bluuebunny/crossref_metadata_2025_split huggingface dataset:
A computational model for heterogeneous flow through low headloss biofilter media
Authors: Chitwood Derek E. , Devinny Joseph S. , Meiburg Eckart 
Published: April 2004

AbstractIn an ideal biofilter, air flows parallel to the biofilter axis and at the same velocity through all parts of the bed. In contrast, non‐uniform flow causes different parcels of air to experience detention times above or below the average, reducing treatment efficiency. Designers and operators have long been aware that medium nonuniformity, bed compaction, fissuring, and separation from the vessel walls can cause flow channeling and damage biofilter performance. However, as biofilters have been designed for lower headloss and higher flowrates, flow heterogeneity has also arisen, as pressure variation in the headspace affects flow in the medium.In an effort to investigate flow heterogeneity, a two‐dimensional steady‐state computational fluid dynamics (CFD) model was developed to simulate flow through a typical biofilter. The model assumes incompressible, two‐dimensional, Navier‐Stokes flow in the spaces above and below the bed and Darcy flow in the porous medium. The modeling effort demonstrated that the optimal design depends on the permeability of the medium, the air flowrate, and biofilter configuration. Several simple options for inlet and outlet location were compared. In very low permeability media, the flow was uniform regardless of the design. With highly permeable media, the optimal design choice depended on the Reynolds number. However, the design with side inlet and same side outlet had the lowest flow heterogeneity of the five designs over a wide range of Reynolds numbers. The model also demonstrated that removal efficiency decreases as flow heterogeneity increases.
Evaluation of continuous flow‐through phytoreactors for the treatment of TNT‐contaminated water
Authors: Medina Victor F. , Larson Steven L. , McCutcheon Steven C. 
Published: April 2004

AbstractThe proof of concept for created wetlands to treat groundwater or industrial water contaminated with trinitrotoluene (TNT) was established using bench‐scale, continuous flow reactors with aquatic plants. Contaminant loadings from 0.0132 to 2.488 g/m3/day were tested on phytoreactors using parrotfeather (Myriophyllum aquaticum) as the plant. Reactor removal efficiency and elimination capacity were linearly related to the load of TNT. An algal reactor was also tested at a loading of 0.9671 g/m3/day and removed 93% of the TNT. Some removal was also found in control reactors that contained no plants and minimized algal growth by shielding them from light. However, the removal efficiencies in the controls were much lower. Transformation products, aminodinitrotoluenes (ADNT) and diaminonitrotoluenes (DANT), were detected in the algae and phytoreactors, but not in the controls, indicating that the TNT was being transformed. However, ADNT persisted in the effluent, representing a reactor‐design issue that must be further investigated. ADNT concentrations in the plant material increased with contaminant loading. TNT was only found in plant tissue at the highest loading of 2.488 g/m3/day. Higher concentrations of ADNT were found in the root of the plant, with approximately equal concentrations in the stem and leaf portions. Ratios of 4‐aminodinitrotoluene (4ADNT) versus 2‐aminodinitrotoluene (2ADNT) were higher in the water phase versus what was found in plant material. Because microbial processes tend to favor the formation of 4ADNT, the higher ratio suggests that the removal of TNT is actually a combination of microbial and phyto processes.
Pilot‐scale in situ bioremediation of gasoline‐contaminated groundwater: Impact of process parameters
Authors: Nakhla George , Niaz Mohammed 
Published: April 2004

