Cultivation of sulfide-driven partial denitrification granules for efficient nitrite generation from nitrate-sulfide-laden wastewater

Sulfide partial denitrification (SPD) is an alternative pathway for nitrite production accompanied with elemental sulfur (S-0) production for nitrate removal from wastewater with anammox. In this study, the SPD granular sludge was cultivated for the first time in an upflow anaerobic sludge bed (UASB) reactor to reach the efficacy of max-imum nitrate-to-nitrite transformation ratio of 92% and an in-situ maximum NO3--N reduction rate of 2.46 kg-N/ m(3)-d, both much higher than literature results. Mature granules had an average particle size of 2.52 mm and hold smooth surface with excess rod bacteria. The elements Ca and S, and proteins in extracellular polymeric sub-stances contributed to granule structure's stability. Enriched Thiobacillus genus was proposed to accumulate ni-trite at moderate HRT (2-6 h). The immobilized functional strains assist efficient partial nitrification reactions to be realized with formed S-0 as byproduct. (C) 2021 Published by Elsevier B.V.

Automated summary

In this study, a sulfur partial denitrification (SPD) granular sludge was cultivated in an upflow anaerobic sludge bed (UASB) reactor, achieving maximum nitrate-to-nitrite transformation ratio and NO3--N reduction rate much higher than literature results. The mature granules had a stable structure with enriched Thiobacillus genus, facilitating efficient partial nitrification reactions.