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Reducing the environmental and health impacts of domestic waste landfills

SUMMARY

Research conducted at the School of Earth and Ocean Sciences at Cardiff University has resulted in significantly mitigating the serious health and environmental risks posed by municipal waste landfills.  Gas and leachate emissions from these sites have been linked to various cancers, respiratory disease, congenital birth defects, low birth weight rates and still births.  Environmental damage includes both surface and ground water contamination, and soil pollution.  Local, national and international concerns about landfills have long been expressed.  However, despite legislative and regulatory measures, the unique nature of each landfill and complications such as heavy rainfall (which results in excessive leachate generation) mean that sites continue to pose major threats.  The research has addressed this by quantifying the transport mechanisms and rates of release, along with determining the toxicity of landfill emissions.  Moreover, the development of techniques such as resistivity has enabled the 3D visualization of leachate generation and its movement within the body of the landfill.  This has led to new understanding of municipal landfill sites, which is essential for environmental and human health risk assessments.  The work has been successfully applied to sixteen landfills during the REF period.  This includes Nant-y-Gwyddon where links with birth defects stimulated international opposition.  Cardiff’s research was instrumental in decisions concerning gas and leachate management and ensuring a safer environment for the local community.

UNDERPINNING RESEARCH

Landfills present a real challenge to researchers because, as aforementioned, every landfill is different, and often presents very different hazards. The Cardiff Geoenvironmental Research Group has developed an integrated approach that includes geophysical research on emissions generation, leading to physico-chemical characterization and toxicology of emissions. This has, uniquely, brought together a very diverse set of knowledge and skills to better understand an issue that is globally recognized as a serious environmental problem.

The evolution of landfill design has produced the two major designs seen today – the ‘dilute and disperse’ and ‘containment’ landfills. Operating landfills generate airborne particles and gases, and landfill leachate (liquid produced by water percolating through the waste mass). Closed landfills generate landfill gas and leachate. Exposure of the human population to landfill emissions can occur via respiratory, dermal and ingestion routes Modern landfills are built as self-containing systems, but it is accepted that all landfills will leak to some extent. To define the distribution of leachate, geophysical techniques such as resistivity have been optimized by the Cardiff Earth Sciences researchers to allow the 3D visualization of leachate generation and its movement within the body of the landfill. These techniques, in conjunction with external monitoring, also give good indications when the leachate is being released or leaked into the subsurface environment [3]. Collected leachates and airborne particulate emissions are physico-chemically analysed, and then assessed for toxicity by a series of screening assays and innovative bioreactivity methods such as in-vitro human cell assays. This research, in collaboration with Cardiff School of Biosciences, has shown that both the liquid [4] and airborne emissions [5] contain or generate reactive oxygen species, which can lead to inflammation, DNA damage and human disease [6]. It is also clear from the Cardiff research that the potential biological damage caused by these emissions is not a simple function of dilution of leachate. In particular, landfill leachate can significantly damage DNA, and even considerable dilution of leachate by surface or groundwater only results in a minor decrease in toxicity.  This work on leachate toxicity is currently being developed to understand the dangers presented to specific types of human cells depending on the nature of exposure to the emissions; inhalation of particles, ingestion or dermal contact.

DETAILS OF RESEARCH IMPACT

Landfill emissions can result in catastrophic health and environmental issues.  DEFRA has estimated annual health costs from landfills as: deaths brought forward £3,100-£110,000; hospital admissions £1,887-£5,271; cancer £1,150,000-£2,260,000 and birth defects £90,500-£423,000.  Cardiff university's research, resulting in markedly enhanced risk assessments and waste management strategies, has served to mitigate these health risks and prevent significant environmental pollution.  From 2008-2013 the expertise and techniques developed at the School of Earth and Ocean Sciences have been applied to 16 projects.  Examples, which illustrate the breath of work and impact achieved, are:

1. Nant-y-Gwyddon (NYG)

Originally a coal opencast mine, the site took waste materials including calcium sulphate that reacted in the reducing environment of the waste mass to generate hydrogen sulphide (H2S) gas. The poisonous gas has an offensive rotten eggs smell, and was accompanied by a large range of other toxic gases generated at lower levels.  Locals objected to the smells, and concerns were raised about a perceived cluster of the congenital birth defect gastrochisis and Non-Hodgkins Lymphoma in the surrounding community.  Residents formed RANT (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC27248/), Rhondda Against Nant-y-Gwyddon Tip.  Epidemiological studies were inconclusive, and the decision was made to close and cap the landfill, with gas management and H2S detection systems in place. 

