Preemptive methodology determining operational parameters for mainstream PN: Evaluating biokinetics of three functional microbiome in seeding sludge

Abstract

Chemical oxygen demand (COD)/N ratio is attracted as an alternative strategy selectively suppressing nitrite oxidizing bacteria (NOB) in mainstream partial nitritation (PN). We investigated a methodology that proper COD/N ratio is preemptively evaluated from seeding sludge through biokinetic analysis for three functional aerobic microbes. The COD/N ratio facilitating PN was preemptively determined as ≥3 from the biokinetic assay using seeding sludge, which was successfully verified in continuous bioreactors. Interestingly, the relative biokinetic properties of NOB in oxygen competition between aerobic microbes were the key indicators to achieve mainstream PN. Microbial community results show that some aerobic heterotrophic bacteria (AHB) became predominant at higher COD/N ratio conditions (≥3) with decreasing Nitrospira spp. In other words, the COD/N ratio, which could deteriorate the relative oxygen competition of NOB depending on the microbial community, could be determined preemptively. Our results could suggest that the proposed methodology can be helpful to provide operational guideline of mainstream PN.