Rapid formation of denitrification granules for nitrite accumulation by increasing nitrogen loading rates and...

The nitrite (NO₂^-) accumulation in partial denitrification (PD) offers the possibility of widespread application of anammox process. In this study, the rapid establishment of PD granular system was achieved by increasing nitrogen loading rates (NLR) from 0.9 to 4.8 kg N/(m³·d), with the nitrate-to-nitrite transforming ratio (NTR) increasing rapidly to 87.0 % within 18 days. Growth evidence indicated that the functional genus Thauera was significantly enriched (12.5 %→76.4 %), with nitrate (NO₃^-) reduction rates (S_NO3) improving by 5.4 times from 13.0 to 70.7 mg N/(g VSS·h). Importantly, the rapid aggregation of PD biomass as granules ensured robustness and resistance of PD feeding with the electroplating tail wastewater (NO₃^--N of 103.0 ± 5.0 mg/L), obtaining stable NTR above 91.5 %. This study demonstrated the achievability of the fast development of PD granules and the adaptability and robustness of treating nitrate-containing industrial wastewater, which provided a promising method for efficient nitrogen transformation in industrial applications.