Nitrite accumulation, denitrification kinetic and microbial evolution in the partial denitrification process: The combined effects of carbon source and nitrate concentration.

The combined effects of carbon source (HAc, HPr, Glu, Glu + HAc) and nitrate concentration (40, 80 mg/L labeling as R, R) on partial denitrification (PD) were discussed at C/N ratio of 2.5 (COD = 100, 200 mg/L). The optimal NO-N and NTR reached to 67.03 mg/L, 99.14% in HAc-R system, and denitrification kinetics revealed the same conclusion, corresponding to higher COD utilization rate (CUR: 58.46 mgCOD/(gVSS·h)), nitrate reduction rate (NRR: 29.94 mgN/(gVSS·h)) and nitrite accumulation rate (NAR: 29.68 mgN/(gVSS·h)). The preference order was HAc > HPr > Glu + HAc > Glu in both R and R systems due to different metabolic pathways, however, the NO-N accumulation and kinetic parameters of R group were dramatically higher than those in R for the same carbon source. The R group facilitated more concentrated biodiversity (607-808 OTUs) with Terrimonas and norank_f_Saprospiraceae responsible for high NO-N accumulation in HAc and HPr served systems, while norank_f_norank_o_Saccharimonadales and OLB13 dominated the Glu containing systems.