Application of Dispersion Modelling for Analysis of Particle Pollution Sources in a Street Canyon

The dominating source of particles in urban air is road traffic. In terms of number concentration, its main contribution is within the range of ultrafine particles (Dp < 100 nm). The dispersion conditions, i.e. transport and dilution, of the submicrometer particles are expected to be like for gases and therefore the particle concentrations in a street canyon can be calculated using gaseous pollutants dispersion models. Such processes, like coagulation or condensation, are less important due to the short residence time within the street canyon environment.Two extensive measuring campaigns were conducted in the street Jagtvej in Copenhagen, Denmark. The particle size distributions were measured by a Differential Mobility Analyser (DMA) coupled to a particle counter, providing high time resolution data (1/2 hourly) on a continuous basis. Measurements of NO_x, CO and meteorological parameters were also available. The measured particle number concentrations, especially below 100 nm, reveal very similar dependence on the meteorological conditions as the NO_x concentrations. This underpins the conclusion that dilution properties are similar for particles and NO_x. For particle sizes over 100 nm, somewhat different behaviour is observed. This points toward existence of additional particle sources, not related to traffic emissions within the street canyon. A significant contribution is believed here to be attributed to long-range transport. The total particle emission from traffic, including daily variation and size distribution, has been calculated using the OSPM dispersion model. Results are in accordance with a previous analysis based on statistical modelling.     

Model calibration and validation for OFMSW and sewage sludge co-digestion reactors

A mathematical model has recently been proposed by the authors to simulate the biochemical processes that prevail in a co-digestion reactor fed with sewage sludge and the organic fraction of municipal solid waste. This model is based on the Anaerobic Digestion Model no. 1 of the International Water Association, which has been extended to include the co-digestion processes, using surface-based kinetics to model the organic waste disintegration and conversion to carbohydrates, proteins and lipids. When organic waste solids are present in the reactor influent, the disintegration process is the rate-limiting step of the overall co-digestion process. The main advantage of the proposed modeling approach is that the kinetic constant of such a process does not depend on the waste particle size distribution (PSD) and rather depends only on the nature and composition of the waste particles. The model calibration aimed to assess the kinetic constant of the disintegration process can therefore be conducted using organic waste samples of any PSD, and the resulting value will be suitable for all the organic wastes of the same nature as the investigated samples, independently of their PSD. This assumption was proven in this study by biomethane potential experiments that were conducted on organic waste samples with different particle sizes. The results of these experiments were used to calibrate and validate the mathematical model, resulting in a good agreement between the simulated and observed data for any investigated particle size of the solid waste. This study confirms the strength of the proposed model and calibration procedure, which can thus be used to assess the treatment efficiency and predict the methane production of full-scale digesters.     

Thermodynamic and experimental studies on condensation behavior of low-boiling-point elements volatilized in the melting process

To study the volatilization and condensation behaviors of low-boiling-point elements in the waste melting process, experiments were conducted to collect the dust from a coke-type incineration residue melting furnace. Then, a comparison was made between the experimental results and the calculated values obtained from a thermodynamic equilibrium model in terms of the chemical composition of the dust. The composition of the dust collected from a cylindrical filter in the exhaust gas duct was determined by chemical methods, scanning electron microscopy/energy-dispersive X-ray spectroscopy, and X-ray analysis. As a result, the sampled dust was classified into two different types: fine particles mainly containing Na, K, Pb, and Zn collected from the side face of the cylindrical filter, and large particles containing Ca, Si, and Al collected from the bottom face of the cylindrical filter. From X-ray analysis of the sampled dust, NaCl, KCl, PbS, and ZnS were identified in the fine-particle dust, while CaO, SiO₂, Al₂O₃ were detected in the large-particle dust. From the results of the thermodynamic equilibrium calculation in the gas cooling process from 2000 to 600 K, it was found that Na, K, Pb, and Zn volatilized as metals in the melting furnace were condensed as alkali chlorides such as NaCl and KCl and heavy metal sulfides such as PbS and ZnS. These computational results were in good agreement with the X-ray diffraction results of the sampled dust at a gas temperature of 823 K for the formation of NaCl, KCl, PbS, and ZnS.     

