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.