In 2015 the U.S.
Geological Survey’s Environmental Health Program conducted nationwide research on
the contamination found in landfill leachate. The study focused on contaminants
of emerging concern (CECs) found in leachate that was disposed of off-site, after on-site
treatment. The study analyzed leachate from 22 landfills for 190 CECs. The study utilized both municipal and private landfills, geographically
distributed, and of different ages in order to get a more comprehensive survey.
The CECs include pharmaceuticals, industrial chemicals, household chemicals,
steroid hormones, and plant/animal sterols. Below is what they found.
“Scientists determined that final leachate samples
contained 101 of the 190 chemicals analyzed for the study, with chemicals
present in every final leachate sample collected at levels ranging from as low
as 2 nanograms per liter (ng/L) to as high as 17,200,000 ng/L. The most
frequently detected CECs were lidocaine (local anesthetic, found in 91 percent
of samples), cotinine (nicotine breakdown product, 86 percent), carisoprodol
(muscle relaxant, 82 percent), bisphenol A (component for plastics and thermal
paper, 77 percent), carbamazepine (anticonvulsant, 77 percent), and
N,N-diethyltoluamide (DEET, insect repellent, 68 percent).”
The levels of CECs were much lower in final leachate compared
to those observed in fresh leachate samples from previous studies, as would be
expected. The final leachate has a path to the environment. Once there it would
be even more diluted, but still present and accumulating.
“The results of the present study provide useful
precedents for future investigations of the fate, risk, and toxicity of CECs in
landfill leachate as they directly or indirectly enter aquatic and terrestrial
environments. Such research provides information that can be used to support
decisions about the regulation of unwanted/unused pharmaceuticals and leachate
treatment methods; better understanding of the fate of CECs in leachate in
landfill systems; and better understanding of the ecological effects posed by
disposal of leachate to potential environmental receptors.”
Landfill Leachate Treatment and Management
A 2022 paper in Materials
Today reviewed landfill leachate treatment methods. From the abstract:
“Landfill leachate is characterized by very high chemical
oxygen demand (COD) and biochemical oxygen demand (BOD) consisting of
unappealing constituents like toxic organic and inorganic pollutants. In
general, leachate parameters such as landfill age, COD/BOD ratio, and COD are
the decisive factors in the selection of appropriate treatment methods. The
various adopted technologies for leachate treatment are assessed and summarized
under heads like biological, physicochemical, and hybrid methods.”
They noted that combination treatment utilizing both biological
and physicochemical treatment had the best outcomes for meeting water quality
standards. They were best at achieving the most efficient satisfactory removal
of COD, BOD, and ammonia nitrogen.
A 2021 paper in
Water Reuse explored the different methods of landfill leachate treatment and
their efficacies. From the abstract:
“Different treatments comprising biological methods (e.g.
bioreactors, bioremediation and phytoremediation) and physicochemical
approaches (e.g. advanced oxidation processes, adsorption,
coagulation/flocculation and membrane filtration) were investigated in this
study. Membrane bioreactors and integrated biological techniques, including
integrated anaerobic ammonium oxidation and nitrification/denitrification
processes, have demonstrated high performance in ammonia and nitrogen
elimination, with a removal effectiveness of more than 90%. Moreover, improved
elimination efficiency for suspended solids and turbidity has been achieved by
coagulation/flocculation techniques. In addition, improved elimination of
metals can be attained by combining different treatment techniques, with a
removal effectiveness of 40–100%. Furthermore, combined treatment techniques
for treating landfill leachate, owing to its high chemical oxygen demand and
concentrations of ammonia and low biodegradability, have been reported with good
performance. However, further study is necessary to enhance treatment methods
to achieve maximum removal efficiency.”
Below is a table of leachate characteristics and treatability based on landfill age. There are significant differences. Some contaminants are volatile and escape, in some cases causing local air quality concerns. Below the table are flow charts showing the most reported landfill leachate treatment methods.
An October 2024
paper in Desalinization and Water Treatment explored the challenges, methods,
and future directions of landfill leachate management. They note that better
solid waste management, more functional circular economies, and higher levels
of recycling would reduce the amount of waste landfilled and the amount of leachate
generated. They also mention the benefits of gas recovery and gasification/pyrolysis
for waste-to-energy applications in reducing leachate volumes. The paper’s
authors note some of the newer treatment methods showing success:
“Advanced treatment technologies, including integrated
advanced oxidation processes (AOPs) with biological processes and
adsorbent-enhanced constructed wetlands, demonstrated promising
cost-effectiveness and high treatment efficiency, with savings of up to 32 % in
treatment costs. Future research should focus on emerging technologies like
nanotechnology and artificial intelligence for process optimization, and the
impact of municipal leachate on air quality. Continued innovation in leachate
treatment and sustainable practices are essential for effective waste
management.”
Since leachate is a contamination source with a highly
variable composition, the treatment methods vary. There are many different
treatment methods that can be used. The authors
of this paper explored the methods shown below along with some models of leachate
fate and transport in the environment and charts of waste types and landfill types based on waste. They also explored several different
combinations of methods.
Company USP
Technologies describes some of the strategies and challenges of landfill
leachate treatment below:
“Landfill leachate can be very challenging to effectively
treat as it is often characterized by significant odor, high COD, phenols and
dissolved metals. In some cases, leachates can be toxic or inhibitory to
downstream biological treatment systems. Furthermore, due to the variability of
landfill material, weather patterns and content age, leachate constituent
levels can change over time, adding to the complex nature of treatment.
