摘要:

Batch shaker‐flask experiments using a consortium of sewage microorganisms were conducted to study the aerobic biodegradation of a plant‐based natural surfactant (Ritha) and four anionic / nonionic commercial surfactants. Foaming potential, foam decay, microbial growth and ultimate biodegradation (mineralization) of natural surfactant were compared to those of synthetic surfactants, namely anionic sodium dodecylbenzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS), and nonionic alcohol ethoxylate Tergitol 15‐S‐12 and Witconol SN‐90. The natural surfactant showed the lowest foaming potential among the selected surfactants (SDBS > SDS > Tergitol > Witconol > Ritha). The natural surfactant also performed better than commercial surfactants in terms of biodegradability at concentrations above critical micelle concentrations (supra‐CMCs). However, surface‐active components resisted biodegradation and foams from the natural surfactant were more persistent than SDS, Tergitol, and Witconol. Concurrent with an increase in initial surfactant concentration to supra‐CMCs, microbial growth rate (μ) was significantly increased for the natural surfactant, whereas a decreased growth rate was noted for some synthetic surfactants at supra‐CMC. Due to the fact that synthetic surfactants have considerable losses via precipitation / adsorption or phase change, toxicity to microorganisms, and have lowered biodegradability at supra‐CMC, natural surfactant may be promising in soil washing and flushing for the clean‐up of contaminated soils.

ISSN:1093-4529    

DOI:10.1080/10934529809376787

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A method for the determination of five halogenated ether priority pollutants using time‐weighted‐average concentrations is described. These compounds permeate through a silicone polycarbonate membrane and are trapped onto a Tenax TA™ adsorbent. Compounds of interest are solvent desorbed by acetone, followed by separation and quantitation by gas chromatography‐mass spectrometry (GC‐MS). A linear relationship was found between the amount of halogenated ether trapped onto the Tenax adsorbent and the product of the concentration of ether in solution and the exposure time. Concentrations ranged from 0.04 to 7.2 mg/L for a twenty‐four hour exposure. The temperature of solution was found to alter the pollutant permeation rate. This sampler offers the advantages of providing time‐weighted‐average concentrations with a relatively simple sampling method.

ISSN:1093-4529    

DOI:10.1080/10934529809376788

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

During the delineation of a recent well‐documented subsurface hydrocarbon spill originating within a tank farm in Virginia, measurement of vapor phase hydrocarbon, VPH, concentrations were gathered during the placement of monitor wells, and subsequent concentrations were measured using hand driven as well as hydraulic press driven soil probes.

ISSN:1093-4529    

DOI:10.1080/10934529809376789

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Data from a multimedia survey on fluoride contamination in the vicinity of an aluminum plant are presented and applied along with multimedia‐based simulation modeling techniques in order to investigate the long term response of fluoride in soils and seasonal trends of accumulation by olive trees. Results from the modeling analysis are in fair agreement with observed data. Soils show elevated fluoride concentrations that decrease with distance from the source and depth below the surface. Fluoride is largely retained in the upper 5 cm of soil. Sensitivity analyses showed that accumulation of fluoride is dominated by atmospheric loading. The strong retention of fluoride in the calcareous soils of the area with high organic matter and clay content, is also an important factor for controlling its accumulation in these soils. In the case of olive tree leaves, direct deposition is the main source for fluoride accumulation during the year; washoff is the dominant sink during the wet months; during dry months, however, physical processes such as wind removal, growth dilution, etc appear to be the dominant sinks controlling fluoride accumulation in vegetation. In general, the modeling effort provides a plausible description of the long term response of fluoride in soils and also of the seasonal dynamics of its accumulation in vegetation.

ISSN:1093-4529    

DOI:10.1080/10934529809376790

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Wide‐angle hydrocyclone tests were conducted to separate fine (‐150 μm) particles based on differences in particle density. Mixtures of ferrosilicon (FeSi) and quartz or lead and soil of similar size ranges were separated in a 25.4 mm diameter hydrocyclone under various test conditions. Separations were made in dense‐medium suspensions of fine magnetite and water to improve the overall separation efficiency compared to water‐only separations. For the FeSi/quartz mixture, when the suspension relative density was raised to 1.4, FeSi recoveries exceeding 89% with quartz recoveries over 90% were obtained in a single pass through the hydrocyclone. For the lead/soil mixture, lead recoveries exceeding 97% with soil recoveries over 95% were possible at a suspension relative density of 1.3.

