The potential to restore eutrophic freshwater systems in the UK with economic benefits

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The biggest threat to global freshwater systems is pollution, and considering the World's population is expected to top 9 billion in less than 30 years (1), the problems are likely to worsen. Initially, the major losers appear to be wildlife, tourists and industry. However, the problem will extend much further as the demand for clean drinking water increases with population size. Global spatial time-series analyses have already linked wars to freshwater availability (1). The main cause is hugely increased nutrient levels over the last 50 years, thanks to discharges of domestic waste and pollution from agricultural practices and urban development. Algal blooms occur due to increased nutrients (nitrogen, N and phosphorus, P), which subsequently lead to increases in oxygen demanding bacteria that resulting in further detrimental effects to the ecosystem, including fish kills (termed eutrophication). Often perceived as a problem for developing countries, it is now known that over 75% of England's surface freshwater is classified as eutrophic (2) and the costs for managment extend from £75-114m per year (3).Efforts to control eutrophication include biomanipulation, e.g. adding predatory fish to alter food web structure and increase presence of 'algae-eaters'. There have also been efforts to limit nutrient input. Both methods have had limited success. Removing the algae by harvesting would potentially produce a more immediate impact and could be used as a stand-alone remediation tool or combined with the aforementioned methods. However, harvesting was an energy intensive process, until now. An award-winning device invented at the University of Sheffield has been shown to be over 99% efficient at harvesting algae and requires very little energy input compared to competitive technologies (4,5). Termed microflotation, it relies on the creation of tiny, non-coalescing, uniform microbubbles. This method of removing the polluting algae would be applied to accelerate remediation of freshwater systems where algal blooms have formed. The recovered algae biomass can then be used as a resource for a variety of applications and this presents the 'hidden' economic benefits with this remediation method.Algae are highly diverse, single- or multi-cellular organisms comprised of mostly lipids, protein, and carbohydrates. Lipid content can each up to 80% and these can be readily converted into bio-diesel, a fuel type that can easily integrate into our current energy-use infrastructure. Although cyanobacteria (blue-green algae) have lower lipid levels (15-20%), these too can be converted to biodiesel. The production of fuel here can be used to offset the costs of harvesting and remediation. Algae are also a rich source of protein which can be used for animal or fish feed. The nutrient content (P and N) means recovered algae can also be used a fertiliser and at the same time, condition agricultural soil which has deteriorated due to generations of cultivation use. In summary, there are arrays of exciting uses for recovered algae from polluting environments. And although tremendous amounts of data on algae in our water systems exist, the numbers have not been collated and translated to quantify the concepts described. This catalyst grant aims to analyse this data. It also aims to assemble a multi-skilled team to look at the impact on the natural environment, landowners, farmers, the public, lake protection groups and tourists. It also aims to draw in expertise from biofuel process engineers. The notion of recovering resources from waste represents an ecological engineering approach to system design, and these concepts will be used to engage students in a local school, widening impact of the research and inspiring next generation engineers and scientists.1.Levy, M., et al., June 21-23, 2005.2.JNCC Report, 2001.3.Pretty, J. N., et al., 2003, 37, 201-208.4.Hanotu, J., et al., 2011.5.Zimmerman, W. B., et al., 2011, 16, 350-356.