Landfill operators contend with additional challenges stemming from general
public odor complaints, discharge compliance and fines or surcharges from
municipal wastewater treatment plants.”
Trends in PFAS Management from Leachate
The so-called “forever
chemicals” that include PFAS are being addressed due to public concerns. In
2023, there were some pilot projects for on-site treatment of PFAS in leachate.
Casella Waste Systems began treating for PFAS at the Coventry Landfill in
Vermont. Vermont has been adopting limits on perfluoroalkyl and polyfluoroalkyl
substances, including PFAS, PFOS, and PFOA. Federal limits for PFAS in drinking
water were adopted by the EPA in April 2024. The EPA’s final rule sets the following
limits
·
Enforceable maximum contaminant levels of 4
parts per trillion for PFOA and PFOS.
·
Non-enforceable maximum contaminant level
goal of 0 ppt for PFOA and PFOS, reflecting that “there is no level of exposure
to these contaminants without risk of health impacts, including certain
cancers.”
·
Enforceable MCL, and a MCL goal, of 10 ppt
for PFNA, PFHxS and HFPO-DA, the last of which are also known as “GenX
Chemicals.”
·
Additional limits for “any mixture of two or
more of” PFNA, PFHxS, PFBS and GenX Chemicals
The 4ppt for PFOA and PFOS is a very small amount that was
unmeasurable with older technology. The low limit suggests the very real
dangers of these chemicals. According to Waste Dive:
“The rule states that public water systems must complete
initial monitoring for the chemicals within three years and inform the public
of those results. If PFAS is found at levels that exceed the standards then
operators must implement solutions within five years. The agency estimates this
will affect 6% to 10% of the United States’ 66,000 public drinking water
systems.”
At the same time, the EPA announced $1 billion in grants to
test for these chemicals as part of the $9 billion set aside for addressing
PFAS in the IRA. Waste Dive also notes that even before these limits were set
there were instances of wastewater treatment facilities not accepting treated
leachate due to PFAS concerns. Thus, PFAS pre-treatment is becoming more common
as well as more demanded.
In New York,
several environmental groups have urged the state DEC to require onsite
leachate treatment at landfills that can reduce PFAS instead of shipping it to
wastewater treatment plants ill-equipped to handle these chemicals. They are
also calling for the DEC to write PFAS limits into wastewater treatment plant water
permits. New state legislation, although delayed in 2024, is expected in 2025.
The groups also noted their own studies that have shown that these chemicals have
been commonly found to exceed limits for drinking water:
“PFAS contamination is a core concern of the groups. They
cite a DEC study that found that groundwater PFOA and PFOS concentrations
exceeded the state’s drinking water standard at 68% of the state’s closed
landfills tested to date. Within the report’s project area, at least eight
closed landfills showed groundwater PFAS concentrations above the drinking
water standard.”
Upgrading
landfills to treat leachate onsite for CECs, including PFAS and related
chemicals, will take time and money, unfortunately. Also uncertain is how the
Trump administration presumably under Lee Zeldin, who is expected to be confirmed,
will treat the issue as deregulation is emphasized and regulation is de-emphasized.
References:
Groups
urge New York DEC to require on-site landfill leachate treatment. Jacob Wallace.
Waste Dive. January 23, 2025. Groups
urge New York DEC to require on-site landfill leachate treatment | Waste Dive
EPA
sets drinking water standards for PFAS, kicking off questions for waste
operators. Coel Rosengren. Waste Dive. April 20, 2024. EPA
sets drinking water standards for PFAS, kicking off questions for waste
operators | Waste Dive
Some
landfills will begin treating PFAS on-site as regulators move to adopt new
limits, April Reese. Waste Dive. January 17, 2023. Some
landfills will begin treating PFAS on-site as regulators move to adopt new
limits | Waste Dive
Landfill
Leachate Released to Wastewater Treatment Plants and other Environmental
Pathways Contains a Mixture of Contaminants including Pharmaceuticals. U.S.
Geological Survey. Environmental Health Program, November 13, 2015. Landfill
Leachate Released to Wastewater Treatment Plants and other Environmental
Pathways Contains a Mixture of Contaminants including Pharmaceuticals | U.S.
Geological Survey
Treatment
of landfill leachate with different techniques: an overview. Amin Mojiri; John
L. Zhou; Harsha Ratnaweera; Akiyoshi Ohashi; Noriatsu Ozaki; Tomonori
Kindaichi; Hiroshi Asakura. Water Reuse (2021) 11 (1): 66–96. Treatment
of landfill leachate with different techniques: an overview | Journal of Water
Reuse and Desalination | IWA Publishing
Landfill
Leachate – Liquid Phase Treatment. USP Technologies. LANDFILL
LEACHATE – LIQUID PHASE TREATMENT - USP Technologies
Sustainable
municipal landfill leachate management: Current practices, challenges, and
future directions. Chinenye Adaobi Igwegbe, Eduardo Alberto López-Maldonado, Andrea
C. Landázuri, Prosper Eguono Ovuoraye, Annex Ifeanyi Ogbu, Nicolás Vela-García,
and Andrzej Białowiec. Desalination and Water Treatment. Volume 320, October
2024, 100709. Sustainable
municipal landfill leachate management: Current practices, challenges, and
future directions - ScienceDirect
A
short review on landfill leachate treatment technologies. Aishi Nath and Animesh
Debnath. Materials Today: Proceedings. Volume 67, Part 8, 2022, Pages 1290-1297.
A
short review on landfill leachate treatment technologies - ScienceDirect
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