bluuebunny/crossref_metadata_2025 huggingface dataset:
Humans and Automation: Use, Misuse, Disuse, Abuse
Authors: Parasuraman Raja , Riley Victor
Published: October 2006

This paper addresses theoretical, empirical, and analytical studies pertaining to human use, misuse, disuse, and abuse of automation technology. Use refers to the voluntary activation or disengagement of automation by human operators. Trust, mental workload, and risk can influence automation use, but interactions between factors and large individual differences make prediction of automation use difficult. Misuse refers to over reliance on automation, which can result in failures of monitoring or decision biases. Factors affecting the monitoring of automation include workload, automation reliability and consistency, and the saliency of automation state indicators. Disuse, or the neglect or underutilization of automation, is commonly caused by alarms that activate falsely. This often occurs because the base rate of the condition to be detected is not considered in setting the trade-off between false alarms and omissions. Automation abuse, or the automation of functions by designers and implementation by managers without due regard for the consequences for human performance, tends to define the operator's roles as by-products of the automation. Automation abuse can also promote misuse and disuse of automation by human operators. Understanding the factors associated with each of these aspects of human use of automation can lead to improved system design, effective training methods, and judicious policies and procedures involving automation use.
The Impact of Signal Bandwidth on Auditory Localization: Implications for the Design of Three-Dimensional Audio Displays
Authors: King Robert B. , Oldfield Simon R.
Published: October 2006

A new type of interlace, the three-dimensional (3D) audio display, is being developed to enhance cockpit displays in military aircraft. In order to synthesize a sound's location in space, head-related transfer functions are measured for many sound source positions (in space) and incorporated in digital filters, which are then used to synthesize location. However, most military aircraft have communication systems that are band-limited in frequency response, as are most recently designed auditory displays currently used in military applications. The present study investigated the effects of limiting signal bandwidth on sound localization. Results show that broadband signals encompassing frequencies from 0 to (at least) 13 kHz are required in order for listeners to accurately localize signals actually presented from a range of spatial locations. These results have clear implications for the design and implementation of 3D spatial synthesis systems in military aircraft. Communications systems should be capable of carrying broadband signals and acoustic signals used in 3D audio displays should also be broadband in nature.
The Reduction of Uncertainty and Troubleshooting Performance
Authors: Teague Ross C. , Allen John A.
Published: October 2006

Two problem-solving experiments were conducted to determine the effects of prior knowledge of problem intermittency on human troubleshooting performance. In-termittency was defined as the rate at which a network component or output, when tested, gave an incorrect report of its status (i.e., reported that it was working when it actually was not). Participants' task was to find faulty components in a set of 18 computer-based problems that caused a network to malfunction. In the first experiment, half the participants were told whether a problem was intermittent or not before they began troubleshooting procedures. In the second experiment, half the participants were given specific rates of intermittency for the problems. It was found that providing participants with only general "intermitten"" or "nonintermtttent" prior information did not affect troubleshooiing performance. Participants given specific problem intermittency rates did, however, perform better on the troubleshooting problems than did participants who were not given this information.
Multiple Factors that Determine Performance with Tables and Graphs
Authors: Meyer Joachim , Shinar David , Leiser David
Published: October 2006

Two experiments assessed the relative efficiency of line graphs, bar graphs, and tables, applying a multiple-factors approach to study the effects of the type of the required information, the complexity of the data, and the user's familiarity with the display. information extraction tasks included reading exact values, comparing values, identifying trends, and reading maximum values. Tables led to faster responses for all tasks, and the accuracy for tables was equally high or higher than for graphs. Bar graphs and line graphs differed in their relative efficiency for the different tasks. The complexity of the data also affected the tasks differentially, as did prior familiarity with the display. Performance for most conditions improved with experience. Our findings demonstrate the benefits of a multiple-factors approach to the study of displays. Generalizations about the relative efficiency of displays and computational models of the task performance with displays must consider the various relevant factors if they are to serve as valid design aids.
Human Factors Field Evaluation of Automotive Headway Maintenance/Collision Warning Devices
Authors: Dingus Thomas A. , McGehee Daniel V. , Manakkal Natarajan , Jahns Steven K. , Carney Cher , Hankey Jonathan M.
Published: October 2006

Three on-road studies were conducted to determine how headway maintenance and collision warning displays influence driver behavior. Visual perspective, visual perspective with a pointer, visual perspective combined with an auditory warning, discrete visual warning, and discrete auditory warning were assessed during both coupled headway and deceleration events. Results indicate that when drivers are provided with salient visual information regarding safe headways, they utilize the information and increase their headway when appropriate. Auditory warnings were less effective than visual warnings for increasing headways but may be helpful for improving reaction time during events that require deceleration. Drivers were some what insensitive to false alarm rates, at least during short-term use. Finally, and most important, driver headway maintenance increased by as much as 0.5 s when the appropriate visual display was used. However, a study to investigate the long term effects of such displays on behavior is strongly recommended prior to mass marketing of headway maintenance/collision warning devices.
Sociology at Play, or Truth in the Pleasant Disguise of Illusion 2006 Presidential Address to the Pacific Sociological Association
Authors: Nardi Peter M.
Published: October 2006

