Nitrite production from partial-denitrification process fed with low carbon/nitrogen (C/N) domestic wastewater: performance, kinetics and microbial community

- High nitrite production increased with NTR achieving at around 90%.
- PD effluent was suitable for the feeding source of ANAMMOX process.
- External carbon demand for PD was reduced after domestic wastewater addition.
- Specific NO3−-N reduction rate was as high as 4.56 g N/g VSS/d.
- Thauera genus responsible for nitrite production was dominated with 54.9-72.9%.

Partial-denitrification (PD, NO3−-N → NO2−-N) has been successfully developed to produce nitrite (NO2−) with acetate as the sole carbon source. In this study, a PD sequencing batch reactor (SBR) fed with high-nitrate (NO3−: 1000 mg N/L) was firstly developed with carbon source obtained from domestic wastewater (NH4+: 59.3 mg N/L, chemical oxygen demand (COD): 186.6 mg/L) as well as a small quantity of external organic matter. The results showed that PD was not degenerated with domestic wastewater addition, and a high nitrite production was still achieved with the nitrate-to-nitrite transformation ratio (NTR) maintained at 90% in the 173-days operation period. By optimizing the nitrate and domestic wastewater feeding volume as well as external carbon dosage, the PD effluent was suitable for ANAMMOX process with a NO2−-N/NH4+-N of 1.46 and COD/NO2−-N of 1.32 obtained under the influent volume of domestic wastewater of 2.8 L, as well as nitrate of 0.4 L, and the external carbon demand was reduced to COD/NO3−-N of 1.7. Nitrate reduction rate was fit to Monod kinetics, with a maximum specific NO3−-N reduction rate of 4.56 g N/g VSS/d and nitrate half-saturation constant of 6.9 mg N/L, respectively. High-throughput sequencing analysis revealed that the diversity of microbial communities was increased with the domestic wastewater added, but the denitrifiers of Thaura genus that was responsible for high nitrite production was still dominant in PD reactor with a percentage of 54.9-72.9%. This study indicated that the high-nitrate and domestic wastewater could be simultaneously treated via the novel PD-ANAMMOX process in a cost-effective way.

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