Nitric oxide for anammox recovery in a nitrite-inhibited deammonification system

The anaerobic ammonium oxidation (anammox) process is widely used for N-rich wastewater treatment. In the current research the deammonification reactor in a reverse order (first anammox, then the nitrifying biofilm cultivation) was started up with a high maximum N removal rate (1.4 g N m(-2) d(-1)) in a moving bed biofilm reactor. Cultivated biofilm total nitrogen removal rates were accelerated the most by anammox intermediate - nitric oxide (optimum 58 mg NO-N L-1) addition. Furthermore, NO was added in order to eliminate inhibition caused by nitrite concentrations (> 50 mg NO2--NL-1) increasing NO2removed-/NH4removed+ (2/1, respectively) along with a higher ratio of NO3produced-/NH4removed+ (0.6/1, respectively) than stoichiometrical for this optimal NO amount added during batch tests. Planctomycetales clone P4 sequences, which was the closest (98% and 99% similarity, respectively) relative to Candidatus Brocadia fulgida sequences quantities increase to 1 x 10(6) anammox gene copies g(-1) total suspended solids to till day 650 were determined by quantitative polymerase chain reaction.