Adsorptive Removal of Diuron Herbicide on Carbon Nanotubes Synthesized from Plastic Waste

In this study, carbon nanotubes (CNTs) were synthesized from waste polyethylene bottles and their use as an adsorbent for the removal of diuron herbicide from aqueous solution was evaluated. Batch adsorption was performed by varying adsorbent dosage, initial concentration, contact time, and temperature. Kinetic models applied to experimental data indicated that the pseudo-second-order model had the best fit. The equilibrium data were analyzed using different isotherm models. The adsorption capacity of CNTs for diuron removal, determined using the Hill isotherm, was approximately 40.37 mg/g at 303 K. From thermodynamic studies, the values of ΔH° (kJ/mol) and ΔS° [kJ/(mol K)] were calculated as ?17.307 and ?0.0528, respectively, which suggested that the adsorption process was exothermic. The negative values of ΔG° at three different temperatures indicated that adsorption of diuron on CNTs was favorable.     

An automated solid waste bin level detection system using a gray level aura matrix

An advanced image processing approach integrated with communication technologies and a camera for waste bin level detection has been presented. The proposed system is developed to address environmental concerns associated with waste bins and the variety of waste being disposed in them. A gray level aura matrix (GLAM) approach is proposed to extract the bin image texture. GLAM parameters, such as neighboring systems, are investigated to determine their optimal values. To evaluate the performance of the system, the extracted image is trained and tested using multi-layer perceptions (MLPs) and K-nearest neighbor (KNN) classifiers. The results have shown that the accuracy of bin level classification reach acceptable performance levels for class and grade classification with rates of 98.98% and 90.19% using the MLP classifier and 96.91% and 89.14% using the KNN classifier, respectively. The results demonstrated that the system performance is robust and can be applied to a variety of waste and waste bin level detection under various conditions.     

Application of quadratic regression model for Fenton treatment of municipal landfill leachate

The effectiveness of Fenton process in municipal landfill leachate treatment, as a pre- or post-treatment approach, has been demonstrated. However, no general recommendations of universal validity could be made in the term of optimized conditions affecting Fenton process. At the first stage of this study, collected leachate samples from Aradkooh site, Tehran, Iran, were investigated using one-factor-at-a-time method to find out optimum coagulation pH and flocculation time values. Subsequently, the obtained results in addition to data issued previously by the authors were employed to develop a predictive model of the true response surface, namely chemical oxygen demand (COD) removal efficiency. Finally, the main parameters of Fenton procedure, i.e. initial pH, [H(2)O(2)]/[Fe(2+)] molar ratio, Fe(2+) dosage, and coagulation pH were optimized taking advantage of the above-mentioned quadratic model. The derived second-order model included both significant linear and quadratic terms and seemed to be adequate in predicting responses (R(2)=0.9896 and prediction R(2)=0.6954). It was found that the interaction between initial pH and Fe(2+) dosage has a significant effect on COD removal. While, the optimal [H(2)O(2)]/[Fe(2+)] molar ratio was independent of ferrous ion dosage. The optimum conditions for the maximum COD removal of 50.76% for the parameters of initial pH, [H(2)O(2)]/[Fe(2+)] molar ratio, Fe(2+) dosage, and coagulation pH were found to be 5.8, 8.0, 22,500mg/L, and 8.7 respectively.     

Mathematical modelling of sewage sludge incineration in a bubbling fluidised bed with special consideration for thermally-thick fuel particles

Fluidised bed combustor (FBC) is one of the key technologies for sewage sludge incineration. In this paper, a mathematical model is developed for the simulation of a large-scale sewage sludge incineration plant. The model assumes the bed consisting of a fast-gas phase, an emulsion phase and a fuel particle phase with specific consideration for thermally-thick fuel particles. The model further improves over previous works by taking into account throughflow inside the bubbles as well as the floating and random movement of the fuel particles inside the bed. Validation against both previous lab-scale experiments and operational data of a large-scale industrial plant was made. Calculation results indicate that combustion split between the bed and the freeboard can range from 60/40 to 90/10 depending on the fuel particle distribution across the bed height under the specific conditions. The bed performance is heavily affected by the variation in sludge moisture level. The response time to variation in feeding rate is different for different parameters, from 6min for outlet H(2)O, 10min for O(2), to 34min for bed temperature.     

Understanding the chemical and mineralogical properties of the inorganic portion of MSWI bottom ash

This paper investigates the changes of mineralogical composition of bottom ash in the environment. The chemical and mineralogical bulk composition was determined by X-ray fluorescence (XRF) and X-ray powder diffraction (XRPD) Rietveld method. Single bottom ash particles were investigated by optical microscopy, scanning electron microscopy with quantitative energy-dispersive X-ray microanalysis (SEM/EDX) and electron probe micro analysis (EPMA). SEM/EDX and EPMA are valuable complement to bulk analysis and provide means for rapid and sensitive multi-elemental analysis of ash particles. The fresh bottom ash consists of amorphous (>30 wt.%) and major crystalline phases (>1 wt.%) such as silicates, oxides and carbonates. The mineral assemblage of the fresh bottom ash is clearly unstable and an aging process occurs by reaction towards an equilibrium mineral phase composition in the environmental conditions. The significant decrease of anhydrite and amorphous contents was observed in the aged bottom ash, leading to the formation of ettringite, hydrocalumite and rosenhahnite under atmospheric conditions. In the water-treated sample, the calcite contents increased significantly, but ettringite was altered by the dissolution and precipitation processes in part, to produce gypsum, while the remaining part reacted with chloride to form hydrocalumite. Gypsum and other Ca based minerals may take up substantial amounts of heavy metals and subsequently control leaching behaviour of bottom ash.     

