In recent years, the wastewater treatment industry has made a concerted effort to become more energy efficient and engage in sustainable practices. Now, a new process gives wastewater operations another avenue to reuse their byproducts.
A team at an Australian university has developed a procedure to create fired-clay bricks made of biosolids, creating useful construction materials out of one of the primary byproducts of wastewater treatment.
“Abbas Mohajerani of RMIT University in Melbourne and his team began experimenting with different recipes for biosolid bricks,” per Smithsonian. “They tried various mixtures, making bricks with 10 to 25 percent biosolid content [then] examined the physical, chemical and thermal properties.”
For five years, the team took biosolids from two local wastewater treatment plants, mixing them with soil to experiment with different consistencies. They fired the bricks for 10 hours at 2,000 degrees Fahrenheit before cooling them and comparing them to normal bricks. Ultimately, the team developed biosolid bricks that satisfied safety standards, are more light and insulating than many other bricks, and can be fired with 50 percent less energy than standard bricks.
“Klein reports that making bricks with 15 percent biosolid content would be enough to eat up the entire world’s stockpile of biosolid waste,” per Smithsonian.
Though many wastewater treatment plants, sometimes called “wastewater reclamation facilities,” are already focused on recycling waste as energy for their own operations or as fertilizer for resale, more can be done to leverage biosolids in sustainable ways.
“In a single day, New York City alone makes 1,200 tons, or about 50 truckloads [of biosolids],” The New York Times reported in an article about the bricks. “About 50 to 70 percent of it is now used, mostly to boost soil quality or fertilize crops. But the rest remains unused or stockpiled. In the United States, it’s estimated that nearly a third of the 7 to 8 million tons of biosolids produced each year still end up in landfills.”
Ideally, production of the bricks would take place directly at or close to wastewater treatment plants, where biosolid stockpiles are nearby. In fact, the participation of treatment facilities may be critical if this new use for biosolids is to get any traction.
“Otherwise, I don’t think it is likely on a large scale in the near future,” Mohajerani told the Times.