Chemical And Biological Treatment Of Mature Landfill Leachate

The challenges imposed on Voltage Regulator Modules (VRM) become difficult to be achieved with the conventional multiphase buck converter commonly used on PC motherboards. For faster data transfer, a decrease in the output voltage is needed. This decrease causes small duty cycle that is accompanied by critical problems which impairs the efficiency. Therefore, these problems need to be addressed. Transformer-based non-isolated topologies are not new approaches to extend the duty cycle and avoid the associated drawbacks. High leakage, several added components and complicated driving and control schemes are some of the trade-offs to expand the duty cycle. The objective of this work is to present a new dc-dc buck-based topology, which extends the duty cycle with minimum drawbacks by adding two transformers that can be integrated to decrease the size and two switches with zero voltage switching (ZVS). Another issue addressed in this thesis is deriving a small signal model for a two-input two-phase buck converter as an introduction to a new evolving field of multi-input converters

Liquid Sodium Ferrate And Fenton\u27S Reagent For Treatment Of Mature Landfill Leachate

As landfills mature, biodegradable matter in leachate is consumed and remaining compounds are increasingly recalcitrant. In this work, ferrate was compared to Fenton\u27s reagent for the purpose of removing nonbiodegradable organic compounds from mature leachate. Oxidation conditions (time, pH, and dose) were optimized to yield maximum organic removal using two leachate samples from 20- and 12-year-old solid waste cells. Results from this study demonstrated that Ferrate and Fenton\u27s reagent had similar optimum pH ranges (3-5), but different organic removal capacities, ranging from 54 to 79% of initial leachate organic contents. An advantage of ferrate was that it was effective over a wide pH range. Advantages associated with Fenton\u27s reagent include that it had higher organic removal capacity, produced more oxidized organic compounds (measured as chemical oxygen demand/dissolved organic carbon), and produced more biodegradable byproducts (measured as chemical oxygen demand/5-day biochemical oxygen demand). Finally, both treatments were found to attack larger molecules (1,000 Dalton), as indicated by an increase in smaller molecule contribution to organic carbon. © 2007 ASCE

An Assessment Of Bioreactor Landfill Costs And Benefits

Because effective operation of bioreactor landfills involves careful operation and construction of infrastructure beyond that necessary in traditional landfills, upfront capital and operating costs are greater than those associated with traditional landfills. Prior to investing in bioreactor landfills, landfill owners must be convinced that larger short-term expenses (e.g., liquid and/or air injection infrastructure) will be balanced by future economic benefits (e.g., extension of landfill life, reduced leachate treatment costs, etc.). The purpose of this paper is to describe an economic model developed to evaluate the impact of various operational (anaerobic, aerobic, or hybrid) and construction (retrofit and as-built) bioreactor landfill strategies on project economics. Model results indicate retrofit bioreactor landfills are more expensive than traditional landfills, while both the as-built and aerobic bioreactor landfills are less costly. Simulation results indicate the parameters that influence bioreactor economics most significantly are airspace recovery, gas recovery and subsequent use to generate electricity, and savings resulting from reduced leachate treatment costs. © 2008 Elsevier Ltd. All rights reserved

Sustainable Disposal Of Municipal Solid Waste: Post Bioreactor Landfill Polishing

Sustainable disposal of municipal solid waste (MSW) requires assurance that contaminant release will be minimized or prevented within a reasonable time frame before the landfill is abandoned so that the risk of contamination release is not passed to future generations. This could be accomplished through waste acceptance criteria such as those established by the European Union (EU) that prohibit land disposal of untreated organic matter. In the EU, mechanical, biological and/or thermal pretreatment of MSW is therefore necessary prior to landfilling which is complicated and costly. In other parts of the world, treatment within highly engineered landfills is under development, known as bioreactor landfills. However, the completed bioreactor landfill still contains material, largely nonbiodegradable carbon and ammonia that may be released to the environment over the long-term. This paper provides a conceptual analysis of an approach to ensure landfill sustainability by the rapid removal of these remaining materials, leachate treatment and recirculation combined with aeration. The analysis in this paper includes a preliminary experimental evaluation using real mature leachate and waste samples, a modeling effort using a simplified mass balance approach and input parameters from real typical bioreactor cases, and a cost estimate for the suggested treatment method. © 2010 Elsevier Ltd

