Showing papers in "Environmental Engineering Science in 2006"
TL;DR: In this article, a computerized falling head permeameter system was used to measure hydraulic conductivity of pervious concrete from samples taken from three different field-placed slabs with known porosity.
Abstract: A computerized falling head permeameter system was used to measure hydraulic conductivity of pervious concrete from samples taken from three different field-placed slabs with known porosities Important differences between samples were found, and these follow the same trend as differences in porosity The relationship between porosity and hydraulic conductivity is suggested as a tool for designing pervious concrete pavements as a stormwater pollution best management practice A quantitative relationship between porosity and hydraulic conductivity was established based on the Carman-Kozeny equation for the samples tested Samples with porosities less than 15% presented limited hydraulic conductivity Important considerations on the measurement of hydraulic conductivity of pervious concrete samples are discussed, and the Ergun equation is used to explore the flow regime inside pervious concrete samples
160 citations
TL;DR: In this paper, an emerging technology that has shown considerable potential for efficient and effective removal of both inorganic and organic contaminants from fine-grained soils of low hydraulic conductivity and large specific area when conditions are favorable.
Abstract: Electrokinetic extraction is an emerging technology that has shown considerable potential for efficient and effective removal of both inorganic and organic contaminants from fine-grained soils of low hydraulic conductivity and large specific area when conditions are favorable. The cleanup technology is basically the application of a direct-current electric field across contaminated soils through electrodes installed in the subsurface. The contaminant is removed by (1) electro-osmotic advection of pore fluid flushing the contaminants; (2) ionic migration or electromigration of contaminants carrying charges; and (3) electrophoresis of charged colloidal-sized particles carrying contaminants. However, many complicated electrochemical phenomena that can change the electrokinetic properties of soil particles and the chemistry of pore fluid occur simultaneously. The resulting soil–chemical interactions may enhance or inhibit the extractability of contaminants by electrokinetics, as various electrochemical proces...
78 citations
TL;DR: In this article, the authors present an engineering program that allows environmental and civil engineering graduate students to obtain Master of Science degrees while serving as engineers in the U.S. Peace Corps.
Abstract: Solutions to global environmental and development problems require engineers to design and construct ecologically and socially just systems, within the carrying capacity of nature and society, without compromising the welfare of future generations. Engineers must also have international perspectives if the discipline is to take a leadership role in improving the lives of the global community. This manuscript provides details of, and the motivation behind, an engineering program that allows environmental (and civil) engineering graduate students to obtain Master of Science degrees while serving as engineers in the U.S. Peace Corps. Drivers of this educational initiative are the U.N. Millennium Development Goals, the direct link of sustainable development to public health and protection of ecosystems and natural resources, and the need for engineering educators to better integrate societal and economic issues with environmental science. Examples are provided on how these issues are incorporated into a stude...
77 citations
TL;DR: Batch water leaching tests (WLTs) and column leaching test (CLTs) were conducted on coal-combustion fly ashes, soil, and soil-fly ash mixtures to characterize leaching of Cd, Cr, Se, and Ag as discussed by the authors.
Abstract: Batch water leaching tests (WLTs) and column leaching tests (CLTs) were conducted on coal-combustion fly ashes, soil, and soil–fly ash mixtures to characterize leaching of Cd, Cr, Se, and Ag. The concentrations of these metals were also measured in the field at two sites where soft fine-grained soils were mechanically stabilized with fly ash. Concentrations in leachate from the WLTs on soil–fly ash mixtures are different from those on fly ash alone and cannot be accurately estimated based on linear dilution calculations using concentrations from WLTs on fly ash alone. The concentration varies nonlinearly with fly ash content due to the variation in pH with fly ash content. Leachate concentrations are low when the pH of the leachate or the cation exchange capacity (CEC) of the soil is high. Initial concentrations from CLTs are higher than concentrations from WLTs due to differences in solid–liquid ratio, pH, and solid–liquid contact. However, both exhibit similar trends with fly ash content, leachate pH, a...
