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Removal Performance (removal + performance)
Selected AbstractsExperimental and neural model analysis of styrene removal from polluted air in a biofilterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2009Eldon R. Rene Abstract BACKGROUND: Biofilters are efficient systems for treating malodorous emissions. The mechanism involved during pollutant transfer and subsequent biotransformation within a biofilm is a complex process. The use of artificial neural networks to model the performance of biofilters using easily measurable state variables appears to be an effective alternative to conventional phenomenological modelling. RESULTS: An artificial neural network model was used to predict the extent of styrene removal in a perlite-biofilter inoculated with a mixed microbial culture. After a 43 day biofilter acclimation period, styrene removal experiments were carried out by subjecting the bioreactor to different flow rates (0.15,0.9 m3 h,1) and concentrations (0.5,17.2 g m,3), that correspond to inlet loading rates up to 1390 g m,3 h,1. During the different phases of continuous biofilter operation, greater than 92% styrene removal was achievable for loading rates up to 250 g m,3 h,1. A back propagation neural network algorithm was applied to model and predict the removal efficiency (%) of this process using inlet concentration (g m,3) and unit flow (h,1) as input variables. The data points were divided into training (115 × 3) and testing set (42 × 3). The most reliable condition for the network was selected by a trial and error approach and by estimating the determination coefficient (R2) value (0.98) achieved during prediction of the testing set. CONCLUSION: The results showed that a simple neural network based model with a topology of 2,4,1 was able to efficiently predict the styrene removal performance in the biofilter. Through sensitivity analysis, the most influential input parameter affecting styrene removal was ascertained to be the flow rate. Copyright © 2009 Society of Chemical Industry [source] Effects of influent C/N ratio, C/P ratio and volumetric exchange ratio on biological phosphorus removal in UniFed SBR processJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2008Chen-hong Zhao Abstract BACKGROUND: UniFed SBR is a novel process that can achieve high levels of nitrogen and phosphorus removal simultaneously in a simple single SBR tank. In this study, effects of influent C/N ratio, influent C/P ratio and volumetric exchange ratio on biological phosphorus removal in UniFed SBR process were investigated in a lab-scale UniFed apparatus treating real domestic wastewater. RESULTS: The results showed that phosphorus removal efficiency increased as C/N ratio increased from 27% at 2.8 to 88% at 5.7. For C/N ratios 6.5 and above, complete phosphorus removal could be achieved. When C/N ratios and volumetric exchange ratio were fixed at 6 and 33%, respectively, phosphorus removal efficiency remained at 100% for C/P ratios higher than 33; effluent phosphate concentration was below the detection limit. For C/P ratios lower than 33, phosphorus removal efficiency decreased linearly with C/P ratio. Under the same influent C/N ratio and C/P ratio, the following factors all contributed to better phosphorus removal performance: greater volumetric exchange ratio; more organic substrate for PAOs to utilize, less inhibition by NOx, of phosphorus release during the feed/decant period; more PHB synthesized; and more aerobic phosphate uptake. CONCLUSION: High influent C/N ratio, high C/P ratio and high volumetric exchange ratio were beneficial to phosphorus removal in this process. Copyright © 2008 Society of Chemical Industry [source] Long-term performance of co-metabolic degradation of trichloroethylene in a fluidized bed reactor fed with benzene, toluene and xyleneJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2008Wei-Min Wu Abstract BACKGROUND: Trichloroethylene (TCE) can be degraded under aerobic condition with toluene and other aromatic compounds. Inhibition by primary substrates and toxicity of TCE oxidation influence TCE degradation. RESULTS: Long-term co-metabolic degradation of TCE was evaluated using a laboratory-scale fluidized bed reactor (12 L) with granular activated carbon (1.57 kg) as media and activated sludge as inoculum. The