IAP-24-022

Developing nature-based solutions for reducing microbial pollution in lakes and rivers

Water security is vital for providing ecosystem services and has far-reaching implications for human health, well-being, and economic stability. Consequently, now, more than ever, there is an urgent need for an integrated research agenda that couples water security with the remediation of anthropogenically impacted aquatic environments and develops nature-based strategies with the potential to reduce microbial pollution reaching surface waters, and sustainably remediates waterbodies already impacted by microbial pollution. In the UK, microbial contaminants, such as E. coli, and pathogens carrying genes for antimicrobial resistance (AMR) are becoming more frequent in our waterways due to the mismanagement of wastewater and sewage. Microbial pollution can have wide ranging impacts on downstream ecosystem services, e.g., drinking water, recreational activities, and fisheries, with significant consequences for environmental and human health with the framework of ‘one-health’.

Aquatic phytoremediation is a nature-based phytotechnology using aquatic plants (macrophytes) for the removal of pollutants from surface waters, and the restoration of impacted water bodies. Using macrophytes for phytoremediation is a non-invasive approach that can strategically target pollutants at points of delivery into waterbodies, and for treating already impacted waterbodies. Macrophytes and the sediments they trap can subsequently be removed from the water, and the sequestered pollutants safely treated or disposed of. The ability of macrophytes to assimilate, trap, and take-up pollutants such as E. coli and microbial pathogens carrying genes for AMR has recently been demonstrated in controlled laboratory experiments and several very small-scale field studies (mainly in China). Therefore, the overarching aim of this project is to optimise a series of context-specific strategies that can improve water quality by exploiting the ability of aquatic plants to assimilate waterborne microbial pathogens. This will contribute towards a strategic blueprint that could be translated to other areas of the world where there is growing pressure on water resources because of increasing population demands and provide the scientific basis for national scaling-up in countries with significant water security challenges and provide innovative low-cost solutions to microbial pollution.

Research objectives:
1. Identify UK native macrophyte species with a high efficiency for binding, uptake, or sequestration of E. coli and other human pathogens.
2. Develop and optimise novel ecological engineering solutions for field deployment.
3. Undertake field-scale experiments to determine realistic in situ pollutant extraction efficiency rates, and model the potential for scaling up.

Using a combined field and laboratory-based experimental approach, this project will provide the fundamental understanding necessary to deliver a step-change in our understanding of novel field-scale ecological engineering phytoremediation strategies. In all cases, locally adapted native species of macrophytes will be used and existing infrastructure, and waterbodies belonging to the University of Stirling (e.g., Airthrey Loch), will be used for the development of field-scale trials and experiments.

1: Identification of candidate macrophytes
The objective of this initial phase of the studentship is to quantify and optimise the ability of specific native UK macrophytes to bind, assimilate, and sequester waterborne E. coli and other pathogens (by either their roots or leaves depending on the growth form of the plant), and assess the synergistic effects of various combinations of different macrophyte species in fully replicated mesocosm tanks. This will then allow the student to manipulate the effects of plant developmental stage, growth form combinations, density-dependent evapotranspiration, and the timing of cultivation and harvesting to optimise pollutant extraction efficiency and sequestration.

2: Maximising removal efficiency of targeted aquatic pollutants through the development of novel ‘Floating Treatment Wetlands (FTWs)’
FTWs consist of artificial floating mats that sustain and support macrophytes and are a sustainable and effective way to remove excessive nutrients from eutrophic waterbodies. FTWs are non-invasive and can contribute to a number of ecosystem services, e.g., by providing habitat. To date however, FTWs have only been tested in hyper-eutrophic lake waters to facilitate the removal of excessive nutrients. Therefore, the aim of this phase of the studentship is to design a completely novel FTW platform that employs a plant community that has been specifically selected to target pathogens. In the few published reports on the performance of FTWs, there is a serious lack of control treatments that allow a proper evaluation of the compartmental effects of the FTW. Therefore, the student will test two types of FTW control treatments, i.e., (1) FTW platforms without plants, and (2) FTW platforms without plants and the floating mat. This approach will provide the evidence for species-specific effects of macrophytes for promoting the biofilm formation that could subsequently facilitate pathogen removal.

Year 1

Following a critical review of the literature (months: 0-4), the student will undertake a comprehensive series of field-relevant controlled laboratory and glasshouse tank experiments (months: 4-12) to identify candidate macrophyte species and manipulate experimental conditions to optimise removal of microbial contaminants and pathogens.

Year 2

During the second phase of the project (months: 12-24), the student will begin to develop an engineering strategy for deploying FTWs in the environment. This will involve designing and testing platforms for different environments (e.g., near point sources, or within highly impacted waters), and assessing background pollutant concentrations and the optimal duration for harvests.

Year 3

During the final year, FTWs will be optimised for remediation for environmental contexts and a range of pathogens and microbial pollutants.

Year 3.5

Writing the thesis and preparing papers for publication.

This studentship will provide a platform to build an interdisciplinary research career in environmental management and environmental public health. Extensive skill development in field work will include comprehensive training in environmental sampling and monitoring techniques. This studentship will broaden the scope of the applicant’s skills base by providing specialist training in the safe handling of microorganisms and microbiological techniques, and by developing expertise in the use of a wide range of skills in the ecological and applied sciences.