AbstractThis study evaluated the impact of groundwater velocity and dissolved oxygen (DO), added as hydrogen peroxide to overcome oxygen solubility limitations, and contaminant concentrations, on the efficiency of an engineered in situ bioremediation (ISB) strategy to treat groundwater contaminated with benzene, toluene, and xylene (BTX). BTX served as model compounds of gasoline contamination. Groundwater velocities of 1, 2, and 4 m/d were studied. At each velocity, two concentrations of BTX were employed—10 and 50 mg/l of each of the contaminants to reflect “hot spot” conditions following a spill or major leak. Similarly DO:BTX mass ratios of 1.5:1 and 3.2:1 were employed.The results of the study indicated that BTX removal efficiencies of 96.7 to 99.7% were achievable at a groundwater velocity of 1 m/d with final concentrations reaching as low as 30 μg/l. BTX removal efficiencies decreased to 70 to 85 percent at a velocity of 2 m/d, and to 37 to 53% at a velocity of 4 m/d. At any given groundwater velocity, BTX removal efficiencies generally increased with increasing DO and BTX concentrations. Mathematical equations for the first‐order biodegradation rate coefficients as a function of the three parameters were derived. Statistical analysis of the data revealed that groundwater velocity was the most significant parameter impacting biodegradation efficiency, accounting for approximately 80% of the variability. Hydraulic conductivity of the aquifer decreased by approximately 80% over the course of the seven‐month study, with 90% of the decline occurring within the first six weeks. Plate counts also impacted hydraulic conductivity. However, it was not possible to model hydraulic conductivity by plate counts only.
Evaluation of cleaning and coating techniques for PCB‐contaminated concrete
Authors: Pizarro Gonzalo E. L. , Dzombak David A. , Smith John R. 
Published: April 2004

AbstractPCB‐contaminated concrete is a significant environmental management issue for many industrial facilities. The U.S. EPA has authorized exposure control in operating facilities via encapsulation or use of physical barriers when complete PCB removal is not technically achievable and/or is not cost‐effective. Achievement of effective encapsulation with epoxy coatings is challenging for PCB‐contaminated concrete as oil and/or other chemicals are often present. This work involved experimental investigation of encapsulation via cleaning and epoxy‐coating of PCB‐contaminated concrete. Experimental studies were performed with three cleaning techniques for removal of PCBs, and three epoxy‐coating systems for encapsulating PCBs. Resurfacing of oils and PCBs from concrete after cleaning, or “bleedback”, was also studied. These tests were conducted using PCB/oil‐contaminated concrete core samples from industrial plants. Results indicated that no cleaning system alone is effective as a long‐term solution for PCB‐contaminated concrete, and that bleedback occurred within days after cleaning due to capillary rise, affected by changes in wetting characteristics of the concrete pore surfaces and by elevated temperature induced by heating, which affects the density of the oil. The presence of free oil on the concrete surface resulted in failure of the coating systems, which occurred faster if heating was applied. Where appropriate surface preparation was performed, the integrity of the coatings remained intact throughout the experimental period (eight months). In such cases, the coating system acted effectively as a barrier against diffusion of PCBs. This study demonstrated that, except in high‐temperature areas, an epoxy coating can be an appropriate encapsulation system if proper surface preparation is applied. Metal sheet barriers can be used for high‐temperature applications.
Evaluation of PCBs biodegradability in sludges by various microbial cultures
Authors: Nakhla George , Kochany Jan , Lugowski Andrew 
Published: April 2004

AbstractThe application of aerobic and anaerobic treatment for removal of PCBs in sludges generated from a groundwater treatment system was investigated. The sludge was characterized by PCB concentrations of > 520 ppm, with Aroclors 1254 and 1260 accounting for 26 and 74%, respectively, as well as total organic carbon (TOC), and oil and grease (O&G) concentrations of 108,500 and 18,600 mg/L, respectively. Four treatments were explored: three aerobic and one anaerobic. Two types of bacterial innocula were aerobically tested: sludge from a poultry processing wastewater treatment plant, and a commercial seed (Petrobio®). Petrobio was tested aerobically with and without a biosurfactant/enzymes product (BOD‐Balance™), and was also tested anaerobically. Over a period of 60 days, PCB concentrations on a volumetric and solids basis were reduced by 73.4 to 88.0% and 64.7 to 80%, respectively. Aroclors 1254 and 1260 concentrations decreased by about 76 to 89%, and 73 to 89%, respectively. TOC and O&G removal efficiencies ranged from 77 to 93%, and from 52 to 86%, respectively.Generally, sludge from the poultry processing facility achieved the best results and exhibited the most rapid biodegradation kinetics. Aerobic PCB biodegradation rates for Aroclors 1254 and 1260 were 13.5% and 23%, respectively, faster than the anaerobic biodegradation rates. Overall PCB biodegradation kinetics conformed to first‐order, with rate constants ranging from 0.017 d−1 under anaerobic conditions to 0.022 d−1 under aerobic conditions, while both TOC and O&G biodegradation kinetics followed first‐order kinetics, with rate coefficients in the ranges of 0.025–0.047 and 0.014 and 0.04 d−1, respectively.
Zeolite synthesis employing alkaline waste effluents from the aluminum industry
Authors: La Iglesia A. , González M. V. , Dufour J. 
Published: April 2004

