Detoxification and Resource Recovery

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.

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 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 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.

Converting Ministry of Defence Waste into foams

In this project we aim to aid UK Defence and Security by developing a bioprocessing prototype system that can aid on-site treatment and recycling of hazardous waste. We propose to develop and combine novel biological, physical and chemical technologies, which will not only de-toxify the waste effluent, but at the same time, generate a by-product to add value to the process. Similar to other waste streams we have successfully worked on (e.g. landfill leachate), the costs of transporting waste to specific designated treatment sites are extremely high and not environmentally friendly. On-site treatment capability can reduce this cost significantly.

The right microbial consortia: Microbial communities can be the cheapest waste transformation option, and certainly the most sustainable. The microbes themselves act as catalysts and are therefore the “active ingredients” within the process, and their ability to reproduce means their effectiveness in treatment can be maintained by ensuring ideal cultivation conditions are provided. As whole cell catalysts, they have the capability to utilise a variety of substrates (e.g. hydrocarbons, benzenes, heavy metals etc.), including the oils present within the waste streams characterised in the MOD Waste. Bacteria produce a suite of biocatalysts (i.e. enzymes such as oxido-reductases and hydrolases) for degradation of hydrocarbons using biochemical mechanisms. Considering the complex mixture of wastes in the effluent, mixed populations with broad enzymatic capabilities are required. A challenge is to select the right strains that can work synergistically, and hence optimal waste transformation performance. This is because the right strains can work in “teams”, where one strains secretes compounds which can be used by another strain as a resource. This also deals with any potential toxic by-products. Moreover, strains that target different substrates are not within the same “niche” and hence are not competing with each other, increasing efficiency. Ultimately, the main objective is produce clean water that can be released into the environment or re-used internally.

Resource recovery Another challenge is to recover resources. Although microbial communities are widely in the waste treatment sector, characterised with an abundance of chemical resources, current modular treatment processes do not tend to incorporate resource recovery beyond clean water and biomass. Due to a recent move towards generating a “circular economy” in the UK, there a some technologies that have been tested at lab-scale, including bioelectrical systems to recover energy, nutrients and metals, strong acid ion exchange resin for recovery of ammonia and very recently the targeted recovery of magnesium. We have a unique approach where microalgae are present within the bacterial consortium. As the complex hydrocarbon-based substrates are degraded by bacteria using oxygen (O2) through respiration, they produce carbon dioxide (CO2), the algae consume this CO2 and produce O2, completing the symbiotic process. The resulting microalgae biomass represent the resource. We aim to demonstrate the conversion of this biomass into synthetic soils, i.e. biodegradable, bio-based polyurethanes, ideal for environments with soils not amenable to plant growth (due to low quality soils i.e. desert conditions). Although they could of course also be used by service personnel to supplement their food rations, adding much needed nutrition and flavour, it is envisaged that synthetic soils could also be exploited by aid organisations who could distribute for refugee camps for example.

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