课程文献中心 更多>>

关键词： adsorption   K-d   membrane bioreactor   municipal wastewater   synthetic polycyclic musk  

摘要： The objective of this study was to investigate the removal of 11 synthetic polycyclic musks in a municipal wastewater treatment plant located in Jilin, China, by using a membrane bioreactor combined with anaerobic-anoxic-oxic process. The analysis of synthetic polycyclic musks was conducted with gas chromatography/mass spectrometry after solid-phase extraction. The removal efficiency of 11 synthetic polycyclic musks ranged from 65.9% (3-methylcyclopentadecanone) to 84.6% (Galoxolide) in the influent. Along the treatment process, it was observed that the anaerobic tank could remove the synthetic polycyclic musks effectively whereas the role of the membrane was to the musks, which could be ascribed to the relatively strong hydrophobic property of the musks. The sludge-water distribution coefficients (K-d values) as indicator of adsorption propensity for the sludge from anaerobic, anoxic, oxic and membrane tanks were measured. The high value of K-d, above 5.0 litres per gram of suspended solids, showed most of the musks could be removed by sludge through the adsorption process;thus the removal rate from the water phase caused by adsorption in the wastewater treatment plant can be predicted.

关键词： WWTP   N2O modelling   Nutrient removal   Greenhouse gases  

摘要： This paper compares two mathematical models (Model I and Model II) to predict greenhouse gases emission from a University Cape Town (UCT) - membrane bioreactor (MBR) plant. Model I considers N2O production only during denitrification. Model II takes into account the ammonia-oxidizing bacteria (AOB) formation pathways for N2O. Both models were calibrated adopting real data. Model comparison was performed in terms of (i) sensitivity analysis (ii) best fit and (iii) model prediction uncertainty. On average 6% of factors of Model I and 9% of Model II resulted to be important. In terms of best fit, Model II had a better capability of reproducing the measured data. The average efficiency related to the N2O model outputs was equal to 0.33 and 0.38 for Model I and Model II, respectively. On average, 73% (Model I) and 86% (Model II) of measured data lay inside the uncertainty bands.

关键词： Drag correlation   Liquid-solid fluidization   Computational fluid dynamics   Bioparticles   Tapered bioreactors  

摘要： Fluidized bed bioreactors have been increasingly applied to wastewater treatment, since they offer advantages when compared to other reactors, such as high mass transfer and low excess of sludge per unit of reactor volume. Numerical techniques such as Computational Fluid Dynamics (CFD) can be applied to study these multiphase reactors in detail. However, in most of the available literature it is possible to find only models developed to predict gas-liquid or gas-solid interactions, even though the dynamics in anaerobic bioreactors is dominated by interactions between the liquid and solid phases. The aim of the present study is to evaluate the effect of the drag force together with the influence of the lift force and particles collisions on the prediction of bioparticles fluidization. Moreover, a modification to the drag model will be presented in order to achieve better agreement with experimental data. Simulations were performed with a two-phase, transient and turbulent approach, applied to a symmetrical three-dimensional geometry. Results show a redistribution of the bioparticles along the radial direction due to the lift force. Moreover, the use of different restitution coefficient values did not significantly affect the height of the fluidized bed. It was also observed that the usual drag models are unsuitable for predicting the height of the liquid-solid fluidized bed in the case considered, i.e. with bioparticles. A modification of the drag force with a dimensionless number provided good agreement with the experimental data under different operational conditions. (C) 2018 Elsevier B.V. All rights reserved.

