Chemical looping combustion (CLC) of municipal solid waste (MSW)

Chemical Looping Combustion (CLC) has been found to be a better alternative in converting Municipal Solid Waste (MSW) to energy and has the potential to reduce the generation of dioxins due to the inhibition of the de-novo synthesis of dioxins. This study comprehensively reviews the experimental studies of CLC of MSW, the oxygen carriers, reactor types, performance evaluation, and ash interaction studies. Modeling and simulation studies of CLC of MSW were also critically presented. Plastic waste is MSW’s most studied non-biomass component in MSW under CLC conditions. This is because CLC has been shown to reduce the emission of dioxins and furans, which are normally emitted during the conventional combustion of plastics. From the several oxygen carriers tested with MSW’s CLC, alkaline earth metals (AEM) modified iron ore was the most effective for reducing dioxin emissions, improving combustion efficiency and carbon conversion. Also, oxygen carriers with supports were more reactive than single carriers and CaSO₄/Fe₂O₃ and CaSO₄ in silica sol had the highest oxygen transport ability. Though XRD analysis and thermodynamic calculations of the reacted oxygen carriers yielded diverse results due to software computation constraints, modified iron ore produced less HCl and heavy metal chlorides compared to iron ore and ilmenite. However, alkali silicates, a significant cause of fouling, were observed instead. The best reactor configuration for the CLC of MSW is the fluidized bed reactor, because it is easy to obtain high and homogeneous solid–gas mass transfer. Future research should focus on the development of improved oxygen carriers that can sustain reactivity after several cycles, as well as the system’s techno-economic feasibility.

     

Novel synthesis of multicomponent porous nano-hybrid composite,theoretical investigation using DFT and dye adsorption applications: disposing of waste with waste

Environmental Science and Pollution Research - Extensive studies have shown that doping can enhance the properties of graphene, but the application to real industrial wastewater treatment and...     

Environmental behaviour of a construction made of a mixture of hydraulic binders and air pollution control residues from municipal solid waste incineration Part 1. Physico-chemical characterisation and modelling of the source term

The reuse of waste materials requires the development of assessment methods for the long-term release of pollutants (source term) from wastes (or materials containing wastes) in contact with water. These methods depend on the scenario conditions: characteristics of the materials (especially physical structure and composition), contact with water. The scenario studied here is a water storage reservoir for fire fighting. The reservoir construction is made of a mixture of hydraulic binders and air pollution control (APC) residues from a municipal solid waste incinerator (MSWI). The modelling of the source term is performed in 5 steps ranging from the physico-chemical characterisation of the material to the validation of the proposed model by means of field simulation devices. This article presents the first steps of the methodology: physico-chemical characterisation of the source term, identification of the main transfer mechanisms and laboratory scale modelling of the source term. During the physico-chemical characterisation, it has been shown that the solidified waste shows a high basic capacity and that a relative decrease in pH during leaching favours retention of the main pollutants. During the first leaching sequences, the dynamic leaching tests show that the release of pollutants such as cadmium, arsenic, zinc and lead is extremely low but that the release of alkaline species (sodium and potassium) and chloride is very high from the beginning, whereas the release of calcium remains very high even after 3600 h of leaching. Identification of the main transfer mechanisms concludes that the release of soluble pollutants is the combined result of diffusional transfer of pollutants in the solution and the physico-chemical specificity of the species. The modelling based on these features enables a good simulation of the release but reveals a deviation from the experimental results after 500 h for alkaline species and 1000 h for Ca and Cl leaching. However, this deviation only appears after release of the major part of these elements.     

Microbial conversion of fungicide vinclozolin

An ecological safety study of using vinclozolin in field and laboratory experiments showed that the effect of the preparation led to a decrease in the abundance of actinomycetes and mycelial fungi and an enhancement of nitrification. The residual amounts of vinclozolin in soil after 12 months were 6-12% of the dose introduced. The persistent chlorinated derivatives of the toxicant were found. Microbial strains pertaining to the genera Pseudomonas and Bacillus were isolated that utilized vinclozolin as the sole source of carbon and energy.     

Lead,zinc and copper accumulation and tolerance in populations of Paspalum distichum and Cynodon dactylon

Both Fankou and Lechang lead/zinc (Pb/Zn) mine tailings located at Guangdong Province contained high levels of total and DTPA-extractable Pb, Zn and Cu. Paspalum distichum and Cynodon dactylon were dominant species colonized naturally on the tailings. Lead, zinc and copper accumulation and tolerance of different populations of the two grasses growing on the tailings were investigated. Tillers of these populations including those from an uncontaminated area were subjected to the following concentrations: 5, 10, 20, 30 and 40 mg l(-1) Pb, 2.5, 5, 10, 20 and 30 mg (l-1) Zn, or 0.25, 0.50, 1 and 2 mg l(-1) Cu for 14 days, respectively, then tolerance index (TI) and EC50 (the concentrations of metals in solutions which reduce 50% of normal root growth) were calculated. The results indicated that both Lechang and Fankou populations of the two grasses showed a greater tolerance to the three metals than those growing on the uncontaminated area, which suggested that co-tolerant ecotypes have evolved in the two grasses. P. distichum collected from Fankou tailings had the highest tolerance to Cu while Lechang population the highest tolerance to Pb and Zn among the tested populations, and tolerance levels in P. distichum were related to metal concentrations in the plants. P. distichum had a better growth performance than C. dactylon when both of them were grown on the tailings sites. Tolerant populations of these species would serve as potential candidates for re-vegetation of wastelands contaminated with Pb, Zn and Cu.     

