Laboratory Bench-scale Testing Research Articles

Analyses of intermediate products during degradation of pyrene in soil by hemoglobin-catalyzed reaction

Hemoglobin (Hb) is a member of heme-protein that can perform catalytic non-specific chain reaction in the presence of hydrogen peroxide (H2O2). Catalytic ability of Hb to degrade pyrene was demonstrated using soil contaminated with 14C pyrene and 10 mg pyrene /kg soil. The composition of soil was similar to previously used soil except that it had lower organic carbon content. Bench scale laboratory tests were conducted in the presence of buffer only, H2O2 only, or Hb with H2O2 for 24 h. After 24 h reaction, 0.1 and 1.3% of 14C pyrene in contaminated soil were mineralized with H2O2 only or Hb plus H2O2. No mineralization to 14CO2 was detected with buffer only. Approximately 12.2% of pyrene was degraded in the presence of H2O2 only while 44.0% of pyrene was degraded in the presence of Hb plus H2O2 during 24 h of catalytic reaction. When degradation intermediate products were examined, two chemicals were observed in the presence of H2O2 only while 25 chemicals were found in the presence of Hb plus H2O2. While most degradation products were simple hydrocarbons, four of the 27 chemicals had aromatic rings. However, none of these four chemicals was structurally related to pyrene. These results suggest that Hb catalytic system could be used to treat pyrene-contaminated soil as an efficient and speedy remediation technology. In addition, intermediate products generated by this system are not greatly affected by composition change in soil organic matter content.

Degradation of Pyrene Contaminated Soil with Spiked 14C Pyrene by Hemoglobin Catalysis

Hemoglobin (Hb) is a member of the hemeprotein family that undergoes non-specific catalytic chain reactions in the presence of hydrogen peroxide (H2O2). The catalytic ability of Hb to degrade the carcinogenic polycyclic aromatic hydrocarbon pyrene was demonstrated using soil contaminated with 14C pyrene. Three bench-scale laboratory tests were performed using 14C pyrene in the presence of a buffer, H2O2, and a combination of Hb and H2O2. The initial pyrene concentration of the contaminated soil was set to 11 mg/kg, with 5,500,000 dpm of 14C pyrene. After a catalytic reaction for 24 h, the results showed that 17% of pyrene was degraded by H2O2, 38% of pyrene was degraded by Hb in combination with H2O2, and 0.13 and 1.2% of 14C pyrene were mineralized by H2O2 and Hb in combination with H2O2, respectively. An analysis of the products from the reaction involving Hb in combination with H2O2 revealed that 15.9% of the 14C intermediates in the acetonitrile fraction were polar products. After the catalytic reaction, 21 intermediate compounds were found via fraction analysis. The results suggested that Hb catalysis could be used to treat pyrene-contaminated soil as a novel catalytic technology for the remediation of hazardous materials in soil.

NDMA formation during drinking water treatment: A multivariate analysis of factors influencing formation

The formation of the carcinogen N-nitrosodimethylamine (NDMA) during drinking water treatment has raised concerns in the drinking water industry. Many bench-scale laboratory tests and pilot plant studies have been completed to try to determine which factors during water treatment increase or decrease the amount of NDMA formed in drinking water. This study used data from over 20 drinking water treatment plants in the United States and Canada to determine which factors are most highly correlated with the NDMA concentration in delivered water using a mixed effects model with a random intercept. This type of analysis has not been used previously with trihalomethane (THM) models due to the fact that those studies did not sample such a large number and range of plants as was done in this NDMA study.Ultraviolet absorbance at 254 nm (UV254) in the plant influent and pre-chlorination time used at the plant were highly correlated in all models with NDMA concentration in finished water as well as the percentage change between NDMA formation potential in the plant influent and actual formation in the finished water. Specifically, an increase in UV254 absorbance in a model was associated with an increase in NDMA and an increase in pre-chlorination time in a model was associated with a decrease in NDMA. Other water quality parameters including sucralose concentration in the plant influent, polyDADMAC polymer dose, pH, and chlorine-to-ammonia weight ratio used in the plant were also correlated with NDMA concentration in the distribution system. Lastly, NDMA precursor loading was correlated with the use of polyDADMAC (where precursors were added) and the use of ozone and granular activated carbon (GAC) treatment (where precursors were removed).