AbstractZeolites 4A, 13X, Y, and HZSM5 have been synthesized from alkaline residues from aluminum finishing plants. These residues could contain concentrations of sodium aluminate and sodium hydroxide between 200 and 300 Kg/m3, and small concentrations of heavy metal cations (Cd, Co, Cr, Cu, Mn, and Zn). These contaminants make handling and disposal of these residues difficult.However, the physicochemical properties of the synthesized zeolites (cation exchange capacity of 3 mmol g−1, specific surface area between 600–900 m2g−1, particle size distribution between 0.5–2 μm and whiteness of 97%) make them useful as detergents and catalysts.Analysis of the chemical composition of the raw materials and the reaction products demonstrates that the heavy metal cation content in the synthesized zeolites is low enough to allow their industrial use (lower than that of the original residues). Therefore, the production of various types of zeolites for industrial use could be used for the elimination of these residues from the aluminum industry.
Removal of zinc and trichloroethylene from water by column extraction with a crude humic acid
Authors: Von Wandruszka Ray , Newell J. David 
Published: April 2004

AbstractThis paper presents an evaluation of the feasibility of removing high levels of zinc from mine run‐off by means of a crude humic substance. The process, in which the material was used as a solid adsorbent in an extraction column, achieved ⩾ 95% removal of the dissolved metal. The elution procedure could tolerate pH values down to 4 before metal leaching from the matrix became a problem. This was circumvented by the inclusion of marble chips in the extractor. Competition by high concentrations of common cations, such as calcium and magnesium, did not seriously impair zinc extraction. Anions were not retained, except for sulfate which was removed with 66% efficiency. Removal of dissolved trichloroethylene from water was virtually quantitative, without subsequent release of the contaminant from the extractant.
Absorption of NO2 in a packed tower with Na2SO3 aqueous solution
Authors: Chen Luke , Lin Jin‐Wei , Yang Chen‐Lu 
Published: April 2004

AbstractThis paper looks at the development of a two‐stage chemical scrubber for NOx control. In the first stage, the most practical oxidizing agents for NO oxidation are sodium chlorite and sodium hypochlorite. Although a considerable amount of work has been done on the reaction kinetics of NO2 with Na2SO3, there are major gaps in developing an Na2SO3 aqueous solution for NO2 absorption in the second stage. Of particular importance is the rate of chemical absorption. A pilot‐scale research program was initiated to evaluate the absorption rate of NO2 with Na2SO3 aqueous solution in a packed tower. The research is directed at obtaining height of a transfer unit (HTU) for NO2 absorption, and to determine reasonable operation conditions for the packed bed scrubber. A sulfite concentration of 0.25 M is essential to have a reasonable HTU in 2 to 5 feet for a gas rate between 1,050 to 2,350 lb/ft2 hr. The results indicate that the scrubbing effectiveness of NO2 increased with the L/G ratio, and an L/G of more than 3 is required for high NO2 absorption.
Hydrophobic pervaporation for environmental applications: Process optimization and integration
Authors: Lipnizki Frank , Field Robert W. 
Published: April 2004