Strategy For Complete Nitrogen Removal In Bioreactor Landfills

Waste acclimation and batch microcosm studies containing digested municipal solid waste were conducted at different temperatures (22, 35, and 45°C) and gas-phase oxygen concentrations (0.7-100%, by volume) to provide guidance for field-scale implementation of in situ nitrogen removal processes. Results demonstrate that in situ ammonia-nitrogen is feasible in decomposed aerated solid waste environments at the gas-phase oxygen concentrations and temperatures evaluated and the potential for simultaneous nitrification and denitrification in field-scale bioreactor landfills is significant due to the presence of both aerobic and anoxic areas. Small amounts of oxygen were found sufficient for nitrification/ammonia removal to proceed, although removal rates increase with oxygen concentration. Laboratory results suggest field-scale implementation of in situ nitrogen removal occur in small dedicated treatment zones containing previously degraded waste (later in the life of a bioreactor landfill). Model simulations indicate removal of ammonia-nitrogen to low levels can occur with relatively short aeration depths (depth estimates ranged from 1.6 to 7.2 m below the point of leachate injection). Field-scale verification of these depth estimates is required prior to routine acceptance. © 2007 ASCE

Experimental Assessment Of The Adequacy Of Clayey Soils In Irbid To Retard Lead From Aqueous Solutions And Leaded Gasoline

Lead is a well-known chemical that is harmful to humans and the environment and can be spread widely, among other sources, by emissions from vehicles that still use leaded gasoline, leaks and spills of leaded gasoline and waste gasoline. Lead that reaches the ground surface may then migrate through the soil and reach groundwater aquifers. This, however, depends on many factors, including the soil type and properties. The ability of clayey soils to retard lead movement from aqueous solutions and leaded gasoline in the subsurface have been explored experimentally in this study. The experimental program conducted included experiments designed to estimate the sorption capacity of natural clayey soils in the Irbid area for lead from both aqueous solutions and leaded gasoline. Two major types of sorption experiments were carried out, namely, sets of experiments to obtain the sorption isotherms for a predetermined dose of soil added to a given aqueous solution and leaded gasoline and sets of experiments based on the Distributed Reactivity Model (DRM), in which lead concentrations varied over orders of magnitude. The results indicate that lead from leaded gasoline is not available for sorption and thus may migrate through soils and hazardous waste dump sites using clayey liners without experiencing retardation, while lead from aqueous solutions is retarded. This is because lead is present in gasoline as a non-polar complex compound called tetraethyl lead. This complex is then subject to biodegradation and may degrade after it penetrates clayey soils or clay liners and reaches the groundwater table to produce water soluble lead cations

The Role of Psychological Factors and Vaccine Conspiracy Beliefs in Influenza Vaccine Hesitancy and Uptake among Jordanian Healthcare Workers during the COVID-19 Pandemic

Vaccination to prevent influenza virus infection and to lessen its severity is recommended among healthcare workers (HCWs). Health professionals have a higher risk of exposure to viruses and could transmit the influenza virus to vulnerable patients who are prone to severe disease and mortality. The aim of the current study was to evaluate the levels of influenza vaccine acceptance and uptake as well as its determinants, among Jordanian HCWs over the last influenza season of 2021/2022. This study was based on a self-administered electronic survey that was distributed in March 2022. Psychological determinants of influenza vaccine acceptance and vaccine conspiracy beliefs were assessed using the previously validated 5C scale questionnaire (confidence, complacency, constraints, calculation and collective responsibility) and the vaccine conspiracy beliefs scale. The study sample comprised a total of 1218 HCWs: nurses (n = 412, 33.8%), physicians (n = 367, 30.1%), medical technicians (n = 182, 14.9%), pharmacists (n = 161, 13.2%) and dentists (n = 87, 7.1%), among others. About two-thirds of the study sample expressed willingness to receive influenza vaccination if provided free of charge (n = 807, 66.3%), whereas less than one-third were willing to pay for the vaccine (n = 388, 31.9%). The self-reported uptake of the influenza vaccine in the last influenza season was 62.8%. The following factors were significantly associated with higher acceptance of influenza vaccination if provided freely, as opposed to vaccine hesitancy/rejection: male sex; physicians and dentists among HCW categories; higher confidence and collective responsibility; and lower complacency, constraints and calculation. Higher influenza vaccine uptake was significantly correlated with nurses and physicians among HCW categories, older age, a higher monthly income, higher confidence and collective responsibility, lower complacency and constraints and lower embrace of general vaccine conspiracy beliefs. The results of the current study can provide helpful clues to improve influenza vaccine coverage among HCWs in Jordan. Consequently, this can help to protect vulnerable patient groups and reserve valuable resources in healthcare settings. Psychological determinants appeared to be the most significant factors for vaccine acceptance and uptake, whereas the embrace of general vaccine conspiracy beliefs was associated with lower rates of influenza vaccine uptake, which should be considered in educational and interventional measures aiming to promote influenza vaccination