Cardiff research was active from the on-set of the problems in 2000, and continued from the capping of the site through to the post-remediation monitoring. Our research findings were used in the informed decisions on the site closure, effectiveness of that closure, design of gas and leachate management systems, and long-term gas and leachate monitoring at the site. We have also advised on the biotoxicity of the leachate, and our research input is still on-going with a project on the NYG gas generation in 2012. The many research findings from this site are of generic value, as offensive and poisonous gas emissions and serious concerns about human health proximal to landfills is a worldwide problem. 

2. Ferry Road

This closed landfill is situated next to Cardiff Bay within the city itself. The site includes a bend in the River Ely that flows into the Bay, and was available for filling when the river was straightened; initially therefore the waste was put directly into the un-lined river bed. The clean-up of derelict and contaminated industrial areas adjacent to the Bay generated huge amounts of toxic waste, including a considerable quantity of asbestos.  Eventually the waste formed a small hill (land raise), which was capped and is now a public park.  The main issue of concern was the landfill leachate and hydraulic connectivity with Cardiff groundwater and the Bay. Specifically the situation changed when the Cardiff Bay barrage was constructed, and the Bay changed from a ‘flushed’ tidal estuary to a freshwater lake. The concerns included a build-up of toxic chemicals and heavy metals in the Bay’s sediments. This required a good knowledge of leachate movement and behaviour within the landfill. Furthermore our investigations have shown that the leachate is toxic to DNA, and different levels of toxicity are found at different locations within the site.

In collaboration with the local authority and landfill operators, we have undertaken studies on this site since 1997. The initial studies looked at the impact on the ground and surface water environments, and proposed systems for leachate control that would protect the Bay from contamination. Later studies, once the site had been capped, used innovative geophysical techniques to map the generation and movement of leachate. This knowledge is essential for the proper management and disposal of leachate via the foul sewer system. The empirical work was supported by 3D modelling of leachate generation and movement, predicting the management requirements for decades to come. In addition to water contamination, there are also concerns about human health issues. Specifically the site is adjacent to a disused gasworks site, and our research indicated that the landfill leachate is being further contaminated by toxic chemicals from that site. Un-lined and mismanaged landfills are a very significant problem worldwide, either as a legacy of past or result of current practices. Our work has impacted on landfill management practice, and informed decision making about often highly complex waste and environmental interactions.

3. Lamby Way

Lamby Way is Cardiff’s current active ‘landraise’, and is situated just to the east of the City. It has just a few more years of active life left until full, when it will be finally capped and the site remediated. It consists of older capped sections that are not well engineered, and the modern active sections which are lined and engineered with leachate and gas systems in-place. The ground consists of clay-rich sediments that act as a natural mineral basal liner; however there are also coarser sediment layers that are known to act as pathways and release leachate into the environment. The environmental concerns at the site include leachate release, possibly reaching the Severn Estuary an environmental site of World importance, and the generation and release of biotoxic respirable airborne particles.

Research by Cardiff University at Lamby Way site extends back to 1997, and continues to this day. Since it is an active site it has allowed us to undertake in-situ research investigations, such as burying geophysical monitoring systems into the growing waste mass and collection of generated emissions not released by closed landfills. Our research has impacted on a number of operating procedures, including their landfill gas management, leachate treatment options, and the design characteristics of the active waste disposal cells. A specific issue of concern at Lamby Way was airborne particulate matter, and we have provided guidance on the management and potential toxicity of respirable particles. In addition guidance was provided on the biotoxicity of leachate from the various locations within the site.

KEY REFERENCES

[1] Andrew George (2004) Geoelectric Monitoring of Sub-surface Characteristics at Nant y gwyddon landfill site, Rhondda, Cardiff University, Report no. NYG-GEO 1.

[2] Brabham P.J., George A., Paris E., Harris C & Ling S. 2005, Geophysical investigations and monitoring at landfill sites in South Wales. Pp 156-164.  In: BASSETT, M.G, DEISLER, V.K  & NICHOL, D. (eds) Urban Geology in Wales II, National Museum of Wales Geological Series No.24, Cardiff.

[3] Sarah Ling (2007). Assessing the effectiveness of landfill restoration and remediation at a closed landfill site. Unpublished Ph.D. thesis, Cardiff University.

[4] Koshy, L., Paris, E., Ling, S., Jones, T. and BéruBé, K. (2007). Bioreactivity of leachate from municipal solid waste landfills - assessment of toxicity. Sci Total Environ, 384(1-3), 171-181.

[5] Koshy, L., Jones, T. and BéruBé, K. (2009). Characterization and bioreactivity of respirable airborne particles from a municipal landfill. Biomarkers, 14(Supplement 1), 49-54.

[6] Koshy, L., Jones, T. and BéruBé, K. (2008). Bioreactivity of municipal solid waste landfill leachates-Hormesis and DNA damage. Water Res, 42(8-9), 2177-2183.