ISSN:1093-4529    

DOI:10.1080/10934529809376791

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The efficiency of electro‐coagulation as a turbidity removal process has been investigated using bentonite as a turbidity source. The influence of certain operational parameters such as current input, contact time, electrolyte concentration, and initial turbidity on the coagulation efficiency were studied. The process was found to achieve excellent turbidity removals. The lowest residual turbidities were 0.5 and 0.75 NTU for the samples with initial turbidities of 112 and 52 NTU, respectively. This was obtained at a current of 0.5 A, a contact time of 5 minutes, and a calculated dissolved iron concentration of 10.8 mg/l. At a constant current of 0.5 A, a reduction in the contact time from 5 to 2 minutes in the case of turbidity level 1 (52 NTU) and from 5 to 1 minute in the case of turbidity level 2 (112 NTU) resulted in better turbidity removals. The optimal operational parameters for turbidity level 1 are a current of 0.5 A, a contact time of 2 minutes and an NaCl concentration of 2 g/l resulting in a calculated amount of iron generated of 4.3 mg/1. However, for the case of turbidity level 2, the optimal values are a current of 0.5 A, a contact time of 1 minute and an NaCl concentration of 5 g/l with a calculated iron amount generated of 2.2 mg/l.

ISSN:1093-4529    

DOI:10.1080/10934529809376792

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Recycling of diatomaceous earth (DE) in a drinking water filtration system was investigated. The plant consists of four stages of cyclones plus a scavenger system for the recover of spent DE.Cryptosporidium, oocysts were seeded into the raw water from the DE pilot plant, at a concentration of 103oocysts per liter. Samples were taken prior to injection from the seeded stock, down stream from the point of injection in the influent stream and from the overflow post‐cyclone separation. In the DE recovery plant the percentage of oocysts detected in the overflow stream (that volume of water and spent DE, which will not be recovered or reused) ranged from 27 to 79% depending on the number of cyclones present. It appears that while 91% of the oocysts were separated from the DE that was slated for recovery. The levels of this organism in the spent DE over time or after a large concentration spike in the influent, could present a problem if the DE is to be reused as body feed without some type of pretreatment to inactivate this organism.

ISSN:1093-4529    

DOI:10.1080/10934529809376793

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper presents a pharmacokinetic modeling of inorganic arsenic deposition in rodents for a short‐term exposure by the oral route. The work involves (i) the development of a physiologically‐based pharmacokinetic (PBPK) model, and (ii) the uncertainty analysis of the model. Efforts on the development of a PBPK model are directed towards the prediction of the kinetic behavior of inorganic arsenic in the body, including tissue and blood concentrations, and especially, the urinary excretion of arsenic and its methylated metabolites. However, large uncertainties are associated with predictions from the model. Some of this uncertainties derives from the uncertainties about model inputs. In order to assess how model predictions are affected by the uncertainties of model inputs, the study performs a quantative uncertainty analysis in conjuction with the developed PBPK model. This approach provides a clear advantage in understanding the kinetic behavior of a chemical and its metabolites in the body for assessing risks associated with inorganic arsenic exposures.

ISSN:1093-4529    

DOI:10.1080/10934529809376794

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper outlines the test procedure and describes how the alternative pad performance is affected by pad thickness and pad materials in the thermal environmental control applications. Many experimental pads were tested including one made of nonwoven fabric perforated pad and one made of coir fiber material. A wind tunnel experiment was performed to obtain equations for heat and mass transfer coefficients for the evaporative process through various thickness of alternative pad media. Heat and mass transfer coefficients are nondimensionalized and curve fitted to yield the working equations: (1) coir fiber pad:hH/ hM=, 0.32paCPaLe,2/3(Les/Le,)1/4, and (2) nonwoven fabric pad:hH/ hM, = 1.899paCPaLe,2/3(Les/ Le,)1/4; wherehH, is heat transfer coefficient,hM, is mass transfer coefficient,pa, is air density,Cpa, is specific heat of air,Le, is Lewis number, andLes,, is Lewis number at water temperature. A determination for cooling efficiency in a wind tunnel system is also developed to relate efficiency, face velocity, and static pressure drop across pads. For a 15 cm pad, static pressure drops across the perforated pad and cooling efficiencies varied from 48 to 108 Pa and 81.19 to 81.89%, while 60 to 130 Pa and 89.69 and 92.86% for coir fiber material pads respectively under operating air velocities of 2.0 to 3.0 m/s.

ISSN:1093-4529    

DOI:10.1080/10934529809376795

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The quantitative prediction abilities of three competing multivariate calibration methods for concentration analysis of FTIR Spectra are compared. The calibration methods compared include classical least squares method (CLS), Kaiman filter method (KFM) and partial least squares method (PLS). The mixtures of seven air toxic organic compounds whose FTIR Spectra are known to seriously overlap were chosen to evaluate the preceding calibration methods. The concentrations of the seven air toxic organic compounds mixtures varied from 1 to 50 or 100 ppm. A relatively simple model involving the mean prediction error (MPE) and mean relative error (MRE) was developed for estimating each calibration method mentioned above. The results showed that PLS is the best calibration method among the three methods examined for a given real spectral data set while CLS and KFM had no obvious difference in the performance. Better predictable results were obtained when the measurement is taken at a series of equispaced wavenumbers of the absorption band for the desired component.

ISSN:1093-4529    

DOI:10.1080/10934529809376796

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor