Science and strategies for the long-term management and remediation of landfills
Lead Research Organisation:
University of Southampton
Department Name: Faculty of Engineering & the Environment
Abstract
Modern waste management is geared towards recycling and re-use. Inevitably, however, there will be some wastes that, having come to the end of their useful life, will require disposal to landfill. Many landfilled wastes are now treated prior to disposal, but the treatment does not necessarily remove all contaminants. In fact some pollutants can be concentrated into the final waste stream.Landfill sites are designed and operated to prevent contaminants contained in the wastes from polluting the surrounding environment (for example, water and air). However, the consequence of keeping the contaminants in the site is that the polluting potential of the site does not reduce and will last for a period measured in centuries rather than decades. This also means that the site will require looking after for a very long period (possibly hundreds of years), and it far from clear that the means to pay for this aftercare will last for that long into the future.The purpose of this research is to help develop techniques (simulations tools) that could be used to shorten the length of time that landfill sites pose a pollution risk. The research will be applicable to cleaning up the backlog of old landfill sites that exist across the UK. The research will also be of use in predicting the potential impact that new types of waste may have in landfills, in advance of any wholesale adoption of the technologies that produce them. This will make a positive and essential contribution to waste management policy and strategic decision making in the UK.The main way in which the pollution load of a landfill reduces is by the passage of water through the waste, accelerating breakdown mechanisms and flushing out contaminants. The introduction of air into landfills to encourage in situ 'composting' is also beneficial. It is important to understand the factors that control the movement of both water and air through landfills, and consequently there is a need to understand the relevant bulk properties of the wastes in landfills. We will develop a classification system that describes the essential characteristics of wastes, and undertake experimental work to quantify the bulk properties of wastes and link them to the description. From this it should be possible to improve predictions about how different waste types will behave in landfills. We will undertake tracer tests in both the laboratory and the field to develop an understanding of the bulk flow properties of wastes. However, very few tracers have previously been used successfully in wastes. Thus an early task will be to identify a range of tracers suitable for use in wastes, primarily by means of carefully controlled laboratory tests. Suitable tracers that we identify will be used in subsequent laboratory and field scale experiments. These experiments will be designed to investigate the process of contaminant flushing at a variety of scales. The results will be used to help develop a theoretical basis (modelling) that describes how efficiently contaminants will be removed from landfills in different situations. These models will be used to develop landfill management strategies by which the timescale of pollution can be reduced from centuries to decades or shorter.It is generally accepted that landfill gas generated within landfills as a result of ongoing degradation affects water movement and that water blocks gas flow. We will undertake laboratory experiments to provide visual evidence of the nature of the interference that gas and water have on each other. We will also develop models to explain and describe what we observe to help improve our understanding of the process.
Publications
Siddiqui A
(2013)
Settlement Characteristics of Mechanically Biologically Treated Wastes
in Journal of Geotechnical and Geoenvironmental Engineering
Siddiqui AA
(2013)
Biodegradation and flushing of MBT wastes.
in Waste management (New York, N.Y.)
Siddiqui AA
(2012)
Investigations into the landfill behaviour of pretreated wastes.
in Waste management (New York, N.Y.)
W. Powrie (Author)
(2007)
Landfill science research needs: after the EU Landfill Directive
White JK
(2013)
Developments to a landfill processes model following its application to two landfill modelling challenges.
in Waste management (New York, N.Y.)
White JK
(2014)
A multi-component two-phase flow algorithm for use in landfill processes modelling.
in Waste management (New York, N.Y.)
White JK
(2011)
Leachate recirculation in a landfill: some insights obtained from the development of a simple 1-D model.
in Waste management (New York, N.Y.)
William Powrie
(2011)
LDAT documentation and programme
Woodman ND
(2015)
Multiple-tracer tests for contaminant transport process identification in saturated municipal solid waste.
in Waste management (New York, N.Y.)
Description | Mechanically biologically treated (MBT) wastes from different sources have significant amounts of plastic, glass, paper and wood, together with unidentifiable material. Reinforcing elements (predominantly 2D) increase the shear strength but only at much lower quantities than normally present in MBT wastes. Shear strength of MBT appears to be controlled by displacement rather than strain. The consolidation coefficient of saturated MBT waste calculated from settlement vs time plot matches that from permeability and stiffness measured independently. Triaxial tests on dense specimens of MBT show "normal" geotechnical behaviour, i.e. the strength does NOT appear to increase indefinitely with strain. The creep and biodegradation of MBT waste can be dealt with using simplified models and laboratory tests can give relevant parameters for analysis. The following relationships can be applied to both treated and raw municipal solid waste: (1) biogas potential vs cellulose plus hemicellulose to lignin ratio (C+H)/L, (2) biodegradation induced settlement vs gas produced, and (3) hydraulic conductivity vs density. Micro CT scanning of degraded MSW showed a pore size distribution 10 x smaller than its particle size distribution. Particle compression, in response to increases in pore pressure and/or total stress, may account for approximately 20% of the total volume change in MBT up to stresses of 320kPa. Fluorescent dyes are useable as tracers in landfills, with fluorescein increasing in strength in landfill leachate owing to the presence of optical brighteners. The double-porosity transport model fits tracer tests at a wide variety of scales. |
Sectors | Environment |
Description | Has strengthened international links with landfill operators. |
First Year Of Impact | 2014 |
Sector | Environment |
Impact Types | Societal Economic Policy & public services |
Description | International Symposium on Geohazards and Geomechanics |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Keynote lecture on geotechnical hazards associated with closed municipal solid waste landfill sites to an international audience. The Symposium brought together the complementary expertise of world leading groups carrying out research on the engineering assessment, prevention and mitigation of natural geohazards. |
Year(s) Of Engagement Activity | 2015 |
URL | http://www2.warwick.ac.uk/fac/sci/eng/research/civil/geo/conference/presentations/william_powrie.pdf |
Description | Landfill Aftercare Forum |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Type Of Presentation | workshop facilitator |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | Provided stakeholder guidance to the building of a decision support system (LANDSS) for landfill aftercare Improvements to design of LANDSS |
Year(s) Of Engagement Activity | 2014,2015 |
URL | http://www.southampton.ac.uk/landss |
Description | Landfill Aftercare Forum, Birmingham, 2016 |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Industry/Business |
Results and Impact | A forum for practitioners to improve national practice in the management of landfill sites. Participants included 8 academia, 36 consultants, 30 private sector, 17 local authority, 22 other public sector, 2 trade organisation and 1 independent. |
Year(s) Of Engagement Activity | 2016 |
URL | https://landss.soton.ac.uk/ |
Description | Uniwin lecture 2018 |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | Prestige lecture at Institution of Civil Engineers: Transitions, Disruptors and the Quest for Sustainability (William Powrie). Some new technologies disrupt, and even those that do not often require complicated, systems-level transitions that are difficult to achieve quickly. The lecture illustrated these points with examples from energy and resource / waste management. It then critically assessed two ongoing efforts to achieve transformational change in transport: railway electrification and decarbonising our cities. Systemic failings that have hindered success were identified. The lecture then discussed what we need from research if we are to do better in realising the benefits of technology in the future, while balancing the often-conflicting goals of affordability, equitability, improved environmental sustainability and quality of life. |
Year(s) Of Engagement Activity | 2018 |