74 citations
TL;DR: In this article, a simple kinetic reaction model was developed to investigate the pathways of plasma reaction and the effects of additional gases injection were described in detail in detail, including N2, O2, air, and H2O.
Abstract: Decomposition of carbon dioxide (CO2) by gliding arc plasma was examined. The plasma device consisted of two or four triangular stainless steel plates. The gas enters through a nozzle tube from the upper part of the cylindrical reactor and exits at the bottom part of the reactor. Some additional gases, such as N2, O2, air, and H2O, have been used to study the dilution effects on CO2 conversion. A simple kinetic reaction model was developed to investigate the pathways of plasma reaction. Experimental results indicate that the conversion of pure CO2 reaches 18% at the total gas flow rate of 0.85 L/min and produces CO and O2 as the final products. The effects of additional gases injection are described in detail in this paper.
60 citations
TL;DR: In this paper, an internal-parameter two-stage chance-constrained mixed integer linear programming (ITCILP) method is developed for municipal solid waste (MSW) management under uncertainty.
Abstract: In this study, an internal-parameter two-stage chance-constrained mixed integer linear programming (ITCILP) method is developed for municipal solid waste (MSW) management under uncertainty. The ITCILP improves upon the existing optimization methods with advantages in uncertainty reflection, policy investigation, and risk analysis. It can directly handle uncertainties presented as both internals and probability density distributions, and can thus support the assessment of the reliability of satisfying (or the risk of violating) various constraints, for accomplishing a minimizing system cost. It can also be used for analyzing various policy scenarios that are associated with different levels of economic penalties when the promised policy targets are violated. Moreover, within a multistage context, the ITCILP can facilitate dynamic analysis for capacity-expansion planning under different constraint-violation risk levels. The developed method is applied to a case study of long-term MSW management planning. Th...
43 citations
TL;DR: In this paper, the effect of thermal hydrolysis and Fenton's peroxidation on the heavy metal content of the dewatered sludge was studied, and it was shown that the presence of heavy metals in the excess sludge poses, however, serious problems, and considerably hampers the final disposal alternatives, especially in the agricultural use (soil improvement/amendment).
Abstract: Waste-activated sludge (WAS) processes are key technologies to treat wastewater: their effluents can meet stringent discharge standards, thus ensuring a minimum residual impact on the aquatic environment. The presence of heavy metals in the excess sludge poses, however, serious problems, and considerably hampers the final disposal alternatives, especially in the agricultural use (soil improvement/amendment). This article studies the effect of thermal hydrolysis and Fenton's peroxidation on the heavy metal content of the dewatered sludge. Acid thermal hydrolysis reduces the heavy metal content in the filter cake except for Cu, Hg, and Pb. Alkaline thermal hydrolysis releases Cu, Pb, and Cr. Fenton's peroxidation transfers Cd, Cu, and Ni from the filter cake into the filtrate. Land application of the residual cake can hence be reconsidered.
43 citations
TL;DR: In this article, the authors studied the leaching of hazardous substances in additives and admixtures that are commonly contained in concrete, and proposed an alternative availability test to NEN 7341, for generation of data for use in models of leaching during the service life of concrete as a monolithic material.
Abstract: The aim of this work was to study the leaching of hazardous substances in additives and admixtures that are commonly contained in concrete. Time-dependent leaching has been analyzed for three types of metal containing concretes: with ordinary Portland cement (OPC), fly ash, and slag. The concretes had uniform leaching patterns, clearly above detection limits. The prolonged diffusion test of 1,700 days showed a substantial decline in metal release. There was no significant difference between the concretes with byproducts and the concrete with Portland cement. This study proposes an alternative availability test to NEN 7341, for generation of data for use in models of leaching during the service life of concrete as a monolithic material. The results of the two different availability tests are compared for naturally carbonated and noncarbonated materials and for different particle sizes. The leaching of concrete with admixtures containing thiocyanate, resin acids, or nonylphenol ethoxylate was also studied, because of their toxic character. The thiocyanate was leached with an initial fast dissolution process followed by a slower continuous diffusion process. The leached amount thiocyanate in the availability test was very high, 71%, due to its high solubility. Resin acids from tall oil-based air-entraining agents in concrete had a continuous diffusional leaching that is proportional to the square root of time. The fraction available for leaching was 17% of the added amount of oil and ∼20-30% of the added amount of nonylphenol ethoxylates. In addition to nonylphenol ethoxylate, nonylphenol was determined-a more toxic, genotoxic and low-degradable substance.
