Achieving efficient nitrogen removal in a single-stage partial nitrification-anammox-partial denitrification (PN/A/PD) membrane aerated biofilm reactor (MABR)

This study is the first to report the start-up and the nitrogen removal performance of a single-stage PN/A/PD MABR without a heating system. It was found that the lumen pressure difference significantly affected the total nitrogen removal efficiency (TNRE), and the dissolved oxygen (DO) changed markedly with the lumen pressure difference. When the lumen pressure difference decreased, the DO tended to decrease, and (partial) denitrification can be enhanced, thus, the TNRE was further improved. And the highest removal efficiency of NH 4 + -N and TN can reach 100 % and 88.03 %, even at 8.7 °C-19.1 °C. At the low temperatures and C/N ratio 3-4, it was found that the relative abundance of Candidatus_Brocadia increased from 3.99 % to 8.64 % from day 45 to day 99 in the PN/A/PD MABR, showing Candidatus_Brocadias low-temperature adaptability, based on 16S rRNA and metagenomics technology. Carbohydrate metabolism and nitrogen metabolism were also analyzed according to the Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolism pathway. The study achieved NO 2 − -N accumulation through partial nitrification and partial denitrification processes in a single-stage Anammox MABR with low-intensity substrates and had engineering application guiding value for mainstream Anammox MABR. • This reactor was easy to achieve NO 2 − -N accumulation by simple operation. • PN/A/PD MABR was firstly established by the lumen pressure difference control. • The NH 4 + -N and TN removal efficiency can reach 100 % and 88.03 % in 8.7°C to 19.1°C. • Candidatus_Brocadia is able to adapt to the low-temperature environment.