Teaching sociology can involve the creative use of play, illusion, and truth. Building on ideas of Postman and Weingartner's Teaching as a Subversive Activity and Paolo Freire's Pedagogy of the Oppressed, this presidential address illustrates how making meaning out of play, using illusions and myths in courses, and seeking truth through praxis in advocacy research and public sociology can challenge our students to higher levels of critical thinking.
Immunoreactive Trypsin/DNA Newborn Screening for Cystic Fibrosis: Should the R117H Variant Be Included inCFTRMutation Panels?
Authors: Scotet Virginie , Audrézet Marie-Pierre , Roussey Michel , Rault Gilles , Dirou-Prigent Anne , Journel Hubert , Moisan-Petit Valérie , Storni Véronique , Férec Claude
Published: October 2006

BACKGROUND. Cystic fibrosis newborn screening is now implemented universally in France, as well as in many states in the United States and in various areas of Europe and Australia. Because the screening protocol usually includes the analysis of the most common CFTR mutations, it is of the utmost importance that only mutations that result in classical cystic fibrosis are included in this test. The panels of mutations used in most cystic fibrosis newborn screening programs enable the detection of a relatively frequent CFTR variant (R117H) whose implication in cystic fibrosis remains unclear. Physicians, therefore, have difficulty managing detected compound heterozygotes with this variant, which raises the issue of the appropriateness of extended testing in families and of the legitimate use of prenatal diagnosis.

OBJECTIVE. The aim of this study was to describe the clinical outcome of the children found to be compound heterozygous for R117H by screening in Brittany (western France), where cystic fibrosis newborn screening was set up in 1989, and to assess whether this CFTR variant should be included in the newborn screening mutation panels.

METHODS. Data on clinical status were obtained by the referring pediatricians.

RESULTS. Since our screening protocol has enabled detection of R117H (ie, in 1995), 360466 newborns have been screened for cystic fibrosis in Brittany, of whom 124 had elevated immunoreactive trypsin and 2 mutations in the CFTR gene. Nine of these children (7.3%) were compound heterozygous for R117H, which in all cases was linked to the 7T_11TG haplotype [IVS8-nT variant/m(TG) repeat]. Their genotypes were F508del/R117H (n = 7), I507del/R117H (n = 1), or G551D/R117H (n = 1). At the time of this writing, the mean age of these 9 children was 7.0 years (the oldest being >10 years of age), and none of them had yet developed any signs of cystic fibrosis; they have been pancreatic sufficient and have had good nutritional status and pulmonary function. Moreover, we observed that, in Brittany, all the patients carrying the R117H variant have been identified exclusively through cystic fibrosis newborn screening.

CONCLUSIONS. In view of the high frequency of R117H-7T identified by cystic fibrosis newborn screening, the uncertain outcome of the asymptomatic children, and physicians' difficulty in managing these situations, we propose the withdrawal of the R117H variant from the panels of CFTR mutations used in cystic fibrosis newborn screening, given the expanding implementation of cystic fibrosis newborn screening.
Electron-diffraction study on ∈-iron nitride powders with various nitrogen contents: Variation of long-range nitrogen ordering
Authors: Liu Z.Q. , Leineweber A. , Mittemeijer E.J. , Mitsuishi K. , Furuya K.
Published: October 2006

Homogeneous ∈-iron nitride powder particles of the compositions Fe3N1.00, Fe3N1.22, Fe3N1.30, and Fe3N1.39were investigated using selected-area electron diffraction. The superstructure reflections, due to N ordering on the octahedral interstitial sites of a hexagonal close-packed (hcp) arrangement of Fe, indicate a hexagonal supercell witha′ = 31/2ahcp,c′ =chcpfor all cases;P6322 space group symmetry for Fe3N1.00, Fe3N1.30, and Fe3N1.39; and lower symmetry (P312) for Fe3N1.22and some of the Fe3N1.30particles. Recognition of the occurrence of double diffraction is essential for correct interpretation of the diffraction patterns. Additionally, diffuse scattering by some of the Fe3N1.39grains was observed.
Shear strength of clay with rubber fiber inclusions
Authors: Özkul Z. H. , Baykal G.
Published: October 2006

Findings from recent research reveal that the ductility, toughness and resistance to tensile cracking of clays can be improved with the inclusion of short fibers. Tire buffings derived from the tire retread process can be elongated in shape and may be utilised as fiber reinforcement elements. The objective of the present research is to study the compaction and shear strength behavior of clay with tire buffing inclusions. Mixtures of low-plasticity kaolinitic clay with 10% by dry weight of tire buffing inclusions were prepared at both standard and modified compaction energy. The drained and undrained responses of the clay and composite soils were evaluated using the direct shear test. It was found that the drained shear strength of the clay was essentially unchanged by the introduction of rubber buffings or by an increase in the level of compaction energy employed. Its undrained strength was also not changed when standard compaction energy was used, but decreased slightly, showing a more ductile failure, when modified energy was employed. Good compaction of the mixture is not possible when the water content is much drier than the plastic limit of the clay.
Effect of foundation yielding on performance of two-tier geosynthetic-reinforced segmental retaining walls: a numerical investigation
Authors: Yoo C. , Song A. R.
Published: October 2006