39 citations
TL;DR: It is found accumulation of intermediates was minimal during normal aerobic growth of acclimated cultures on EDTA and NTA, and small levels of intermediate relative to the original amount of chelate were observed to accumulate and persist in systems where biodegradation proceeded in unbuffered systems.
Abstract: Widely used anthropogenic chelating agents EDTA and NTA are ubiquitous in wastewaters and natural waters. Chelating agents may enhance the mobility of heavy metals and radionuclides or increase eutrophication. Biodegradation of these chelates may reduce metal mobility, offering a remediation solution. Formation of metabolic intermediates was previously reported during the biodegradation of EDTA and NTA. These intermediates could sequester carbon and electrons, slowing the overall rate of biodegradation. We found accumulation of intermediates was minimal during normal aerobic growth of acclimated cultures on EDTA and NTA. Small levels of intermediates relative to the original amount of chelate were observed to accumulate and persist in systems where biodegradation proceeded in unbuffered systems. Among the metabolic intermediates, ethylenediaminetriacetate (ED3A) is most likely to persist if released into the environment, and can spontaneously cyclize to form the more recalcitrant 3-ketopiperazine-N,Ndiace...
39 citations
TL;DR: In this article, the use of synthetic precipitation leaching (SPLP) for assessing risk to groundwater from a granular waste that is land applied in a manner consistent with use as fill material was examined.
Abstract: Scientists and engineers often rely on results from the synthetic precipitation leaching procedure (SPLP) to assess the risk of groundwater contamination posed by the land application of granular solid wastes. The concentrations of pollutants in SPLP leachate can be measured and compared to groundwater quality criteria to determine if groundwater contamination is likely. These results are applied, however, inconsistently among regulatory agencies because of uncertainty over whether the SPLP leachate concentrations represent the actual pore water concentrations expected in the waste, or whether they represent diluted concentrations as might be expected in an underlying aquifer. Depending on the waste in question, the SPLP results can represent either condition. Research was conducted to examine the use of the SPLP for assessing risk to groundwater from a granular waste that is land applied in a manner consistent with use as fill material. Theoretical considerations were first explored. The complexities ass...
38 citations
TL;DR: In this article, the feasibility of a chemical absorption and a biological oxidation process to remove high H2S concentrations (500-1500 ppm) was evaluated and the experimental results indicated that a long gas retention time could elevate the removal efficiency under all operating conditions.
Abstract: The feasibility of a chemical absorption and a biological oxidation process to remove high H2S concentrations (500–1500 ppm) was evaluated. The experiment included the effects of gas retention time (GRT) and H2S concentration on H2S removal efficiency, Fe3+ oxidation rate, and Fe2+ production rate in the chemical absorption reactor. The effects of carbon source and liquid flow rate on pH value, Fe2+ oxidation rate, Fe3+ production rate, total iron concentration, and growth of Thiobacillus ferrooxidans CP9 in the biological oxidation reactor were also examined. The optimal operating conditions for the individual process and design guidelines for the serial processes were established. The results of this study indicated that a long GRT could elevate H2S removal efficiency under all operating conditions. However, a high H2S concentration (e.g., 1,500 ppm) resulted in a significant difference. H2S removal efficiency stayed above 99.5% for the first 10 h of reaction, but it then decreased because of the decrea...
