| Summary: | Four granular sequencing batch reactors (GSBRs) were inoculated with four denitrifying Pseudomonas strains carrying <i>nosZ</i> to study the process of granule formation, the operational conditions of the bioreactors, and the carbon concentration needed for nitrate removal. The selected <i>Pseudomonas</i> strains were <i>P. stutzeri</i> I1, <i>P. fluorescens</i> 376, <i>P. denitrificans</i> Z1, and <i>P. fluorescens</i> PSC26, previously reported as denitrifying microorganisms carrying the <i>nosZ</i> gene. <i>Pseudomonas denitrificans</i> Z1 produced fluffy, low-density granules, with a decantation speed below 10 m h<sup>−1</sup>. However, <i>P. fluorescens</i> PSC26, <i>P. stutzeri</i> I1, and <i>P. fluorescens</i> 376 formed stable granules, with mean size from 7 to 15 mm, related to the strain and carbon concentration. <i>P. stutzeri</i> I1 and <i>P. fluorescens</i> 376 removed nitrate efficiently with a ratio in the range of 96%, depending on the source and concentration of organic matter. Therefore, the findings suggest that the inoculation of GSBR systems with denitrifying strains of <i>Pseudomonas</i> spp. containing the <i>nosZ</i> gene enables the formation of stable granules, the efficient removal of nitrate, and the transformation of nitrate into nitrogen gas, a result of considerable environmental interest to avoid the generation of nitrous oxide.
|
|---|