Growth and lipid composition of scallop juveniles, Placopecten magellanicus, fed the flagellate Isochrysis galbana with varying lipid composition and the diatom Chaetoceros muelleri

The effect of feeding the flagellate Isochrysis galbana (Parke; clone T-Iso) of modified lipid composition on the growth and lipid composition of juvenile scallops [Placopecten magellanicus (Gmelin)] was investigated in the spring of 1993. I. galbana grown in 85-liter cage culture turbidostats under conditions of nitrogen limitation had a significantly higher total lipid content than when grown under nutrient-replete conditions. This was due mainly to a doubling in the amount of less unsaturated triacylglycerol in the cells. The concentrations of methyl and ethyl ketones were also greater in nitrogen-limited cells. Diets of nitrogen-limited I. galbana and nutrient-replete I. galbana grown in continuous and semi-continuous cultures were compared. Scallop juveniles were batch fed daily, and measurements of ingestion were determined. Samples of juveniles were removed periodically for determination of organic weight. The juveniles did not grow when fed nitrogen-limited or nutrient-replete I. galbana alone; however, when each diet was supplemented with 20% of the diatom Chaetoceros muelleri (Lemm.), there was a significant increase in growth in the juveniles receiving the nitrogen-limited I. galbana compared with juveniles on other diets. In comparison with I. galbana,  C. muelleri provided a rich source of carbohydrates and the essential fatty acid 20:4ω6. This study shows the importance of providing optimal dietary levels of ω3 and ω6 polyunsaturated fatty acids, as well as less unsaturated fatty acids and carbohydrates. Received: 29 September 1997 / Accepted: 2 October 1998     

Micromorphology and chemistry of airborne particles in Brussels during agriculture working periods in surrounding region

The main objective of our research was to compare the airborne particle micromorphology and chemistry in the Brussels environment during agriculture working periods in the surrounding farming region. We used specific methods and instrumentation that are adapted to the climate peculiarities of the Brussels region, the period of investigations (12 months) and the proposed objectives. For the agricultural works we defined the following six periods: before sowing, sowing, after sowing, before harvest, harvest and after harvest. The results indicate a possible temporal correlation between agricultural work periods and airborne particle concentration, micromorphology and chemistry in the Brabant-Brussels region. For wheat and corn plant-growth periods, the average particle size, defined as the area obtained by a planar projection of the particulate, showed important variations in time. For sugar beet and endive, the average area size variations are less important. The roughness and sphericity parameters for the growth periods of the four different plants also showed significant differences. Many of the larger particulates (> 10 microm) are aggregates of even finer particles coated with many still finer ones. The airborne particle chemistry averages (atomic percentage At%), showed that three constituents (Si, S and Fe) dominate all the samples (except for particles 3-10 microm in size, which contain a relatively large percentage of Al). Applying similar investigation methods to study the correlations between airborne particle dynamics in urban zones and the agriculture working periods in their surrounding regions could be of interest to better understand the complexity of the PM problematic.     

Domestic water conservation potential in Saudi Arabia

Domestic water conservation in arid climates can result in efficient utilization of existing water supplies. The impacts of conservation measures such as the installation of water-saving devices, water metering and pricing schemes, water rationing and public awareness programs, strict plumbing codes, penalties for wasting water, programs designed to reduce leakage from public water lines and within the home, water-efficient landscaping, economic and ethical incentives are addressed in detail. Cost savings in arid climates, with particular reference to Saudi Arabia, in relation to some conservation techniques, are presented. Water conservation technology and tentative demonstration and implementation of water conservation programs are discussed.     

Effects of calibration on L-THIA GIS runoff and pollutant estimation

Urbanization can result in alteration of a watershed's hydrologic response and water quality. To simulate hydrologic and water quality impacts of land use changes, the Long-Term Hydrologic Impact Assessment (L-THIA) system has been used. The L-THIA system estimates pollutant loading based on direct runoff quantity and land use based pollutant coefficients. The accurate estimation of direct runoff is important in assessing water quality impacts of land use changes. An automated program was developed to calibrate the L-THIA model using the millions of curve number (CN) combinations associated with land uses and hydrologic soil groups. L-THIA calibration for the Little Eagle Creek (LEC) watershed near Indianapolis, Indiana was performed using land use data for 1991 and daily rainfall data for six months of 1991 (January 1-June 30) to minimize errors associated with use of different temporal land use data and rainfall data. For the calibration period, the Nash-Sutcliffe coefficient was 0.60 for estimated and observed direct runoff. The calibrated CN values were used for validation of the model for the same year (July 1-December 31), and the Nash-Sutcliffe coefficient was 0.60 for estimated and observed direct runoff. The Nash-Sutcliffe coefficient was 0.52 for January 1, 1991 to December 31, 1991 using uncalibrated CN values. As shown in this study, the use of better input parameters for the L-THIA model can improve accuracy. The effects on direct runoff and pollutant estimation of the calibrated CN values in the L-THIA model were investigated for the LEC. Following calibration, the estimated average annual direct runoff for the LEC watershed increased by 34%, total nitrogen by 24%, total phosphorus by 22%, and total lead by 43%. This study demonstrates that the L-THIA model should be calibrated and validated prior to application in a particular watershed to more accurately assess the effects of land use changes on hydrology and water quality.