Lime Stabilization of Soils Underlying a Salt Evaporation Pond: A Laboratory Study

The purpose of this article is to investigate a possible use of lime for the stabilization of base soils underlying salt evaporation ponds in Çamaltı Solar Marine Salt Plant. The plant is located on the old Gediz River Delta, on the north shore of the Izmir Bay-Turkey, where alluvial deltaic soft marine sediments constitute the local soil condition. The low bearing capacity of the pond base soils results in some problems on the mechanical harvest of the solar salt. Therefore, stabilization was taken into consideration for improving the productivity of the salt plant. For this purpose, bench-scale laboratory tests were performed on the specimens that had been sampled from the bases of the salt evaporation pond to investigate the influence of lime on the unconfined compressive strength (UCS) of these marine sediments. By interpreting the pH test results and consistency limits of the lime stabilized soils, optimum lime content was determined as 8%. The verification of the long-term pozzolanic reactions for the optimum lime content was conducted by performing UCS tests with up to six months curing periods, along with the microstructural analysis through X-ray diffraction analysis (XRD) and a scanning electron microscope (SEM). Long-term tests revealed that the optimum lime content successfully sustained the required pozzolanic reactions, and a strength gain of 500% was achieved for a six-month curing period.

OIL RECOVERY WITH NOVEL SKIMMER SURFACES UNDER COLD CLIMATE CONDITIONS

ABSTRACT Increasing oil exploration, production and transport in Arctic waters will increase the risk of an oil spill occurring in cold and ice-infested waters. The mechanical oil spill recovery equipment currently used in warmer waters was not designed to collect much more viscous oils, or oil-ice mixtures. The presence of ice crystals in oil emulsions affects the adhesion processes between an oil slick and the surface of an oleophilic skimmer and prevents oil from being efficiently recovered. Novel drum skimmer surface geometry and materials, tailored to the conditions present under cold climates, are expected to significantly increase the rate of oil recovery, reducing cost and risk. The objective of this project was to perform a comprehensive analysis of the adhesion between oil or ice-in-oil mixtures and various surface patterns and materials, under cold climate conditions. This knowledge was then applied to improve existing mechanical response equipment so that it can be applied efficiently under these conditions. The novel recovery surfaces that proved to increase the recovery efficiency of a drum skimmer up to two times in warm waters were also successful in cold climate conditions. In the first phase of the project, laboratory bench-scale tests of different surface materials were conducted, to determine contact angle and amount of oil adhered at sub-freezing conditions, with and without ice. It became clear that the physicochemical property that would be most significantly influence by cold climate conditions would be viscosity, and that the presence of ice would also have an important effect on viscosity, although to a varying degree depending on the initial oil viscosity. Neoprene was the best material surface, of those tested here, for adhering oil even under oil/ice conditions. Based on the results of the laboratory tests at subfreezing conditions, we selected materials and surface patterns with the highest oil recovery potential under cold climate conditions, and performed field scale oil spill recovery tests with three different oils at the U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL), located in Hanover, NH. This provided valuable information about the correlation between the laboratory tests and full scale experiments. It also demonstrated the potential of the skimmer modifications under conditions similar to response operations. The field tests were very successful, with high rates of oil recovery under cold climates, with and without ice present. However, the presence of ice does decrease the overall rate of oil recovery to some extent. The outcome of this project advanced our understanding of the adhesion of oil and oil emulsions (water containing and ice-containing) to recovery surface material under cold climate conditions. This research will facilitate selection of materials and surface configurations that result in significantly higher recovery rates of oil spills in cold and ice-infested waters. This will ultimately lead to a faster oil spill cleanup and greater protection of natural resources.

