Landfill Leachate Released to Wastewater Treatment Plants and other Environmental Pathways Contains a Mixture of Contaminants including Pharmaceuticals

Science Center Objects

New scientific research from the U.S. Geological Survey (USGS) details how landfill leachate, disposed from landfills to environmental pathways, is host to numerous contaminants of emerging concern (CECs).

Four sample bottels filled with leachate

Sample bottles like these filled with leachate were analyzed for contaminants of emerging concern (CECs) including pharmaceuticals, industrial chemicals, household chemicals, steroid hormones, and plant/animal sterols. Photo Credit: Dana W. Kolpin, USGS

Landfills are the final repository for a heterogeneous mixture of liquid and solid waste from residential, industrial, and commercial sources, and thus, have the potential to produce leachate—a liquid waste product that consists of a diverse mixture of chemicals as precipitation or applied water moves through the waste. Landfills are often not the final repository for leachate which can be discharged to surface waters following onsite or offsite wastewater treatment.

In this national-scale study, scientists provide an assessment of CECs in landfill leachate disposed offsite that has undergone treatment or storage processes (final leachate) at landfills across the United States to gain a greater understanding of this potential contaminant source to the environment. This study follows and advances previous USGS research of leachate prior to onsite treatment, storage processes, and offsite disposal (fresh leachate).

In this study, final leachate samples from 22 landfills were collected and analyzed for 190 CECs including pharmaceuticals, industrial chemicals, household chemicals, steroid hormones, and plant/animal sterols. The sampling network included municipal and private landfills with varying landfill waste compositions; geographic and climatic settings; ages of waste, waste loads, and leachate production; and leachate management strategies.

Manhole access

In some cases USGS scientists collected leachate samples from manhole access points like this one. Photo Credit: Dana W. Kolpin, USGS

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).

A detailed comparison of CEC concentrations between final leachate in landfills included in this study and the previous study of fresh leachate indicated that levels of CECs were significantly less in final leachate compared to those observed in fresh leachate samples. Nevertheless, final leachate still contained a complex mixture of CECs at concentrations that may be potential cause for concern if released to the environment.

This research is part of continuing USGS efforts to quantify the contribution of contaminants in leachate released from landfills to various pathways that ultimately lead to the environment. Use of landfills as a means of waste disposal will likely increase as the global population continues to increase. Despite advancements in recycling, source reduction, and composting, the amount of municipal solid waste discarded in U.S. landfills increased from 150 million tons in 1985 to 165 million tons in 2010. The study is intended to inform landfill managers, stakeholders, and regulators about chemicals present in landfill leachate disposed offsite to environmental pathways.

The study was supported by the USGS Toxic Substances Hydrology Program.

U.S. Geological Survey (USGS) scientists processing leachate samples

U.S. Geological Survey (USGS) scientists processing leachate samples collected for a national-scale study on the occurrence of contaminants of emerging concern (CECs) in landfill leachate disposed offsite. Photo Credit: Jason R. Masoner, USGS

Frequently Asked Questions

1. Why were landfills targeted for study?

Landfills are the final depository for much of the solid waste we generate. While it is known that such landfill waste can contain a wide variety of contaminants, little research to date has been conducted regarding contaminants of emerging concern (CECs) in final landfill leachate.

2. What is meant by "final" leachate?

Final leachate is leachate that is collected after all storage and treatment processes that are in place within a given landfill. This sample type is in contrast to the sampling of "fresh" leachate (i.e. before all storage and treatment processes with a given landfill).

3. Why were both public and private landfills used for this study?

This study was comprised of a mix of public (16) and private (6) landfills to properly capture the range operating conditions that exist for the landfills present within the United States.

4. How were the sites selected for this study?

The landfills were selected to provide a range of hydrogeologic setting, climate, size, and leachate treatment and disposal practices. Ultimately, however, we could only collect samples at landfills that were willing to participate in this research.

5. Who collected the leachate samples for this study?

Samples were collected via a combination of U.S. Geological Survey (USGS) scientists (when a sampled landfill was in close proximity to a USGS office) and personnel form State environmental agencies, County and municipal governments and environmental firms on contract by private solid waste companies. All sampling personnel followed stringent, predetermined protocols for collecting, processing, and shipping the leachate samples collected for this study.

6. Why was it decided to keep the landfills and their specific locations anonymous?

Our experience has shown that many landfill operators are reluctant to participate in this type of research if their specific name and locations are provided. As such locational information has no bearing on the interpretations of study results, we made the decision to keep all landfill locations anonymous for this study to maximize the sampling options during the site selection process.

7. Were there any safety concerns for the personnel collecting these leachate samples?

The safety of personnel collecting environmental samples is always paramount for the USGS. Thus, the field protocols were designed to minimize any personal exposure to the landfill leachate being collected while still collecting samples that are representative of the landfills in question.

8. How were the target contaminants selected for study?

The 190 CECs analyzed for this study were those available from existing analytical capabilities available within the USGS. These target CECs within these available methods were selected based on annual use, chemical/physical properties (e.g. mobility, persistence, etc.), and known or suspected environmental effects.

9. What were the major findings for this study?

At least one CEC was detected in every leachate sample collected (median = 22, max = 58). The most frequently detected CECswere lidocaine (91 percent, local anesthetic), cotinine (86 percent, nicotine degradate), carisoprodol (82 percent, muscle relaxant), bisphenol A (BPA, 77 percent, plastics and thermal paper), carbamazepine (77 percent, anticonvulsant), DEET (68 percent, insect repellent). Detected concentrations ranged from 2 ng/L (estrone) to 17,200,000 ng/L (BPA). CEC concentrations were greater in landfills that were still operating and actively accepting waster compared to closed, unlined landfills. CEC concentrations where significantly greater in fresh leachate (from our previously published landfill research) compared to the final leachate from this study.

10. Are there any human or environmental health issues regarding final leachate that the public should be concerned about?

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.

11. How does this research inform current pharmaceutical disposal policies?

This study was designed only to assess the occurrence of targeted contaminants in leachate. For more information on disposal of unused medicines consult the U.S. Food and Drug Administration and the U.S. Environmental Protection Agency.

Related Featured Science Activities