Surfactant enhanced electrokinetic remediation of DDT from soils

Electrokinetic remediation has been investigated extensively as one of the noble technologies in remediation of metal contaminated soils. However, its applications in remediation of organic contaminants have been limited due to low solubilities of organics in water. In addition, most organic contaminants are non-ionic and therefore, they are not mobile under electrical field. The use of surfactants may increase the remediation efficiency by increasing the solubility of organics. Significant fraction of organics associated with soil, can be transferred to micellar phase, which then can be transported toward either cathode or anode, depending on the ionic group of surfactants. In this study, the removal of hydrophobic organic contaminants from a soil using electrokinetic method was investigated in the presence of surfactants. A nonionic surfactant, Tween 80, and an anionic surfactant, SDBS, were used in the experiments. DDT was chosen as the model organic contaminant. Phase distribution studies and column experiments were conducted. It was found that both Tween 80 and SDBS had similar solubilization potentials for DDT. It was also shown that the aqueous DDT mass could reach from 0.01 to 13% of the total mass in the presence of 7500 mg/L of SDBS. No significant movement of DDT was observed when Tween 80 was used in the column experiments. This was attributed to low rates of electroosmotic flows and strong interaction of Tween 80 with the soil. The amount of surfactant was not enough to mobilize DDT significantly in the column studies. On the other hand, electrokinetic transport with SDBS yielded much better results. DDT transport toward the anode within the negatively charged micelles overcame the opposite electrosmotic flow. This was attributed to the lower degree of interaction between the soil and SDBS, and the electrokinetic transport of negatively charged micelles.     

Effects of alcohols, anionic and nonionic surfactants on the reduction of PCE and TCE by zero-valent iron

The effects of surfactants, sodium dodecyl sulfate (SDS) and Triton X-a00 (TX), and alcohols (methanol, ethanol, and propanol) on the dehalogenation of TCE and PCE by zero-valent iron were examined. Surface concentrations of PCE and TCE on the iron were dependent on aqueous surfactant concentrations. At concentrations above the CMC, sorbed halocarbon concentrations declined and concentrations associated with solution phase micelles increased. The anionic surfactant SDS ([SDS] < CMC) did not affect reduction rates, until the CMC was exceeded after which reactivity decreased, possibly due to sequestering of the TCE and PCE in mobile micelles. The nonionic TX showed a mixed effect on reactivity, increasing the PCE reduction rate, but not affecting TCE removal. Production of TCE from PCE increased in the presence of TX. Similar experiments showed that methanol, ethanol, and propanol inhibited reduction of TCE and PCE by metallic iron. Zero-valent iron may be useful in recycling soil washing effluents contaminated with TCE and PCE.     

Enhanced soil flushing of phenanthrene by anionic-nonionic mixed surfactant

Laboratory column experiments were conducted to investigate the performance of anionic-nonionic mixed surfactant, sodium dodecyl sulfate (SDS) with Triton X-100 (TX100), in enhancing phenanthrene flushing for contaminated soil in an aim to improve the efficiency of surfactant remediation technology. The experimental results showed that the sorption of TX100 onto soil was severely restricted in the presence of SDS in batch and column experiments and decreased with the increasing mass fraction of SDS in mixed surfactant solutions; meanwhile the enhanced solubilization of phenanthrene by SDS-TX100 mixed surfactant was greater than that by individual surfactant. These results can be attributed to the formation of mixed surfactant micelles in solution. The column flushing experiments showed that the flushing efficiencies for phenanthrene-contaminated soil by SDS-TX100 mixed surfactants were greater than that by individual surfactant and increased with the increasing mass fraction of SDS in mixed surfactant solutions.     