Bench and full-scale studies for odor control from lime stabilized biosolids: The effect of mixing on odor generation

Lime stabilization is a means to raise the pH of biosolids to meet specific pathogen requirements. Along with controlling the microbial growth, lime stabilization reduces the potential for offensive odors. Lime stabilized biosolids can be beneficially used as a soil amendment and also for land reclamation. However, if biosolids are not properly incorporated with the lime, there is a potential for microbial growth, which consequently leads to the emanation of offensive odors and growth of pathogens. Proper mixing was found to be an important factor for the reduction of offensive odors in biosolids treatment. To better understand the effects of mixing on odorous products, bench-scale and full-scale tests were conducted to assess the lime stabilization process and investigate mixing quality at a wastewater treatment plant to help reduce odors associated with known odorants. The results of 4-week laboratory bench-scale tests showed that mixing had the largest effect on odor. The hedonic tone test of the control samples with poor mixing showed a hedonic tone of −2.9 initially and then dropped to −7.3 on Day 29. The hedonic tone of the 3.5%, 7%, and 10% lime mixed biosolids had similar hedonic tones (−2.8 to −2.5) on Day 1 and slightly fluctuated over time and ended at −1.6 to −2.7 on Day 29, which was less odorous than the controls. The control sample with poor mixing showed a rapid pH drop from 12.1 on Day 1 to 8.4 on Day 7. The pH of the control sample was considerably lower than the mixed samples and ended up on Day 28 with a pH of 8.0. The pH of the 7% and 10% samples were relatively stable throughout the 4-week period with a pH still higher than 12 on Day 28. The biosolids with better mixing had a less offensive odor and weaker odor strength than the controls collected at the plant with poor mixing. The lime stabilization process in the wastewater treatment plant was modified in a full-scale study by prolonging the mixing time. The samples collected from the modified process had a less offensive odor and weaker odor strength than the controls from the original lime addition process with short mixing time. The hedonic tone of the two biosolid samples taken from the modified process (−2.5 to −3.0) was less negative than the controls (−3.5 to −4.5). The pH of the biosolid samples taken from the modified process was still above 12 on Day 21, while the pH notably drooped in the controls from 11 on Day 1 to 7.5–8.5 on Day 7. In addition, headspace analysis from both bench and full-scale tests indicated that the sulfur compounds were more prominent in poorly mixed samples than well mixed samples.

Passive Flux Meter Measurement of Water and Nutrient Flux in Saturated Porous Media: Bench‐Scale Laboratory Tests

The passive nutrient flux meter (PNFM) is introduced for simultaneous measurement of both water and nutrient flux through saturated porous media. The PNFM comprises a porous sorbent pre-equilibrated with a suite of alcohol tracers, which have different partitioning coefficients. Water flux was estimated based on the loss of loaded resident tracers during deployment, while nutrient flux was quantified based on the nutrient solute mass captured on the sorbent. An anionic resin, Lewatit 6328 A, was used as a permeable sorbent and phosphate (PO4(3-)) was the nutrient studied. The phosphate sorption capacity of the resin was measured in batch equilibration tests as 56 mg PO4(3-) g(-1), which was determined to be adequate capacity to retain PO4(3-) loads intercepted over typical PNFM deployment periods in most natural systems. The PNFM design was validated with bench-scale laboratory tests for a range of 9.8 to 28.3 cm d(-1) Darcy velocities and 6 to 43 h deployment durations. Nutrient and water fluxes measured by the PNFM averaged within 6 and 12% of the applied values, respectively, indicating that the PNFM shows promise as a tool for simultaneous measurement of water and nutrient fluxes.

Remediation of PAH-contaminated sediments by chemical oxidation

The aim of this experimental investigation was to assess the feasibility of using chemical oxidation to degrade sorbed polycyclic aromatic hydrocarbons (PAHs) in case of old date sediment contamination. For this purpose several bench scale laboratory tests were performed, with the following liquid reactants: hydrogen peroxide, modified Fenton's reagent, activated sodium persulfate, potassium permanganate, as well as a combination of potassium permanganate and hydrogen peroxide, and a combination of activated sodium persulfate and hydrogen peroxide. The main target of the study was to find out what liquid oxidant was more effective in reducing the pollutant content and to assess the optimal reactant doses. The initial total PAH concentration in sediment samples was about 2800 mg/kg SS (light PAHs about 1600 mg/kg SS, heavy PAHs about 1200 mg/kg SS) and a 95% degradation was required to meet the remediation goals. Based on the results of this study, chemical oxidation proved to be an effective remediation technology, amenably applicable for the ex situ remediation of the sediments of concern. Different reactants resulted however in different removal efficiencies. The best remediation performances were achieved with the use of modified Fenton's reagent, hydrogen peroxide and potassium permanganate, with oxidant dosages about 100 mmols per 30 g sediment sample. In all these cases the residual heavy PAH concentration in the treated samples was below 100 mg/kg SS. The optimal oxidant dosages determined in this study were quite high, as sorbed PAH mineralization requires very vigorous oxidation conditions, especially for soils and sediments with high organic matter content. The results indicated that the optimal oxidant dose must be carefully determined under site-specific conditions. In fact, if the oxidation conditions are not strong enough, the reactants cannot be able to attack the most recalcitrant compounds, while also too high oxidant doses can result in a decrease in the oxidation efficiency, thus failing in meeting the remediation goals.

