The hydrogeological and geotechnical properties of household waste in relation to sustainable landfilling.

PhDThis thesis reports an investigation into the hydrogeological and geotechnical properties of household wastes within the context of sustainable landfilling and, particularly, the development of a high rate flushing bioreactor. The design and construction of a large-scale (2-metre diameter) purpose built compression cell used in the research are described. Tests on a number of different household waste materials (including pulverised and aged wastes) were undertaken at varying applied loads up to 600 kPa, equivalent to a 60 metre depth of landfill. Results of variations in refuse density, stiffness, absorptive capacity, effective porosity and hydraulic conductivity are reported against average effective stress in the waste. It was concluded that the hydrogeological properties of household waste vary considerably with effective stress and, hence, with depth in landfills. For example, the hydraulic conductivity of crude household waste could reduce by over three orders of magnitude from approximately lxi O mis to lxi 4 rn/s between placement (with minimal compaction) and burial to a depth of 60 metres. The principles of sustainable development are considered and applied to landfilling. The view that the polluting potential of landfills should be reduced to acceptable levels within a generation is supported. In most cases this will require that contaminants in the landfill are removed by introducing water into the site and recirculating and flushing leachate from it. The feasibility of achieving this with a variety of different leachate recirculation systems is examined in the light of the findings of the research. A new module has been written for MODFLOW, the USGS's groundwater flow model, to allow hydraulic conductivity to vary throughout simulations with effective stress. The altered code is used to model a grid of leachate abstraction and injection wells to illustrate the potential for flushing. It is concluded that changes are needed to current landfill design and operational practices to enable wastes to be flushed efficiently within landfills. It is argued, in particular, that there are significant benefits of operating landfills with large saturated zones.Waste Technical Division of the department of thr Environment and Cleanaway Ltd

Review of responses to a landfill modelling Challenge

This paper reviews the responses from various international research groups to a challenge to model and predict the performance of a well-constrained laboratory experiment on the settlement and biodegradation of municipal solid waste (MSW). The paper outlines and compares the modelling approaches taken by the various groups and compares their predictions against actual long-term data from the experiment. The opportunity to compare models side-by-side against a common dataset has been extremely valuable in highlighting differences in approach, input parameters and identifying areas that need further investigation. One of the main differences identified related to hydrolysis, with three different algorithms used. Within the context of this modelling challenge it was not clear which was the appropriate formulation to use and thus the need for further work in this area was highlighted. This is also an example where the need to standardise on one pathway (or algorithm) could be investigated. There appears to be a clear imperative for settlement models to include a component for mechanical creep. An objective of the modelling challenge was to create a framework by which various models can be compared and act as a starting point for discussion and further collaboration in the future. This paper forms a starting point to this process

Coastal landfills and rising sea levels: a challenge for the 21st century

Populated coastal areas worldwide have a legacy of numerous solid waste disposal sites. At the same time, mean sea level is rising and likely to accelerate, increasing flooding and/or erosion. There is therefore concern that landfill sites located at and near the coast pose a growing risk to the environment from the potential release of liquid and solid waste materials. This paper aims to assess our present understanding of this issue as well as research and practise needs by synthesising the available evidence across a set of developed country cases, comprising England, France, Germany, the Netherlands and the USA (Florida). Common insights gained here include: (1) a lack of data and limited appreciation of waste release from coastal landfill as a potential problem; (2) recognition of the scale and diversity of coastal landfill waste within a range of generic settings (or situations); and (3) a lack of robust protocols that allow the impact of different categories of waste release to the coast to be assessed in a consistent and evidence-based manner, most particularly for solid waste. Hence, a need for greater understanding of the following issues is identified: (1) the amount, character and impact of waste that could be released from landfill sites; (2) the acceptability and regulation of waste eroding from coastal landfills; (3) present and future erosion rates at landfill sites suggesting the need for more monitoring and relevant predictive tools; (4) the full range of possible management methods for dealing with waste release from landfills and the science to support them; and (5) relevant long-term funding mechanisms to address this issue. The main focus and experience of current management practise has been protection/retention, or removal of landfills, with limited consideration of other feasible solutions and how they might be facilitated. Approaches to assess and address solid waste release to the marine/coastal environment represent a particular gap. Lastly as solid waste will persist indefinitely and sea levels will rise for many centuries, the long timescale of this issue needs wider appreciation and should be included in coastal and waste policy

Coastal landfills and rising sea levels: A challenge for the 21st century

Populated coastal areas worldwide have a legacy of numerous solid waste disposal sites. At the same time, mean sea level is rising and likely to accelerate, increasing flooding and/or erosion. There is therefore concern that landfill sites located at and near the coast pose a growing risk to the environment from the potential release of liquid and solid waste materials. This paper aims to assess our present understanding of this issue as well as research and practice needs by synthesizing the available evidence across a set of developed country cases, comprising England, France, Germany, the Netherlands, and the United States (Florida). Common insights gained here include: (1) a lack of data and limited appreciation of waste release from coastal landfill as a potential problem; (2) recognition of the scale and diversity of coastal landfill waste within a range of generic settings (or situations); and (3) a lack of robust protocols that allow the impact of different categories of waste release to the coast to be assessed in a consistent and evidence-based manner, most particularly for solid waste. Hence, a need for greater understanding of the following issues is identified: (1) the amount, character and impact of waste that could be released from landfill sites; (2) the acceptability and regulation of waste eroding from coastal landfills; (3) present and future erosion rates at landfill sites suggesting the need for more monitoring and relevant predictive tools; (4) the full range of possible management methods for dealing with waste release from landfills and the science to support them; and (5) relevant long-term funding mechanisms to address this issue. The main focus and experience of current management practice has been protection/retention, or removal of landfills, with limited consideration of other feasible solutions and how they might be facilitated. Approaches to assess and address solid waste release to the marine/coastal environment represent a particular gap. Lastly, as solid waste will persist indefinitely and sea levels will rise for many centuries, the long timescale of this issue needs wider appreciation and should be included in coastal and waste policy