reactor was fed with TCE and a mixture of benzene, toluene and xylene (BTX) and operated with one-pass (hydraulic retention time (HRT) of 5,6 min) for 6 months and then with recirculation (HRT of 20,30 min) for 18 months. BTX/TCE-degrading biofilm was developed within 1 month. TCE was effectively degraded with influent TCE concentrations from 48 to 280 µg L,1. BTX inhibited TCE degradation. Recirculation (or long HRT) increased TCE removal efficiency from 30% with one-pass to 90%. BTX/TCE load ratio influenced TCE removal efficiency and TCE/BTX removal ratio. TCE degradation fitted first-order kinetics. The biomass grown in the reactor also degraded cis -1,2-dichloroethylene (DCE), trans -1,2-DCE and vinyl chloride efficiently except for 1,1-DCE. CONCLUSION: Co-metabolic degradation of TCE by BTX-degrading biomass from activated sludge is sustainable in the long term. BTX/TCE load ratio is a key parameter for TCE removal performance. Copyright © 2008 Society of Chemical Industry [source] Equilibrium and heat of adsorption of phosphine on CaCl2 -modified molecular sieveASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Qiongfen Yu Abstract Adsorption characteristics of the virgin and CaCl2 -immersed molecular sieves at 298 K were investigated to select the adsorbent with high adsorption capacity to phosphine. Adsorption isobars and adsorption isotherms over the phosphine partial pressure and temperature ranged 0 , 1000 Pa and 298 , 343 K were measured. The adsorption equilibrium data for phosphine at various temperatures were fitted to Langmuir and Freundlich isotherm models and their isosteric heats of adsorption were determined by the Clausius-Clapeyron equation. It was found the Freundlich was more suitable for description of phosphine adsorption process through calculating average absolute relative error, and the fitted result about Langmuir model showed the heterogeneous characteristics of modified adsorbent. The isosteric heat of adsorption was about 15 kJ/mol, which indicated adsorptive phosphine removal performance may be a dominant of physical adsorption being easy for desorption. The isosteric heat of adsorption decreased with an increase of the surface loading on CaCl2/5A, which means that CaCl2/5A molecular sieve had an energetically heterogeneous surface. The present study confirmed that the CaCl2/5A molecular sieves would be one of the candidates for separation and recycle of phosphine. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Effect of packing density of hollow fibers on solute removal performances of dialyzersHEMODIALYSIS INTERNATIONAL, Issue 2009Akihiro C. YAMASHITA Abstract Solute removal performances of dialyzers are dependent not only on the solute permeabilities of the membrane but also on the module design. We have investigated how the packing density of hollow fiber (PDF) affects the solute removal performances. A series of 4 polyester polymer alloy membrane test dialyzers were assembled with varying PDFs of 29.6%, 35.3%, 44.1%, and 53.1%. Clearances (CL) were measured in vitro for creatinine (MW113), vitamin B12 (MW1355), and chymotrypsin (MW25300) with various QB=100 to 400 and QD=350 to 650 mL/min in the absence of net ultrafiltration. When QB was ,300 mL/min, no significant changes were found in creatinine CL with the increase of PDF up to 35.3%. A slightly greater increase was found in CL when QB=400 mL/min. Clearances for vitamin B12, however, increased with the increase of PDF in the range of 29.6% to 35.3%. The effects of PDF on CL were greater with larger QB. More importantly, an abrupt increase of CL was found when PDF was increased from 44.1% to 53.1%. According to a rigorous mathematical model, this may be caused by the internal filtration, which is reverse ultrafiltration occurring in a dialyzer at any given time. No significant increase was found in chymotrypsin CL when the PDF was ,35.3%, which suggested that CL for large molecules was strongly dependent on the solute permeability rather than the conditions of flow patterns. A very steep increase was also found in CL for chymotrypsin when the PDF was >44.1%, which was also considered to be due to the internal filtration. Packing density of hollow fiber can be optimized in terms of solute removal performances when the target solute and therapeutic conditions are specified. [source] | ||||||||||