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