TL;DR: In this paper, the use of lime to reduce the leachability of coal combustion fly ash was evaluated in the laboratory and the results suggest that lime addition reduces the leACHability for Cd, Se, and to some extent As.
Abstract: As part of a larger investigation that included numerical and field-based components, the use of lime to reduce the leachability of a coal combustion fly ash was evaluated in the laboratory. The focus of this paper is on the experimental assessment of lime–fly ash leachability through sequential leach (SL), freeze–thaw (FT), and wet–dry (WD) leaching as well as multileachant sequential extraction (SE) tests. The objectives were to study the leachability of trace elements, including arsenic (As), cadmium (Cd), chromium (Cr), and selenium (Se). These results suggest that lime addition reduces the leachability for Cd, Se, and to some extent As. They also suggest that Cr is rendered more leachable with increasing lime content, for the conditions and low levels tested. It appears that there is a threshold lime content (>1.0%) that must be exceeded prior to reducing the leachability of As and Se. In particular, this threshold likely corresponds to the level at which appreciable cementitious reactions have devel...
TL;DR: The Stocks and Flows project at Yale University examines the full life cycle of anthropogenically mobilized material on a variety of spatial levels, including city-, country-, regional-, and global-level cycles.
Abstract: Industrial ecology is frequently regarded as the organizing framework for studying interactions of technological societies with the environment. A theme central to industrial ecology is the way that materials are used which, in turn, relates to environmental and resource availability concerns. The material fluxes seen between the production of raw materials, the manufacture and use of products, and their fate at their end of life are quantified using material flow analysis, the record keeping of atoms mobilized by humans within a bounded system. The Stocks and Flows project at Yale University examines the full life cycle of anthropogenically mobilized material on a variety of spatial levels, including city-, country-, regional-, and global-level cycles. Different temporal levels are also examined, with research conducted on historical studies, contemporary studies, and scenario development. Material cycles have been completed for copper, zinc, and silver, with current work including iron and steel, chromi...
TL;DR: In this article, the results of a chemometric treatment of data from such experiments and describes the development of a model based on an artificial neural networks topology were presented. But the model was not applied to the analysis of the data collected from the column leaching experiments.
Abstract: The contamination of the soil by heavy metals is still of great interest to environmental scientists because of further metal mobilization and the possibility of groundwater and surface water pollution. One of the most efficient tools for risk assessment is a combination of an ex situ column leaching experiment with computer modeling. This paper presents the results of a chemometric treatment of data from such experiments and describes the development of a model based on an artificial neural networks topology. The column leaching experiments have been used to find dependencies between different physiochemical parameters of soil and heavy metals concentrations in leachate. Investigations of three different soil types has been found to be sufficient to create the local model of heavy metal transport within soil profile.
TL;DR: In this paper, three kinetic models were evaluated for suitability in describing anaerobic hydrolysis of particulate wastes, including first-order reaction in particulate substrate concentration, second-order reactivity in acidogenic biomass and substrate concentrations, and a two-parameter surface-limiting reaction model.
Abstract: Three kinetic models were evaluated in this study for suitability in describing anaerobic hydrolysis of particulate wastes. The three models evaluated were: first-order reaction in particulate substrate concentration, second-order reaction in acidogenic biomass and particulate substrate concentrations, and a two-parameter, surface-limiting reaction model. Process models incorporating the three hydrolysis reaction models were developed to describe the hydrolysis-acidogenesis phase in the fermentation of cattle manure. Batch reactors were run with cattle manure as the substrate under five different conditions to calibrate and validate the process models. The two-parameter, surface-limiting reaction model and the single-parameter, second-order reaction model were found to fit the experimental results better than the simple first-order reaction model with r 2 values of 0.914, 0.913, and 0.881, respectively.
TL;DR: In this article, ammonia-neutralized acid mine drainage sludge was collected from an active treatment of mine drainage and the sludge characteristics included high pH and alkalinity, high total Fe and Al, elevated sulfate, and low solids content.
