“`html
Numerous wastewater treatment facilities are designed to handle refuse through anaerobic digestion, where the sewage sludge is maintained in an oxygen-deprived environment to ferment and decompose. During this breakdown, biogas such as methane can be extracted from the sludge. However, this method can be costly as it necessitates electric generators to transform the biogas into a more beneficial form like electricity, and such transformation may not be financially feasible on a small scale of biogas production.
Jason He, the Laura and William Jens Professor of Energy, Environmental, and Chemical Engineering at Washington University in St. Louis, sought to identify more effective methods to extract value from waste.
“Is it possible for us to extract something potentially more valuable than biogas?” he inquired.
He and his team examined short-chain volatile fatty acids (VFA), a frequent intermediate compound for various materials, including bioplastics.
VFAs can additionally act as the feedstock to purify the sewage at a reduced cost. Treatment plants could utilize VFAs from their own sewage to provide a carbon source for nitrogen converters and biological phosphorus removers, He stated.
Besides lowering the costs of sewage treatment, VFAs can be retrieved in liquid form and potentially marketed for use in manufacturing and agricultural processes to further offset the expenses of sewage treatment.
In research published in Water Research, the McKelvey School of Engineering team demonstrates how applying hydrogen peroxide to the sewage will hinder methanogenesis and redirect sewage toward VFA production instead.
Hydrogen peroxide is an inexpensive addition that results in more than 30 times the VFA yield in sludge compared to controls. Even greater efficiencies became apparent when Jiasi Sun, He’s PhD student and the paper’s lead author, observed that light exposure further enhanced the process’ efficiency.
Sun noticed that two identical reactors yielded varying outcomes. Initially, she suspected a measurement error but then recognized that one reactor was located nearer to a light source.
“I discovered that light was accelerating the decomposition of hydrogen peroxide into reactive species. That minor observation fundamentally altered my understanding of the VFA reclamation process,” she noted.
The fortunate twist of scientific discovery is leading the team into new research avenues: reintroducing light to the dark fermentation tanks.
“With light, the dosage of hydrogen peroxide can be significantly minimized,” He added.
Currently, they are investigating the incorporation of LED lights into the reactors and modifying reactor design to further enhance efficiencies.
“It all stems from these unforeseen results,” He remarked.
Sun J, He Z. Light stimulated H2O2 inhibition on methanogenesis during anaerobic digestion towards enhanced VFAs production. Water Research, Volume 286. https://doi.org/10.1016/j.watres.2025.124229
This research was financially supported by the U.S. National Science Foundation (award # 2150613).
Originally published on the McKelvey Engineering website
The post A silver lining in sewer sludge: volatile fatty acids first appeared on The Source.
“`