Response Characteristics of Nitrifying Bacteria and Archaea Community Involved in Nitrogen Removal and Bioelectricity Generation in Integrated Tidal Flow Constructed Wetland-Microbial Fuel Cell.

Longmian Wang,Chengcheng Ding,Qingqing Pang,Xiang Zhu,Fei Yang,Yimin Zhang,Yiping Li,Yueming Zhu,Fuquan Peng,Yibin Cui,Jianjun Lian,Aiguo Zhang,Ying Zhou

doi:10.3389/fmicb.2020.01385

Abstract

This study explores nitrogen removal performance, bioelectricity generation, and the response of microbial community in two novel tidal flow constructed wetland-microbial fuel cells (TFCW-MFCs) when treating synthetic wastewater under two different chemical oxygen demand/total nitrogen (COD/TN, or simplified as C/N) ratios (10:1 and 5:1). The results showed that they achieved high and stable COD, NH4+-N, and TN removal efficiencies. Besides, TN removal rate of TFCW-MFC was increased by 5–10% compared with that of traditional CW-MFC. Molecular biological analysis revealed that during the stabilization period, a low C/N ratio remarkably promoted diversities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in the cathode layer, whereas a high one enhanced the richness of nitrite-oxidizing bacteria (NOB) in each medium; the dominant genera in AOA, AOB, and NOB were Candidatus Nitrosotenuis, Nitrosomonas, and Nitrobacter. Moreover, a high C/N ratio facilitated the growth of Nitrosomonas, while it inhibited the growth of Candidatus Nitrosotenuis. The distribution of microbial community structures in NOB was separated by space rather than time or C/N ratio, except for Nitrobacter. This is caused by the differences of pH, dissolved oxygen (DO), and nitrogen concentration. The response of microbial community characteristics to nitrogen transformations and bioelectricity generation demonstrated that TN concentration is significantly negatively correlated with AOA-shannon, AOA-chao, 16S rRNA V4−V5-shannon, and 16S rRNA V4−V5-chao, particularly due to the crucial functions of Nitrosopumilus, Planctomyces, and Aquicella. Additionally, voltage output was primarily influenced by microorganisms in the genera of Nitrosopumilus, Nitrosospira, Altererythrobacter, Gemmata, and Aquicella. This study not only presents an applicable tool to treat high nitrogen-containing wastewater, but also provides a theoretical basis for the use of TFCW-MFC and the regulation of microbial community in nitrogen removal and electricity production.

Highlights

Earth’s biogeochemical cycles have been largely affected by human activities (Yu et al, 2019), especially by a large amount of nitrogen released from agriculture and animal husbandry, which is the root of many environmental issues such as eutrophication and drinking water pollution
We demonstrated that the removal of COD, NH4+N, and total nitrogen (TN) from wastewater with different C/N ratios (10:1 and 5:1) using Tidal flow constructed wetland (TFCW)-microbial fuel cell (MFC) were not significantly different
The high-throughput sequencing analysis confirmed that a low C/N led to enhanced ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) diversities in the cathode layer during the stabilization period, causing the community structure of the dominant genera to change drastically

Summary

Introduction

Earth’s biogeochemical cycles have been largely affected by human activities (Yu et al, 2019), especially by a large amount of nitrogen released from agriculture and animal husbandry, which is the root of many environmental issues such as eutrophication and drinking water pollution. To this end, various methods have been purposed to remove nitrogen. Removal of nitrogen in wastewater has been investigated by biological method, and/or its combination with natural and ecological approaches (Wu et al, 2017). With two prominent challenges nowadyas, i.e., energy scarcity and non-point sourced nitrogen, finding economical and sustainable nitrogen removal technologies is difficult

Methods

Results

Conclusion