Bench- and field-scale evaluation of chromium and cadmium extraction by electrokinetics

The results of bench-scale laboratory tests and in situ, pilot-scale demonstration of electrokinetic extraction of chromium and cadmium from contaminated soil are presented. The laboratory tests were conducted using 10 cm long samples under current density of 5 A/m 2 for 1200 h. Tests were conducted with and without citric acid amendment at the cathode. The results showed that citric acid improved extraction, especially in the sections near the cathode. However, processing was not enough to result in complete cleanup. The field demo was conducted at the Naval Air Weapon Station (NAWS), Point Mugu, California. Three cathodes were centered between six anodes. The anode–cathode spacing was 4.45 m (15 ft). Constant voltage of 60 V (∼13 V/m) was applied for 20 days and then was reduced to 45 V (10 V/m) for 6 months. Citric acid was used to maintain the cathode pH at 4. After 6 months of treatment, 78% of the soil volume has been cleared of chromium or treated to below natural background levels. The results also indicated that 70% of the soil between the electrodes had been cleared of cadmium contamination. A comparison between the bench-scale and field demo showed that the field process was more effective than the lab tests. This indicated that small sample size will induce a negative effect on the efficiency of the process due to an increased impact of the boundaries on the overall process.

Anaerobic treatment of condensates: trial at a kraft pulp and paper mill.

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 on-site 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 (0.35 L/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%).

98/00518 Characteristics of char combustion in a high temperature advanced furnace for the high performance power system

A high performance power system (HIPPS) with a thermal-to-electric conversion efficiency of more than 47% is being developed by Foster Wheeler Development Corporation under the sponsorship of the United States Department of Energy-Pittsburgh Energy Technology Center. This system is a coal-fired combined cycle system that employs a high temperature advanced furnace (HITAF) to transfer the heat to the air and steam working fluids. In the HIPPS plant, pulverized coal and sorbent are fed into the pyrolyzer where the coal is partially gasified to produce a low-Btu fuel gas and combustible char. The fuel gas is supplied to the gas turbine combustor and the char is burned in the HITAF. This paper examines char combustion in the HITAF. It presents laboratory characterization of char combustion and numerical simulation of char combustion in a sub-scale test combustor. The laboratory characterization tests are conducted to determine the char ignition index, relative fuel reactivity, and drop-tube furnace performance. Sub-scale furnace tests are planned at Foster Wheeler`s Combustion and Environmental Test Facility (CETF) and University of Tennessee Space Institute`s combustion test facility, the firing rate at both facilities being 10 MW{sub t} (35 MMBtu/hr). Numerical simulation of char combustion at the Foster Wheeler CETF ismore » performed using a state-of-the-art furnace combustion computational fluid dynamics (CFD) code. The CFD modeling of furnace char combustion is a three-dimensional Eulerian representation of turbulent reacting gas flow with a Lagrangian simulation of char particle conservation equations. Char particles interact with the continuum gas flow field via mass, momentum and energy exchanges. Radiative heat transfer and pollutant formation mechanisms are included in the CFD model. The results of the laboratory bench-scale tests to characterize the char and CFD simulation of a sub-scale test combustor are detailed in the paper.« less

An investigation into alternative eluants from activated carbon at atmospheric pressure