关键词： Flow pattern   Fouling control   Nutrients removal   Optimization technique  

摘要： In Al-Rustamiyah sewage treatment plant in the east of Baghdad city, capital of Iraq, the membrane bioreactor suffering from a severe biofouling problem. The main reason for this problem is inefficient and inadequate aeration process. The objective of this work is to control fouling and to improve the energy efficiency of the submerged membrane bioreactor. Fouling control is achieved by optimizing the two-phase hydrodynamic parameters (air bubble diameter and shear stress), while energy efficiency improved through analysis of flow field. An experimental rig similar to real plant was built, and several operating and design parameters were experimentally tested. The parameters were air flow rate (1-9 L/min), membrane sheets spacing (3, 5, and 7 mm), and air diffuser design (pipe diffuser and disk diffuser). The bubble sizes were measured experimentally using high-speed camera. It was found that larger bubbles were produced at narrow channels between the membrane sheets. Optimization using computational fluid dynamic with ANSYS FLUENT was employed;the results showed that a bubble diameter of 2.5 mm had a slug flow pattern, resulting in better energy saving for a 3 mm space between membrane sheets with a 5 L/min air flow, while maximum shear stress obtained was (4 Pa). Nutrients removal results from synthetic sewage were 97.32, 79.68, and 13% for COD, NH3-N, and PO4-3, respectively, at 6 days retention time. The results obtained are quite significant in practice because it contributes to improve the efficiency of membrane bioreactor in Al-Rustamiyah sewage treatment plant.

关键词： Bacterial peroxidase   Fixed-bed reactor   Biofilm   Biodegradation   Acetaminophen  

摘要： The biodegradation and mineralization of acetaminophen (ACT) was evaluated in the upflow fixed-bed bioreactor (UFBR) inoculated with a biomass containing mixture of Pseudomonas spp. and Bacillus spp. as the dominant bacteria under H2O2 stimulation. The effect of various main operational variables was evaluated on the performance of the UFBR for ACT removal. The maximum ACT removal was obtained at the H2O2:ACT molar ratio of 14. H2O2 induced the bacteria in biofilm for the in-situ generation of peroxidase resulted in the acceleration of ACT decomposition into more biodegradable intermediates. Over 99% of ACT and 72% of its TOC at initial ACT concentrations up to 300 mg/L could be eliminated under optimum H2O2:ACT molar ratio in the batch UFBR within 12 h recirculation time. The specific biodegradation rate of ACT increased from 1.0 to 4.1 mg ACT/g(biomass).h when the inlet loading rate was increased from 8.3 to 41.7 g ACT/m(3).h. In addition, the complete biodegradation and TOC removal of ACT was observed in the continuous UFBR at the hydraulic retention time of 6 h and the presence of 1-20 g/L. salinity without inhibition. The presence of H2O2 could efficiently stimulate the production of bacterial peroxidase, which in turn resulted in the acceleration of ACT biodegradation and mineralization. Therefore, the H2O2-stimulated UFBR is an efficient and viable technique for in-situ production of peroxidase used for acceleration of ACT biodegradation. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： bioreactor   continuous fermentation   fed-batch fermentation   PHAs   polyhydroxyalkanoates   productivity   scale-up  

摘要： Microbial polyhydroxyalkanoates (PHAs) are promising biodegradable polymers that may alleviate some of the environmental burden of petroleum-derived polymers. The requirements for carbon substrates and energy for bioreactor operations are major factors contributing to the high production costs and environmental impact of PHAs. Improving the process productivity is an important aspect of cost reduction, which has been attempted using a variety of fed-batch, continuous, and semi-continuous bioreactor systems, with variable results. The purpose of this review is to summarize the bioreactor operations targeting high PHA productivity using pure cultures. The highest volumetric PHA productivity was reported more than 20 years ago for poly(3-hydroxybutryate) (PHB) production from sucrose (5.1 g L-1 h(-1)). In the time since, similar results have not been achieved on a scale of more than 100 L. More recently, a number fed-batch and semi-continuous (cyclic) bioreactor operation strategies have reported reasonably high productivities (1 g L-1 h(-1) to 2 g L-1 h(-1)) under more realistic conditions for pilot or industrial-scale production, including the utilization of lower-cost waste carbon substrates and atmospheric air as the aeration medium, as well as cultivation under non-sterile conditions. Little development has occurred in the area of fully continuously fed bioreactor systems over the last eight years.

