Researchers have recovered valuable resources from waste water

If you find the trash close to the trash, you may struggle to find any redeemable value; however, researchers at UBC’s Bioreactor Technology Group see it differently.

Using a combination of heat, water and phase separation, UBC researchers have developed a cost-effective method to concentrate phosphorous—which can be effectively recovered through extraction—from wastewater sludge.

“Phosphorous is a non-renewable, but essential, element for life and has many industrial uses,” explained Huan Liu, a doctoral student with the School of Engineering at UBCO and lead author of a new study examining this approach.

Phosphorus is a natural mineral essential for human health and essential to food security as a commercial fertilizer; however, it is also listed as a critical raw material as many countries rely on imports.

“The uneven distribution of phosphate rock creates political and economic risks,” he said. “On the other hand, phosphorus discharge from waste sources, such as wastewater, is a major contributor to aquatic eutrophication, causing serious environmental challenges including algae blooms and dead zones in lakes.”

Liu and his supervisor, principal investigator Dr. Cigdem Eskicioglu, investigated a promising process combining hydrothermal liquefaction.

The process converts the organic components of municipal waste sludge into a petroleum-like bio-crude and concentrates the phosphorous into a solid residue called hydrochar. Hydrochar can contain 100 times higher total phosphorus than raw sludge, making it comparable to rock phosphate used in commercial fertilizers.

Liu describes the extraction process as mirroring what happens when you mix minerals and acids. “We were able to identify, for the first time, the kinetic reactions of phosphorus leaching from hydrochar to optimize the recovery of useful materials, such as those required for fertilizer,” said Liu.

According to Dr. Eskicioglu, their latest findings are important for waste utilities aimed at developing a process to recover usable nutrients from the system.

“At a time when we are trying to be more sustainable and looking for alternative fuels, extruding usable materials from waste is important,” he said. “Recovery and recycling is the solution that also provides the double benefit of providing a second source of phosphorus that can be distributed around the world and also helps to conserve the environment.”

The work is published in the journal Water Research.