Improving nitrogen removal performance from rare earth wastewater via partial denitrification and anammox process with Fe(II) amendment

Abstract

Treating rare earth wastewater which contains low concentration of nitrogen with little chemical oxygen demand (COD) is an increasing demand. In this study, a partial-denitrification/anammox (PD/A) process with Fe(II) amending for rare earth wastewater treatment was proposed and stably operated for 218 days. The total nitrogen removal efficiency (TNRE) reached up to 89.32 % for actual rare earth wastewater treatment. Continuously Fe(II) addition stimulated more secretion of extracellular polymeric substance (EPS), furthering enhancing the aggregation ability of microbial and adhesion of hydrophobic bacteria. The enrichment of denitrification genera Denitratisoma, Ignavibacterium, Thauera and Limnobacter provided sufficient nitrite substrate from nitrate reduction for subsequent anammox reaction, which was primarily carried out by Candidatus Brocadia (with relative abundance of 5.86 %). Metagenomic analysis indicated the relative abundance of genes hzo, hzsA/B/C and hdh responsible for anammox process increased by 12.84 %, 9.00 %, 9.25 %, 4.21 %, 1.32 %, respectively, which was significantly facilitated nitrogen removal performance of PD/A process.