Understanding the microbial trends in a nitritation reactor fed with primary settled municipal wastewater

Partial nitritation was pointed out as the key step to implement autotrophic nitrogen removal processes at low temperature. This study investigated initiation and maintenance of a process with simultaneous COD in sequencing batch reactor (SBR) run 15 °C fed primary settled urban wastewater characterized by 42 ± 10 mg TOC/L 45 4 NH4+-N/L. A nitrite accumulation ratio nearly 100% observed long-term (354 days) stability successfully maintained despite municipal composition fluctuations. The absence oxidizing bacteria (NOB) activity attributed free nitrous acid (FNA) in-situ accumulated high levels (0.02–0.20 HNO2-N/L). Despite nitrate production not observed, quantification bacterial groups indicated that NOB were present SBR sludge throughout entire operational period. Ammonium (AOB) abundance community structure significantly influenced organic matter feeding. Average efficiencies 80% obtained without observing any detrimental effect over performance, due functional redundancy within both chemoheterotrophic AOB communities.