AbstractThe focus of this paper is on the design of pervaporation units for wastewater treatment taking into account technical, economic, and environmental aspects. Two different sized industrial wastewater streams of water‐chloroform, and of water‐methyl‐isobutylketone (MIBK) are considered. Based on a wastewater stream of 1,500 kg/d, a semi‐batch process combining pervaporation with a decanter recycle loop is developed. Using this process, it is possible to recover over 99% of the organic components at concentrations of more than 98 wt. %. The treatment costs are between 0.11 to 0.16 $/kg wastewater. For the treatment of a wastewater stream of 1,000 kg/h, pervaporation combined with a decanter and recycling loop, as well as integrated in a hybrid process with adsorption, is considered. For MIBK, pervaporation with a decanter is the most attractive option taking economic and environmental aspects into account, while, for chloroform, the hybrid process is the better option. Treatment costs in all cases are about 0.03 $/kg wastewater. The recovery rate of the organic compounds is over 99% at concentrations over 98 wt. %. The authors concluded that pervaporation as a stand‐alone unit, or integrated into hybrid processes, offers significant advantages over conventional alternatives.
LCAccess: A global directory of life cycle assessment resources
Authors: Curran Mary Ann , Skone Timothy J. 
Published: April 2004

AbstractLCAccess is an EPA‐sponsored Web site intended to promote the use of Life Cycle Assessment (LCA) in business decision‐making by facilitating access to data sources useful in developing a life cycle inventory (LCI). While LCAccess does not, itself, contain data, it is a searchable global directory of potential data sources, and serves as a central source for LCA information.
The photocatalytic oxidation of low concentration MTBE on titanium dioxide from groundwater in a falling film reactor
Authors: Almquist Catherine B. , Sahle‐Demessie Endalkachew , Enriquez Julius , Biswas Pratim 
Published: April 2004

AbstractThis study is focused on three main objectives: (1) to determine the feasibility of using a falling‐film slurry photocatalytic reactor for the degradation of methyl tertiary‐butyl ether (MTBE) in water, (2) to assess the feasibility of MTBE photo‐oxidation on TiO2 at low initial MTBE concentrations (< 1 mg/L), and (3) to compare the effectiveness of MTBE photo‐oxidation on TiO2 in synthetically‐contaminated water, and in actual MTBE‐contaminated groundwater samples.The MTBE degradation rates observed in a laminar falling film photocatalytic reactor for synthetic samples, with concentrations ranging from 50 μg/L to 1 mg/L, were high, achieving nearly complete (99+%) degradation of 1 mg/L MTBE and its by products in less than 120 minutes. The calculated single‐pass conversions were as high as 60%, corresponding to residence times of approximately 5 seconds in the falling film reactor. The observed degradation products of MTBE oxidation were predominantly tert‐butyl alcohol (TBA) and tertbutyl formate (TBF).However, tests conducted using groundwater samples showed significantly reduced photoactivity of TiO2 towards the degradation of MTBE. Aromatic species and dissolved metal and chloride ions present in the field samples compete with MTBE and molecular oxygen on the TiO2 surface, and hence delay and retard MTBE degradation.
An integrated industrial management facility for biological treatment of high nitrate and carbonaceous wastewater
Authors: Beeman Ralph E. , Reitberger Joseph H. 
Published: April 2004

AbstractBiological wastewater treatment is not typically used for wastewater with high nitrate and carbonaceous content. Hence, facilities demonstrating effective treatment are of interest to the worldwide environmental community. DuPont's Nylon Intermediates manufacturing plant at Victoria, Texas, started operating such a wastewater facility approximately three years ago. The new wastewater management facility features an innovative anoxic/oxic (A/O) biological treatment plant, a constructed wetland, and land application pilot area for demonstrating beneficial reuse of the biosolids. The wastewater treatment process is working well, with Chemical Oxygen Demand (COD) removal above 99%, complete removal of nitrate and nitrite, and 100% permit compliance, since start‐up. The wetland has exceeded expectations for polishing, buffering, and community value. Land application has demonstrated beneficial reuse of biosolids by producing excellent quality hay, which is being fed to animals in a non‐human food chain pathway. The waste treatment facility has won numerous awards including the 2001 Texas Natural Resource Conservation Commission (TNRCC) Award for Wetland Education, the 2000 Water Environmental Federation (WEF) Industrial Water Quality Award, the 2001 WEF Award for Education, and the 2002 DuPont Sustainable Growth Award.
Robustness of a full‐scale biological system treating industrial CS2 emissions
Authors: Kraakman N. J. R. (Bart) 
Published: April 2004