关键词： bioreactors   post-treatment   sulfide oxidation   sulfur bacteria   UASB reactor  

摘要： Two bioreactors were investigated as an alternative to post-treatment of effluent from an upflow anaerobic sludge blanket (UASB) reactor treating domestic sewage, with an aim of oxidizing sulfide into elemental sulfur, and removal of solid and organic material. The bioreactors were operated at different hydraulic retention times (HRTs) (6, 4, and 2 h) and in the presence or absence (control) of packing material (polypropylene rings). Greater sulfide removal efficiencies - 75% (control reactor) and 92% (packed reactor) - were achieved in both reactors for an HRT of 6 h. Higher organic matter (COD) and solid (TSS) removal levels were observed in the packed reactor, which produced effluent with low COD (100 mg CODL-1) and TSS concentrations (30 mg TSSL-1). Denaturing gradient gel electrophoresis results revealed that a metabolically diverse bacterial community was present in both bioreactors, with sequences related to heterotrophic bacteria, sulfur bacteria (Thiocapsa, Sulfurimonas sp., Chlorobaculum sp., Chromatiales and Sulfuricellales), phototrophic purple nonsulfur bacteria (Rhodopseudomonas, Rhodocyclus sp.) and cyanobacteria. The packed reactor presented higher extracellular sulfur formation and potential for elemental sulfur recovery was seen. Higher efficiencies related to the packed reactor were attributed to the presence of packing material and higher cell retention time. The studied bioreactors seemed to be a simple and low-cost alternative for the post-treatment of anaerobic effluent.

关键词： Anaerobic digestion   Forward osmosis   Membrane bioreactor   Microbial community   Magnesium chloride  

摘要： This work elucidates the effects of model reversed salt MgCl2 on methane production in an anaerobic digestion bioreactor treating waste sludge. Along with MgCl2 concentration being raised stepwise, the methane production was only slightly less than in the control when MgCl2 was 20 g/L and under, and then suddenly reduced to only about 10 mL/(L.d) at a MgCl2 concentration of 30 g/L, and finally stopped when the MgCl2 concentration reached 50 g/L. However, the total relative abundance of methanogens Methanomicrobia and Methanobacteria still accounted for 84.97% of the archaeal community when MgCl2 was 50 g/L. The high correlation between live/dead cell ratio and methane production suggests that the live/dead cell ratio instead of the inhibition of methanogen might be the major cause for the halt of methane production at a magnesium chloride concentration of 50 g/L.

关键词： cost performance evaluation   kinetic models   removal efficiency   substrate utilization rate  

摘要： The simultaneous biological removal of COD, TN and phosphorus from meat industrial wastewater (MIW) using a lab-scale high rate up-flow anaerobic-anoxic-oxic bioreactor (A(2)O bioreactor) was investigated. The bioreactor was operated at different HRT, COD/TN ratio and aerated volume fractions to monitor the COD and nutrient removal efficiency. The maximum COD removal rate was detected at HRT of 5 h and COD/TN ratio of 100 : 12. The total nitrogen removal efficiency was changed between 65.8 and 94.4% and the lowest effluent nitrate concentration was measured as 1.6 mg/l. Seven kinetic models were applied to experimental data to determine the substrate utilization rate. The Monod and Haldane models were ideal to estimate the reactor performance. Moreover, the cost performance evaluation indicated the A(2)O bioreactor capability in low energy consumption for MIW treatment. According to the modeling results, integrating anaerobic and aerobic zones within a single bioreactor could be beneficial and cost-effective due to the high effluent quality and low operational costs.

关键词： Sulfonamide antibiotics   Sponge-plastic biocarriers   Extracellular polymeric substances   Intermediates   Integrated aerobic membrane bioreactor  

摘要： A novel laboratory-scale aerobic submerged membrane bioreactor integrating sponge-plastic biocarriers (SPSMBR) was conducted to study the removal and degradation mechanisms of sulfonamide antibiotics (SAs). Experimental results indicated that SPSMBR had a better removal of sulfadiazine (91% SDZ) and sulfamethoxazole (88% SMZ) than that of a conventional aerobic submerged membrane bioreactor (CSMBR) (76% SDZ and 71% SMZ, respectively). Material balance calculations suggested that biodegradation is the primary removal mechanism of SDZ and SMZ. Protein (tyrosine-like materials) significantly affected the removal of SAs. Moreover, the SPSMBR exhibited its better performance in removing SAs due to more abundance of tyrosine-like materials. The 16S rRNA sequencing showed that biocarriers could promote the enrichment of slow growing bacteria, especially Thermomonas, associated with the removal of SAs. Valuable insights into the removal and degradation mechanisms of SAs in the SPSMBR systems are documented here.