One of the slowest steps in the extraction of gold by CIP/CIL techniques is the desorption of the metal from the loaded activated carbon. This paper seeks to examine ways of improving the kinetics of this desorption in an economic way through the use of organic additives to the traditional NaClNaOH elution solutions. Several organic agents such as propylene glycol, ethanolamine, urea, N,N-dimethylformamide, acetonitrile and ethanol were trialed. This was done in laboratory bench scale tests, and tests also carried out using an electrowinning cell in tandem with the elution column. Comparisons are made with previous work and results compared with the Zadra elution system which serves as a benchmark. It is shown that a solution of 3.0% w/w thiourea, 2.0% w/w NaOH, and 0.05% w/w NaCN represents the best prospects for greatly improved throughput in industrial cells. A subsequent paper will report pilot and commercial scale tests. The procedure is now standard alternative practice at the gold heap leaching complex of Perseverance Exploration in Fosterville.

New Approaches to Toxicity: A Seven-Gas Predictive Model and Toxicant Suppressants

ABSTRACTTwo new research approaches in combustion toxicology are: 1. the prediction of smoke toxicity from mathematical equations, which are empirically derived from, experiments on the toxicological interactions of complex fire gas mixtures and 2. the use of toxicant suppressants in materials or products to prevent the formation of toxic combustion products. The predictive approach consists of burning materials using a bench-scale method that simulates realistic fire conditions, measuring the concentrations of the primary fire gases -CO, CO2, low O2, HCN, HCl, HBr, and NO2 - and predicting the toxicity of the smoke using either the 6- or 7-gas N-Gas Model. These models are based on the results of toxicological studies of these primary gases as individual gases and as complex mixtures. The predicted toxic potency is checked with a small number of animal (Fischer 344 male rats) tests to assure that an unanticipated toxic gas is not generated or an unexpected synergistic or antagonistic effect has not occurred. The results indicate if the smoke from a material or product is extremely toxic (based on mass consumed at the predicted toxic level) or unusually toxic (based on the gases deemed responsible). The predictions based on bench-scale laboratory tests have been validated with full-scale room burns of a limited number of materials of widely differing characteristics chosen to challenge the system. The advantages of this new approach are 1. the number of test animals is minimized by predicting the toxic potency from the chemical analysis of the smoke, 2. smoke may be produced under conditions that simulate the fire scenario of concern, 3. fewer tests are needed, thereby reducing the overall cost of the testing and 4. information is obtained on both the toxic potency of the smoke and the responsible gases. The N-Gas Models have been developed into the N-Gas Method (described in this paper) and these results have been used in computations of fire hazard. The 6-Gas Model is now part of the international standard ISO 13344 approved by 16 member countries of the International Standards Organization (ISO) and is also included in the U.S. national standard ASTM El 678 approved by the American Society for Testing and Materials (ASTM). In addition, the 6-Gas Model is used in the American National Standard -NFPA 269 - approved by the National Fire Protection Association (Quincy, MA).The second new research approach, toxicant suppressants, examines the potential of chemical compounds, which when added to a material, to inhibit or reduce the concentration of a specific toxic gas normally generated during the material's thermal decomposition. The effectiveness of this approach was demonstrated at the National Institute of Standards and Technology (NIST) when HCN generation was reduced by 90% and the resultant toxicity of the combustion products was lowered by 50% when a flexible polyurethane foam (FPU) was treated with 0.1% (by weight) cuprous oxide (CU2O). Copper and cupric oxide (CuO) also reduced the HCN generation but were not as efficient as Cu2O. Although melamine-treated FPU foams are being promoted as more fire safe than standard foams, a melamine-treated foam generated 10 times more HCN than a foam without melamine. The addition of Cu2O to this melamine foam also reduced the HCN generation by 90%.

Industrial catalysis, the science and the challenge: Conversion of fossil fuels

Progress in surface science and in computer methods has resulted in a change from bench-scale laboratory tests to fundamental studies and large scale pilot operation. Examples are given on the use of in-situ methods coupled to scale-up to pilot units. Catalysis may play a major role in solving future problems in converting fossil fuels in a way being more efficient and environmentally acceptable. Examples are given for gas conversion comparing direct and indirect conversion routes, and it is illustrated how coal based power plants may apply catalyst technology. A positive attitude to longterm research is required to meet these challenges to catalysis.