This paper presents the results of an investigation into the effect of foundation yielding on the performance of two-tiered geosynthetic-reinforced segmental retaining walls using a calibrated plane-strain finite element model. Variables considered in this study include the offset distance and reinforcement distribution. The results indicate among other things that an unexpected foundation yielding may affect both the internal and external stability of the lower tier owing to the absence of toe resistance. Also revealed is the finding that the upper-tier reinforcement length has a significant influence on the lower-tier lateral deformation. Design implications and findings from this study are discussed.
Resilient modulus and plastic deformation of soil confined in a geocell
Authors: Mengelt M. , Edil T. B. , Benson C. H.
Published: October 2006

Resilient modulus tests were conducted on two coarse-grained soils (gravel and sand) and a fine-grained soil (lean silty clay) in a large-size cell with and without confinement in a geocell. The effect of the geocell on resilient modulus depended on the infill (soil in the geocell). Resilient modulus increased by only 1.4–3.2% when the infill was coarse-grained, but increased by 16.5–17.9% when the infill was fine-grained. The effect on resilient modulus was larger when the fine-grained infill was compacted wet of optimum water content. Larger deformations occurred in the tests on the fine-grained soil, which most likely contributed to the greater increase in resilient modulus when confined in a geocell. Tests with the coarse-grained soils indicated that the rate of long-term strain accumulation in the sand and gravel under constant cyclic loading decreased by approximately 2% when they were confined in geocells.
Mechanism of post-peak strength reduction for textured geomembrane–nonwoven geotextile interfaces
Authors: Li M.-H. , Gilbert R. B.
Published: October 2006

This note is intended to provide insight into the cause of post-peak strength reductions for textured geomembrane–nonwoven geotextile interfaces. Direct shear tests were conducted with incremental displacements, where one of the two interface materials was replaced, and also with continuous displacement. The results indicate that post-peak shear strength reduction is primarily due to a small-scale wearing of the geomembrane texture, either co-extruded or laminated. This conclusion applies to normal stresses from 16 to 690 kPa.
Weathering properties of geotextiles in ocean environments
Authors: Hsieh C. , Wang J.-B. , Chiu Y.-F.
Published: October 2006

This paper provides data on weathering properties and reduction factors for two geotextiles in ocean environments. The study included outdoor ultraviolet (UV) exposure tests performed at the Harbor and Marine Technology Research Center in Taiwan using a black polypropylene and a white polyester geotextile. Ultraviolet exposure was the most significant factor in reducing the strength properties of the geotextiles tested in an ocean environment. Seawater immersion had the least weathering effect on the engineering properties of the test geotextiles among the test conditions. The effect on engineering properties of placing samples within the tidal zone was slightly higher than that for the immersion condition. Reduction factors for UV exposure and seawater weathering for the test geotextiles are reported.
Preferred balance between luminance and color gamut in mobile displays
Authors: Xia Jun , Yin Han Chun , Heynderickx I.
Published: October 2006

Abstract— To improve the image quality of a mobile display, the balance between color‐gamut size and luminance was studied in two subjective experiments. The first experiment was performed during the Asian Society for Information Display (ASID) conference in Nanjing, February 2004. Nearly 600 participants ranked the quality of images displayed for fixed combinations of color‐gamut size and display luminance on small color supertwisted nematic (CSTN) and thin‐film transistor (TFT) twistednematic (TN) displays. In the second experiment, a broader range of color‐gamut sizes and luminance levels were simulated on a cathode‐ray tube (CRT) display, and 20 participants were asked to score perceived image quality. The results of these experiments were used to model image quality as a function of color‐gamut size and display luminance for images differing in the level of chromaticity of their content. This model can be used to estimate the increase in luminance required to compensate for a reduction in color‐gamut size.
Introgression of Resistance to Cabbage Seedpod Weevil to Canola from Yellow Mustard
Authors: Dosdall L. M. , Kott L. S.
Published: October 2006

The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), is an insect pest of major economic importance in the production of canola (Brassica napus L. and B. rapa L.) in Europe and North America. Studies were conducted to test intergeneric germplasm, produced by crossing Sinapis alba L. (yellow mustard) × B. napus and then backcrossing progeny to the B. napus parent, as potential sources of resistance to the weevil. Of 230 intergeneric genotypes evaluated in field trials in 2001, 18 had an average of fewer than 0.05 weevil exit holes per pod, a level of resistance selected as conferring appropriate resistance and used for further testing. Subsequent tests confirmed several genotypes that evidently carried genes for resistance to C. obstrictus from the S. alba parent. In field assessments, mean exit holes per pod in the common commercial variety, B. napus cv. Q2, ranged from approximately 2.5 to 8.3 times more than those observed in the resistant lines. Some genotypes appeared to exhibit both antixenotic and antibiotic resistance to C. obstrictus, as indicated by fewer eggs laid per pod and larval development that was significantly lengthened in the resistant germplasm compared with the B. napus check. Introgression produced several genotypes with resistance to cabbage seedpod weevil that can now be crossed with agronomically superior B. napus germplasm; when the weevil‐resistant canola is available to producers it can comprise an important component in the integrated management of this pest, resulting in substantial reductions in insecticide use in this crop.
Laboratory Study of Biological Retention for Urban Stormwater Management
Authors: Davis Allen P. , Shokouhian Mohammad , Sharma Himanshu , Minami Christie
Published: September 2006

