University of Bath students design system to prevent algal blooms

Students are experimenting with a way to extract harmful phosphates from wastewater for reuse as fertiliser.

Researchers at the University of Bath have said a genetically engineered bacterium could one day solve the twin problems of nutrient pollution and phosphate depletion.

It is hoped that synthetic biology could help end agriculture’s reliance on phosphate mining to make fertilizer.

At the same time, the new “closed-loop” system could reduce the occurrence of devastating algal blooms, they said.

Pho Bac

Dubbed the PhoBac project, the team genetically engineered the benign bacterium bacillus subtilis to absorb much more phosphate than needed.

The goal is to release it into wastewater at treatment plants, because even treated wastewater can still contain very high levels of nutrients when released into the environment.

Phosphates, in combination with nitrates, can cause eutrophication – an excessive growth of plants or algae that deprives other life forms of light and oxygen, sometimes creating large dead zones.

Algal blooms can be devastating to aquatic ecosystems

Meanwhile, phosphate rock is found in only a handful of countries and is a rapidly depleting resource.

Gregorio Nepomuceno Queiroz, who led the project, said: “The phosphate that has been painstakingly extracted enters our body through food and is then discharged down the drain.”

Speaking to BBC West, Queiroz said: ‘(Phosphate) is a resource that will deplete over time and it’s important to find a sustainable alternative, and that’s where we come in.’

The PhoBac project has already received a gold medal at the iGEM international synthetic biology competition.

‘We have to be careful’

The first phase of the project, the development of a bacterium that removes phosphates from water and releases them in response to plant signals when in the soil, has been completed.

Queiroz warned that it could be many years before PhoBac receives regulatory approval.

“We have to be cautious about things – some people are quite wary of genetically modified organisms and to some extent I think that’s quite important,” he said.

“It’s important that we are kept in check.”

Waste water

Currently, the team expects the final PhoBac system to see bacteria encased in tiny beads with a semi-permeable membrane that allows water in but prevents bacteria from escaping.

The pearls could then be filtered out of the water at the end of the treatment process.

Treborth Sewage Treatment Plant

PhoBac could be used in wastewater treatment plants in the future

Despite its potential to mitigate algal blooms, the system is unlikely to ever be released directly into waterways.

Queiroz said: “We’re already quite hesitant about putting him on a field, for example, which is already a bit isolated.

“In a river we would have very, very limited control, unless we found an extremely secure system, where we knew the pearls would never be released or go beyond our controlled area.

“But we’re not really thinking about this avenue, we’re just thinking about wastewater treatment plants at the moment.”

Jeremy Boyle, a final year biology student involved in the project, said he was confident about what PhoBac could achieve in the future.

“Large-scale PhoBac promises to stabilize and reduce agricultural costs, which are currently volatile and rising,” he said.

“It also has the potential to reduce phosphate levels in our rivers and streams, rehabilitating aquatic ecosystems along with fish and invertebrate biodiversity.”

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