Background

Current practice

In 2010, 252 million tonnes of total municipal solid waste (MSW) was produced in Europe (45% was sent to landfill). In 2008 approximately 1.4 million m³ of MSW leachate was collected for treatment from MSW landfills in Ireland. Leachate is the product of water that has percolated through waste deposits and undergone aerobic and anaerobic microbial decomposition. The main options for leachate treatment and disposal are:

• treatment and disposal on‐site (disposal to surface or ground waters)
• treatment onsite (to a greater or lesser extent) and disposal to a wastewater treatment plant (WWTP)
• direct transport and disposal to a WWTP for treatment

National and international relevance

Council Directive 99/31/EC  and the Water  Framework Directives (2000/60/EC)  are among the main European regulations  regarding  landfilling  and  its  impacts.  The  directives regulate the  nature  of wastes that  landfills  can receive  but  also the  execution of aftercare (normally 30 - 60 years). However, recent research suggests that aftercare timelines of up to 200 years  may  be required.  Where  excellent management  practices  are  in  place, this may  be reduced to  75  years. Therefore, in addition to the current challenge of disposal of leachate from operational landfills, there is a significant legacy challenge associated with landfills after they have ceased receiving waste. There are approximately 150,000 landfill sites in Europe, and it is estimated that between €10 and 17 billion is spent on leachate treatment in Europe annually. The immediate relevance of this problem (both environmental and economic)  is reflected  in recent FP7 and European Commission (JRC) supported research and publications (CleanLeachate ‐ http://www.cleanleachate.fraunhofer.eu).     

In Ireland, current practice is guided by the EPA Landfill Manuals, which recognise the need for careful management of landfill leachate treatment at WWTPs. However, as with other European countries, the implementation of the Water Framework Directive (2000/60/EC) has a significant impact on landfill leachate management by (1) regulating discharges to all waters and (2) resulting in stricter discharge limits being imposed on wastewater treatment facilities. Where landfill leachate is treated in WWTPs, plant managers are increasingly concerned over its impact on their ability to meet discharge limits – in particular removal of NH₄-N, N and organic carbon. The Government’s recent document “Our Sustainable Future” outlines meeting the WFD as one of the key measures in the timeframe to 2020. Therefore, there are clear economic, environmental and policy‐led requirements for a comprehensive investigation into best practice for treatment of landfill leachate at WWTPs and the steps that can ensure this process is sustainable for both the MWWTP and landfill operators. This research aims to achieve dual goals of improved cost efficiency for leachate treatment, while helping ensure WWTPS meet discharge limits.