Urban stormwater runoff contains a broad range of pollutants that are transported to natural water systems. A practice known as biological retention (bioretention) has been suggested to manage stormwater runoff from small, developed areas. Bioretention facilities consist of porous soil, a topping layer of hardwood mulch, and a variety of different plant species. A detailed study of the characteristics and performance of bioretention systems for the removal of several heavy metals (copper, lead, and zinc) and nutrients (phosphorus, total Kjeldahl nitrogen [TKN], ammonium, and nitrate) from a synthetic urban stormwater runoff was completed using batch and column adsorption studies along with pilot‐scale laboratory systems. The roles of the soil, mulch, and plants in the removal of heavy metals and nutrients were evaluated to estimate the treatment capacity of laboratory bioretention systems. Reductions in concentrations of all metals were excellent (>90%) with specific metal removals of 15 to 145 mg/m2 per event. Moderate reductions of TKN, ammonium, and phosphorus levels were found (60 to 80%). Little nitrate was removed, and nitrate production was noted in several cases. The importance of the mulch layer in metal removal was identified. Overall results support the use of bioretention as a stormwater best management practice and indicate the need for further research and development.
Surfactant‐Enhanced Solubilization and Anaerobic Biodegradation of 1,1,1‐ Trichloro‐2,2‐bis(p‐chlorophenyl)‐ethane (DDT) in Contaminated Soil
Authors: Walters Glenn W. , Aitken Michael D.
Published: September 2006

The hydrophobic pesticide 1,1,1‐trichloro‐2,2‐bis(p‐chlorophenyl)‐ethane (DDT) is a persistent contaminant in soils and sediments, although it has long been known to be biodegradable under anaerobic conditions. Addition of a nonionic surfactant was evaluated as a means of enhancing the solubilization, potential bioavailability, and anaerobic biodegradability of DDT and its metabolites—1,1‐dichloro2,2‐bis(p‐chlorophenyl)‐ethane (DDD) and 1,1‐dichloro‐2,2‐bis(pchlorophenyl)‐ethylene (DDE)—in an aged contaminated soil. Approximately 12 mg surfactant/g soil was required before concentrations greater than the critical micelle concentration were observed in the liquid phase in soil microcosms. At greater doses, solubilization of each DDT, DDD, and DDE isomer increased linearly with the surfactant dose. Solubilization data were consistent with equilibrium models that account for simultaneous partitioning of hydrophobic compounds between the aqueous, soil, and pseudomicellar phases. Significantly greater rates and extents of DDT degradation were observed in anaerobic microcosms that were regularly fed a cellulose substrate or amended with surfactant (with or without cellulose) relative to controls. The surfactant substantially increased the rate of DDT degradation during the first 9 weeks, although there were no significant differences between cellulose‐fed microcosms and surfactant‐amended microcosms after 31 weeks. In addition, DDD accumulated at less than stoichiometric amounts in surfactant‐amended microcosms, whereas DDD accumulated nearly stoichiometrically with DDT loss in all other microcosms. Concentrations of DDE were unchanged throughout the course of the microcosm experiment.
Comparison of Trace Metals in the Intake and Discharge Water of Power Plants Using “Clean” Techniques
Authors: Salvito Daniel T. , Allen Herbert E. , Parkhurst Benjamin R. , Warren‐Hicks William J.
Published: September 2006

Once‐through, noncontact condenser cooling water at power plants is frequently discharged back to the fresh or saline water body used for its intake water. This study evaluated the potential effect that trace metals, collected using “clean” sampling and analytical techniques and discharged from a once‐through, noncontact cooling water system from a power plant, have on receiving water bodies. A paired t‐test was used to compare the intake and discharge concentrations of the metals. The metals analyzed were antimony, arsenic, barium, beryllium, boron, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, thallium, and zinc. “Clean” is a term applied to field and analytical procedures that are designed to reduce or eliminate ubiquitous metal contamination from samples collected for environmental monitoring. Study results indicate that there is no measurable difference between intake and discharge samples from a noncontact cooling water system, and, therefore, there is no net contribution of metals to receiving water bodies from this system.
Influence of Cations on Activated‐Sludge Effluent Quality
Authors: Murthy Sudhir N. , Novak John T.
Published: September 2006

Laboratory experiments and field tests were conducted to determine the effect of inorganic cations on effluent from activated‐sludge systems. Laboratory experiments showed that monovalent cations tend to increase the concentration of solution biological polymers(biopolymers), whereas divalent cations tend to retain the biopolymers in the floc. Biopolymers in solution affect effluent chemical oxygen demand (COD). Coagulation tests were performed on the effluent with ferric chloride. Ferric hydroxide can coagulate protein through possible adsorptive interactions and may be responsible for some biopolymer retention in the flocs. In the field study, it was found that sodium ions in the influent wastewater caused an increase in proteins and polysaccharides in solution, thereby increasing the effluent COD concentration of the treated municipal wastewater. The attachment or release of these microbially derived organic biopolymers and recalcitrant influent substrate may depend on the monovalent‐to‐divalent cation ratio and the concentration of iron. Modeling of effluent organics in the activated‐sludge process can be enhanced through incorporation of concepts that take into account the partitioning (between floc and solution) of microbial biopolymers and influent recalcitrant substrate.
Lead and Zinc Removal by Laboratory‐Scale Constructed Wetlands
Authors: Song Ying , Fitch Mark , Burken Joel , Nass Linda , Chilukiri Somnath , Gale Nord , Ross Chad
Published: September 2006