Abstract: A major problem in the active treatment of acid mine drainage (AMD) is the generation of large volumes of sludge through pH neutralization and subsequent metal precipitation. The sludge typically contains a low concentration of solids, resulting in associated handling and disposal difficulties. Anhydrous ammonia is one reagent commonly used to neutralize AMD due to its quick reaction rate, easy implementation, and relatively low chemical and operational costs. However, very limited information is available in the literature related to the detailed characterization and dewaterability of ammonia-treated AMD sludge. In this study, sludge was collected from an AMD treatment facility where ammonia neutralization was used. The sludge characteristics included high pH and alkalinity, high total Fe and Al, elevated sulfate, and low solids content (0.72 ± 0.24%). Coagulants and flocculants were not effective in reducing the settled sludge volume. Based on filtration tests, ammonia-treated AMD sludge demonstrated re...
TL;DR: Diuron, a preemergent or early post-emergent herbicide, predominantly applied in late fall and early winter in California, is the third most applied herbicide in the state.
Abstract: Diuron, a preemergent or early postemergent herbicide, predominantly applied in late fall and early winter in California, is the third most applied herbicide in the state. Previous studies showed t...
TL;DR: In this paper, the effectiveness of a quicklime-based stabilization/solidification (s/s) technique to reduce the leachability of Cr(III) and Cr(VI) in laboratory-prepared soil was investigated.
Abstract: The purpose of this study is to investigate the effectiveness of a quicklime-based stabilization/solidification (s/s) technique to reduce the leachability of Cr(III) and Cr(VI) in laboratory-prepared soil. The soils were prepared by mixing kaolinite or montmorillonite with fine quartz sand and then subjecting the samples to s/s treatment. Treatment included quicklime, fly ash, and quicklime–fly ash additions. The effectiveness of the treatment was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) test. To elucidate the controlling Cr(VI) immobilization mechanisms, slurry mixtures were prepared with potassium chromate (K2CrO4), quicklime, and fly ash. X-ray diffraction (XRD) analyses were performed to investigate the reaction products responsible for Cr(VI) immobilization. Experimental results indicate very low Cr(III) leachability upon quicklime treatment. All samples treated with quicklime and quicklime–fly ash show TCLP Cr(III) concentrations below the U.S. EPA TCLP limit of 5 ppm. H...
TL;DR: In this paper, the effects of Pb transformation products (Pb forms in the soil) on Pb leachability by evaluating Toxicity Characteristic Leaching Procedure (TCLP) data from samples taken out of six different firing ranges.
Abstract: This study focuses on investigation of the effects of Pb transformation products (Pb forms in the soil) on Pb leachability by evaluating Toxicity Characteristic Leaching Procedure (TCLP) data from samples taken out of six different firing ranges. In all the soils tested, TCLP Pb leachability levels and total Pb concentrations were found to be above the regulatory limits set by the U.S. EPA and state agencies. However, TCLP Pb leachability levels did not always correlate well with total Pb concentrations. Formation of Pb carbonates was found to play an important role in controlling Pb leachability and precipitation was found to be an important Pb immobilization mechanism in all soils tested. The effect of posttumbling TCLP (leaching) pH, soil buffering capacity, grain size, and mineralogy on Pb leachability was also considered. The leaching pH effect was most pronounced in the range that showed the lowest Pb leachability, and was attributed to the presence of buffering compounds in this soil. Pb leachabili...
TL;DR: Two equal-size biofilters with perlite as the packing material were used to investigate the effect of amending silicone oil to the bed of a biofilter for removal of n-hexane from a contaminated air stream, showing that the silicone oil amended biofilter performed better than the other consistently during the period of investigation.
