How can microalgae solve agricultural pollution?

I get it… the idea of growing microalgae in space is both epic and inspiring.

Movies like “The Martian”, or papers on algae life support systems (LSS) can also send my mind into overdrive. But could these space technologies solve other planetary problems too?

Martin et al. sure think so, and in this article we’ll consider their 2020 piece which explores the use of microalgae for agricultural waste water treatment.

Summary

In 2022, the agriculture sector is a known major polluter as farms often squeeze every inch of productivity out of their land using all manner of fertilisers. In the worst-case scenarios, untreated water runoff from these farms can heavily contaminate rivers, and lead to seriously dangerous algal blooms.

(If you don’t know much about algal blooms and their issues, check out this short clip from our friends over in Florida:)

But what if we harnessed this algal reactivity to wastewater and used it for good? This is the subject of investigation in Martin et al.’s 2020 paper, which hopes to utilise research on microalgae LSS to reduce nitrate pollution in groundwater runoff.

Figure 1 showcases the experimental setup Martin et al. use in their attempt to valorise wastewater. Synthetic groundwater first flows through a prefiltration mechanism to concentrate the nitrate, before the water passes through an algal photobioreactor. A special LED system then illuminates the bioreactor to encourage optimal algal growth.

 

Figure 1: Polluted water runs through a prefiltration device. The nitrate concentrate then flows into the microalgae photobioreactor and biomass is collected. (credit Martin et al.)

 

Figure 2: The setup of two one-litre reactors in the lab (Martin et al.)

The results?

Overall, the results were good, and the team reduce nitrate concentration substantially in this setup! In addition, by using flashing light they maintained solid algal growth and reduced the energy consumption (improved light efficiency).

Evaluation

For starters, the flashing light observation was interesting given the experimental setup, and it’s always fun to read research from teams who have microalgae for space travel in mind.

While the flashing light observation may not be novel, it sure adds energy savings into the mix which makes the process cheaper, better for the environment and perhaps better for intergalactic colonisation!

Unfortunately, I’m not sure how this process stacks up against alternative procedures for treating wastewater. Even in the realm of microalgae, many researchers have previously explored cost effective wastewater treatment. For example, Professor Moheimani, a big advocate of microalgae in this field, had this to say about the subject:

I believe wastewater treatment using algae will commercialise soon. I would be highly sceptical if it didn’t, especially in parts of the world where you have enough sunlight.

Professor Moheimani

Given the competitiveness of wastewater treatment, and the technological readiness level of alternatives, it’s hard to picture how this research will fare. Nevertheless, harmful algal blooms still cause $4¬†billion¬†dollars of damage every year (United Nations). Therefore, we shouldn’t underestimate the size of this market and the potentially better scalability of this project.

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