The application of magnetic fields for landfill leachate treatment

This research is mainly focused on the capability of magnetic application of 0.55 Tesla magnetic field strength on reduction of suspended solid (SS), BOD5 and COD in landfill leachate through a circulation magnetic device which was conducted using the settling column test. The parameters monitored which effect the reduction of suspended solids and organic concentration were the magnetic exposure time of between 1 hour and 6 hours, operating flow rate of between 1 mL/s and 5 mL/s, and pH of between 2 and 13. Empirical mathematical models of sedimentation and column settling test were investigated to fulfill the behaviour of sedimentation under operating conditions due to the effect of magnetic exposure time, operating flow rate, and pH of the sample. Using the empirical mathematical models were analysed based on total suspended solids (SS), BOD5 and COD removal efficiency to variation of the operating flow rate, magnetic exposure time and pH. The model coefficients were derived from combined analysis of correlated sets of data, thus giving an indication for their possible general applicability. The pH had significant effects on the percentage of SS, BOD5 and COD removal, but pH increased the starting SS, BOD5 and COD removal rate. The study reveals that percentage of SS, BOD5 and COD removal efficiency decreased as the pH below 7 was increased, but it increased as the pH of between 7 and13 was increased the reduction of SS, BOD5 and COD in the sample. The experimental design at an exposure time to magnetic field of 6 hours, a flow rate of 2 mL/s with pH of 13 show that the removal efficiency of SS, BOD5 and COD at 72.57%, 63.93% and 56.97% respectively. Statistically tested by SPSS, there was a significant linear increase in average treatment efficiency to the magnetic exposure time and pH of sample at 95% confidence level. The experimental results were also generated empirical mathematical model relating percentage of SS, BOD5 and COD removal efficiency to flow rate, magnetic exposure time and sample of pH using MINITAB statistical software. The empirical mathematical models can be helpful in designing application of magnetic fields for landfill leachate treatment

Sustainable landfill leachate treatment using refuse and pine bark as a carbon source for biodenitrification

Raw and 10-week composted commercial garden refuse (CGR) materials and pine bark (PB) mulch were evaluated for their potential use as alternative and sustainable sources of carbon for landfill leachate bio-denitrification. Dynamic batch tests using synthetic nitrate solutions of 100, 500 and 2000 mg NO3 L−1 were used to investigate the substrate performance at increasing nitrate concentrations under optimal conditions. Further to this, sequential batch tests using genuine nitrified landfill leachate with a concentration of 2000 mg NO3 L−1 were carried out to evaluate substrates behaviour in the presence of a complex mixture of chemicals present in leachate. Results showed that complete denitrification occurred in all conditions, indicating that raw and composted CGR and PB can be used as sustainable and efficient media for landfill leachate bio-denitrification. Of the three substrates, raw garden refuse yields the fastest denitrification rate followed by 10-week composted CGR and PB. However, the efficiency of the raw CGR was lower when using genuine leachate, indicating the inhibitory effect of components of the leachate on the denitrification process. Ten-week composted CGR performed optimally at low nitrate concentrations, while poor nitrate removal ability was found at higher nitrate concentrations (2000 mg L−1). In contrast, the PB performance was 3.5 times faster than that of the composted garden refuse at higher nitrate concentrations. Further to this, multi-criteria analysis of the process variables provided an easily implementable framework for the use of waste materials as an alternative and sustainable source of carbon for denitrification

Recent developments in the application of risk analysis to waste technologies.

The European waste sector is undergoing a period of unprecedented change driven by business consolidation, new legislation and heightened public and government scrutiny. One feature is the transition of the sector towards a process industry with increased pre-treatment of wastes prior to the disposal of residues and the co-location of technologies at single sites, often also for resource recovery and residuals management. Waste technologies such as in-vessel composting, the thermal treatment of clinical waste, the stabilisation of hazardous wastes, biomass gasification, sludge combustion and the use of wastes as fuel, present operators and regulators with new challenges as to their safe and environmentally responsible operation. A second feature of recent change is an increased regulatory emphasis on public and ecosystem health and the need for assessments of risk to and from waste installations. Public confidence in waste management, secured in part through enforcement of the planning and permitting regimes and sound operational performance, is central to establishing the infrastructure of new waste technologies. Well-informed risk management plays a critical role. We discuss recent developments in risk analysis within the sector and the future needs of risk analysis that are required to respond to the new waste and resource management agenda

A decision support tool for landfill methane generation and gas collection

This study presents a decision support tool (DST) to enhance methane generation at individual landfill sites. To date there is no such tool available to provide landfill decision makers with clear and simplified information to evaluate biochemical processes within a landfill site, to assess performance of gas production and to identify potential remedies to any issues. The current lack in understanding stems from the complexity of the landfill waste degradation process. Two scoring sets for landfill gas production performance are calculated with the tool: (1) methane output score which measures the deviation of the actual methane output rate at each site which the prediction generated by the first order decay model LandGEM; and (2) landfill gas indicators’ score, which measures the deviation of the landfill gas indicators from their ideal ranges for optimal methane generation conditions. Landfill gas indicators include moisture content, temperature, alkalinity, pH, BOD, COD, BOD/COD ratio, ammonia, chloride, iron and zinc. A total landfill gas indicator score is provided using multi-criteria analysis to calculate the sum of weighted scores for each indicator. The weights for each indicator are calculated using an analytical hierarchical process. The tool is tested against five real scenarios for landfill sites in UK with a range of good, average and poor landfill methane generation over a one year period (2012). An interpretation of the results is given for each scenario and recommendations are highlighted for methane output rate enhancement. Results demonstrate how the tool can help landfill managers and operators to enhance their understanding of methane generation at a site-specific level, track landfill methane generation over time, compare and rank sites, and identify problems areas within a landfill site