Constructed wetlands have the potential to trap and remove metals in mine wastewater. To determine the effectiveness of constructed wetlands for treating selected heavy metals in neutral mine effluent typical of lead mines, eight laboratory‐scale constructed wetlands were set up to treat a synthetic, slightly alkaline, mine water containing 34.2 mg/L sulfate (SO42−), 50 μg/L lead (Pb), and 300 μg/L zinc (Zn). After 45 days, one of the wetlands was switched to treat a synthetic smelter effluent with a much greater load of SO42−, sodium (Na+), and Pb. Temperature, hydraulic loading, and substrate composition typically did not affect treatment efficiency. The pH of the effluent was reduced from 8.0 to 8.5 to near neutral. The average removal in the eight wetlands was 90% for Pb and 72% for Zn. In wetlands operating on synthetic mine water, SO42− was completely removed, likely by conversion to sulfide by sulfate‐reducing bacteria. In the wetland operating on synthetic smelter effluent, only approximately 25% of 6 g/L influent sulfate was removed, and a breakthrough period of 4 days for Na+ was observed. Whole effluent toxicity assays on undiluted wetland effluent from wetlands treating mine and smelter water had 100% survival of fathead minnows and Daphnia magnia. Survival of Ceriodaphnia dubia was zero in undiluted effluent, but 75 to 100% survival was observed when the effluent was diluted to one‐half strength.
Posttreatment of a Brewery Wastewater Using a Sequencing Batch Reactor
Authors: Rodrigues Ana C. , Brito António G. , Melo Luís F.
Published: September 2006

This study concerns the application of a sequencing batch reactor (SBR) for the posttreatment of an effluent rejected by an upflow anaerobic sludge blanket (UASB) reactor operating in a brewery. The goal was to achieve the required wastewater quality for discharge to surface water. The primary target was the removal of nitrogen compounds, but chemical oxygen demand and suspended solids were also concerns. Phosphorus concentration and protozoan population were also monitored during SBR operation. Two different strategies were tested: an operation based on an aerobic–anoxic sequence and another based on applying a predenitrification step, that is, an anoxic–aerobic–anoxic sequence. Ammonium (NH4–N) removal was achieved in all assays. Nitrification efficiency reached 97%, and the maximum observed rate was 0.175 kg NH4–N/kg volatile suspended solids z d. A denitrification process was detected during the aerated periods, despite a dissolved oxygen concentration in the bulk liquid of 2.8 to 3.7 mg O2/L. However, denitrification was suppressed when the bulk liquid oxygen concentration was increased to 7 mg O2/L. The carbon‐to‐nitrogen ratio of the UASB effluent was too low and hindered the postdenitrification phase. This fact was confirmed by complete nitrate removal when an acetate supplement was added. On the other hand, the insertion of a primary anoxic phase in the reaction cycle was the best treatment strategy, leading to nitrogen values within the legal framework. The protozoan population showed significant changes in response to the aerobic–anoxic conditions. However, periodic nonaerated conditions were not detrimental to aerobic protozoa, which recovered as soon as oxygen was again available.
Characterization of Drinking Water Treatment Residuals for Use as a Soil Substitute
Authors: Dayton E.A. , Basta N.T.
Published: September 2006

.The beneficial use of drinking water treatment residuals (WTRs) as a potential source of topsoil for land reclamation was evaluated. Seventeen WTRs were characterized for use as soil substitutes by comparing chemical and physical properties and plant nutrients of the WTRs with soil. A tomato (Lycopersicon esculentum) bioassay was performed to determine the ability of soil chemical tests to measure WTR phosphorus (P) adequacy. The WTR chemical and physical properties were typically adequate for crop growth. None of the WTRs were considered unsuitable as soil substitutes based on plant nutrients, with the exception of P. Tomato vegetative yield and tissue P were poor either because of phytotoxic nitrite‐nitrogen (NO2–N) (>10mg/kg) generated during the bioassay or because of WTR P deficiency. Limited data suggest that WTRs with NO2–N less than 10 mg/kg and Olsen P greater than 50 mg/kg, water soluble P greater than 580 m g/L, or Mehlich III P greater than 54 mg/kg support growth but still produce inadequate tissue P in tomatoes.
Oxygen Mass‐Transfer Coefficients for Different Sample Containers Used in the Headspace Biochemical Oxygen Demand Test
Authors: Logan Bruce E. , Kohler David
Published: September 2006

To accurately measure the oxygen demand of a wastewater sample in a headspace biochemical oxygen demand (HBOD) or other respirometric test, the rate of oxygen transfer to the aqueous phase must be greater than the oxygen exertion rate by the sample. Oxygen mass‐transfer coefficients (Kawa) measured for 28‐, 55‐, and 160‐mL, partially full (18 to 89%) containers placed on their sides on a shaker table and mixed at 200 r/min averaged 8.0 h−1 (range 5.4 to 9.9 h−1). For this mass‐transfer coefficient, HBOD values as great as 1340 mg/L·d are possible at the start of an HBOD test, although the maximum daily HBOD declines to 192 mg/L·d at the end of the test because of oxygen depletion in the sample headspace. Mass‐transfer coefficients for shaken samples decreased only at low shaking speeds (<50 r/min). Oxygen mass‐transfer coefficients for shaken samples were always larger than those (average of 1.8 h−1) measured for samples in a 250‐mL bottle mixed with a stir bar on a stir plate. These mass‐transfer coefficients indicate that the oxygen demand of typical full‐strength municipal wastewaters can be measured in HBOD tests without oxygen transfer limiting the reaction rate.
Chemical Oxygen Demand Analysis of Wastewater Using Trivalent Manganese Oxidant with Chloride Removal by Sodium Bismuthate Pretreatment
Authors: Miller Donald G. , Brayton Scott V. , Boyles Wayne T.
Published: September 2006

