Achieving advanced nitrogen removal from low-carbon municipal wastewater using partial-nitrification/anammox and endogenous partial-denitrification/anammox

To achieve advanced nitrogen removal from low-carbon wastewater, a partial-nitrification/anammox and endogenous partial-denitrification/ anammox (PN/A-EPD/A) process was developed in a sequential batch biofilm reactor (SBBR). Advanced nitrogen was achieved with the effluent total nitrogen (TN) of 3.29 mg/L when the influent COD/TN and the TN were 2.86 and 59.59 mg/L, respectively. This was attributed to a stable PN/AEPD/A, which was achieved through the integration of four strategies, including treating the inoculated sludge with free nitrous acid, inoculating anammox biofilm, discharging excess activated sludge and residual ammonium at the end of oxic stage. The 16S rRNA high-throughput sequencing results demonstrated that anammox bacteria coexisted with ammonia oxidizing bacteria, nitrite oxidizing bacteria, denitrifying glycogen accumulating organisms (DGAOs) and denitrifying phosphorus accumulating organisms (DPAOs) in biofilms. The abundance of anammox bacteria in the inner layer of the biofilm is higher, while that of DGAOs and DPAOs is higher in the outer layer.

Automated summary

A partial-nitrification/anammox and endogenous partial-denitrification/anammox (PN/A-EPD/A) process was developed in a sequential batch biofilm reactor (SBBR) to achieve advanced nitrogen removal from low-carbon wastewater. The effluent total nitrogen (TN) reached 3.29 mg/L when the influent COD/TN and the TN were 2.86 and 59.59 mg/L, respectively. The stable PN/A-EPD/A process was achieved through four strategies, including treating the inoculated sludge with free nitrous acid, inoculating anammox biofilm, discharging excess activated sludge and residual ammonium at the end of oxic stage. The 16S rRNA high-throughput sequencing results showed the coexistence of anammox bacteria, ammonia oxidizing bacteria, nitrite oxidizing bacteria, denitrifying glycogen accumulating organisms (DGAOs) and denitrifying phosphorus accumulating organisms (DPAOs) in the biofilms, with higher abundance of anammox bacteria in the inner layer and higher abundance of DGAOs and DPAOs in the outer layer.