Improving MSW landfilling system of developing countries: An assessment of current conditions and situations in Kedah, Malaysia

This article is about finding key structural and institutional adjustments that,if undertaken, would allow for realisation of continuous improvements to any municipal solid waste (MSW) landfilling system. Our analysis of the MSW landfilling systems of the developed nations had shown that every modern MSW landfilling system is comprised at least four major components that are interconnected. These four components are rules and regulations, environmental protection measures consisting of procedures, engineering, and technology, organisation and personnel arrangement, and revenues and costs. With the objective of finding what changes are necessary so as to cause improvement to the Kedah’s landfilling system, data on all four components were collected. The data gathering methods that were employed included a self-administered questionnaire, field observations, and structured interviews.Our assessment of the landfilling system of Kedah yielded the following results: the majority of landfill facilities in Kedah consisted of crude open dumping operations and the contributory factors to this situation include; facility operations were not overseen by higher level of governmental bodies; badly or improperly site, design, and construction criteria; facility management by either untrained or unskilled managers; and lack funds. The structural and institutional adjustments that we think should be undertaken include development of clearer laws and re-assignment of oversight responsibilities,adoption of appropriate landfilling practices and technology, creation of landfill worker training programmes, and the development of new financing devices to pay for higher costs associated with safer landfilling technology and management. Not until all of these four adjustments have been simultaneously 18 IJMS 14 (2), 17-33 (2007)considered, any attempts to cause improvements to the Kedah’s MSW landfilling systems will only just be a temporary solution

Tomographic inversion of time-domain resistivity and chargeability data for the investigation of landfills using a priori information

In this paper, we present a new code for the modelling and inversion of resistivity and chargeability data using a priori information to improve the accuracy of the reconstructed model for landfill. When a priori information is available in the study area, we can insert them by means of inequality constraints on the whole model or on a single layer or assigning weighting factors for enhancing anomalies elongated in the horizontal or vertical directions. However, when we have to face a multilayered scenario with numerous resistive to conductive transitions (the case of controlled landfills), the effective thickness of the layers can be biased. The presented code includes a model-tuning scheme, which is applied after the inversion of field data, where the inversion of the synthetic data is performed based on an initial guess, and the absolute difference between the field and synthetic inverted models is minimized. The reliability of the proposed approach has been supported in two real-world examples; we were able to identify an unauthorized landfill and to reconstruct the geometrical and physical layout of an old waste dump. The combined analysis of the resistivity and chargeability (normalised) models help us to remove ambiguity due to the presence of the waste mass. Nevertheless, the presence of certain layers can remain hidden without using a priori information, as demonstrated by a comparison of the constrained inversion with a standard inversion. The robustness of the above-cited method (using a priori information in combination with model tuning) has been validated with the cross-section from the construction plans, where the reconstructed model is in agreement with the original design

Balancing the Scales of Environmental Justice

This Essay discusses various ways to weave principles of justice and equity into solving the problem of environmental racism. This Essay also demonstrates the enormous potential of the waste management industry to act as an agent for environmental equity. Part I identifies problems that have led to accusations of environmental racism and conditions that have contributed to the definition of environmental racism. Part II discusses issues of the actual and perceived risks posed by waste treatment facilities, and the need for an understanding of these risks. The Essay next considers the issues raised in siting facilities, and the importance of community involvement and corporate responsibility in the decision-making process

Altered chemical evolution in landfill leachate post implementation of biodegradable waste diversion

Within the UK implementation of the European Union Landfill Directive (1999) has led to the diversion of biodegradable waste (BW) from municipal solid wastes away from landfills. It has been widely anticipated, but thus far not verified, that the diversion of BW and consequent reduction in BW reaching landfill would lead to a change in the degradation processes occurring within landfills and that this would be reflected in an altered evolution in leachate chemistry compared to pre-Directive landfills. This paper provides evidence based on leachate chemistry from two operational landfills together with calculations of the reduced BW content, that demonstrate the acetogenic phase that characterised pre-Directive landfill leachates is missing and is now more typical of methanogenic phase leachate. The paper demonstrates how data from national datasets and detailed landfill records can be used to constrain likely and upper estimates of the amount of BW going into post-Directive landfills, and the observed change in the evolution of leachate chemistry which has resulted from a decrease in BW content from typical values of BW (pre-Landfill Directive) of 22% to an inferred 12% in the case-study landfills. Data provided here add to the growing literature that estimates the amount of BW in recent post-Directive landfills which importantly allow the quantitative linkage between a decrease in landfilled BW and observed changes in leachate chemistry to be established such that future landfill operators can increase confidence in the effect of Directive implementation on landfill operational parameters

Mathematical modeling and numerical simulation of a bioreactor landfill using Feel++

In this paper, we propose a mathematical model to describe the functioning of a bioreactor landfill, that is a waste management facility in which biodegradable waste is used to generate methane. The simulation of a bioreactor landfill is a very complex multiphysics problem in which bacteria catalyze a chemical reaction that starting from organic carbon leads to the production of methane, carbon dioxide and water. The resulting model features a heat equation coupled with a non-linear reaction equation describing the chemical phenomena under analysis and several advection and advection-diffusion equations modeling multiphase flows inside a porous environment representing the biodegradable waste. A framework for the approximation of the model is implemented using Feel++, a C++ open-source library to solve Partial Differential Equations. Some heuristic considerations on the quantitative values of the parameters in the model are discussed and preliminary numerical simulations are presented