Current chemical oxygen demand (COD) analyses generate wastes containing hexavalent and trivalent chromium, mercury, and silver. Waste disposal is difficult, expensive, and poses environmental hazards. A new COD test is proposed that eliminates these metals and shortens analysis time, where trivalent manganese oxidant replaces hexavalent chromium (dichromate). A silver catalyst is not required. Optional pretreatment removes chloride via oxidation to chlorine using sodium bismuthate, eliminating the need for mercury. Sample aqueous and solid components are separated for chloride removal, then recombined for total COD measurement. Soluble and nonsoluble COD can be determined separately. Digestion at 150 °C is complete in 1 hour. Results are determined by titration or by spectrophotometric reading. Test wastes contain none of the metals regulated for disposal under the Resource Conservation and Recovery Act. Results are shown for selected organic compounds and various wastewaters. Statistical comparisons are made with dichromate COD and biochemical oxygen demand (BOD5) test values.
Fate and Toxicity of Aircraft Deicing Fluid Additives Through Anaerobic Digestion
Authors: Gruden Cyndee L. , Dow Sarahann M. , Hernandez Mark T.
Published: September 2006

Benzotriazole derivatives are widely used corrosion inhibitors and their fate during wastewater treatment processes is unknown. The purpose of this research was to study the toxic effects and fate of the two commercially significant benzotriazole isomers used in aircraft deicing fluids (4‐, and 5‐, methylbenzotriazole [MeBT]) during anaerobic digestion. Experiments were executed in microcosms using mesophilic anaerobic biomass co‐digesting wastewater sludge and propylene glycol. Sorption of MeBT to digesting solids could be approximated with a Freundlich model, and no anaerobic breakdown of either MeBT isomer was detected. Digesters fed more than 300 mg/L MeBT responded with a significant decrease in methanogenic microbial activity and volatile solids production and a concomitant increase in accumulation of volatile fatty acids. Direct microscopic measurements using fluorescent phylogenetic probes applied to digesting biomass revealed that members of both Archaea and Bacteria domains were sensitive to MeBT. Granular activated carbon (GAC) (volatile solids: GAC = 10%) reduced the apparent toxic effects of MeBT; GAC addition nearly restored the baseline activity of digesters fed MeBT (500to 1000 mg/L).
Heavy Metal Mobility in Biosolids‐Amended Glaciated Soils
Authors: Nikolaidis Nikolaos P. , Chheda Pradeep
Published: September 2006

The mobility of heavy metals from one‐time application of biosolids (i.e., compost, pellet, and cement kiln dust stabilized biosolids) onto glaciated soils (Paxton soil) was studied because previous work on metal leachate characteristics from different biosolids is limited for glaciated soils. Two types of batch tests were performed: first, a pH‐edge adsorption study to evaluate the effect of pH on heavy metal adsorption to Paxton soil and, second, a pH‐edge leaching study to evaluate the effect of pH on the leaching potential of heavy metals from biosolids‐amended Paxton soil. Finally, a semicontinuous soil column study was performed to assess the mobility of heavy metals from biosolids‐amended Paxton soil. The pH‐edge leaching results showed that the leaching potential of heavy metals was lower with the compost product. Desorption concentrations for arsenic, chromium, and lead were found to be greatest in the cement kiln dust stabilized product whereas cadmium, copper, and nickel were present at the greatest concentrations in the pellets. The total organic carbon results measured during the pH‐edge leaching study indicated that there is a minimum leachable concentration in the pH range of 4 to 5 for all three biosolids. Overall, the column studies indicated that heavy metals were not readily leached from the three biosolids‐amended Paxton soils. The results from this study suggest that a one‐time land application of these biosolids will not adversely affect groundwater quality.
Biological Surfactant Production in a Biological Slurry Reactor Treating Diesel Fuel Contaminated Soil
Authors: Cassidy Daniel P.
Published: September 2006

A sandy loam with aged diesel fuel contamination was treated for 90 days in an 8‐L soil slurry–sequencing batch reactor (SS‐SBR). The purpose was to investigate biological surfactant production and its effect on slurry properties and reactor performance. The SS‐SBR was operated with a 10‐day retention time and a 5‐day cycle. Track studies were performed to monitor the fluctuation in slurry properties during a single cycle. Surfactants were produced faster than they were degraded or sorbed during the first 1.5 days of each cycle, resulting in increasing concentrations from less than the critical micelle concentration (CMC) to 60 times the CMC and an increase in aqueous diesel fuel concentration from 0 to 1.2 g/L. Only after the concentration of surfactants and emulsified diesel fuel began to decrease through biodegradation (after 1.5 days) was foaming observed. Foam thickness increased from 0 mm at 1.5 days to 48 mm on day 3, and then decreased to 0 mm again by the end of the cycle. Surfactants were completely degraded by the end of each cycle. Coinciding profiles of foam thickness and emulsification capacity (i.e., ability to emulsify spiked hydrocarbon) indicate that foaming resulted from the temporary accumulation of free surfactant molecules. Biological surfactant production occurred without cell multiplication during the first day, but was later growth associated. The ratio of oxygen to diesel fuel consumed was 1.7, and the microorganism yield on a chemical oxygen demand basis (YCOD) was 0.43.
pH and Oxidation–Reduction Potential Control Strategy for Optimization of Nitrogen Removal in an Alternating Aerobic–Anoxic System
Authors: Kim Hyunook , Hao Oliver J.
Published: September 2006

