In a recent study, researchers discovered that a straightforward setup using woodchips combined with a special type of biochar — essentially enhanced sawdust — can significantly lower levels of nitrogen, phosphorus, and several common pharmaceuticals found in wastewater.
Have you ever wondered what becomes of ibuprofen after it alleviates your headache? Like many other medications, it can remain active even after our bodies expel it. This poses a significant issue because, while wastewater treatment facilities effectively reduce nutrient pollutants, they are not designed to eliminate pharmaceuticals and personal care products. Consequently, antibiotics, hormones, and other substances re-enter natural water bodies and agricultural land.
A research team from the University of Illinois Urbana-Champaign has illustrated that a simple combination of woodchips and specially treated sawdust can effectively reduce nitrogen, phosphorus, and various pharmaceuticals in wastewater.
“Even in small amounts, pharmaceuticals and personal care products (PPCPs) can harm water quality, disrupt ecosystems, encourage antibiotic resistance, and accumulate in wildlife. While nutrients like nitrogen and phosphorus can lead to visible issues such as harmful algal blooms, PPCPs pose serious risks, especially for vulnerable communities over prolonged exposure. Both problems highlight the urgent need for improved wastewater management,” explained Hongxu Zhou, a lead author of the study, who conducted this research as a doctoral student in the Department of Agricultural and Biological Engineering (ABE) at the College of Agricultural, Consumer and Environmental Sciences and The Grainger College of Engineering at the University of Illinois.
Zhou and his colleagues were aware that woodchip bioreactors — systems filled with woodchips that water flows through — effectively eliminate excess nitrogen due to microbes that thrive on the wood, converting nitrate into benign nitrogen gas. They then created a novel form of biochar — sawdust treated with lime sludge and then charred — capable of binding phosphorus and specific PPCPs. The biochar’s large surface area and unique composition allow it to capture chemical compounds tightly.
With this knowledge, the researchers experimented in the lab with a “treatment-train” method to assess how well the two treatments functioned together. They gathered water from a local creek and spiked it with nitrogen, phosphorus, ibuprofen, naproxen, the diabetes medication sitagliptin, and an estrogen derivative. This mixture passed through small woodchip bioreactors and then flowed through tubes containing biochar. The process, referred to as B2 (bioreactor-biochar), allowed the team to measure the concentrations of remaining compounds.
“On average, the B2 system successfully removed 77% of nitrate, 99% of phosphorus, around 70% of ibuprofen, 74% of naproxen, 91% of sitagliptin, and 97% of estrone,” reported Wei Zheng, a co-author of the study and principal research scientist at the Illinois Sustainable Technology Center (ISTC), part of the Prairie Research Institute at the University. “The biochar acted similarly to activated carbon, efficiently extracting pharmaceutical residues from the contaminated water.”
Results varied with the different flow rates of water through the system; slower flow rates showed greater nitrogen removal. Additionally, they tested the biochar’s form — granules versus pellets — discovering that granules were more effective at capturing pharmaceuticals and phosphorus.
Since microbes are integral to nitrogen removal in woodchip bioreactors, the researchers were curious if pharmaceuticals would affect the microbial communities. They observed shifts in the abundance of specific bacteria, but the core function of the microbial community remained stable.
“The most thrilling aspect of our findings is confirming that the woodchip bioreactor’s nitrogen removal efficiency is not compromised by PPCPs, despite microbial composition changes,” Zhou noted. “This indicates that the bioreactor system can maintain its performance under various conditions, which is crucial for practical applications.”
While the investigation was conducted on a small scale in the lab, the researchers modeled the effectiveness of the B2 system at larger scales, indicating promising possibilities for industrial uses.
“We believe that with routine upkeep and optimizing the system’s design, many scaling-related challenges can be managed. For instance, clogging in continuous flow systems can impair performance and lifespan, necessitating periodic biochar replacement,” explained co-author Rabin Bhattarai, an associate professor in ABE.
“These design and operational considerations are vital to ensure both the efficiency and longevity of B2 systems in real-world applications, ultimately improving their effectiveness in tackling environmental concerns,” he added.
Zhou is currently serving as a postdoctoral research associate at ISTC. Zheng also holds an adjunct faculty position in ABE.