Degradation of soil-sorbed trichloroethylene by stabilized zero valent iron nanoparticles: effects of sorption, surfactants, and natural organic matter

Zero valent iron (ZVI) nanoparticles have been studied extensively for degradation of chlorinated solvents in the aqueous phase, and have been tested for in-situ remediation of contaminated soil and groundwater. However, little is known about its effectiveness for degrading soil-sorbed contaminants. This work studied reductive dechlorination of trichloroethylene (TCE) sorbed in two model soils (a potting soil and Smith Farm soil) using carboxymethyl cellulose (CMC) stabilized Fe-Pd bimetallic nanoparticles. Effects of sorption, surfactants and dissolved organic matter (DOC) were determined through batch kinetic experiments. While the nanoparticles can effectively degrade soil-sorbed TCE, the TCE degradation rate was strongly limited by desorption kinetics, especially for the potting soil which has a higher organic matter content of 8.2%. Under otherwise identical conditions, ∼44% of TCE sorbed in the potting soil was degraded in 30 h, compared to ∼82% for Smith Farm soil (organic matter content = 0.7%). DOC from the potting soil was found to inhibit TCE degradation. The presence of the extracted SOM at 40 ppm and 350 ppm as TOC reduced the degradation rate by 34% and 67%, respectively. Four prototype surfactants were tested for their effects on TCE desorption and degradation rates, including two anionic surfactants known as SDS (sodium dodecyl sulfate) and SDBS (sodium dodecyl benzene sulfonate), a cationic surfactant hexadecyltrimethylammonium (HDTMA) bromide, and a non-ionic surfactant Tween 80. All four surfactants were observed to enhance TCE desorption at concentrations below or above the critical micelle concentration (cmc), with the anionic surfactant SDS being most effective. Based on the pseudo-first-order reaction rate law, the presence of 1×cmc SDS increased the reaction rate by a factor of 2.5 when the nanoparticles were used for degrading TCE in a water solution. SDS was effective for enhancing degradation of TCE sorbed in Smith Farm soil, the presence of SDS at sub-cmc increased TCE degraded by ∼10%. However, effect of SDS on degradation of TCE in the potting soil was more complex. The presence of SDS at sub-cmc decreased TCE degradation by 5%, but increased degradation by 5% when SDS dosage was raised to 5×cmc. The opposing effects were attributed to combined effects of SDS on TCE desorption and degradation, release of soil organic matter and nanoparticle aggregation. The findings strongly suggest that effect of soil sorption on the effectiveness of Fe-Pd nanoparticles must be taken into account in process design, and soil organic content plays an important role in the overall degradation rate and in the effectiveness of surfactant uses.     

Parameter optimization on compressive strength of steel fiber reinforced high strength concrete

This paper illustrates parameter optimization of compressive strength of steel fiber reinforced high strength concrete (SFRHSC) by statistical design and analysis of experiments. Among several factors affecting the compressive strength, five parameters that maximize all of the responses have been chosen as the most important ones as age of testing, binder type, binder amount, curing type and steel fiber volume fraction. Taguchi analysis techniques have been used to evaluate L₂₇ (3¹³) Taguchi’s orthogonal array experimental design results. Signal to noise ratio transformation and ANOVA have been applied to the results of experiments in Taguchi analysis. The confirmation runs were conducted for the optimal parameter level combination, which is obtained from the results of the above methodologies. The maximum compressive strength has been observed as around 124 MPa. By using the optimal parameter level combination, the direct tensile strength and flexural strength tests have been conducted. The mean values at the age of 28 days are obtained as 7.5 MPa and 13 MPa respectively. In this study, it is clearly demonstrated that all main factors except steel fiber significantly contribute to the compressive strength of steel fiber reinforced high strength concrete, yet age and binder type are the most significant contributors.     

Prediction and optimization of fireproofing properties of intumescent flame retardant coatings using artificial intelligence techniques

A multi-structured architecture of artificial intelligence techniques including artificial neural network (ANN), adaptive neuro-fuzzy-inference-system (ANFIS) and genetic algorithm (GA) were developed to predict and optimize the fireproofing properties of a model intumescent flame retardant coating including ammonium polyphosphate, pentaerythritol, melamine, thermoplastic acrylic resin and liquid hydrocarbon resin. By implementing ANN on heat insulation results of coating samples, prepared based on a L₁₆ orthogonal array, mean fireproofing time (MFPT) values were properly predicted. The predicted data were then proved to be valid through performing closeness examinations on fuzzy inference systems results regarding their experimental counterparts. However, the possible deviations tapped into phenomena like foam detachment and char cracking were alleviated by ANFIS modeling embedded with pertinent fuzzy rules based on the sole and associative practical role of used additives. The contribution of each intumescent coating component on the formulation with optimized fireproofing behavior was then explored using GA modeling. A similar optimization procedure was also conducted using conventional Taguchi experimental design but the GA based optimized intumescent coating was found to exhibit higher MFPT value than that suggested by the Taguchi method.     