An alternating aerobic and anoxic (AAA) system is a continuous‐flow, activated‐sludge process in which the environmental conditions necessary to meet the specific requirements for aerobic nitrification and anoxic denitrification are created. Because of stricter regulations on wastewater effluent and concerns on energy consumption, the process control of the system is now becoming more important. A bench‐scale AAA system with different fixed aeration ratios was operated for more than 8 months to evaluate effects of the total cycle time and aeration ratio on the system performance and to develop a feasible control scheme. With supplemental organic addition, the system shows removal efficiencies of 85 to 90% and 78 to 82% for chemical oxygen demand and total nitrogen, respectively. The oxidation–reduction potential (ORP) and pH profiles indicate that the aerobic cycle can be controlled by a control point (ammonia valley) on the pH profile indicating the end of nitrification and the anoxic cycle controlled by another point (nitrate knee) on the ORP profile signifying the end of denitrification. Thus, a dual control strategy with the pH and ORP control points was used for terminating aerobic–anoxic and initiating anoxic–aerobic cycles in an AAA system. The performance of the online control system is excellent, with a significant energy saving (average aeration ratio, fa = 0.23) as compared to the fixed time systems (fa = 0.33 to approximately 0.5).
Anaerobic Treatment of Condensates: Trial at a Kraft Pulp and Paper Mill
Authors: Dufresne Robert , Liard Alain , Blum Murray S.
Published: September 2006

The Domtar Papers pulp and paper mill in Windsor, Quebec, Canada, investigated the potential for anaerobic treatment of contaminated kraft mill condensates. The objectives of this project were to assess the technical feasibility of replacing the steam stripper with anaerobic treatment, to provide basic information for the design of an anaerobic treatment process for condensates, and to provide information on treated condensate quality for eventual reuse. The project involved extensive chemical characterization of condensates, followed by treatability tests. The tests included laboratory bench‐scale tests and onsite pilot testing using direct feed from the process. Characterization showed that the organic content of the condensates was essentially methanol, as expected, but that foul evaporator condensates had high sulfide contents. It was found that undiluted foul condensates at the Windsor mill are toxic to the anaerobic biomass because of these high concentrations of sulfides. Treatment of combined condensates is possible at an approximate volumetric loading of 10 to 12 g/L·d chemical oxygen demand (COD) with good production of biogas (0.35L/g of COD removed) and excellent methanol removal (better than 95%). The biogas produced is of excellent fuel quality with close to 90% methane, but with a high sulfide content (close to 4%).
Generalized Model of Pentachlorophenol Distribution in Amended Soil–Water Systems
Authors: Fall Cheikh , Chavarie Claude , Chaouki Jamal
Published: September 2006

This paper describes laboratory experiments and subsequent statistical data analysis performed to reevaluate the overall effect of soil characteristics and liquid‐phase composition on the extent of pentachlorophenol (PCP) adsorption in complex soil–water systems. The PCP adsorption isotherms were first generated for eight soils of varying physical and chemical properties. Binding tests were then performed in the presence of different additives (surfactant, oil, etc.) and conditions (temperature and pH) based on a fractional factorial design. Statistical analysis of data showed strong interdependencies among several of the soil parameters, but confirmed that organic carbon content(foc) and pH of the soils were the best predictors of the adsorption constant of PCP (Kd) for nonamended soil–water systems. It was determined that the effect on Kd of a 0.2 unit decrease in soil pH was approximately the same as increasing foc by 1%. From studying the effect of the amendments, two interactions (surfactant–pH and surfactant–oil) and two primary effects (surfactant and oil) have been detected. The effectiveness of the surfactant in decreasing Kd varied depending on the pH and oil content of the soil. A generalized nonlinear model expressing Kd as a function of pH, foc, oil content of soil, and surfactant dose was developed for the range of conditions studied. The proposed model and modeling approach can be adapted to other types of contaminants or variables for specific natural and engineered systems.
Biological Sulfate Reduction Using Molasses as a Carbon Source
Authors: Annachhatre Ajit P. , Suktrakoolvait Saovapak
Published: September 2006

The feasibility of using a laboratory‐scale upflow anaerobic sludge blanket process for sulfate reduction with molasses as a carbon source was demonstrated. Competition between methane‐producing bacteria (MPB) and sulfate‐reducing bacteria (SRB) was influenced by the chemical oxygen demand‐to‐sulfur (COD:S) ratio in the feed. Sulfate removal greater than 80% could be achieved at COD:S greater than 10 when MPB predominated. Activity of MPB and SRB was inhibited at a dissolved sulfide concentration of approximately 200mg/L. Competition between MPB and SRB was intense as the COD:S was reduced from 5 to 2. Further reduction in the COD:S to 0.7 led to the formation of sulfidogenic granules. The COD removal decreased to approximately 30% at a COD:S less than 2 because of accumulation of sulfurous precipitates and the nonbiodegradable portion of molasses in the sludge. Reduced gas production rates further imposed limitations on diffusion of the organic substrate into granules. Sulfidogenic process operation yielded sulfate removal as great as 70% at a COD:S of approximately 3.5.
Size‐Fractionated Alkaline Phosphatase Activity in the Hypereutrophic Villerest Reservoir (Roanne, France)
Authors: Jamet Dominique , Amblard Christian , Devaux Jean
Published: September 2006

