The high-rate partial-denitrification via effluent residual nitrate controlling by carbon dosage optimization was investigated based on the analysis of microbial mechanism of nitrite accumulation in this study. With the COD/N was changed from 4.0 to 1.8 and the effluent nitrate was above 8.48 mg/L, the nitrate accumulation ratio (NAR) and nitrate removal ratio (NRR) were achieved to 60 and 90%, respectively. With the electron donor starvation (EDS) strategy, the nitrite accumulation was increased, which is related to the reduced utilization of carbon sources. In addition, the rapidly increased of Thauera (0.21% to 53.29%) and inhibited of Others and Unclassified (96.93% to 16.99%), and the significantly different expression between reductase genes contributed to nitrite production (narG, 1,727.44 copies/mg) and nitrite reduction (nirS, 208.27 copies/mg; nirK, 203.94 copies/mg) commonly involved to PD start-up and stable operation. While another reactor can be quickly started by controlling effluent residual nitrate within 19 days.

  • Partial denitrification process was quickly start up within 19 days via EDS strategy.

  • Critical concentration of NO3-N inhibiting NO2-N reduction was proved to be exist.

  • The average NAR and NRR could reached 60 and 89%, respectively.

  • Thauera increased from 0.21% to 53.29% when effluent NO3-N was above the critical value.

  • Nir gene expression was 4.2 times than the Nir gene so that nitrite was accumulated.

Graphical Abstract

Graphical Abstract
Graphical Abstract
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