Remediation of PCE-contaminated aquifer by an in situ two-layer biobarrier: laboratory batch and column studies

The industrial solvent tetrachloroethylene (PCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to develop an in situ two-layer biobarrier system consisting of an organic-releasing material layer followed by an oxygen-releasing material layer. The organic-releasing material, which contained sludge cakes from a domestic wastewater treatment plant, is able to release biodegradable organics continuously. The oxygen-releasing material, which contained calcium peroxide, is able to release oxygen continuously upon contact with water. The first organic-releasing material layer was to supply organics (primary substrates) to reductively dechlorinate PCE in situ. The second oxygen-releasing material layer was to release oxygen to aerobic biodegrade or cometabolize PCE degradation byproducts from the first anaerobic layer. Batch experiments were conducted to design and identify the components of the organic and oxygen-releasing materials, and evaluate the organic substrate (presented as chemical oxygen demand (COD) equivalent) and oxygen release rates from the organic-releasing material and oxygen-releasing materials, respectively. The observed oxygen and COD release rates were approximately 0.0368 and 0.0416 mg/d/g of material, respectively. A laboratory-scale column experiment was then conducted to evaluate the feasibility of this proposed system for the bioremediation of PCE-contaminated groundwater. This system was performed using a series of continuous-flow glass columns including a soil column, an organic-releasing material column, two consecutive soil columns, and an oxygen-releasing material column, followed by two other consecutive soil columns. Anaerobic acclimated sludges were inoculated in the first four columns, and aerobic acclimated sludges were inoculated in the last three columns to provide microbial consortia for contaminant biodegradation. Simulated PCE-contaminated groundwater with a flow rate of 0.25 L/d was pumped into this system. Effluent samples from each column were analyzed for PCE and its degradation byproducts. Results show that up to 99% of PCE removal efficiency was obtained in this passive system. Thus, the biobarrier treatment scheme has the potential to be developed into an environmentally and economically acceptable remediation technology for the in situ treatment of PCE-contaminated aquifer.     

DOE applied to multi-response optimisation study on performance,combustion and emission characteristics of a VCR diesel engine

There are various parameters which may influence the IC engine performance. The trial and error method is a technique used to identify the best parameters. However, this method demands extensive experimental work and results in a great waste of time and resources. Thus, the design of experiments (DOEs) developed by Taguchi is employed. The multi-responses which need to be maximised are brake thermal efficiency, mechanical efficiency, cylinder pressure and cumulative heat release rate, whereas the responses which are to be minimised are specific fuel consumption, oxides of nitrogen and carbon monoxide. In the present study, an optimised DOE(L9) orthogonal array based on the Taguchi statistical method was formulated and a series of experiments were conducted under controlled supervision by considering three different injection operating pressures (IOPs) (200, 220 and 240 bar) and three different compression ratios (CRs) (16.5, 17.5 and 18.5). The main objective of this paper is to find the best suited IOP and CR values which obtain higher performance, better combustion and lower emissions.     

Simulation-based process optimization for surfactant-enhanced aquifer remediation at heterogeneous DNAPL-contaminated sites

