Zaps of electricity clean up wastewater from biofuel production

Scientists are getting creative with new ways to produce fuels and electricity, but they can introduce their own problems too. Making biofuel from algae, for example, is showing promise, but it does create large amounts of toxic wastewater. Now, researchers in Australia have found a way to clean up that wastewater, with a simple and scalable electrical process.

The study started as an offshoot of another project where a team of scientists at the University of Sydney are running a pilot plant that’s farming microalgae, for the purpose of producing biofuels. Through a process called hydrothermal liquefaction, the algae biomass is converted into a high-energy substance similar to crude oil, which can be used as a kind of “green” fuel.

The problem is, the process creates large amounts of heavily contaminated wastewater that contains high levels of carbon, nitrogen and phosphorus. To make sure that this alternative fuel source is as environmentally friendly as possible, the researchers set out to find a way to clean up that water.

The team used a technique called electrochemical oxidation, which involves placing two electrodes into the water, one of which is made of diamond coated in boron. By sending an electrical current through, oxidation reactions are triggered at the surface of the electrodes, which converts many of the contaminants into less harmful products.

“We have employed an incredibly powerful process that eliminates even the most persistent non-biodegradable pollutants, such as pharmaceuticals and pesticides, as well as various classes of organic compounds that can be found in many industrial effluents,” says Julia Ciarlini Jungers Soares, lead author of the study. “The process is relatively simple, does not require the addition of chemicals or severe operation conditions, and does not produce additional waste streams.”

A sample of the wastewater before, during and after the electrochemical oxidation process
A sample of the wastewater before, during and after the electrochemical oxidation process

Julia Ciarlini Jungers Soares, University of Sydney

The team reports that the electrochemical oxidation process removed up to 99 percent of the carbon from the water, and cleared out 96 percent of the unsightly color. Nitrogen was converted from organic to inorganic forms like ammonia and nitrate.

These aren’t ideal to still have in water, but are less hazardous than other forms. That means this newly-cleaned water probably isn’t up to code for drinking, but it could still find similar use to recycled water, for things like watering gardens, washing vehicles, agriculture, firefighting and other industrial uses.

The team says the method is relatively simple, and could be scaled up to treat wastewater from industries like pulp and paper processing, wineries, pharmaceutical production and other facilities.

The research was published in the journal Algae Research.

Source: University of Sydney

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