AbstractCarbon disulfide (CS2) emissions must be treated for health and safety reasons. In this paper, an illustration of a full‐scale bioreactor system to treat industrial CS2 emissions is presented. A definition of robustness could be used to determine the risks of the bioreactor installation for various applications, and to define effective operational procedures. Examples from field experience show that the bioreactor system described in this paper is robust for situations that are likely to occur under industrial conditions. Experience indicates that the overall risk for operating this system is less than 4% loss of total removal per year. Therefore, it is concluded that this system is a reliable technology for reducing industrial CS2 emissions.
A novel reactor for exploring the effect of water content on biofilter degradation rates
Authors: Ranasinghe Milinda A. , Gostomski Peter A. 
Published: April 2004

AbstractA novel batch recycle reactor was developed to investigate the effect of water content changes on the biological degradation rate of gas phase contaminants in low water content systems, such as biofilters. The reactor tightly controlled the water content of the unsaturated packing material using the principle of a suction cell. Matric potential in the compost was controlled between −6 and −36 cm H2O. A soil water retention curve relating matric potential to gravimetric water content was generated for the compost. Periodic dry weight analyses of reactor samples, together with the water retention curve, verified moisture content control. Runs were performed with toluene as the contaminant using unamended compost at a constant temperature of 30°C. Degradation results indicated a linear, biologically limited degradation region, followed by a non‐linear region at lower concentrations. Elimination capacities were calculated for the linear region for different matric potentials along both the wetting and drying curves, and both changes in the water content and direction of approach affected the removal rates in the linear region. The elimination capacity ranged from 155 g/m3 hr to 24 g/m3 hr for toluene over the matric potential range investigated. Repeatability studies indicated that moisture content was most likely the parameter that influenced changes in performance.
Particle size distribution in slaughterhouse wastewater before and after coagulation‐flocculation
Authors: Sanchis María Isabel Aguilar , Sáez José , Lloréns Mercedes , Soler Antonio , Ortuño Juan F. 
Published: April 2004

AbstractSolid particles were removed from a slaughterhouse liquid effluent by physicochemical treatment (coagulation‐flocculation process) using aluminium sulfate as the coagulant, and activated silica, powdered activated carbon, precipitated calcium carbonate, polyacrylic acid, or anionic polyacrylamide as coagulant aids to improve the settling time.Once the optimal conditions of the coagulation‐flocculation process had been established (speed and time of stirring during flocculation, pH, coagulant and coagulant aid doses), the particle number and size distribution were measured before and after the addition of aluminium sulfate as the coagulant and the different coagulant aids, to determine the efficiency of the coagulation‐flocculation process. When aluminium sulfate was used without the coagulant aids, overall efficiency of particle removal was 87%. Use of powdered activated carbon, polyacrylic acid, or anionic polyacrylamide improved removal to values between 92 and 98%.
Comparison of in‐furnace dry sorbent injection full‐scale tests with laboratory‐scale sulfation correlations
Authors: Collado Francisco J. 
Published: April 2004

AbstractIn an effort to limit SO2 emissions to the current EU air pollutant regulations, flue gas desulfurization tests were performed with in‐furnace dry sorbent, Ca(OH)2, injection technology in the Spanish coal power station “Litoral.” The measured SO2 removals—19.5% using a Ca‐S ratio of 3 for a coal containing 0.53% of sulfur, and 26.4% with Ca/S = 1.75 for a coal with 0.73% of sulfur—were lower than predicted through a 1‐D model. Hence, it was thought that a 3‐D computational fluid dynamics (CFD) simulation of the injection of sorbent particles would assist in understanding this complex process. After the turbulent velocity and temperature fields in the furnace were modeled, representative sorbent particles were injected, obtaining the temperature and SO2 concentrations encountered by the particles as a function of time. These data were the input to the global sulfur capture model used to simultaneously analyze calcination, sintering and sulfation. The simulation compared well with the data measured in the power station, thus verifying laboratory‐scale correlations. The main conclusion is that the first temperatures encountered by the particles—in addition to the mean diameter, the sulfur content and the Ca/S ratio—control the sulfur retention. Further more, it is extremely difficult to accurately predict these temperatures without a CFD simulation. Low retentions were due to low sulfur concentration, the high mean diameter of the particles, and the position of the injection nozzles.