Abstract
Although desalination by membrane processes is a possible solution to the problem of freshwater supply, related cost and energy demands prohibit its use on a global scale. Hence, there is an emerging necessity for alternative, energy and cost-efficient methods for water desalination. Cyanobacteria are oxygen-producing, photosynthetic bacteria that actively grow in vast blooms both in fresh and seawater bodies. Moreover, cyanobacteria can grow with minimal nutrient requirements and under natural sunlight. Taking these observations together, a consortium of five British Universities was formed to test the principle of using cyanobacteria as ion exchangers, for the specific removal of Na+ and Cl− from seawater. This project consisted of the isolation and characterisation of candidate strains, with central focus on their potential to be osmotically and ionically adaptable. The selection panel resulted in the identification of two Euryhaline strains, one of freshwater (Synechocystis sp. Strain PCC 6803) and one of marine origin (Synechococcus sp. Strain PCC 7002) (Robert Gordon University, Aberdeen). Other work packages were as follows. Genetic manipulations potentially allowed for the expression of a light-driven, Cl−-selective pump in both strains, therefore, enhancing the bioaccumulation of specific ions within the cell (University of Glasgow). Characterisation of surface properties under different salinities (University of Sheffield), ensured that cell–liquid separation efficiency would be maximised post-treatment, as well as monitoring the secretion of mucopolysaccharides in the medium during cell growth. Work at Newcastle University is focused on the social acceptance of this scenario, together with an assessment of the potential risks through the generation and application of a Hazard Analysis and Critical Control Points plan. Finally, researchers in Imperial College (London) designed the process, from biomass production to water treatment and generation of a model photobioreactor. This multimodal approach has produced promising first results, and further optimisation is expected to result in mass scaling of this process.
Highlights
In the year 2014, we are reaching the fulfilment of the “International Decade for Action WATER FOR LIFE—2005–2015” [1]
Cyanobacteria are oxygen-producing, photosynthetic bacteria that actively grow in vast blooms both in fresh and seawater bodies
This project envisages the utilisation of photosynthetic bacteria for the removal of specific ions from seawater, providing a sustainable alternative to seawater desalination, when compared to current methods [7,8]
Summary
In the year 2014, we are reaching the fulfilment of the “International Decade for Action WATER FOR LIFE—2005–2015” [1]. Developing countries are more prone to these effects [5] and these factors put together allowed for the conception of “Biodesalination: From cell to tap” [6] This project envisages the utilisation of photosynthetic bacteria for the removal of specific ions from seawater, providing a sustainable alternative to seawater desalination, when compared to current methods [7,8]. Cyanobacteria, or fractions that they secrete in response to salt stress, have been shown to remove Na+ from aqueous solutions and soils, as well as enhancing seed germination rates [9,10] This in turn generated the first challenge in the “Biodesalination” scenario. Biomass should be grown in a sustainable manner, utilising solar energy and the minimal addition of nutrients
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