitation for the removal of high ammonium content of leachate was evaluated. Optimum molar concentration and pH conditions were analyzed to minimize the struvite solubility. Since solubility of magnesit in water is low, HCl was used to obtain soluble Mg. Maximum soluble Mg was obtained for the addition of 2 M HCl to the 1 M MgCO(3). Struvite precipitation with magnesit was effective for the removal of ammonium, suspended solid, phosphate and turbidity. Economical evaluation was made comparing the costs of two magnesium sources, MgCl(2) and MgCO(3). The economical analysis has shown that operation cost of struvite precipitation can be reduced about 18% by using MgCO(3) instead of MgCl(2). High salt concentration after struvite precipitation has no inhibitory effect on the anaerobic reactor performance.
Asunto(s)
Contaminantes Ambientales/aislamiento & purificación , Magnesio/química , Compuestos de Amonio Cuaternario/aislamiento & purificación , Precipitación Química , SolubilidadRESUMEN
Removal of ammonium ion (NH(4)(+)) from leachate from Odayeri sanitary landfill, located in the European part of Istanbul, was examined using Gördes (Turkish) clinoptilolite. The effects of pH, flow rate, ammonium concentration and competitive cations on the removal efficiency were investigated in both batch and column studies. Thomas model were used to analyze the breakthrough data. Nonlinear least square method was applied for fitting the column data. The competitive effect was observed more effective in lower ammonium concentration and higher cation concentrations. Conditioning and regeneration using NaCl improved removal efficiency of ammonium from leachate.
Asunto(s)
Compuestos de Amonio Cuaternario/química , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Zeolitas/química , Metales/química , Eliminación de ResiduosRESUMEN
Ammonium ion exchange from aqueous solution using clinoptilolite zeolite was investigated at laboratory scale. Batch experimental studies were conducted to evaluate the effect of various parameters such as pH, zeolite dosage, contact time, initial ammonium concentration and temperature. Freundlich and Langmuir isotherm models and pseudo-second-order model were fitted to experimental data. Linear and non-linear regression methods were compared to determine the best fitting of isotherm and kinetic model to experimental data. The rate limiting mechanism of ammonium uptake by zeolite was determined as chemical exchange. Non-linear regression has better performance for analyzing experimental data and Freundlich model was better than Langmuir to represent equilibrium data.
Asunto(s)
Compuestos de Amonio Cuaternario/química , Contaminantes Químicos del Agua/química , Zeolitas/química , Concentración de Iones de Hidrógeno , Intercambio Iónico , Análisis de Regresión , Factores de Tiempo , Eliminación de Residuos Líquidos/métodos , Purificación del Agua/métodosRESUMEN
A study on ion exchange kinetics and equilibrium isotherms of ammonium ion on natural Turkish clinoptilolite (zeolite) was conducted using a batch experiment technique. The effects of relevant parameters, such as temperature, contact time and initial ammonium (NH(4)(+)) concentration were examined, respectively. The pseudo first-order, pseudo second-order kinetic models and intraparticle diffusion model were used to describe the kinetic data. The pseudo second-order kinetic model provided excellent kinetic data fitting (R(2)>0.990) and intraparticle diffusion effects ammonium uptake. The Langmuir and Freundlich models were applied to describe the equilibrium isotherms for ammonium uptake and the Langmuir model agrees very well with experimental data. Thermodynamic parameters such as change in free energy (DeltaG(0)), enthalpy (DeltaH(0)) and entropy (DeltaS(0)) were also determined. An examination of the thermodynamic parameters shows that the exchange of ammonium ion by clinoptilolite is a process occurring spontaneously and physical in nature at ambient conditions (25 degrees C). The process is also found to be exothermic. The results indicate that there is a significant potential for the natural Turkish clinoptilolite as an adsorbent material for ammonium removal from aqueous solutions.