Flushing Out New Options

Most of us take America's waste management system for granted, happy to flush it and forget it. But where that waste ultimately ends up and how it affects the environment is the subject one doctoral student is trying to understand.

“We have to put waste somewhere; the toilets aren’t going to stop flushing,” said Emileigh Lucas, a Ph.D. student in the Department of Environmental Science and Technology (ENST). “We are going to continue to produce this waste, and if we don’t reapply it, it goes to the landfills and I don’t think people like that idea either.”

Currently, after a flush reaches the wastewater treatment plant, the water is separated, purified, and safely released, leaving the solid materials behind, which are further treated to eliminate pathogens, odor, and stabilize other chemical compounds. What is left is known as biosolids, which is rich in nutrients and makes good fertilizer. In Maryland, about 12% of biosolids are sent off to landfills, while nationally the amount is much higher, according to the National Biosolids Data Project.

Working with Dr. Gurpal Toor, Professor and Extension Specialist, Lucas is partnering with DC Water, the Washington D.C. water treatment authority, and other regional utilities to understand how biosolids interact with nutrients in soils. DC Water operates one of the largest wastewater treatment plants and produces a highly-conditioned, commercially available biosolids product called Bloom®. Studying Bloom, along with other regionally produced biosolids, to better understand how the application of these materials impacts the levels and availability of phosphorus, Lucas hopes to optimize biosolids applications to meet environmental thresholds.

"What we’ve discovered is that the metals added during the treatment process, such as iron and aluminum, interact with the phosphorus present in the soil,” said Lucas, who was born and raised in Maryland and received her Bachelors and Masters degrees from AGNR. “If you apply this material to a soil also high in phosphorus, it may reduce the amount of phosphorus runoff from fields where it can enter the watershed and can cause harmful algal blooms.” Although that seems counterintuitive, lab tests indicate that Bloom® and other lime-stabilized biosolids may bind existing phosphorus in the soil, reducing its ability to runoff. Currently, Maryland farmers with high field phosphorus may not be able to use biosolids, but a study like this could change how they apply fertilizers.

While lab test results are promising, field studies will be conducted over the next few years to assess how biosolid products react with the phosphorus in the soils, as well as the uptake of phosphorus by the plants. 

by Laura Wormuth : Momentum Magazine Winter 2025