Detoxification and Multi-Resource Recovery from Landfill Leachate

Despite improved recycling infrastructure and public awareness, the UK still sends a staggering 17 million tonnes of municipal solid waste into landfill every year. This leads to the build up of leachate, the liquid which drains from a landfill site. Leachate contains trace chemicals, which can have strong contaminating effects on the environment, and therefore effective treatment methods are required. More to the point, however, ambitions for waste management should go beyond protection of human health and the environment, with conservation of energy and recovery of natural resources high on the agenda.

This translational project aims to demonstrate an integrated process for leachate treat went and resource recovery. It involves three innovations: a novel physical pre-treatment, enhanced treatment with adaptively evolved microbial consortia and resource recovery through efficient biomass harvesting, and hence, contributing to the UK circular economy. The outcomes cut across several NERC research priority themes e.g. 'sustainable use of natural resources' and 'environment, pollution and human health.'

Leachate can vary considerably in composition, depending on the age and type of waste within the landfill, containing both dissolved and suspended organic and inorganic material. Viridor Waste Management Ltd is the third largest waste management organisation in the UK, owning over 40 sites. Approximately half the sites use foul sewers to carry contaminated wastewater to a sewage works for treatment, the rest is either transported using tankers or released to surface waters. The total annual leachate production is 1,056,716 m3 and the operational costs vary between £4-£10 per m3 (e.g. disposal costs, energy or chemicals used).

The previous work includes isolation of natural microbial consortia from leachate, novel harvesting method development and estimation of potential resources recovered. The main translational activities in this project are to design and build a pilot scale photobioreactor that is fitted with all the innovations from previous NERC and non-NERC funded research. This will be installed by Varicon Solutions, TUOS Research Technician and staff at Viridor at a local landfill site (Erin). Pre-processed leachate will be fed into the photobioreactor and growth and operating parameters carefully monitored. The data will be used in a techno economic assessment for Viridor but also other end-users. An easy-to-use Resource Recovery calculator will also be created. The process will be filmed in time-lapse and used to make a video for marketing, knowledge exchange and educational purposes. Both the video and photobioreactor system will be demonstrated at a relevant Trade Show in late 2017/early 2018.

The ultimate aim is to demonstrate the progress of the NERC funded research up technology readiness levels with industrial, societal and environmental impact, together with economic benefits for the project partner and wider waste management community.

Presently, the core of our infrastructure in regard to resource production as well as waste treatment relies on unsustainable means i.e. fossil fuels. A more viable approach is desperately required, where energy inputs are reduced or sourced renewably and resources are recycled. From this perspective, the most elegant template for engineering an ideal but complex system is a natural system where nothing is left unused; waste from one component is the resource for another. This project is inspired by a microfluidic device but also natural communities of microorganisms that form the basis of biological treatment of toxic waste. Biological treatment is often cheaper and more energy efficient than chemical and physical methods, but crucially, have reduced negative environmental impacts. The project is not solely focused on treatment but also on resource recovery and helping form a sustainable circular economy. By recovering resources from waste means efforts to gain resources by traditional energy intensive means can be reduced, for example, ammonia production by the Haber process or mining of metals. Microalgae will provide the mechanism for resource recovery and gain energy through photosynthesis, further confirming the sustainability of the approach.

The development of advanced engineering approaches and modifications to traditional landfill practice have been spurred on since the first European Directive in 1975 (Surface water 1975/440/EEC) where attempts have aimed to minimise the adverse impact of waste on the environment. However, the existence of contaminated leachate is an inevitable consequence of the process. Furthermore, regulatory standards (EU Urban Waste Water Directive 91/271/EEC) have become stricter. This project aims to develop an advanced and novel physical and biological based methodology that can be applied for treatment of a variety of wastes and therefore help achieve these standards.

The primary beneficiaries include the growing waste management industry. As well as more efficient and reduced cost of leachate treatment, the resources recovered can be used internally. For example, Viridor spend £25m per year on diesel and generating a liquid fuel from their waste would lower their demand for transportation fuel and overall carbon footprint. They also use heavy metals and recovering these would reduce purchasing costs.

Indeed, any industries related to water use including water companies, fisheries and tourism would see indirect impact of this research as treated leachate will reduce the chances of contamination of nearby ground and surface water. This includes recreational water use, e.g. fishing, water sports, swimming, boat clubs etc. Regulatory bodies such as the Environment Agency would benefit from improved water surface characteristics near landfill leachates, and land/water body owners such as the Canal and River Trust and Natural England will also feel the value.

Ultimately, the detoxification of leachate will benefit the natural environment, wildlife and society and increase the opportunity to achieve "good ecological status" (National UK Ecosystem Assessment by Defra). Currently, 95% of municipal solid waste (450-500 million tonnes) is disposed of annually Worldwide in landfills and this continuously contaminates surface and ground water. Furthermore, one tonne of landfill is estimated to generate about 125 m3 of greenhouse gases (65% CH4, 34% CO2) contributing to approximately 20% of the Worlds anthropogenic methane production and hence manmade global warming.

Finally, companies with expertise in photobioreactor technology required to cultivate the algal microbial communities will benefit from the knowledge created here.