Fate of microplastics in waste waters and sewage sludge used in agriculture – impacts on the terrestrial environment

   Faculty of Engineering, Computing and the Environment

   Applications accepted all year round  Self-Funded PhD Students Only

About the Project

Microplastics and fibres are widespread in the environment with significant work undertaken in marine environments looking at the fate and uptake of microplastics through the food chain. Microplastics are present in wastewater and associated discharges are cited as one of the main routes by which microplastics reach the marine environment. However, a very limited number of studies have suggested that >90% microplastics are partitioned to the solid fraction during wastewater treatment. This suggests that in countries such as the UK where sewage sludge cannot be disposed direct to the ocean, application to land via recycling of sewage sludge is the main (re-)entry point into the environment.

Knowledge of levels of microplastics in sewage sludge, and subsequent fate and transport in the receiving agricultural environment are practically unknown. This knowledge gap presents a significant challenge in the assessment and regulation of sewage sludge recycling. This PhD project will provide empirical evidence on levels of microplastics and fibres in sewage sludge, application rates to land; as well as understanding the influence of soil type on leaching potential. Novel investigations into whether microplastics or their break-down derivatives are taken up into growing food crops will also be undertaken. These studies can be used to improve current risk assessment models and provide recommendations for managing sewage sludge recycling to land.

The overarching aim of this project is to better understand the largely ignored role of the terrestrial environment in the introduction and dispersal of microplastics and fibres. Given the physico-chemical characteristics of the wastewater treatment process, sewage sludge is a likely sink for microplastics. Because the primary disposal routes of sewage sludge are incineration or recycling to land, it is likely that the agricultural environment plays a key role in the routes by which microplastics eventually reach the aquatic environment. There is also potential in the agricultural setting for microplastics and/or their breakdown products to be transferred to food crops or via direct ingestion into meat and milk products. There is little/no data on the potential for this route as a source of microplastic exposure to people. Given that microplastics are known to have strong sorption potential, there is by extension the likelihood that substances deleterious to health could be delivered via microplastic carriers.

The outcomes of this work will be to fill data gaps present in existing models used to evaluate risk from sewage sludge recycling and thus make recommendations for future management of sewage sludge recycling.

The project requires q strong background in organic chemistry and organic chemical analysis.

Biological Sciences (4) Chemistry (6) Environmental Sciences (13)

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