Widespread use of dense non-aqueous phase liquids (DNAPLs) such as TCE and PCE has resulted in contamination of enormous valuable groundwater resources and become high-priority environmental problems. However, experiences from the past decades have demonstrated that DNAPL-contaminated sites were difficult to investigate and challenging to remediate. In this study, a simulation-based process optimization system was developed through integrating a multidimensional simulator, a multivariate statistical tool and an optimization model within a general framework for supporting decisions of surfactant-enhanced aquifer remediation (SEAR). A 3D multiphase and multi-component subsurface model was first provided to simulate SEAR process; dual-response surface models were then established to build a bridge between remediation actions and system performance; a nonlinear optimization model was then formulated for identifying optimal operating conditions for SEAR operations. The results in simulating a typical PCE spill event and the associated SEAR remediation operations in a heterogeneous subsurface indicated that SEAR would be capable of cleaning up the contaminated aquifer with improved efficiencies and cost-effectiveness compared with direct pump-and-treat actions. The regression-analysis results demonstrated that the proposed dual-response surface models were able to predict system responses under given operating conditions. The optimization results demonstrated that the developed simulation-optimization approach was effective in seeking cost-effective SEAR strategies for DNAPL-contaminated sites. With the developed method, optimum operation conditions under various environmental and economic considerations could be compiled into a database that would supports further studies of on-site process-control with injection and extraction rates being the main control variables.     

Derivation of risk based wipe surface screening levels for industrial scenarios

The environmental characterization of building interiors and other surfaces has generally been performed with wipe-sampling because it is a non-destructive technique. There is no consensus, however, as to the interpretation of the results of wipe-sampling. Specifically, there is not a standardized method to determine if chemicals found at sampled levels pose a threat to human health. A methodology was developed, based on acceptable health risk levels, to derive screening levels for evaluating wipe-sampling results pertaining to industrial scenarios. The methodology was based on the United States Environmental Protection Agency (USEPA) Region IX Preliminary Remediation Goal (PRG) approach; a multi-exposure methodology commonly used for evaluating soil concentrations. PRGs are the USEPA determined health based goals for soil preliminary remediation efforts. Probabilistic techniques were used to conduct a sensitivity analysis of the methodology to determine which variables drive the ultimate screening levels. Discrete values were then selected based on standard industrial scenarios common to the US Army. The wipe surface screening levels reported are for use as preliminary guidelines which help to determine whether further sampling or cleanup are necessary. The levels are not meant as cleanup or compliance criteria.     

Dechlorination of tetrachloroethylene by palladized iron in the presence of humic acid

The dechlorination of tetrachloroethylene (PCE) by palladized irons in the presence of humic acid was investigated to understand the feasibility of using Pd/Fe for the in situ remediation of contaminated groundwater. Untreated zerovalent iron (ZVI) was amended with Pd(II) ions to form palladized irons. X-ray photoelectron spectroscopy showed that Pd(II) was completely reduced to metallic Pd on the surface of ZVI. PCE was catalytically dechlorinated via beta-elimination to ethane and ethylene by palladized irons. The carbon mass balances were in the range of 78--98%. The dechlorination followed the pseudo first-order rate equation and the normalized surface reaction rate constant (k(sa)) for PCE dechlorination was 33.47+/-7.21 L/m(2)h in the absence of humic acid. Humic acid competed the reactive sites on the palladized irons with PCE, and thus lowered the dechlorination efficiency and rate of PCE. After 24h of equilibrium between humic acid and palladized irons prior to the injection of PCE, however, the efficiency and rate of PCE dechlorination could increase with increasing concentrations of humic acid. Addition of quinones having low redox potentials including AQDS, lawsone and hydroquinone also enhanced the dechlorination efficiency of PCE after 24h, depicting that humic acids serve as the electron shuttles to effectively transfer electrons and to accelerate the dechlorination efficiency and rate of PCE.     

Solubilization and desorption of methyl-parathion from porous media: a comparison of hydroxypropyl-beta-cyclodextrin and two nonionic surfactants

The removal of hydrophobic organic compounds (HOCs) from soils and sediments by water flushing is often constrained by sorption interactions. The development of improved methods for remediation of contaminated soils has emerged as a significant environmental priority. Increasing HOCs desorption and mobility in soil using surfactants is considered to be one of the most suitable on-site techniques for soil remediation. A major concern regarding the use of surfactants for environmental restoration is the potential loss to the environment of large amounts of surfactant through sorption of nonionic types. A study was conducted to investigate whether surfactants and cyclodextrins can be used to enhance the transport of methyl-parathion in a contaminated soil. At aqueous concentrations of surfactants tested, the proportion of each surfactant sorbed to the soil increased with increasing surfactant concentrations. The maximal adsorbed mass is about 5,130 and 14,200 microg/g for Brij 35 and Tween 80, respectively. In the case of nonionic surfactants, sorption attenuates surfactant effectiveness by increasing the organic carbon content of the soil matrix and retarding transport of methyl-parathion through batch and soil column experiments. However, in contrast with the surfactants, hydroxypropyl-beta-cyclodextrin (HPCD) does not interact with the soil tested. The nonreactive nature of cyclodextrins, combined with its large affinity for HOCs suggests that it should have an advantage versus adsorbing surfactants for decreasing HOC distribution coefficients in subsurface systems.     