Abstract: Two equal-size biofilters with perlite as the packing material were used to investigate the effect of amending silicone oil to the bed of a biofilter for removal of n-hexane from a contaminated air stream. The bed particles of one of the biofilters were partially coated with silicone oil. An n-hexane degrading bacterial culture was used as a biocatalyst in both biofilters. The biofilters operated in parallel under the same conditions for 70 days. The results showed that the silicone oil amended biofilter performed better than the other consistently during the period of investigation. The maximum elimination capacity for the silicone oil amended biofilter was 167 g · m−3 bed · h−1 compared to 114.9 g · m−3 bed · h−1 for the control biofilter. Sorption capacity of a biofilter plays an important role in damping shock changes at entering concentration. To determine how the amended oil could affect the sorption capacity of the biofilter, the responses of the biofilters to step and pulse changes at the inlet co...
TL;DR: The efficiency of a solid enzymatic preparation, produced through solid-state fermentation by the fungus Penicillium restrictum with waste from the babassu oil industry, was evaluated in a pretreatment stage of a dairy effluent.
Abstract: The efficiency of a solid enzymatic preparation (SEP), produced through solid-state fermentation by the fungus Penicillium restrictum with waste from the babassu oil industry, was evaluated in a pretreatment stage of a dairy effluent. A range of oil and grease (O&G) contents in the effluent were tested (400, 600, and 800 mg O&G/L). Two parallel activated sludge systems were operated continuously with a hydraulic retention time of 20 h during a 240-day period, one of which treated raw effluent (Control) and the other of which treated enzymaticaly prehydrolyzed effluent (Test). In the trials with 800 mg O&G/L in the delivered effluent, a significantly improved waste treatment outcome was obtained with the Test bioreactor than the Control bioreactor, including chemical oxygen demand removal (13% higher), O&G accumulation in flocs (40% lower), biomass concentration (1.7 times higher), degradation constant (4.7 times higher), and specific oxygen uptake rate (1.3 times higher). Only the Test bioreactor attained...
TL;DR: In this paper, the use of a biological process for perchlorate and nitrate destruction in spent brine from ion exchange processes was evaluated. The salt-tolerant, anaerobic culture consistently reduced perchlorates and nitrates to below detection limits within 24 hours in the presence of varying concentrations of brine constituents such as salt, NaCl, nitrate, sulfate, and pH.
Abstract: The use of a biological process for perchlorate and nitrate destruction in spent brine from ion exchange processes was evaluated. The salt-tolerant, anaerobic culture consistently reduced perchlorate and nitrate in spent brine to below detection limits within 24 h in the presence of varying concentrations of brine constituents such as salt (3 to 10% NaCl), nitrate (400 to 4,000 mg/L), sulfate (600 to 6,000 mg/L) and pH (5 to 9). These are the first results to show that rapid biological degradation of perchlorate can be achieved in ion-exchange spent brine containing very high NaCl concentrations (up to 10%).
TL;DR: In this article, the treatment efficiencies for gully pot liquor of experimental vertical flow constructed wetland filters containing Phragmites australis (Cav.) Trin. ex Steud.
Abstract: The aim of this research was to assess the treatment efficiencies for gully pot liquor of experimental vertical-
flow constructed wetland filters containing Phragmites australis (Cav.) Trin. ex Steud. (common
reed) and filter media of different adsorption capacities. Six out of 12 filters received inflow water spiked
with metals. For 2 years, hydrated nickel and copper nitrate were added to sieved gully pot liquor to simulate
contaminated primary treated storm runoff. For those six constructed wetland filters receiving heavy
metals, an obvious breakthrough of dissolved nickel was recorded after road salting during the first winter.
However, a breakthrough of nickel was not observed, since the inflow pH was raised to eight after
the first year of operation. High pH facilitated the formation of particulate metal compounds such as nickel
hydroxide. During the second year, reduction efficiencies of heavy metal, 5-days at 20°C N-Allylthiourea
biochemical oxygen demand (BOD) and suspended solids (SS) improved considerably. Concentrations of
BOD were frequently �20 mg/L. However, concentrations for SS were frequently �30 mg/L. These are
the two international thresholds for secondary wastewater treatment. The BOD removal increased over
time due to biomass maturation, and the increase of pH. An analysis of the findings with case-based reasoning
can be found in the corresponding follow-up paper (Part B).
