Ammonium and organic carbon co-removal under feammox-coupled-with-heterotrophy condition as an efficient approach for nitrogen treatment

Chung Phuong Le,Quyen Huynh Minh Nguyen,Hai Thi Nguyen,Hai The Pham,Hang Thuy Dinh,Toi Duy Nguyen

doi:10.1038/s41598-020-80057-y

Chung Phuong Le, Quyen Huynh Minh Nguyen + Show 4 more

Open Access

https://doi.org/10.1038/s41598-020-80057-y

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Journal: Scientific Reports	Publication Date: Jan 12, 2021
Citations: 9	License type: open-access

Affiliation: VNU University of Science, Nha Trang University

Abstract

Nitrification is the rate limiting step in the nitrogen removal processes since nitrifiers have high oxygen demand, but poorly compete with aerobic heterotrophs. In a laboratory-scaled system, we investigated a process of ammonium oxidation under ferric-iron reducing condition (feammox) in the presence of organic carbon using influents with high NH4+ and COD contents, and ferrihydrite as the only electron acceptor. Batch incubations testing influents with different NH4+ and COD concentrations revealed that the [COD]/[NH4+] ratio of 1.4 and the influent redox potential ranging from − 20 to + 20 mV led to the highest removal efficiencies, i.e. 98.3% for NH4+ and 58.8% for COD. N2 was detected as the only product of NH4+ conversion, whereas NO2− and NO3− were not detected. While operating continuously with influent having a [COD]/[NH4+] ratio of 1.4, the system efficiently removed NH4+ (> 91%) and COD (> 54%) within 6 day retention time. Fluorescence in situ hybridization analyses using Cy3-labeled 16S rRNA oligonucleotide probes revealed that gamma-proteobacteria dominated in the microbial community attaching to the matrix bed of the system. The iron-reduction dependent NH4+ and COD co-removal with a thorough conversion of NH4+ to N2 demonstrated in this study would be a novel approach for nitrogen treatment.

Highlights

Wastewaters with high ammonia content if discharged inappropriately can cause adverse environmental effects to aquatic systems, i.e. toxicity to living organisms and eutrophication in water b odies[1]
In the practice of wastewater treatment, COD if presented at high concentrations is needed to be removed prior to N H4+ removal step, because nitrifying microorganisms are litho-autotrophic, highly require oxygen for the ammonium oxidation, they poorly compete with heterotrophic species for oxygen in environments where organic carbon sources are available[12]
The NH4+ oxidation coupled with ferric iron reduction called feammox was first proposed in2 as an important step of the nitrogen cycle in saturated sediment[8]

Summary

Introduction

Wastewaters with high ammonia content if discharged inappropriately can cause adverse environmental effects to aquatic systems, i.e. toxicity to living organisms and eutrophication in water b odies[1]. An alternative technology for NH4+ removal is the partial nitritation/anammox process in which half NH4+ is first oxidized to nitrite by nitrifying bacteria, afterward the other half is oxidized with nitrite to N2 by Planctomycetes species[3] Both technologies employ nitrification step which is highly demanding in oxygen and responsible for the elevated cost of the treatment process. The first pure culture of feammox bacterium was strain A6 of the Acidimicrobiaceae group (supposed to be a new taxon) isolated from a low pH ferrihydrite-containing enrichment culture This strain grew under autotrophic and acidic condition (at pH 5) and used ferric iron to oxidize N H4+ to n itrite[9]. In the practice of wastewater treatment, COD if presented at high concentrations is needed to be removed prior to N H4+ removal step (via anaerobic technologies such as biogas reactor, upflow anaerobic sludge blanket—UASB), because nitrifying microorganisms are litho-autotrophic, highly require oxygen for the ammonium oxidation, they poorly compete with heterotrophic species for oxygen in environments where organic carbon sources are available[12]

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