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关键词： anaerobic membrane bioreactor   palm oil mill effluent   fouling   organic loading rate   microfiltration   thermophilic  

摘要： Anaerobic treatment processes have achieved popularity in treating palm oil mill effluent due to its high treatability and biogas generation. The use of externally submerged membranes with anaerobic reactors promotes the retention of the biomass in the reactor. This study was conducted in thermophilic conditions with the Polytetrafluoroethylene hollow fiber (PTFE-HF) membrane which was operated at 55 degrees C. The reactor was operated at Organic Loading Rates (OLR) of 2, 3, 4, 6, 8, and 10 kg Chemical Oxygen Demand (COD)/m(3)d to investigate the treatment performance and the membrane operation. The efficiency of the COD removal achieved by the system was between 93-98%. The highest methane yield achieved was 0.56 m(3) CH4/kg CODr. The reactor mixed liquor volatile suspended solids (MLVSS) was maintained between 11.1 g/L to 20.9 g/L. A dead-end mode PTFE hollow fiber microfiltration was operated with the constant flux of 3 LMH (L/m(2)h) in permeate recirculation mode to separate the clear final effluent and retain the biomass in the reactor. Membrane fouling was one of the limiting factors in the membrane bioreactor application. In this study, organic fouling was observed to be 93% of the total membrane fouling.

关键词： Microbial community   Denitrification   Illumina MiSeq sequencing   Nitrification   Recirculating aquaculture system  

摘要： An experimental recirculating aquaculture system was constructed under ambient seawater conditions to compare microbial community diversity of nitrifying and denitrifying biofilters that were derived from a commercial inoculum used for aquarium applications. Next generation sequencing revealed distinct and diverse microbial communities in samples analyzed from the commercial inoculant and the denitrification and nitrification biofilters. In all samples, communities were represented by a few dominant operational taxonomic units (OTUs). Bacteria having the capacity to carry out ammonia and nitrite oxidation were more abundant in the nitrification biofilter. Similarly, the proportion of the bacterial taxa known to carry out heterotrophic and autotrophic denitrification and participate in sulfur cycling were found in the denitrification bioreactor, and likely originated from the ambient environmental water source. Our results indicated that environmental seawater can be a favorable enhancement to the bacterial consortium of recirculating aquaculture systems biofilters.

关键词： hydrogel   RADA 16-I   dexamethasone   perfusion bioreactor   osteodifferentiation   human mesenchymal stem cells  

摘要： The main goal of this study was the formation of bone tissue using dexamethasone (DEX)-loaded [COCH3]-RADARADARADARADA-[CONH2] (RADA 16-I) scaffold that has the ability to release optimal DEX concentration under perfusion force. Bone-marrow samples were collected from three patients during a hip arthroplasty. Human mesenchymal stem cells (hMSCs) were isolated and propagated in vitro in order to be seeded on scaffolds made of DEX-loaded RADA 16-I hydrogel in a perfusion bioreactor. DEX concentrations were as follows: 4 x 10(-3), 4 x 10(-4) and 4 x 10(-5) M. After 21 days in a perfusion bioreactor, tissue was analyzed by scanning electron microscopy (SEM) and histology. Markers of osteogenic differentiation were quantified by real-time polymerase chain reaction (RT-PCR) and immunocytochemistry. Minerals were quantified and detected by the von Kossa method. In addition, DEX release from the scaffold in a perfusion bioreactor was assessed. The osteoblast differentiation was confirmed by the expression analysis of osteoblast-related genes (alkaline phosphatase (ALP), collagen I (COL1A1) and osteocalcin (OC). The hematoxylin/eosin staining confirmed the presence of cells and connective tissue, while SEM revealed morphological characteristics of cells, extracellular matrix and minerals-three main components of mature bone tissue. Immunocytochemical detection of collagen I is in concordance with given results, supporting the conclusion that scaffold with DEX concentration of 4 x 10(-4) M has the optimal engineered tissue morphology. The best-engineered bone tissue is produced on scaffold loaded with 4 x 10(-4) M DEX with a perfusion rate of 0.1 mL/min for 21 days. Differentiation of hMSCs on DEX-loaded RADA 16-I scaffold under perfusion force has a high potential for application in regenerative orthopedics.

关键词： anaerobic digestion   fine sieve fraction   financial modeling   biogas plant  

摘要： Anaerobic technology is a well-established technique to wean the fossil fuel-based energy off with various positive environmental inferences. Biowaste treatment is favorable due to its low emissions. Biogas is merely regarded as the main product of anaerobic digestion with high energy value. One of the key concerns of the waste water treatment plants is the vast amount of cellulosic residuals produced after the treatment of waste waters. The fine sieve fraction, collected after the primary sludge removal, has great energy value. In this study, the economic performance of a biogas plant has been analyzed based on net present value and pay-back period concepts. The plant in the base scenario produced 309,571 m(3) biogas per year. The annual electricity production has been 390,059 kWh. The producible heat energy has been 487,574 kWh or 1755 GJ per year. The plant depicts a positive economic situation with 11 years pay-back time, earning low profits and showing a positive net present value of 11,240 euro.

