Achieving fast start-up of anammox process by promoting the growth of anammox bacteria with FeS addition

Chunzhen Zou,Liying Ren,Zhuangming Qiao,Zhaojie Cui,Beibei Guo,Shou-Qing Ni,Jinglan Hong,Shakeel Ahmad,Xuming Zhuang

doi:10.1038/s41545-020-00088-w

Abstract

The effects of FeS on nitrogen removal performance and microbial community of anammox process were studied. During the start-up period, the removal efficiencies of nitrite and total nitrogen were significantly improved by FeS. The addition of FeS increased the content of iron ions in the reactor and promoted the synthesis of heme c, which was involved in the formation of various enzymes. Compared with the control, the abundance of anammox bacteria in the FeS reactor was increased by 29%, and the expression level of the nirS gene (encoding cd1 type nitrite reductase containing heme) was nearly doubled. The content of nitrite reductase (ammonia-forming) in the community was increased by 26.4%. The difference in functional bacteria and enzyme contents in the microbial community resulted in a difference in nitrogen removal rate (NRR) between the two reactors. High-throughput results indicated that FeS increased the richness and diversity of microbial community and enhanced the metabolic function of the microbial community. The addition of FeS did not change the dominant position of Ca. Kuenenia in both reactors. But the relative abundance of heterotrophic denitrifying bacteria was reduced with FeS, which may be related to the inhibition effect of S2− produced by FeS.

Highlights

The increasing concentrations of inorganic nitrogen in surface water have had a serious impact on many aquatic organisms, leading to the deterioration of freshwater, estuaries and marine ecosystems
Effects of FeS on nitrogen removal The start-up period could be divided into two phases based on nitrifying bacteria, denitrifying bacteria and anammox bacteria
The first phase was characterized by high hydraulic retention time (HRT) and low substrate cell lysis phase was over and denitrifying bacteria activity began to concentration, in which the HRT was 48 h and the concentrations of influent NH4+-N and NO2−-N were 50 and 60 mg L−1, respectively

Summary

INTRODUCTION

The increasing concentrations of inorganic nitrogen in surface water have had a serious impact on many aquatic organisms, leading to the deterioration of freshwater, estuaries and marine ecosystems. Microbial oxidation of FeS, which links to the efficiency of denitrification, dissimilatory nitrate reduction to ammonium (DNRA) and anammox, plays an important role in the N cycle and S cycle[15]. In the present study, the influence of FeS on anammox process was investigated with three main objectives: (1) evaluate the start-up time and performance of anammox process in a UASB reactor with/without the addition of qPCR results indicated that NOB abundance was higher in the inoculation sludge as shown in the section “Effect of FeS on functional bacteria abundance”. From day 1 to day 18, the accumulation of NO3−-N in R1 and R2 gradually decreased from 10 mg L−1 to 0 mg L−1 These phenomena indicated that NOB was gradually eliminated in the low-oxygen environment and the activity of anammox bacteria was increasing. FeS, (2) reveal the microbial community variations in anammox reactor driven by FeS, and (3) explore the influence mechanism of FeS

RESULTS AND DISCUSSION

Zou et al 4

METHODS