For the first time, U.S. Geological Survey (USGS), Virginia Institute of Marine Science, and the University of Connecticut scientists have detected active anammox bacteria in groundwater.
Anaerobic (without oxygen) ammonium oxidation, or anammox, is a process carried out by naturally occurring bacteria that can simultaneously remove ammonium and reduce nitrite to produce harmless nitrogen gas.
Scientists have known about anammox bacteria, but its presence in groundwater has not been confirmed until this study. In the past, denitrification (the process by which nitrate [NO3-] is reduced to form nitrites, other nitrogen oxides, and eventually nitrogen gas) was thought to be the only major process in groundwater that transformed nitrogen compounds to nitrogen gas. The scientists determined that anammox bacteria were active in the subsurface in a variety of geochemical conditions. The scientists then demonstrated that anammox activity in groundwater can rival that of bacteria responsible for denitrification, with the added benefit that anammox simultaneously removes ammonia, and that water-resource managers may need to consider it when assessing nitrogen contamination in groundwater.
Field Experiment
The scientists conducted a natural gradient tracer test at the Toxic Substances Hydrology Program's Cape Cod Research Site. The tracer test consisted of injecting a solution of chemical tracers into the subsurface and monitoring the groundwater chemistry and tracer concentrations downstream from the injection well (see diagram). The tracer solution consisted of isotopically labeled nitrite (15NO2, not radioactive) and bromide (Br). The 15NO2 allowed the scientists to determine rates of denitrification and anammox by measuring changes in the isotopic composition of the reaction products. Bromide was used to monitor the location of the injected solution in the subsurface. Advanced molecular techniques were used to detect genes from anammox bacteria (16S ribosomal ribonucleic acid genes [16S rRNA]) and the transcriptional products of those genes (16S messenger RNA [16S mRNA]).
The Results
The scientists determined that anammox was active in the subsurface in a variety of geochemical conditions, even where groundwater ammonium concentrations were low. Many of the geochemical conditions are commonly present in the groundwater and indicate that anammox can be an important process in many types of groundwater conditions. The report documented the competition between anammox and denitrification for nitrogen oxides and explored the effect of altered organic carbon concentrations on that competition.
Environmental Health Implications
Nitrogen contamination of groundwater used for drinking water is a public-health concern. Ingestion of nitrate by infants can interfere with oxygen-carrying capacity of blood in infants, leading to blue skin color known as methemoglobinemia or "blue baby disorder." The results from this study provide information needed to understand processes that remove nitrate from groundwater. Denitrification is usually considered by scientists to be the main mechanism for removal, but the confirmation of anammox in groundwater indicates that the biogeochemical processes affecting the fate and transport of nitrogen in groundwater are more complex than was previously thought. This could be especially true where groundwater has been affected by wastewater with excess nutrients.
This research was funded by the USGS Ecosystems Mission Area’s Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology), along with grants from the National Science Foundation—Earth Sciences (EAR) Grants 1024662, 1329284, and 1024900.
Below are other science projects associated with this project.
Drinking Water and Wastewater Infrastructure Science Team
Toxins and Harmful Algal Blooms Science Team
Algal and Other Environmental Toxins — Lawrence, Kansas
Per- and Polyfluoroalkyl Substances From Firefighting and Domestic Wastewater Remain in Groundwater for Decades
Nitrate Addition Enhances Arsenic Immobilization in Groundwater
Nutrients in Dust from the Sahara Desert cause Microbial Blooms on the East Coast of the United States
Importance of Lake Sediments in Removal of Cyanobacteria, Viruses, and Dissolved Organic Carbon
Sewage-Contaminated Ground Water
Contaminants Affect Fish and Wildlife in the Chesapeake Bay
Below are publications associated with this project.
Role of anaerobic ammonium oxidation (anammox) in nitrogen removal from a freshwater aquifer
Below are news stories associated with this project.
- Overview
For the first time, U.S. Geological Survey (USGS), Virginia Institute of Marine Science, and the University of Connecticut scientists have detected active anammox bacteria in groundwater.
U.S. Geological Survey (USGS) scientists prepare a tracer solution to conduct a natural gradient tracer test to measure anammox activity in groundwater. The tracer solution is prepared by pumping groundwater into a gas impermeable bladder to maintain the in situ dissolved oxygen concentration and then mixing in the tracer chemicals. The bladder is contained in an ice-cooled water pool to maintain the groundwater temperature until the solution is pumped back into the aquifer. Photo Credit: Deborah Repert, USGS. Anaerobic (without oxygen) ammonium oxidation, or anammox, is a process carried out by naturally occurring bacteria that can simultaneously remove ammonium and reduce nitrite to produce harmless nitrogen gas.
Scientists have known about anammox bacteria, but its presence in groundwater has not been confirmed until this study. In the past, denitrification (the process by which nitrate [NO3-] is reduced to form nitrites, other nitrogen oxides, and eventually nitrogen gas) was thought to be the only major process in groundwater that transformed nitrogen compounds to nitrogen gas. The scientists determined that anammox bacteria were active in the subsurface in a variety of geochemical conditions. The scientists then demonstrated that anammox activity in groundwater can rival that of bacteria responsible for denitrification, with the added benefit that anammox simultaneously removes ammonia, and that water-resource managers may need to consider it when assessing nitrogen contamination in groundwater.