TL;DR: In this paper, the influence of various design, operational, and water quality parameters (filter depth, media size, filtration rate, temperature, turbidity, running time, etc.) on the performance of waste-tire-made crumb rubber filter was investigated.
Abstract: Removal of turbidity, phytoplankton, and zooplankton from ballast water with waste-tire-made crumb rubber filtration was evaluated in this study. The influences of various design, operational, and water quality parameters (filter depth, media size, filtration rate, temperature, turbidity, running time, etc.) on filtration performance were investigated. Statistical approaches were used to develop empirical models, including a head loss model which partially resembles the Kozeny equation, to evaluate these factors. Regression models, validated with data from the field study, were used for predicting the influence of operational parameters on crumb rubber filtration. Sensitivity analyses of the significance of each factor were conducted. Results showed that media size played a very important role in the removal of suspended matter, while temperature, filter depth, influent turbidity, and running time did not have a significant influence. Head loss was most affected by filtration rate and media size. These results indicated that the behaviors of the crumb rubber filtration for ballast water treatment cannot be described by the theories and models for conventional granular media filtration without modification.
TL;DR: In this paper, a series of batch equilibrium tests with a range of Cr(VI) doses was performed and the overall behavior of the removal mechanism was adequately described by a Langmuir isotherm, indicating a finite capacity of cement pastes in removing chromate oxyanions.
Abstract: Kinetic experiments using cement pastes for Cr(VI) removal revealed that cement hydration products can uptake Cr(VI) considerably in the high pH region. The removal mechanism was investigated by a series of batch equilibrium tests with a range of Cr(VI) doses. The overall behavior of Cr(VI) removal was adequately described by a Langmuir isotherm, indicating a finite capacity of cement pastes in removing chromate oxyanions. The Cr(VI) removal behavior in the batch equilibrium tests was conceptually modeled as precipitation of Cr(VI)-bearing ettringite in lower Cr(VI) dose conditions, followed by anionic exchange with interlayer sulfate ions of ettringite at doses above a certain level. This model was well supported by the experimental results and the SEM images that exhibited development of the more acicular crystals of ettringite with the higher dose of chromate ions. The Cr(VI) removed by cement pastes was completely released upon dissolution of ettringite phases at pH 10.5 in the Cr(VI) release experiments.
TL;DR: In this article, the results of technical-scale work carried out at a landfill site for municipal waste in Poland are presented, showing a significant impact of the addition of sodium acetate in both enhancing the methane content of biogas and accelerating the onset of methanogenesis.
Abstract: The results of technical-scale work carried out at a landfill site for municipal waste in Poland are presented. Sewage sludges (raw and digested) were introduced into the waste layer at the site and the composition of the generated biogas was determined. Addition of the sludge to the deposited waste once every 3 months assured production of biogas with methane concentration above 30% v/v, even as early as 1.5 months after addition. A significant impact of the addition of sodium acetate in both enhancing the methane content of biogas and accelerating the onset of methanogenesis, was observed. The latter effect—in combination with the elimination of interruptions in its supply—would allow for its more efficient use in power-generation.
TL;DR: In this article, an adaption and photocatalytic degradation of 4BS dye over fine particulate TiO2 was studied in an opened batch slurry reactor, where the influence of mixing of solid-liquid and external diffusion on degradation rate were eliminated by increasing stirred rate.