Seasonal changes in size‐fractionated alkaline phosphatase activity (APA) were studied in the hypereutrophic Villerest reservoir (Roanne, France) to determine whether the APA showed seasonal variations coupled to abiotic and biotic variables. Samples were collected at different depths from November 1992 to October 1993. The phosphatase activities were measured spectrophotometrically with p nitrophenyl phosphate as the substrate and related to protein concentrations. No correlations were found between APA and soluble reactive phosphorus concentrations during an annual cycle. Free phosphatases were particularly high in the epilimnion (54.5% of total activity was at 5 m) and decreased with depth (4% of total APA at 40 m). The contribution of small microorganisms to APA increased with depth. It was concluded that APA is not a valid quantitative test of the phosphorus status of aquatic microorganisms.
Pre‐Fermentation of a Low‐Strength Meat‐Processing Wastewater in an Upflow Sludge Blanket Reactor
Authors: Roš Milenko , Vrtovšek Janez
Published: September 2006

Pre‐fermentation of low‐strength wastewater from a meat processing facility (at 20 °C) was studied. A laboratory‐scale upflow sludge blanket (USB) reactor was used for the experiments; 10 different operating conditions were tested with regard to the hydraulic residence time (HRT). At HRTs from 0.4 to 2.4 hours, the USB reactor produced effluent with acetate chemical oxygen demand from 82 to 100 mg/L. At HRTs shorter than 0.4 hours and upflow velocities greater than 0.5 m/h, biomass washout was observed. At HRTs longer than 2.4 hours, acetate concentration in the effluent and acetate production efficiency decreased. The transformation of organic nitrogen to ammonia‐nitrogen occurred simultaneously with acetate production. Minimal accumulation of biomass in the USB reactor was observed. Pre‐fermentation of the low‐strength industrial wastewater in the USB reactor could be beneficial for biological nitrogen removal. The produced acetate is directly available for denitrification and the transformed ammonia‐nitrogen is directly available for nitrification in the subsequent wastewater treatment steps.
Design of a Sequencing Batch Reactor Sequence with an Input Load Partition in a Simulation‐Based Experimental Environment
Authors: Hvala Nadja , Zec Mario , Roš Milenko , Strmčnik Stanko
Published: September 2006

A study is presented that considers optimization of a sequencing batch reactor (SBR) operational sequence. Optimization is performed with the aid of a laboratory pilot plant and a process model. The model was included in the study to facilitate a search for optimal operating conditions because performing experiments solely on the pilot plant would be rather extensive, expensive, and time‐consuming. The model used in the study is the well‐known Activated Sludge Model No. 1 with minor modifications. The optimization addresses a split‐feed operating mode with input load partitioned into two parts and with two successions of aerobic–anoxic phases. In the study, the duration of batch phases and the time of the second input addition are optimized so that the desired effluent nitrogen concentration is achieved and the need for external carbon addition in the anoxic phase is reduced or eliminated. When an optimal SBR sequence computed by the model was verified on the pilot plant, better performance of the actual process was also achieved, although some phenomena were observed that were not predicted by the model. Results of the study indicate that the available wastewater treatment plant models, although a simplification of reality, can be usefully applied for process optimization.
Ammonia Inhibition in the Anaerobic Treatment of Fishery Effluents
Authors: Aspé E. , Martí M.C. , Jara A. , Roeckel M.
Published: September 2006

Inhibition of the organic matter consumption rate of a saline and rich proteic effluent by free ammonia was assessed in anaerobic filters at 37 °C. Inhibition of substrate (total organic carbon, TOC) consumption rate by ammonia was fitted by the Luong and noncompetitive models. Calculated kinetic parameters using the Luong model were maximum specific growth rate, μmax = 0.28 day 2−1; average saturation constant, KS = 568 mg TOC/L; Luong inhibition parameter, KNH3 = 1707mg ammonia‐nitrogen (NH3–N)/L; and Luong exponent, γ = 0.283 and the noncompetitive calculated parameters were μmax = 0.26 day 2−1, KS = 703 mg TOC/L, and inhibition parameter, INH3 = 325 mg NH3–N/L. The Luong and noncompetitive models predicted 50% inhibition of the substrate consumption rate at ammonia concentrations of 147 and 325 mg NH3–N/L, respectively, suggesting biomass adaptation to the ammonia concentration (80 mg NH3–N/L as average) at which the anaerobic filters were previously operating. Ammonia formation by anaerobic digestion of fishing effluent would produce a maximum of 65.1 and 58.6% inhibition of the efficiency, predicted by the Luong and noncompetitive models, respectively. Ammonia influence on the digestion steps was determined by comparing fishing effluent with volatile fatty acids as substrates. The noncompetitive model predicted a 50% inhibition of methane production rate at ammonia concentrations of 196.6 and 188.6 mg NH3–N/L for fishing effluent and volatile fatty acids, respectively, suggesting that the methanogenic step is the one most affected by ammonia.