Estimation and allocation of solid waste to bin through geographical information systems.

This study presents a geographical information system (GIS)-based procedure for the precise estimation of solid waste generation, computed using the local population density and income group distribution. Using a triangulated irregular network (TIN) in a GIS environment, the procedure further determines the command area for waste allocation to a particular bin which is generally located so the route slopes towards the collection points for ease of transportation by cart pullers. Computational results of bin location, type, size and the frequency of removal are presented for a typical urban area with known population density, income group distribution, road network and topology.     

Kinetics of steel slag leaching: Batch tests and modeling

Reusing steel slag as an aggregate for road construction requires to characterize the leaching kinetics and metal releases. In this study, basic oxygen furnace (BOF) steel slag were subjected to batch leaching tests at liquid to solid ratios (L/S) of 10 and 100 over 30 days; the leachate chemistry being regularly sampled in time. A geochemical model of the steel slag is developed and validated from experimental data, particularly the evolution with leaching of mineralogical composition of the slag and trace element speciation. Kinetics is necessary for modeling the primary phase leaching, whereas a simple thermodynamic equilibrium approach can be used for secondary phase precipitation. The proposed model simulates the kinetically-controlled dissolution (hydrolysis) of primary phases, the precipitation of secondary phases (C-S-H, hydroxide and spinel), the pH and redox conditions, and the progressive release of major elements as well as the metals Cr and V. Modeling indicates that the dilution effect of the L/S ratio is often coupled to solubility-controlled processes, which are sensitive to both the pH and the redox potential. A sensitivity analysis of kinetic uncertainties on the modeling of element releases is performed.     

Metal speciation in landfill leachates with a focus on the influence of organic matter

This study characterises the heavy-metal content in leachates collected from eight landfills in France. In order to identify heavy metal occurrence in the different size fractions of leachates, a cascade filtration protocol was applied directly in the field, under a nitrogen gas atmosphere to avoid metal oxidation. The results of analyses performed on the leachates suggest that most of the metals are concentrated in the <30 kDa fraction, while lead, copper and cadmium show an association with larger particles. Initial speciation calculations, without considering metal association with organic matter, suggest that leachate concentrations in lead, copper, nickel and zinc are super-saturated with respect to sulphur phases. Speciation calculations that account for metal complexation with organic matter, considered as fulvic acids based on C1(s) NEXAFS spectroscopy, show that this mechanism is not sufficient to explain such deviation from equilibrium conditions. It is therefore hypothesized that the deviation results also from the influence of biological activity on the kinetics of mineral phase precipitation and dissolution, thus providing a dynamic system. The results of chemical analyses of sampled fluids are compared with speciation calculations and some implications for the assessment of metal mobility and natural attenuation in a context of landfill risk assessment are discussed.     

Insight into the Adsorption Properties of Chitosan/Zeolite-A Hybrid Structure for Effective Decontamination of Toxic Cd (II) and As (V) Ions from the Aqueous Environments

Chitosan/zeolite-A hybrid structure (CS/Z.A) was synthesized and characterized as a multifunctional and environmental adsorbent for the Cd (II) and As (V) ions. The adsorption capacities of CS/ZA for Cd (II) and AS (V) are 170 mg/g and 125 mg/g, respectively which are higher values than several adsorbents in literature. The kinetic study demonstrates Pseudo-First-order behavior for the Cd (II) adsorption process and Pseudo-second order for the As (V) uptake reactions. The Cd (II) and As (V) uptake reactions follow the Freundlich equilibrium behavior with heterogeneous and multilayer adsorption properties. The kinetic and equilibrium studies in addition to the Gaussian energy {6.35 kJ/mol [Cd (II)] and 9.44 kJ/mol [As (V)]} demonstrate physical properties for the Cd (II) adsorption mechanism and more chemical behavior for the As (V) adsorption mechanism. The thermodynamic study declares exothermic, spontaneous, and favorable adsorption reactions for Cd (II) and As (V) by CS/Z.A composite. The CS/Z.A is of significant capacity for Cd (II) and As (V) ions in the existence of other competitive dissolved anions (PO₄^3?, NO₃^?, and SO₄^2?) and other metals [Zn (II), Co (II), and Pb (II)]. Finally, the CS/Z.A composite is a recyclable product and can be applied in effective Cd (II) and As (V) decontamination processes for five runs.

