Sulfur as a stimulant for biological treatments removing nitrogen and contaminants from wastewater, soil, and groundwater

Background

Nitrogen pollution is a significant environmental concern, particularly in aquatic ecosystems where excess nitrogen, primarily in the form of ammonium, can lead to eutrophication, algal blooms, and subsequent oxygen depletion (anoxia). These conditions threaten aquatic life and degrade water quality, necessitating effective nitrogen removal from wastewater, soil, and groundwater. Traditional biological treatment methods, such as nitrification followed by denitrification, are widely used to convert ammonium to nitrogen gas, thereby mitigating its environmental impact. However, these processes are often energy-intensive and require specific operational conditions, such as the presence of oxygen and controlled temperature ranges, which can limit their efficiency and scalability, especially in regions with limited resources or variable climates.

Current approaches to nitrogen removal face several challenges that hinder their widespread adoption and effectiveness. Conventional nitrification-denitrification systems demand continuous aeration, which significantly increases operational costs and energy consumption. Alternative processes, such as anaerobic ammonium oxidation (anammox), offer some improvements but still require partial aeration and relatively high temperatures (28–35°C) for optimal performance, making them less suitable for cooler climates or decentralized applications. Furthermore, these methods may struggle to address the simultaneous removal of other contaminants, such as heavy metals, radionuclides, and recalcitrant organic compounds, often present in complex waste streams. As a result, there is a pressing need for more robust, low-energy, and versatile biological solutions capable of efficient nitrogen and contaminant removal under a broader range of environmental conditions.

Technology

This technology leverages the unique metabolic capabilities of the Acidimicrobiaceae Feammox bacterium A6, in combination with elemental sulfur, to efficiently remove ammonium and a range of contaminants from wastewater, soil, and groundwater under anaerobic, iron-reducing conditions. The process operates optimally in acidic environments (pH 2–7) and at moderate temperatures (4–35°C), using ferric iron as an electron acceptor to convert ammonium into nitrite or nitrogen gas. The addition of elemental sulfur at concentrations above 0.05 mM/L significantly enhances the bacterium’s metabolic activity, growth rate, and production of the Feammox Ammonium Monooxygenase (FMO) enzyme, resulting in higher rates of contaminant removal. This system can be implemented in various reactor designs—including membrane, batch, and electrogenic reactors—or applied directly in situ, offering a versatile solution for treating nitrogen pollution, heavy metals, radionuclides, and persistent organic pollutants without the need for aeration.

What differentiates this technology is its ability to achieve high-efficiency nitrogen and contaminant removal in environments where conventional biological processes struggle—such as low-temperature or acidic settings—while eliminating the energy costs associated with aeration. The stimulation of Feammox activity by elemental sulfur is a novel approach that not only boosts ammonium oxidation but also broadens the range of treatable contaminants, thanks to the bacterium’s metabolic versatility. Unlike traditional nitrification/denitrification or anammox processes, this system functions robustly in anaerobic conditions and can be integrated with other biological treatments for synergistic effects. Its adaptability to diverse reactor configurations and environmental conditions, combined with demonstrated effectiveness in laboratory and pilot-scale studies, positions it as a low-energy, scalable, and innovative solution for sustainable water and soil remediation.

Benefits

• Efficient ammonium and nitrogen removal under anaerobic, acidic conditions without the need for aeration
• Enhanced bacterial growth and metabolic activity through elemental sulfur stimulation
• Capability to remove a broad range of contaminants including heavy metals, radionuclides, and organic pollutants
• Operates effectively at moderate temperatures (4–35°C), suitable for diverse climates and wastewater streams
• Versatile application in reactors or in situ for wastewater, soil, and groundwater treatment
• Lower energy consumption compared to conventional nitrification/denitrification and anammox processes
• Potential for genetic engineering to expand Feammox activity in various host organisms

Applications

• Municipal wastewater nitrogen removal
• Industrial wastewater heavy metal remediation
• In situ groundwater decontamination
• Soil remediation at contaminated sites
• Radionuclide removal from waste streams

Additional info

This biological system leverages *Acidimicrobiaceae* Feammox bacterium A6 and elemental sulfur (>0.05 mM/L) to catalyze ammonium oxidation in anaerobic, iron-reducing environments. Utilizing ferric iron as an electron acceptor, the process converts nitrogenous compounds and reduces heavy metals or radionuclides under acidic conditions (pH 2–7). Sulfur stimulation optimizes metabolic flux and FMO enzyme expression, facilitating non-aerated remediation of wastewater, soil, and groundwater at moderate temperatures (4–35°C).