RESUMEN
To improve the hydrogen yield from biological fermentation of organic wastewater, a co-culture system of dark- and photo-fermentation bacteria was investigated. In a pureculture system of the dark-fermentation bacterium Clostridium butyricum, a pH of 6.25 was found to be optimal, resulting in a hydrogen production rate of 18.7 ml-H2/l/h. On the other hand, the photosynthetic bacterium Rhodobacter sphaeroides could produce the most hydrogen at 1.81 mol-H2/mol-glucose at pH 7.0. The maximum specific growth rate of R. sphaeroides was determined to be 2.93 h⻹ when acetic acid was used as the carbon source, a result that was significantly higher than that obtained using either glucose or a mixture of volatile fatty acids (VFAs). Acetic acid best supported R. sphaeroides cell growth but not hydrogen production. In the co-culture system with glucose, hydrogen could be steadily produced without any lag phase. There were distinguishable inflection points in a plot of accumulated hydrogen over time, resulting from the dynamic production or consumption of VFAs by the interaction between the dark- and photofermentation bacteria. Lastly, the hydrogen production rate of a repeated fed-batch run was 15.9 ml-H2/l/h, which was achievable in a sustainable manner.
Asunto(s)
Carbono/metabolismo , Clostridium butyricum/metabolismo , Técnicas de Cocultivo/métodos , Hidrógeno/metabolismo , Rhodobacter sphaeroides/metabolismo , Ácidos Grasos Volátiles/metabolismo , Fermentación , Glucosa/metabolismo , Concentración de Iones de HidrógenoRESUMEN
Wastewater treatment performance of the combined process of sequencing batch reactor (SBR) and mesh filtration bio-reactor was investigated with a synthetic wastewater. In this system, the filtration was performed only by the water level difference between the reactor and the effluent port, with the help of a sludge layer which accumulated on the mesh filter. A half volume of the mixed liquor was filtrated for ca. 1 h, and the filtration time was not affected by the initial pressure within the range of 0.5-2.0 m-H2O. Since the mesh filter could effectively reject the biomasses in the reactor, the effluents contained SS of less than 1 mg/L and BOD of less than 10 mg/L under continuous or intermittent aeration conditions. Nitrogen was also removed effectively with the adjustment of aeration time under the intermittent aeration conditions. The results obtained in this work indicate that mesh filtration could be effectively combined with SBR and improve the performance of SBR. In addition, it was shown that the performance of the mesh filtration such as filtration time and solids separation was influenced significantly by the saccharide content in the exocellular polymer of the activated sludge.
Asunto(s)
Reactores Biológicos , Eliminación de Residuos Líquidos/métodos , Biopolímeros , Filtración , Concentración de Iones de Hidrógeno , Aguas del Alcantarillado , Eliminación de Residuos Líquidos/instrumentaciónRESUMEN
The removal of ammonium from coagulated tannery wastewaters was investigated by an electrochemical method using Ti/IrO2 as an anode. Operating variables including the current density, pH and chloride concentration were considered in order to determine their effect on the ammonium removal efficiency. A maximum ammonium removal rate of 78.9% was achieved after 30 min of electrochemical treatment with 4 A dm(-2) of current density. During the electrolysis, it had been observed that the ammonium removal was accompanied with an elimination of the organics. Generation of hydroxyl radical was identified during the experiment with hydroxyl radical probe compound of pCBA. Chloride ion worked as the scavenger of hydroxyl radical. Role of free chlorine was the main oxidant for the elimination of ammonium and organic substances. As a result, the biodegradability of tannery wastewater increased after electrochemical treatment. The energy consumed per 1 kg of ammonium removal was 26.6 kWh for initial NH4-N concentration of 870 mg L(-1).
Asunto(s)
Compuestos de Amonio Cuaternario/aislamiento & purificación , Eliminación de Residuos Líquidos/métodos , Purificación del Agua/métodos , Biodegradación Ambiental , Electroquímica , Radical Hidroxilo/análisis , Radical Hidroxilo/química , Iridio/química , Oxidantes/análisis , Oxidantes/química , Titanio/químicaRESUMEN
Phosphate is generally analyzed by color intensity of phosphoantimonylmolybdenum blue (PAMB): especially by a spot test based on spectrophotometric or visual determination. Visual determination is one of the simplest and most inexpensive methods; however, it is believed to be of low precision. In this work, we have developed an alternative phosphate spot test, where phosphate concentration is measured by the color band length of PAMB formed in a detection tube similar to a gas detection tube. The color band is formed by the entrapment of the hydrophobic ion pair of PAMB and quaternary ammonium ions in the column; we demonstrated that this color band length correlates quantitatively with the phosphate concentration. In order to optimize the measurement performance, systematic investigations have been carried out for various experimental parameters such as phosphate concentration, preparation conditions of the column packing material, the type of support material (either silica-gel or PVC), the solution feeding conditions (filtration or penetration), and volume of the sample solution. The effects from some co-existing components were also studied for the measurement of real samples. Determination of phosphate concentrations in actual wastewaters was successfully carried out by this method, indicating that the quantification range achievable was of 3-18 mg PO(4) L(-1) without dilution prior to the analysis. No interference was observed from suspended solid (SS) and organic pollutants (COD, TOC) during the wastewater analysis. Because of the simplicity and rapid processing of the samples (not requiring any special instruments) this newly developed method can be applied to the on-site analysis of wastewater.