Powering biological nitrogen removal from the environment by geobatteries

doi:10.1016/j.tibtech.2021.10.008

Trends in Biotechnology

Volume 40, Issue 4, April 2022, Pages 377-380

https://doi.org/10.1016/j.tibtech.2021.10.008 Get rights and content

Geobatteries are redox-active substances that can take up, store, and release electrons reversibly. Provided that their redox activity can be maintained by fluctuations of oxidizing and reducing redox conditions, geobatteries could also improve the performance of engineered systems, such as in biological nitrogen removal from wastewater or constructed wetlands.

Section snippets

Geobattery technology for nitrogen redox removal

Geobatteries [1] are natural redox-active substances covering a wide range of redox potentials which can reversibly donate, store, and accept electrons in biogeochemical redox processes without or with only minor changes in their chemical composition and structure [2]. Examples of geobatteries are carbon-based materials such as natural organic matter (NOM) and pyrogenic carbon (e.g., biochar) harboring both electron-donating (e.g., polyphenolic and hydroquinone moieties) and electron-accepting

Role of geobatteries in biological N removal

Geobatteries can support microbially mediated N removal processes by acting as either electron acceptors for ammonium oxidation or electron donors for N-oxide reduction (see Figure I in Box 1). Growing evidence has revealed redox couplings between compounds that can function as geobatteries and different nitrogen species under laboratory or environmental conditions (Box 1). For instance, on one hand, NOM and biochar can be electron sinks [serving as terminal electron acceptors or intermediary

Sustainability of geobatteries

Considering the microbial geobattery–N redox couplings outlined above, we conclude that geobatteries, unlike classical electron acceptors or donors, hold promise for continuously fueling biological N-removal processes in water treatment without being consumed. Geobatteries could minimize the demands of organic carbon (e.g., acetate) as electron sources. Present biological N-removal techniques include nitrification, denitrification, and anammox processes, along with combinations of these

Activating and maintaining the redox functioning of geobatteries

Redox fluctuations – alternation between oxidized and reduced conditions – may activate and maintain the functioning of geobatteries in N removal (Figure 1). In a recent landmark work, Peiffer and colleagues [2] propose that preserving the high reactivity of geobatteries in natural aquatic environments requires activation by redox fluctuations. They relate geobatteries to redox-active metastable phases. Ripening can increase their stability but decrease their reactivity for electron transfer

Enhancing the redox functioning of geobatteries

We propose that the efficacy of geobatteries can be enhanced by tailoring its redox properties (Figure 1). Redox properties comprise redox capacity and redox state. Redox capacity refers to the total electron exchange capacity (EEC): the sum of the electron-accepting capacity (EAC) and electron-donating capacity (EDC) of a given geobattery substance. The ratio of EAC/EEC or EDC/EEC represents the redox state. Mediated electrochemical analysis (MEA) is an emerging tool for accurately determining

Concluding remarks

Future technologies for improved biological N removal from wastewater or constructed wetlands may take advantage of geobattery compounds as durable and sustainable electron sinks and sources for microbial N-removal processes. Repeated oscillation between oxidizing and reducing conditions could activate and maintain the high reactivity of geobatteries in reactors or constructed wetlands. Suitable sorbents that can bind geobattery substances and maybe also capture N species could be applied to

Acknowledgments

Financial support was provided by the National Natural Science Foundation of China (Grant No. 42007294 and 42021005). A.K. gratefully acknowledges the infrastructural support by the German Research Foundation under Germany’s Excellence Strategy, cluster of Excellence EXC2124, project ID 390838134. S.H. is supported by Collaborative Research Center 1253 CAMPOS (Project 4: Floodplain Biogeochemistry), funded by the German Research Foundation (Grant Agreement SFB 1253/1 2017 and HA 5453/14-1). We

Declaration of interests

No interests are declared.

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Trends in Biotechnology

ForumPowering biological nitrogen removal from the environment by geobatteries

Section snippets

Geobattery technology for nitrogen redox removal

Role of geobatteries in biological N removal

Sustainability of geobatteries

Activating and maintaining the redox functioning of geobatteries

Enhancing the redox functioning of geobatteries

Concluding remarks

Acknowledgments

Declaration of interests

Earth-Sci. Rev.

Rapid electron transfer by the carbon matrix in natural pyrogenic carbon

Nat. Commun.

A biogeochemical–hydrological framework for the role of redox-active compounds in aquatic systems

Nat. Geosci.

Redox properties of plant biomass-derived black carbon (biochar)

Environ. Sci. Technol.

Magnetite and green rust: synthesis, properties, and environmental applications of mixed-valent iron minerals

Chem. Rev.

Anaerobic ammonium oxidation linked to microbial reduction of natural organic matter in marine sediments

Environ. Sci. Technol. Lett.

Electron shuttles enhance anaerobic ammonium oxidation coupled to iron(III) reduction

Environ. Sci. Technol.

Forum
Powering biological nitrogen removal from the environment by geobatteries