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Anaerobic ammonium oxidation (anammox) is a key process in the removal of nitrogen from wastewater, in which episodes of substrate inhibition may occur. In this study, the effect of nitrite on anammox in the short and long term was investigated using granules from a full-scale SBR reactor in operation. In the short term, maximum activity was achieved at 100 mg N-NO2−/L, with higher concentrations being inhibitory. It was determined that the biomass behavior is well interpreted (R2 = 0.955) by a non-competitive substrate inhibition model (Andrews model), with a KS of 55.6 mg N-NO2−/L and a KI of 116.7 mg N-NO2−/L, and also well interpreted by the Edwards model (R2 = 0.957), with a KS of 36 mg N-NO2−/L and a KI of 287 mg N-NO2−/L. In the long term, the biomass retained its anammox activity at 15 mg N-NO2−/L over a three TRH horizon; however, at 30 mg N-NO2−/L, anammox activity decreased by 50% at the end of the experiment. Finally, the effect of temperature on the activity of the anammox granules from a different source was studied, revealing that the activity increases with temperature within the range of 25–35 °C, which can be useful if a rapid increase in activity is desired. Operationally, maintaining nitrite below 30 mg N-NO2−/L ensures stability, while exceeding 100 mg N-NO2−/L causes immediate SAA inhibition and slower recovery.

Aerosol-assisted catalytic chemical vapor deposition (AACCVD) is a powerful one-step process to produce vertically aligned carbon nanotubes (VACNTs), characterized by the continuous supply of the catalyst precursor (metallocene). The behavior of catalyst species all along the synthesis is essential for the continuous growth of VACNTs. It is there investigated through detailed observations and elemental analyses at scales of VACNT carpets and of individual CNTs. Our approach is based on two complementary experiments: quenching of the sample cooling, and sequential injection of two distinct metallocenes. Metal-based nanoparticles nucleated in the gas-phase during the whole synthesis duration are shown to diffuse in between the growing VACNTs from the top of the CNT carpet towards the substrate. They are much smaller than the catalyst particles formed on the substrate in the initial steps of the process and evidences are given that they continuously feed these catalyst particles at the VACNT roots. Particularly, the electron energy-loss spectroscopy (EELS) analyses of metal-based segments found into a single CNT show that the second injected metal is very gradually incorporated in the particle initially formed from the metal firstly injected. The feeding of the catalyst particles by the nanoparticles continuously nucleated in the gas-phase is therefore an essential feature of the base-growth of CNTs by AACCVD.