Advanced nitrogen removal from wastewater by combining anammox with partial denitrification

•A novel process combining anammox with partial denitrification was established.•The excess NO3−-N was efficiently converted to NO2−-N via partial denitrification.•The maximum NRE of 94.06% was achieved with effluent TN under the limiting value.•The process had potential in treatment for both high and low strength wastewater.

The anammox (anaerobic ammonium oxidation) process has attracted much attention for its cost-saving. However, excess nitrate is usually produced which should be further treated. In this study, an innovative process combined anammox with partial denitrification (nitrate → nitrite) was proposed for advanced nitrogen removal in two sequencing batch reactors (SBRs). The nitrate produced in anammox-SBR (ASBR) was fed into partial denitrification-SBR (DSBR), in which the nitrate was reduced to nitrite, and then removed by backflow of the nitrite to ASBR for secondary anammox process. Results showed that ∼80% nitrate in the effluent of previous anammox was converted to nitrite in DSBR. And the maximum nitrogen removal efficiency (NRE) of 94.06% was obtained with total nitrogen (TN) in the effluent of 10.98 mg/L in average. It indicated that desired effluent quality could be achieved, and the advanced nitrogen removal performance was attributed to the successful achievement of partial denitrification.

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