关键词： floating MBR   syngas-to-biomethane conversion   high gas hold-up   inoculum-to-syngas ratio  

摘要： The low gas-to-liquid mass transfer rate is one of the main challenges in syngas biomethanation. In this work, a new concept of the floating membrane system with high gas hold-up was introduced in order to enhance the mass transfer rate of the process. In addition, the effect of the inoculum-to-syngas ratio was investigated. The experiments were conducted at 55 degrees C with an anaerobic mixed culture in both batch and continuous modes. According to the results from the continuous experiments, the H-2 and CO conversion rates in the floating membrane bioreactor were approximately 38% and 28% higher in comparison to the free (suspended) cell bioreactors. The doubling of the thickness of the membrane bed resulted in an increase of the conversion rates of H-2 and CO by approximately 6% and 12%, respectively. The highest H-2 and CO consumption rates and CH4 production rate recorded were approximately 22 mmol/(L center dot d), 50 mmol/(L center dot d), and 34.41 mmol/(L center dot d), respectively, obtained at the highest inoculum-to-syngas ratio of 0.2 g/mL. To conclude, the use of the floating membrane system enhanced the syngas biomethanation rates, while a thicker membrane bed resulted in even higher syngas conversion rates. Moreover, the increase of the inoculum-to-syngas ratio of up to 0.2 g/mL favored the syngas conversion.

关键词： Membrane bioreactor (MBR)   Nanocomposite   Polycitrate-Alumoxane (PC-A)   Hydrophilicity   Antifouling  

摘要： Novel nanocomposite ultrafiltration (UF) membranes were designed and fabricated using hydrophilic polycitrate-Alumoxane (PC-A) nanoparticles and polyethersulfone (PES) to achieve desirable performance for membrane bioreactor (MBR) system. Pure water flux (PWF) and fouling tests were employed to examine the effects of PC-A nanoparticles on the UF performance. FTIR spectra of the PC-A nanoparticles revealed that carboxylic acid and hydroxyl groups are created on the surface of the PC-A. The presence of these hydrophilic groups in PC-A resulted in greater hydrophilicity for the PC-A-modified UF membranes. Therefore, the PC-A-modified UF membranes exhibited higher PWFs compared to the unfilled PES membrane. Fouling resistance of the membranes was evaluated by activated sludge suspension filtration disclosed that the membrane modified with only 0.5 wt% of PC-A had the best antifouling characteristic as well as the greatest PWF. Hence, this optimal nanocomposite membrane was used in the MBR and variations of fluxes exanimated at different mixed liquor suspended solids (MLSS) concentrations of 6000, 10,000 and 14,000 mg/L. During filtration of the activated sludge, the fluxes increased with an increase in MLSS. A decrease in soluble microbial products, extracellular polymeric substance (EPS) from the bacterial cells, and cake formation fouling may result in gentler permeation flux decline over time.

关键词： Agar sphere   heat and mass transfer model   packed-bed bioreactor   solid-state fermentation   void fraction  

摘要： This research develops on our previous semi-mechanistic model that describes the dynamic physical and biochemical processes taking place in a packed-bed bioreactor to analyze the relationship of nutrient limitation, biomass accumulation, metabolic heat generation, and mathematical description of packed-bed porous media. The experimental and simulation data proved that glucose concentration gradients in the biofilm could be neglected due to small biofilm thickness and high diffusivity of glucose in the biofilm. The prediction results also showed that an increase in the initial substrate concentration leads to a rise in the temperature gradient in the bed. The model proposes that if the diameter of substrate particle is too large (r > 0.1 cm), the growth rate will decrease significantly due to the high biomass accumulation in the biofilm, and temperature gradients decrease in the column. This can be used as a strategy to control the overheating problem in the bed.

关键词： Mass transfer   Electrolytes   Glucose and sucrose   Antifoam   Bubble coalescence inhibition   Bubble column  

摘要： The effects of the concentration of three kinds of constituents of aqueous culture media (mixed electrolytes, glucose, sucrose, and commercial antifoam) on oxygen transfer were studied in a bubble column bioreactor. The volumetric mass transfer coefficient (k(L)a) and the specific interfacial area (a) were measured at five superficial gas velocities under the homogeneous bubbling regime. The mixed electrolytic salts (0 <= ionic strength <= 0.4126 M) and, to a lesser extent, the glucose (0 <= c <= 0.222 M) caused the increase of k(L)a up to a maximum value, followed by a either a slight decrease, or no significant change. The higher values of k(L)a corresponded to critical concentrations, indicating a maximum inhibition of bubble coalescence. The k(L)a was governed by changes in interfacial area up to the critical concentrations, where the dominant contribution shifted to k(L);at the studied concentrations, the sucrose had no significant effect on k(L)a. Finally, low concentrations of commercial antifoam caused an overall decrement in k(L)a due entirely to the hindering effects of antifoams on k(L).