This new bioreactor uses algae to remove hazardous nitrates and pesticides from groundwater

June 2, 2021

A new bioreactor system can use algae to remove chemicals from water that has been contaminated with runoff from fertilizer. (Unsplash/Jordan Whitfield)

Researchers have invented a natural bioreactor system to remove organophosphate pesticides and nitrate from groundwater, using algae to filter well water before it can enter a treatment facility and contaminate an area's water supply.

Nitrogen, phosphorus and potassium are often called the "Big Three" in commercial fertilizers as plants need these macronutrients to survive. The novel system leverages the power of the nutrients themselves – which, in the form of nitrates and organophosphates, are harmful to humans – to grow algae biomass for harvesting while simultaneously filtering water. The invention is a collaboration between a team at the University of Nebraska-Lincoln and the government-funded Nebraska Environmental Trust. The patent application for this method and system was published by the U.S. Patent and Trademark Office on May 6.

The invention's aims are twofold. Its main purpose is to remove organophosphate and nitrate contaminants from water to make it safer for human consumption. At the same time, those contaminants promote the fast growth of algae, which can later be sold as a high-value product. 

The innovation addresses a key public health issue, particularly in the American Midwest and other agricultural regions across the planet: Phosphate-based pesticides can easily infiltrate the groundwater in farming communities, posing a hazard to human health. 

"People chronically exposed to low concentrations of organophosphates are at risk for nerve- and cancer-related disorders as well as diabetes," the researchers noted in the patent application. 

"Water remediation is sure to be a big industry as populations continue to grow and fresh water becomes more of a scarcity," lead inventor and assistant professor James W. Allen told The Academic Times.

Allen's interest in biological solutions comes from his appreciation of the wildlife and natural world around him. "Wandering around the resaca lakes in southern Texas and seeing their huge biological diversity, I became deeply interested in how organisms adapt to different environments," he said. 

"I think that algae researchers are generally interested in solving intractable problems in the intersection between humanity and the environment," Allen continued. "Biochemistry is really the branch of biology that answers those kinds of 'how' questions at their most basic level."

For Allen, algae research is nothing new. His first project after getting his Ph.D. was to develop next-generation biofuels from algae, which showed Allen the sustainable potential of these aquatic organisms. 

"With somewhere around 70,000 known and mostly unstudied algal species, I learned to see algae as a massive untapped biological resource," he explained.

Allen credits former Hastings, Nebraska Mayor Vern Powers as an inspiration. Powers is known as an advocate for the environment; he once sent an email responding to a plan to drill groundwater testing holes in the local area without the city's permission that began, "To put it bluntly, WTF!" 

Allen and his team partnered with Powers to develop bioreactors – made with algae, of course – to treat groundwater. "The resulting company, Vestal W2O, is now working with local municipalities to pilot scale the technology," said Allen

The main goal of the algal bioreactor is to remove chemicals from water saturated with runoff from fertilizer. According to the co-inventors, organophosphate pesticides are of particular concern. Organophosphates, which affect the nervous system of insects and other fauna, account for almost half of all pesticides used in the world. When left unchecked, they can reach toxic levels in fish and bioaccumulate in land animals.

 A photobioreactor is a relatively cheap and low-maintenance system to remove impurities within the water – in this case, nitrates and organophosphates. A unique feature of this water remediation system is that it also yields a very valuable product in the form of algae. Allen said that the algae grown inside the system can offset the costs of production; farmers can use the nitrogen-rich algae as a natural fertilizer for the crops, which has the added benefit of further decreasing the number of pesticides needed on the farm.

When fully operational, the system will consist of algae grown in a glass tube that is placed between an existing water well and a water treatment plant. The system is fitted with a pump to circulate the groundwater and a light source to enable photosynthesis. When the water filters through the tube, the phosphate and nitrate fuel the growth of the algae, which can then be gathered as a crop.

The invention is cheaper and less labor-intensive than current methods of removing nitrates and phosphates from the water, said Allen. Somewhat ironically, those methods require additional chemicals or enzymes to break down the chemicals in organophosphates. That's why natural systems involving algae have a leg up in the field.

Allen's laboratory is currently working with Vestal W2O to computationally model the system, which will help the team to test its economic feasibility. The team has also partnered with the Nebraska Environmental Trust and the City of Hickman to install the system in a nitrate-contaminated well and treat groundwater. Allen noted that rural towns without the money or access to sophisticated water systems that exist in larger metropolitan cities are at a particular disadvantage when it comes to making groundwater safe to drink.

"The groundwater nitrate problem in Nebraska is only going to get worse in the coming decades," Allen said. "The time is soon coming when farming towns will face a choice to either set up a system to purify their water from excess nitrate or simply not produce potable water and instead rely on bottled sources."

"That's a tough decision given the huge costs associated and the crazy tax burdens it places on the people living there," he added.

The application for this patent, "Biological remediation of groundwater using an algal photobioreactor system," was filed Nov. 4, 2020 with the U.S. Patent and Trademark Office. It was published May 6 with the application number 17/089472. The earliest priority date was Nov. 5, 2019. The inventors of the pending patent are Paul N. Black, James W. Allen and Timothy J. Nicodemus, University of Nebraska-Lincoln.

Parola Analytics provided technical research for this story.

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