Matt Davey and several other members of Alison Smith’s group have shown that algae can successfully grow on nitrates sourced from a local drinking water processing plant. Excess nitrates must be removed from ground water that is extracted for drinking, before being allowed into the public water supply. This nitrate removal process is expensive and results in large volumes of a high nitrate, salt solution called brine wash.
Davey and Smith investigated whether the removed nitrate could be used for growing algae, which in turn could be used for bioenergy. Experiments were carried out at laboratory and pilot scales at the Algal Innovation Centre located within the Cambridge University Botanic Garden. They studied which algal species were able to grow on the brine wash, what the optimal blend of brine wash and growth media is for algae growth and whether the origin of the brine wash affected how well the algae could uptake the nitrates. In small scale laboratory experiments, they found five marine algal species that were able to grow in liquid growth media containing nitrate sourced from the brine wash. Further experiments showed that three of those species could grow on the modified growth media in the larger experiments at the Algal Innovation Centre, with one species performing well even up to a 100 L bioreactor scale. As well as taking up the nitrate, the algal biomass could be used effectively in biogas production in small-scale trials. Our results suggest that it may be possible to derive value from nitrate brine wash as a sustainable source of nitrate for the bulk growth of microalgae.
Highlights
- Water industry brine wash was assessed as a nitrate source for microalgal growth.
- Algae were unable to grow directly on the crude brine wash.
- Algae could grow in growth media substituted with nitrate sourced from brine wash.
- Algae could remediate up to 1700 mg nitrate at the 100 L bioreactor scale.
- Brine wash could be a sustainable source of nitrate for algae after optimisation.