Feasibility of reinforced post-endogenous denitrification coupling with synchronous nitritation, denitrification and phosphorus removal for high-nitrate sewage treatment using limited carbon source in municipal wastewater.

Abstract Post-endogenous denitrification (PED) process, utilizing internal rather than external carbons, has been proposed for nitrogen removal from wastewaters. However, its potential nitrogen removal capacity has not been approached, especially when facing simultaneous phosphorus removal. Here, the nitrogen removal ability of PED was further investigated by treating municipal and high-nitrate wastewaters in a novel process combined with synchronous nitritation, denitrification and phosphorus removal (SNiDPR). After optimization, the anoxic specific nitrite (and nitrate) reduction rate was increased from 0.41 to 1.13 mgN gVSS-1 h-1, accompanied with PED efficiency raising from 16.8% to 80.9%. It ensured that, by utilizing the limited organic carbons in municipal wastewater, deep-level nutrient removal could still be achieved (total nitrogen and phosphorus removal efficiencies were 93.1% and 99.9%, respectively). Nitrospira (0.1-0.4%) was outcompeted by Nitrosomonas (4.7-3.3%), which contributed to accumulation of nitrite in aerobic stage (99.6%) and dramatically reduced the carbons demand of following PED. Enriched Dechloromonas (8.5-5.6%) and Candidatus_Competibacter (9.1-11.3%) might play key roles in sufficient utilization of organic carbons in municipal wastewater anaerobically, and respectively facilitate aerobic phosphorus removal (100%) and anoxic PED (60.7% of overall nitrogen removal).