Field Experiment
The scientists conducted a natural gradient tracer test at the Toxic Substances Hydrology Program's Cape Cod Research Site. The tracer test consisted of injecting a solution of chemical tracers into the subsurface and monitoring the groundwater chemistry and tracer concentrations downstream from the injection well (see diagram). The tracer solution consisted of isotopically labeled nitrite (15NO2, not radioactive) and bromide (Br). The 15NO2 allowed the scientists to determine rates of denitrification and anammox by measuring changes in the isotopic composition of the reaction products. Bromide was used to monitor the location of the injected solution in the subsurface. Advanced molecular techniques were used to detect genes from anammox bacteria (16S ribosomal ribonucleic acid genes [16S rRNA]) and the transcriptional products of those genes (16S messenger RNA [16S mRNA]).
A diagram of the natural gradient tracer test used to detect anammox in groundwater. The tracer solution was injected in the well on the left, and wells on the right were used to monitor the subsurface plume caused by the tracer injection. Analytical testing for the isotopic ratios of nitrogen gas (30N2 or 29N2) helped determine rates for the denitrification of nitrate (NO3-) to nitrogen gas (N2) and for anammox of ammonium (NH4+) to N2. From Smith and others, 2015. The Results
The scientists determined that anammox was active in the subsurface in a variety of geochemical conditions, even where groundwater ammonium concentrations were low. Many of the geochemical conditions are commonly present in the groundwater and indicate that anammox can be an important process in many types of groundwater conditions. The report documented the competition between anammox and denitrification for nitrogen oxides and explored the effect of altered organic carbon concentrations on that competition.
Environmental Health Implications
Nitrogen contamination of groundwater used for drinking water is a public-health concern. Ingestion of nitrate by infants can interfere with oxygen-carrying capacity of blood in infants, leading to blue skin color known as methemoglobinemia or "blue baby disorder." The results from this study provide information needed to understand processes that remove nitrate from groundwater. Denitrification is usually considered by scientists to be the main mechanism for removal, but the confirmation of anammox in groundwater indicates that the biogeochemical processes affecting the fate and transport of nitrogen in groundwater are more complex than was previously thought. This could be especially true where groundwater has been affected by wastewater with excess nutrients.
This research was funded by the USGS Ecosystems Mission Area’s Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology), along with grants from the National Science Foundation—Earth Sciences (EAR) Grants 1024662, 1329284, and 1024900.
- Science
Below are other science projects associated with this project.
Drinking Water and Wastewater Infrastructure Science Team
The team studies toxicants and pathogens in water resources from their sources, through watersheds, aquifers, and infrastructure to human and wildlife exposures. That information is used to develop decision tools that protect human and wildlife health.Toxins and Harmful Algal Blooms Science Team
The team develops advanced methods to study factors driving algal toxin production, how and where wildlife or humans are exposed to toxins, and ecotoxicology. That information is used to develop decision tools to understand if toxin exposure leads to adverse health effects in order to protect human and wildlife health.Algal and Other Environmental Toxins — Lawrence, Kansas
About the Laboratory The Environmental Health Program collaborates with scientists at the Organic Geochemistry Research Laboratory (OGRL) in Lawrence, Kansas, to develop and employ targeted and non-targeted analytical methods for identification and quantitation of known and understudied algal/cyanobacterial toxins. The laboratory contructed in 2019 is a 2,500 square foot modern laboratory facility...Per- and Polyfluoroalkyl Substances From Firefighting and Domestic Wastewater Remain in Groundwater for Decades
New study explores the persistence and transport of poly- and perfluoroalkyl substances (PFASs) that originated from both firefighting and domestic wastewater sources. Although the fire training area and wastewater facility were decommissioned over 20 years ago, both sites continue to be sources of PFASs to groundwater.Nitrate Addition Enhances Arsenic Immobilization in Groundwater
The addition of nitrate in a low oxygen groundwater resulted in the immobilization of naturally occurring dissolved arsenic and the conversion of nitrate to innocuous nitrogen gas.Nutrients in Dust from the Sahara Desert cause Microbial Blooms on the East Coast of the United States
Saharan dust nutrients, particularly iron, deposited episodically in tropical marine waters stimulate marine microbial bloom growth and change microbial community structure.Importance of Lake Sediments in Removal of Cyanobacteria, Viruses, and Dissolved Organic Carbon
U.S. Geological Survey (USGS) scientists determined that the colmation layer (top 25 centimeters of lake sediments) was highly effective in removing cyanobacteria, viruses, and dissolved organic carbon during water passage through the lake bottom to aquifer sediments.Sewage-Contaminated Ground Water
The USGS is investigating a wastewater plume in a shallow aquifer near Cape Cod, Massachusetts, to increase the understanding of the physical, chemical, and microbiological processes that affect the fate and transport of contaminants in groundwater.Contaminants Affect Fish and Wildlife in the Chesapeake Bay
“Legacy contaminants” and “contaminants of emerging concern” that persist in the environment are affecting the health of fish and wildlife in the Chesapeake Bay and its watershed. State continue to report impaired water resources due to the persistence and toxicity of some previously banned pollutants. In addition, other contaminants of emerging concern are released to the environment at levels... - Publications
Below are publications associated with this project.
Role of anaerobic ammonium oxidation (anammox) in nitrogen removal from a freshwater aquifer
Anaerobic ammonium oxidation (anammox) couples the oxidation of ammonium with the reduction of nitrite, producing N2. The presence and activity of anammox bacteria in groundwater were investigated at multiple locations in an aquifer variably affected by a large, wastewater-derived contaminant plume. Anammox bacteria were detected at all locations tested using 16S rRNA gene sequencing and quantific - News
Below are news stories associated with this project.