Overview of lead remediation effectiveness

A Symposium on Lead Remediation Effectiveness, sponsored by the US Environmental Protection Agency, was held at Coeur d'Alene, Idaho, USA from 22-25 May, 2000. International participants from various levels of government, educational institutions, industry, and community representatives presented papers and posters on themes that ranged from engineering practices through community participation in the remediation processes. The papers in this volume represent a global distribution of sites, especially those outside the USA. In providing an overview of the symposium and the theme of Lead Remediation Effectiveness we have drawn on information from some presentations at the symposium, besides those described in this volume.     

Influence of injection parameters on NOx emission from biodiesel powered diesel engine by Taguchi technique

ABSTRACT

This paper studies the effect of injection parameters on reduction of nitrogen oxide (NOx) emission in a multicylinder diesel engine using Taguchi orthogonal array. To obtain good performance in experiments, we have employed L9 Taguchi array on mixed level fractional design. The engine is fuelled with corn oil methyl ester biodiesel. From the experiment validation, it is found that the urea concentration and the spray angle reduce the production of NOx in the diesel engine. However, it is found that the mixing length does not support the diminution of NOx emission effectively. Additional, ANOVA outcome also reveals that the urea flow rate, urea concentration and the spray angle plays an imperative role in the reduction of NOx emission. The values of the experiments are in accordance with the Taguchi technique.     

Investigating mix proportions of high strength self compacting concrete by using Taguchi method

In this study, mix proportion parameters of high strength self compacting concrete (HSSCC) are analyzed by using the Taguchi’s experiment design methodology for optimal design. For that purpose, mixtures are designed in a L₁₈ orthogonal array with six factors, namely, “water/cementitious material (W/C) ratio”, “water content (W)”, “fine aggregate to total aggregate (s/a) percent”, “fly ash content (FA)”, “air entraining agent (AE) content”, and “superplasticizer content (SP)”. The mixtures are extensively tested, both in fresh and hardened states and to meet all of the practical and technical requirements of HSSCC. The experimental results are analyzed by using the Taguchi experimental design methodology. The best possible levels for mix proportions are determined for maximization of ultrasonic pulse velocity (UPV), compressive strength, splitting tensile strength and for the minimization of air content, water permeability, and water absorption values.     

Grundwasser-Zirkulations-Brunnen (GZB) zur In-situ-Grundwassersanierung

In recent years experimental investigations regarding enhanced remediation of contaminated aquifers by employing vertical circulation flow systems were carried out at the Institute for Hydromechanics (IfH), University of Karlsruhe. These investigations were focused on large scale three-dimensional remediation experiments with a groundwater circulation well (GZB) at field-like conditions in the research facility VEGAS, University of Stuttgart. Small scale laboratory experiments in columns and a two-dimensional flume at the IfH as well as field experiments completed the multiple-scale investigations. The experimental results on different scales showed the dominance of the mass transfer processes on the in situ remediation of a contamination source and their dependence on the flushing intensity. The remediation progress could be explained and also predicted by the mass removal coefficient. The GZB is a robust and well controllable technology, whose operation could be adapted well to natural aquifer conditions and the physical-chemical properties of the contaminants. Developing different efficiency numbers results of the experiments and generally remediation variants could be evaluated due to their effect and expenditure.     

