Scientists Investigate Wastewater-Based Fertilizers

A new nationwide analysis of biosolids — the byproducts of wastewater treatment often used as fertilizer — finds a plethora of unregulated organic compounds, including some that may have potential impacts on human health.

It’s not clear yet whether there is any negative impact of using biosolids, cautions study author Carsten Prasse, an assistant professor of environmental health and engineering at Johns Hopkins Univ. For one thing, researchers don’t yet know the quantities of these organics or if they enter the environment in any significant way.

“Risk is a combination of exposure and toxicity,” Prasse says. The new study is a first step toward evaluating risk, he says. While other studies of biosolid samples have turned up concerning organic chemicals in the past, there had not been a large-scale study seeking to catalogue the many possible organics that might be found in these products.

“The idea behind this is to come up with a priority list of compounds that might be — and that ‘might’ is very important — that might be problematic and have to be assessed in detail in the future,” Prasse says.

Biosolids are treated sewage sludge, largely consisting of the biomass of bacteria that are used to degrade waste. About 3.76 million dry m.t. were produced as of 2022, according to the U.S. Environmental Protection Agency (EPA). Of that, 56% was recycled as fertilizer (the rest was incinerated or landfilled). About half of biosolid fertilizer is...