RESUMEN
In this study, hydrodynamic cavitation (HC) was employed as a physical means to improve alkaline pretreatment of reed. The HC-assisted alkaline pretreatment was undertaken to evaluate the influence of NaOH concentration (1-5%), solid-to-liquid ratio (5-15%), and reaction time (20-60 min) on glucose yield. The optimal condition was found to be 3.0% NaOH at solid-to-liquid (S/L) ratio of 11.8% for 41.1 min, which resulted in the maximum glucose yield of 326.5 g/kg biomass. Furthermore, simultaneous saccharification and fermentation (SSF) was conducted to assess the ethanol production. An ethanol concentration of 25.9 g/L and ethanol yield of 90% were achieved using batch SSF. These results clearly demonstrated HC system can be indeed a promising pretreatment tool for lignocellulosic bioethanol production.
Asunto(s)
Biocombustibles , Biotecnología/métodos , Etanol/metabolismo , Lignina/química , Biomasa , Fermentación , Glucosa/metabolismo , Hidrólisis , Poaceae , Saccharomyces cerevisiae/metabolismo , Ultrasonido/métodosRESUMEN
To overcome fouling issue in membrane-based algae harvesting and thus make an otherwise promising harvesting option more competitive, a bubble-generator plate was developed. According to computational fluid dynamics analysis, the plate generated substantial hydrodynamic power in terms of high pressure, velocity, and shear stress. When installed in a membrane filtration system with membranes of different surface and structural characteristics (one prepared by the phase inversion method, and a commercial one) the bubble-generator was indeed effective in reducing fouling. Without the plate, the much cheaper homemade membrane had the similar performance as the commercial one. Use of the bubble-generator considerably improved the performance of both membranes, and revealed a valuable synergy with the asymmetrical structure of the homemade membrane. This result clearly showed that the ever-problematic fouling could be mitigated in a rather easy manner, and in so doing, that membrane technology could indeed become a practical option for algae harvesting.
Asunto(s)
Incrustaciones Biológicas/prevención & control , Filtración/instrumentación , Hidrodinámica , Membranas Artificiales , Microalgas/aislamiento & purificación , Microalgas/crecimiento & desarrollo , PermeabilidadRESUMEN
In this article, we report the preparation, characterization and microalgae recovery potential of a new family of fouling-resistant polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes embedded with hydrophilic and PEGylated polymeric particles. To optimize membrane performance for microalgae harvesting, we investigate the effects of three hydrophilic additives (Pluronic F-127, polyvinylpyrrolidone and polyethylene glycol) on the morphology, pore size, bulk composition, surface composition, wettability and surface charge, flux and fouling resistance of the mixed matrix PVDF membranes with in situ PEGylated polyethyleneimine (PEI) particles. Our filtration experiments show that a mixed matrix PVDF membrane with PEGylated PEI particles and Pluronic F-127 additive (PNSM-1) has an algae retention of 100% with a permeate flux of 96 L/m(2)/hr that is larger (by â¼50%) than that of a commercial and hydrophilic PVDF UF membrane with a molecular weight cut-off of 30 kDa using a suspension of Chlorella sp. KR-1 microalgae with 1.2-1.4 g/L of dry biomass. The algae and water flux recovery rates of our new PNSM-1 are equal toâ¼ 94% and 100%, respectively, following a simulated membrane wash with deionized water and two subsequent water and microalgae filtration cycles.
Asunto(s)
Microalgas , Polietileneimina/química , Polivinilos/química , Ultrafiltración , Purificación del Agua/métodos , Interacciones Hidrofóbicas e HidrofílicasRESUMEN
The purpose of the present study is to reduce fouling formation, a fatal problem of membrane technology by means of surface-coating with a functional coating material, i.e., hydrophilic polyvinyl alcohol (PVA) polymer. The PVA coating caused the membrane surface to become more hydrophilic and it was confirmed by decreased contact angles up to 64% compared to the un-modified membranes. The surface-coated membrane found to exhibit substantially enhanced performance: a maximum flux increase of 36% and almost 100% recovery rate. Maximum concentration factor of 77 also was modeled in the present study. These results show that the membrane performance can be improved simply by applying a surface-active coating, even to the level of economic feasibility.
