Enhanced Nitrogen Removal from Domestic Wastewater by Partial-Denitrification/Anammox in an Anoxic/Oxic Biofilm Reactor

Yu Huang,Jiarui Fan,Donghui Huang,Rui Du,Yongzhen Peng

doi:10.3390/pr10010109

Abstract

A partial-denitrification coupling with anaerobic ammonium oxidation (anammox) process (PD/A) in a continuous-flow anoxic/oxic (A/O) biofilm reactor was developed to treat carbon-limited domestic wastewater (ammonia (NH4+-N) of 55 mg/L and chemical oxygen demand (COD) of 148 mg/L in average) for about 200 days operation. Satisfactory NH4+-N oxidation efficiency above 95% was achieved with rapid biofilm formation in the aerobic zone. Notably, nitrite (NO2−-N) accumulation was observed in the anoxic zone, mainly due to the insufficient electron donor for complete nitrate (NO3−-N) reduction. The nitrate-to-nitrite transformation ratio (NTR) achieved was as high as 64.4%. After the inoculation of anammox-enriched sludge to anoxic zones, total nitrogen (TN) removal was significantly improved from 37.3% to 78.0%. Anammox bacteria were effectively retained in anoxic biofilm utilizing NO2−-N produced via the PD approach and NH4+-N in domestic wastewater, with the relative abundance of 5.83% for stable operation. Anammox pathway contributed to TN removal by a high level of 38%. Overall, this study provided a promising method for mainstream nitrogen removal with low energy consumption and organic carbon demand.

Highlights

Nitrogen discharge to water bodies can cause eutrophication and brings serious threats to human health
Nitrogen removal is the major purpose in current wastewater treatment plants (WWTPs)
The continuous-flow A/O biofilm reactor was made of transparent plexiglas, which was divided into nine compartments (Figure 1)

Summary

Introduction

Nitrogen discharge to water bodies can cause eutrophication and brings serious threats to human health. Nitrogen removal is the major purpose in current wastewater treatment plants (WWTPs). Nitrification/denitrification are commonly employed as traditional biological nitrogen removal technologies in WWTPs. In the first step, ammonia (NH4 + -N). Can be oxidized to nitrite (NO2 − -N) by ammonia-oxidizing bacteria (AOB), and to nitrate (NO3 − -N) by nitrite-oxidizing bacteria (NOB) in the second step [1,2]. NO3 − -N is converted to nitrogen gas (N2 ) by denitrification bacteria with organic carbon as the electron donor. This requires a carbon source and considerable consumption of oxygen, especially for meeting stricter standards [3]

Methods

Results

Conclusion