A little-known process for cleaning toxic wastewater could be the key to more efficient plant management.
Electrochemical oxidation involves treating wastewater with electricity using specialised electrodes. Discharged electricity drives oxidation reactions near the electrode surfaces, transforming the organic contaminants into harmless gasses, ions or minerals.
A team of engineers at the University of Sydney, led by Associate Professor Alejandro Montoya and PhD candidate Julia Ciarlini Junger Soares, has developed a solution to clean a specific type of wastewater heavily contaminated with a mix of organic and inorganic elements during a biofuel production process.
The study focuses on nitrogenated compounds commonly found in dyes, pesticides and pharmaceuticals, and how they break down.
“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,” she said.
“The process is relatively simple, does not require the addition of chemicals or severe operation conditions, and does not produce additional waste streams.”
The wastewater, which contained carbon, nitrogen and phosphorus, was generated in a pilot plant, designed by the team for the production of biofuels using naturally abundant microalgae.
“Wastewater is a significant issue for our environment, as well as for many industries who use substantial volumes of water in their processes, such as in reactions, transport, and washing and cooling. Finding suitable solutions for reuse or disposal is often very challenging and costly,” said Soares.
“The electrochemical method that we used can be readily applied to industries that must comply with strict regulations for wastewater disposal, such as pulp and paper processing, wineries, as well as pharmaceutical production facilities.”
“There are some commercial applications already, but it is not really widely applied,” Together with the fundamental knowledge we develop, then we create an optimised solution for a real application to industry.”
“Getting to know this process very deeply, and what we are generating out of this process, and what the by products are, and what we can do with the by-products, is important,” said Soares. “Coupled with the development of renewable energy, this is an ideal scenario that can solve current problems that industry has.”
Biological treatments (aerobic and anaerobic digestion) are the most common forms of treatment for wastewater in industries that only works for non-toxic wastewater streams. Other processes include the application of ultraviolet and the Fenton process.
The Fenton process requires hydrogen peroxide and ion salts. “You generate another stream of pollutants, and it’s not as efficient as the electrochemical oxidation, and not as controllable as well. You need certain conditions of pH and concentrations of ion salts, so I don’t see these processes can compete in terms of efficiency. We set the pace of degradation of pollutants by the electrical current that we put in the system.” she said.
“Processes that businesses are looking for are ones that are easily automated, that don’t require much maintenance, that don’t require many operators.”
Although electrochemical oxidation has existed for decades, according to Soares, there is space out there to explore this option. Currently, little is known about commercial applications.
The next step for the team is to build a pilot plant or a prototype to test in the field. “We have the know-how. From there, if that works really well, then we can upscale even more, and use different strategies as well,” Soares said.
Although she does not see that technology being used in a large scale at present, due to the absence of a reliable and renewable source of electricity, Soares believes the potential outcomes are promising.
“I think it’s important to keep pushing for and developing this process because it definitely works well for organic pollution,” she said. “As we develop more and more renewable energy sources and processes, then we could supply that kind of energy to the system.”
However, she believes it is entirely possible to develop real applications in Australia.
“From what I know, no-one’s really applying it right now in Australia. In the agricultural, poultry and winemaking sectors, it could be applied,” she said.
“There’s nothing that prevents this technology from being applied. Worldwide, researchers are investigating methods for the development of biofuels from algae. Developing alternatives for the treatment and reuse of this industrial effluent is a hot research topic and can bring opportunities for energy and resource recovery within a circular bio-economy framework.”
The team is currently focused on specific contaminants to better understand the chemical transformations that take place during electrochemical oxidation.
A 2017 UNESCO report found that the opportunities from exploiting wastewater as a resource were vast, and that safely managed wastewater is an affordable and sustainable source of water, energy, nutrients and other recoverable materials.
One of the biggest challenges currently faced by industry with wastewater management infrastructure is the space required and maintenance of a healthy biological system. The next step for the team is to build a pilot plant or a prototype to test in the field. A/Prof Montoya is working with industry partners in Australia to construct small-scale plants that can be controlled remotely, and can be set up easily in distant locations with reliable safety protocols,”
The study of Soares and Montoya was published in Algal Research, an international journal covering emerging algal technologies.