Abstract: Adsorption and photocatalytic degradation of 4BS dye over fine particulate TiO2 are studied in an opened batch slurry reactor. The influences of mixing of solid–liquid and external diffusion on degradation rate are eliminated by increasing stirred rate. The adsorption experimental results indicate that pH and temperature of solution affect adsorption considerably, a Langmuir equilibrium adsorption isotherm can be used to described them. Meanwhile, catalyst dosage, reaction time, pH of solution, stirring speed, initial concentration, direct irradiation area, and illumination intensity of UV light can affect the reaction rate. Favorable pH for 4BS dye degradation is about 3.5, suitable dosage of catalyst is about 1.0 g • L−1. After numeric analysis to experimental data, a kinetics model is established; the rate constants are different for catalyst dosage in 0.5 g • L−1 or 1.0–6.0 g − L−1.
TL;DR: Analysis of ammonia oxidizing bacterial communities from a full-scale municipal wastewater treatment plant revealed a weak correlation between the quantity of N. oligotropha-like populations and nitrification efficiency, suggesting that these quantification of these bacteria would be useful for monitoring nitrification in wastewater treatment bioreactors.
Abstract: The purpose of this study was to examine the ammonia oxidizing bacterial (AOB) communities from a full-scale municipal wastewater treatment plant, and to relate these analyses to treatment efficiency. Although almost complete nitrification was observed for extended periods of the year, nitrification efficiency decreased to about 60–80% during December through March. Substantial changes in the AOB community structure were detected using a nested PCR-DGGE approach. Quantification of Nitrosomonas oligotropha- like bacterial populations by competitive quantitative PCR targeting amoA gene fragments revealed that these populations varied more than eightfold throughout the year. Statistical analysis revealed a weak correlation between the quantity of N. oligotropha-like populations and nitrification efficiency, suggesting that these quantification of these bacteria would be useful for monitoring nitrification in wastewater treatment bioreactors.
TL;DR: In this paper, a new empirical model and a two-layer neural network approach for the determination of optimum body diameter (OBD) of air cyclones were presented by help of a MATLAB® algorithm for 505 different artificial scenarios given in a wide range of five main operating variables.
Abstract: This paper presents a new empirical model and a two-layer neural network approach for the determination of optimum body diameter (OBD) of air cyclones. OBD values were calculated by help of a MATLAB® algorithm for 505 different artificial scenarios given in a wide range of five main operating variables. The predicted results obtained from each proposed approach were compared with the wellknown Kalen and Zenz's model. The computational analysis showed that the empirical model and neural network outputs obviously agreed with the Kalen and Zenz's model, and all the predictions proved to be satisfactory, with a correlation coefficient of about 0.9998 and 1, respectively. The maximum diameter deviations from Kalen and Zenz's model were recorded as only ±1.3 cm and ± 0.0022 cm for the proposed model and NN outputs, respectively. In addition to proposed approaches, the pressure drop problem was controlled using a MATLAB® algorithm, and results were obtained rapidly and practically for varying data used in the cy...
TL;DR: In this paper, liquid chromatography coupled with a photodiode array detector (HPLC-DAD) and atmospheric pressure chemical ionization ion sources (LC-APCI-MS) were used for the determination of a variety of nitrophenols in air and rainwater samples after solid phase extraction using silica gel and XAD-7 resin adsorbents (rainwater).
Abstract: Liquid chromatography coupled to a photodiode array detector (HPLC-DAD) and atmospheric pressure chemical ionization ion sources (LC-APCI-MS) were used for the determination of a variety of nitrophenols in air and rainwater samples after solid-phase extraction using silica gel and XAD-7 resin adsorbents (rainwater). Five field experiments were performed: (1) in a preliminary campaign air samples were obtained in 1998 in an urban site in the northern part of Milano; (2) in winter 1999, air samples were obtained in three urban sites in the Great Milano area, in one semirural site and in a rural site in the Protected Area named Ticino Valley; (3) in summer 1999, air samples were obtained in one urban site in Central Milano; (4) in summer 1999, air samples were obtained in an urban tunnel in Central Milano; (5) in spring 1999, rainwater was collected in five occasions in two urban sites located in the northern part of Milano area. Benzene, toluene, phenol, 2-nitrophenol, 4-nitrophenol, 3-methyl-4-nitrophenol,...