     

废水生化处理出水吸收SO2过程相平衡关系的确定

应用相平衡理论对吸收液－ＳＯ２体系的相平衡关系进行了系统研究,确定了吸收相平衡的数学模型,并通过试验对数学模型进行了验证,结果表明,数学模型计算值与试验实测值基本吻合。     

气相置换合成Zn-Cu-BTC及其吸附脱硫性能

采用气相置换法制备了Zn-Cu-BTC双金属有机骨架化合物,运用XRD,SEM-EDS,BET等技术对材料进行了分析表征,并以二苯并噻吩-正辛烷为模拟油（硫含量450 μg/g）,通过吸附脱除二苯并噻吩评价了材料的吸附脱硫性能。表征结果显示,Zn的引入改变了Cu-BTC特有的八面体结构。实验结果表明：在模拟油与吸附剂的质量比100∶1、吸附温度30 ℃的条件下,吸附90 min后Zn-Cu-BTC对硫的吸附达到平衡,吸附量可达38.8 mg/g,脱硫率为94.20%,而Cu-BTC吸附120 min后达到平衡,吸附量仅为26.6 mg/g;Langmuir等温吸附模型可有效描述Zn-Cu-BTC对硫的吸附过程。     

Assessing Aerobic Biodegradability of Plastics in Aqueous Environment by GC-Analyzing Composition of Equilibrium Gaseous Phase

Testing biodegradability of plastics under varied conditions of the environment as well as under laboratory conditions in accordance with valid international standards is very laborious, lengthy and often also economically demanding. For this reason, applicability was verified of gas chromatography to analyze gaseous phase when investigating the biodegradation course of plastics in an aqueous environment as an alternative to customary employed methods. A mathematical model of acid–basic CO₂ equilibrium in a gas–liquid system was worked out, enabling to determine quantity of produced CO₂ through chromatographic analysis of gaseous phase, in dependence on ratio of liquid and gas phase volumes (V _l/V _g) and on actual pH of liquid phase. Experimental conditions for organizing the tests were optimized. A ratio that proved suitable was V _l/V _g ≅ 0.1 at pH ≈ 7.1 of liquid phase. Under these test conditions, biodegradability of model samples, PHB, Gellan gum and Xanthan gum, was explored; course of biodegradation was studied through produced CO₂ (values ) determined by analyzing gaseous phase through gas chromatography on the one hand, and through customary “titration” procedure on the other. With water-soluble polymers, the decrement in dissolved organic carbon (values D _DOC) was also studied. Difference between values does not exceed 5%. The procedures in question are alternative “substituting” procedures for observing course of aerobic biodegradation of substances in an aqueous environment.     

Monitoring household waste recycling centres performance using mean bin weight analyses

This paper describes a modelling approach used to investigate the significance of key factors (vehicle type, compaction type, site design, temporal effects) in influencing the variability in observed nett amenity bin weights produced by household waste recycling centres (HWRCs). This new method can help to quickly identify sites that are producing significantly lighter bins, enabling detailed back-end analyses to be efficiently targeted and best practice in HWRC operation identified. Tested on weigh ticket data from nine HWRCs across West Sussex, UK, the model suggests that compaction technique, vehicle type, month and site design explained 76% of the variability in the observed nett amenity weights. For each factor, a weighting coefficient was calculated to generate a predicted nett weight for each bin transaction and three sites were subsequently identified as having similar characteristics but returned significantly different mean nett bin weights. Waste and site audits were then conducted at the three sites to try and determine the possible sources of the remaining variability. Significant differences were identified in the proportions of contained waste (bagged), wood, and dry recyclables entering the amenity waste stream, particularly at one site where significantly less contaminated waste and dry recyclables were observed.     