Asunto(s)
Incrustaciones Biológicas/prevención & control , Chlorella/crecimiento & desarrollo , Filtración/instrumentación , Membranas Artificiales , Reología , Purificación del Agua/instrumentación , Purificación del Agua/métodos , Tereftalatos Polietilenos/química , Alcohol Polivinílico/química , Polivinilos/químicaRESUMEN
Tailings are mine wastes in the form of slurries stacked in mine sites abandoned after the exhaustion of ores. There are approximately 5000 abandoned mine sites in Korea, and tailings have become a serious environmental problem. Long-term environmental exposure of tailings can cause release of acidic and high concentrations of sulfate- and metal-contaminated water (acid mine drainage, AMD). Organic and/or inorganic amendments have been studied for AMD prevention and passive in situ treatment of pore water. This study tests locally available food waste-based compost as a viable amendment, in addition to the need for sustainable ways to dispose of compost, in response to a new environmental law. To examine the feasibility, three bioreactors were constructed, filled with mixtures of tailings, food waste-based compost, and zeolite. During the 4-wk experimental period, feeding water ormedium were poured in one reactor. The leachates were investigated in terms of chemistry and microbiology. Compared with the unamended reactor, the leachate from two mixture-filled reactors showed increased pH, formation of sulfate reduction conditions, and highly efficient metal removal. Black-colored precipitates observed at the end of the experiment suggested the formation of metal biosulfides, following the activity of sulfate reduction mediated by sulfate-reducing bacteria (SRB). Mineralogical analysis of these precipitates confirmed the presence of biosulfides, mainly of Fe and Pb. Moreover, microbial and molecular biological analyses revealed that several species of heterotrophic bacteria (SRB and iron-reducing bacteria) were present in the solids recovered from the bioreactors. Microbial consortium, such as SRB species (), and cellulosic-degrader ( sp.) were identified. This study provides promising results on the application potential of food waste-based compost for prevention of AMD generation and passive in situ treatment of pore water in weathered tailings in Korea and elsewhere.
Asunto(s)
Alimentos , Residuos Industriales/análisis , Eliminación de Residuos/métodos , Suelo , Sulfuros/química , Zeolitas/química , Precipitación Química , Electroforesis en Gel de Gradiente Desnaturalizante , Monitoreo del Ambiente , Microscopía Electrónica de Rastreo , Minería , Lluvia , Microbiología del Suelo , Factores de Tiempo , Contaminantes Químicos del Agua/químicaRESUMEN
Pilot-scale field-testing of passive bioreactors was performed to evaluate the efficiency of a mixture of four substrates (cow manure compost, mushroom compost, sawdust, and rice straw) relative to mushroom compost alone, and of the effect of the Fe/Mn ratio, during the treatment of acid mine drainage (AMD) over a 174-day period. Three 141 L columns, filled with either mushroom compost or the four substrate mixture (in duplicate), were set-up and fed with AMD from a closed mine site, in South Korea, using a 4-day hydraulic retention time. In the former bioreactor, effluent deterioration was observed over 1-2 months, despite the good efficiency predicted by the physicochemical characterization of mushroom compost. Steady state effluent quality was then noted for around 100 days before worsening in AMD source water occurred in response to seasonal variations in precipitation. Such changes in AMD quality resulted in performance deterioration in all reactors followed by a slow recovery toward the end of testing. Both substrates (mushroom compost and mixtures) gave satisfactory performance in neutralizing pH (6.1-7.8). Moreover, the system was able to consistently reduce sulfate from day 49, after the initial leaching out from organic substrates. Metal removal efficiencies were on the order of Al (â¼100%) > Fe (68-92%) > Mn (49-61%). Overall, the mixed substrates showed comparable performance to mushroom compost, while yielding better effluent quality upon start-up. The results also indicated mushroom compost could release significant amounts of Mn and sulfate during bioreactor operation.