Newmeyer MN, Lyu Q, Sobus JR, Williams AJ, Nachman KE, Prasse
C. Combining Nontargeted Analysis with Computer-Based Hazard Comparison
Approaches to Support Prioritization of Unregulated Organic Contaminants in
Biosolids. Environ Sci Technol. 2024 Jul 9;58(27):12135-12146. doi:
10.1021/acs.est.4c02934. Epub 2024 Jun 25. PMID: 38916220.
The blog post contains excerpts from the above cited article
and the Press Release from Johns Hopkins University.
Wastewater treatment processes use screens to remove large
solids (human waste) from wastewater, and skim off grease, oil and fat.
Wastewater sits in settling tanks where most of the heavy solids fall to the
bottom of the tank, where they become thick slurry known as primary sludge. The
sludge is separated from the wastewater during the primary treatment is further
screened and allowed to gravity thicken in a tank.
Then the sludge is mixed with the solids collected from the
secondary and denitrification units in the wastewater treatment plants. The
combined solids are pumped to tanks where they are heated to destroy pathogens
and further reduce the volume of solids. With treatment sludge is transformed
(at least in name) to Biosolids. The U.S. produces 3.76 million tons of biosolids
half of which is used to fertilize agricultural lands, golf courses and other
landscaped areas (according to the EPA), the remainder is incinerated or
disposed of in landfills. Biosolids are the byproduct of wastewater
treatment and have been for decades used a cheap fertilizer.
U.S. EPA regulations limit metals and pathogens in biosolids
intended for land applications, but no organic contaminants are currently
regulated under 40 CFR
Part 503 Rule created in 1989 and still in effect today. It categorizes
Biosolids as Class A or B, depending on the level of fecal coliform and
salmonella bacteria in the material and restricts the use based on
classification. The presence of other emerging contaminants in the Biosolids is
not tracked, but has become an emerging area of concern. Previously, research
at the University of Virginia found that organic chemicals persist in Biosolids
and can be introduced into the food chain.
Land application of biosolids is a widespread practice
across the US and remains an approved method by the US EPA. In Maine they had
been spreading biosolids on its farms and fields since it was first
allowed. Its application on farms had been seen as an inexpensive way to fertilize.
Unfortunately, the biosolids became contaminated with PFAS from both
residential and industrial wastewater sent to the wastewater treatment plants.
Biosolids were land applied and buried in landfills. Animals grazed on the
land, food grown on the land picked up some of the PFAS and passed traces into
food. PFAS also leached from the land and landfills into groundwater. People
passed it onto other wastewater treatment plants and the circle widened.
At last report the Maine Department of Environmental
Protection (DEP) had found more than 70 PFAS-contaminated farms, a handful
of which have had to cease all food production. In 2022, Maine became the first state to ban land application
of biosolids and the sale of compost containing biosolids, but not before the
farms had to stop producing food. Only Minnesota has done as much
testing for PFAS in the agricultural food chain.
Now, the work the work begins to see what is in the
biosolids. The above cited research study is the most comprehensive looks at
the chemical composition of biosolids across the country and is the first step
toward identifying common chemical contaminants that may need government
regulation. The findings could help the U.S. Environmental Protection Agency
prioritize which organic compounds to investigate further, the researchers
said. The research was supported by a U.S. EPA grant and U.S. Centers for
Disease Control and Prevention grant.
In the study the researchers used analytical chemistry
techniques capable of identifying thousands of chemicals and developed in Dr. Prasse
lab. The researchers screened 16 samples of biosolids from wastewater treatment
plants in nine U.S. and three Canadian cities. Samples contained traces of
pharmaceuticals, industrial chemicals, and a variety of fragrances. Among them
were bisphenol A (BPA), commonly found in plastics, and carbamazepine, a drug
used to treat epilepsy and bipolar disorder, ketoconazole and so many others.
There were so many that the researchers had to narrow the list focusing on
chemicals that appeared in at least 80% of samples.
There were 92 organic compounds that met that criteria: present
in 80% or more of the samples. Interestingly enough PFAS was only present in 70%-75%
of the samples and did not make the cutoff.
“Because there are so many compounds in biosolids, the
question we had was how do we triage? How do we find the chemicals that are
widespread and could potentially be problematic, that the EPA and other
scientists would need to investigate before proposing regulations,” Professor Carsten
Prasse said.
The researchers then created lists of the chemicals found in
each sample and compared them to compounds that popped up in multiple places
across the country. They identified 92 compounds that were present in 80% or
more of the samples.
“Regulators need to
know what these types of fertilizers are made of to determine how they can be
responsibly used.” Prasse said.
“We’re not saying that these compounds pose a risk right now
because we haven’t done a formal risk assessment,” said Matthew
Newmeyer, a research associate at the Bloomberg School of Public Health and
first author on the paper. “We’re saying that these have a potential to be
problematic and we need more information in order to make sure these biosolids
are safe.”
The team plans to measure the identified compounds in the
biosolids and vegetables grown in biosolid-amended soil to determine if their
concentration levels warrant concern. The researchers are also investigating
risks to farmers, landscapers, and composters who work with biosolids.
Read more:
No comments:
Post a Comment