Hybrid sensor for metal grade measurement of a falling stream of solid waste particles

A hybrid sensor system for accurate detection of the metal grade of a stream of falling solid waste particles is investigated and experimentally verified. The system holds an infrared and an electromagnetic unit around a central tube and counts all the particles and only the metal particles, respectively. The count ratio together with the measured average particle mass ratio (k) of non-metal and metal particles is sufficient for calculation of grade. The performance of the system is accurately verified using synthetic mixtures of sand and metal particles. Towards an application a case study is performed using municipal solid waste incineration bottom ash in size fractions 1-6mm, which presents a major challenge for nonferrous metal recovery. The particle count ratio was inherently accurate for particle feed rates up to 13 per second. The average value and spread of k for bottom ash was determined as 0.49 ± 0.07 and used to calculate grade within 2.4% from the manually analysed grade. At higher feed rates the sensors start missing particles which fall simultaneously through the central tube, but the hybrid system still counted highly repeatable. This allowed for implementation of a count correction ratio to eliminate the stationary error. In combination with averaging in measurement intervals for suppression of stochastic variations the hybrid system regained its accuracy for particle feed rates up to 143 per second. This performance and its special design, intended to render it insensitive to external interference and noise when applied in an eddy current separator, make the hybrid sensor suitable for applications such as quality control and sensor controlled separation.     

Effects of hydrodynamic chromatography on colloid-facilitated migration of radionuclides in the fractured rock

The performance assessment of high level radioactive waste disposal has emphasized the role of colloids in the migration of radionuclides in the geosphere. Previous literature [Nagasaki S, Tanaka S, Suzuki A. Fast transport of colloidal particles through quartz-packed columns. J. Nucl. Sci. Technol. 1975;30(11):1136] indicates that owing to hydrodynamic chromatography the colloid velocity may not be equal to that of groundwater. Using hydrodynamic chromatography, this work investigates the effects of the size of colloidal particles on the radionuclide migration facilitated by colloids in a single fractured porous rock. Also, a methodology is proposed to develop a predictive model to assess transport within the fracture rock as well as various other phenomenological coefficients, particularly the size of colloidal particles. In addition, a fully developed concentration profile for non-reactive colloids in the fracture is developed to elucidate hydrodynamic chromatography of colloids in geological media. The external forces acting on colloidal particles hypothesized in the model proposed herein include inertial force, van der Waals attractive force, double layer force as well as gravitational force. The dispersion coefficient of colloids and the distribution coefficient for radionuclides with colloids are also considered as they pertain to the size of the colloid. In addition, the size distributions of colloids are utilized to investigate the effects of polydispersed colloids.     

Comparison of recycling outcomes in three types of recycling collection units

Commercial institutions have many factors to consider when implementing an effective recycling program. This study examined the effectiveness of three different types of recycling bins on recycling accuracy by determining the percent weight of recyclable material placed in the recycling bins, comparing the percent weight of recyclable material by type of container used, and examining whether a change in signage increased recycling accuracy. Data were collected over 6 weeks totaling 30 days from 3 different recycling bin types at a Midwest University medical center. Five bin locations for each bin type were used. Bags from these bins were collected, sorted into recyclable and non-recyclable material, and weighed. The percent recyclable material was calculated using these weights. Common contaminates found in the bins were napkins and paper towels, plastic food wrapping, plastic bags, and coffee cups. The results showed a significant difference in percent recyclable material between bin types and bin locations. Bin type 2 was found to have one bin location to be statistically different (p = 0.048), which may have been due to lack of a trash bin next to the recycling bin in that location. Bin type 3 had significantly lower percent recyclable material (p < 0.001), which may have been due to lack of a trash bin next to the recycling bin and increased contamination due to the combination of commingled and paper into one bag. There was no significant change in percent recyclable material in recycling bins post signage change. These results suggest a signage change may not be an effective way, when used alone, to increase recycling compliance and accuracy. This study showed two or three-compartment bins located next to a trash bin may be the best bin type for recycling accuracy.     

Influence of Filler Particle Size on Physical Properties and Biodegradation of Biocomposites Based on Low-Density Polyethylene and Lignocellulosic Fillers

This study examined biocomposites based on low-density polyethylene (LDPE) and lignocellulosic fillers [wood flour (WF) and oil flax straw (FS)] selecting four size fractions of each lignocellulosic material as fillers for the composites. The primary aim was to evaluate the influence of fraction size on the composites’ basic properties; to accomplish this, the composites’ mechanical properties, thermal oxidation, thermophysical characteristics, and water absorption capacity were examined. Then microphotographs of the samples were created and length-to-diameter (L/D) ratio of the fillers was calculated, finding that the L/D ratio increased with increasing particle size. The particle size influenced the oxidative degradation and water absorption processes in composites with oil flax but not in those with WF. Biodegradation tests performed on the recovered soil found that the loss of mass in composites based on LDPE and FS was higher than in the same composites with WF. Moreover, at the initial stage of composting, the biodegradation rate correlated with the size of filler particles (i.e., the larger the particles, the higher the degradation rate of the biocomposite).