Experimental investigation of the fire extinguishing capability of ferrocene-containing water mist

This study focuses on the fire-suppression capabilities and corrosive properties of ferrocene dispersions. The motivation behind the present study was to develop a high-performance, phosphorus-free fire suppressant. Aqueous dispersions containing micron-sized ferrocene particles and surfactants were prepared using sonication techniques. In this study, Triton X-100 (TX), Noigen TDS-80 (NT), Tween 60 (T60), and Tween 80 (T80) were used as surfactants. Suppression experiments involving pool fires clearly indicated that aqueous ferrocene dispersions containing TX and micron-sized ferrocene with a d₅₀=16.9 μm exhibit shorter extinguishing times than a conventional wet chemical. Corrosion trials using steel plates immersed in ferrocene dispersions containing TX confirmed that there was no pitting corrosion, implying that ferrocene dispersions containing TX do not present a corrosion risk.     

Impact of Trucks on Signalized Intersection Capacity

Abstract: The most common method used for the analysis of signalized intersections in the United States is contained in the Highway Capacity Manual (HCM). In this method, the base saturation flow rate of the signalized intersection is defined in units of passenger cars per hour green per lane (pc/hg/ln). To account for the presence of large trucks in the traffic stream, the HCM includes a Passenger Car Equivalency (PCE) value. In the current edition of the HCM, a PCE value of 2.0 is applied for all large trucks, with no distinction between different sizes of trucks. The HCM also recommends a single value of 2.0 seconds for startup lost time, regardless of queue composition. Many transportation professionals have questioned the validity of the PCE value and startup lost time recommended by the HCM. They are concerned that the impact of trucks at signalized intersections is being underestimated. If this is the case, then capacity is being overestimated and intersections are not being adequately designed. The objective of this study was to identify appropriate truck PCE values and a relationship for startup lost time as a function of truck percentage in the traffic stream. To accomplish this objective, a custom simulation tool was developed based on the modified Pitt car‐following model, calibrated with field data, and applied to a comprehensive experimental design. The PCE values determined from this study are 1.8, 2.2, and 2.8 for small, medium, and large trucks, respectively. A model for estimating startup lost time based on the same small, medium, and large truck classifications was also developed.     

Reactor design and kinetics study of 4,4'-dichlorobiphenyl photodecay in surfactant solution by using a photosensitizer and hydrogen source

The system design based on the photodegradation kinetics of 4,4'-dichlorobiphenyl (4,4'-DCB) in surfactant solution with the aid of solvents (acetone and/or squalane) has been studied. Organic solvents acetone and squalane were added as a photosensitizer and a hydrogen source, respectively, to achieve better photolysis performance. The quantum yield of 4,4'-DCB photodecay in Tween 80 micellar solution in the presence of added acetone was increased from 0.032 to 0.043 at its optimal condition. Acetone was shown to be an effective photosensitizer at low concentration, but an overdose would quench the reaction. Furthermore, the addition of squalane could further promote the photodechlorination of 4,4'-DCB in the Tween 80/acetone solutions for an additional 59% of rate improvement. However, an overdose of either solvent was found to cause UV light attenuation and to reduce the observed quantum yield. This effect has been justified and quantified in this study by a proposed light attenuation model, which has also been incorporated into the kinetic equation so that the resulted formula can be used to design the UV reactors for water and wastewater treatment works.     

Optimisation of intake parameters for diesel engine fuelled with diesel-tamarind seed methyl ester biodiesel blend by Taguchi method

ABSTRACT

The present experimental work is focused on the use of Taguchi method to evaluate the optimum intake parameters to obtain the enhanced engine performance characteristics of diesel engine fuelled with TSME 20 (80% diesel and 20% Tamarind seed methyl ester) biodiesel blend. Injection pressure (IP), injection timing (IT) and exhaust gas recirculation (EGR) were considered as input parameters and each parameter at three levels. Brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), hydrocarbon (HC), oxides of nitrogen (NO_X) and smoke opacity (SO) were chosen as performance parameters. In this study, Taguchi L₂₇ orthogonal array (OA) was considered. Taguchi method is highly effective when dealing with responses influenced by several parameters; it significantly minimises the number of tests needed to model and optimise the responses influenced by various input parameters. In addition, an ANOVA test was conducted for the performance parameters to evaluate individual input parameters and its percentage contribution. It was found that IT has most significant on BTE; NO_X and smoke emission was highly influenced by EGR rate, followed by IT and IP.